GROWTH OF ADIPOSE TISSUE VOLUME AND MATURITY IN CHILDREN

Linda F. Blade B.Sc., University of Maryland, 1985 M.Sc., University of Saskatchewan, 1987

THESIS SUBMllTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Doctor of Philosophy

in the School of Kinesiology

O Linda F. Blade 1993 SIMON FRASER UNIVERSITY September 1993

All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission of the author. APPROVAL

Name: Linda I?. Blade Degree: Ph.D. Kinesiology Title of Thesis: Growth of Adipose Tissue Volume and Maturity in Children

Examining Committee: Chair: Dr. Glen Tibbits

Dr. William D. Ross Senior Supervisor

Dr. Susan Crawfardl

Dr. Alan Martin

Dr. Igor Mekjavic

Dr. William R. .Krane Department of Psychology, SFU Internal Examiner

Dr. Robert Malina Department of Kinesiology & Health Education, and Department of Anthropology University of Texas at Austin External Examiner PARTIAL COPYRIGHT LICENSE

I hereby grant to Simon Fraser University the right to lend my thesis, project or extended essay (the title of which is shown below) to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. I further agree that permission for multiple copying of this work for scholarly purposes may be granted by me or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without my written permission.

Title of Thesis/Project/Extended Essay

GROWTH OF ADIPOSE TISSUE VOLUME AND MATURITY IN CHILDREN

Author: (s ignature]

Linda F. Blade

(name) Abstract

Controversy in the literature surrounding the relationship between adiposity and biological maturity in children prompted a re-examination of this relationship using a novel measure of adiposity - adipose tissue volume (ATV). The purpose of this thesis was twofold: 1. to document An/ growth by estimating ATV of the arms, trunk and legs from anthropometric measurements and, then, by describing its timecourse through childhood, particularly in comparison to changes in corresponding skinfolds (Section A) and 2. to test the hypothesis that ANis related to the following maturity indicators (Section B): (a) onset of puberty in girls and boys, (b) menarche in girls, (c) time interval between puberty onset and menarche in girls and (d) skeletal age (SA) in boys. Anthropometric data were used from the following sources: the Coquitlam Growth Study ('COGRO'; n=l105; ages 5-21 ; cross-sectional), the lbadan Growth Study ('lbadan'; n=108; ages 6-1 1 ; cross-sectional), the Saskatchewan Growth and Development Study ('SASK'; n=237; ages 7-16; longitudinal) and 6 the Kormend Growth Study ('Kormend', n=7023, ages 3-18, secular trend). Section A. An/ is observed to grow in a sigmoidal fashion, with takeoff at 7 to 8 years of age and a slowing of growth from 14 to 16 years of age onward (girls and boys), a time course distinct from growth of non-adipose tissue volume (NATV). Curves of An/ growth diverge from skinfold curves during adolescence, with skinfolds decreasing as ATV continues to increase. A greater divergence in boys than girls and in limbs than trunk suggests that adipose tissue can be 'stretched' and 'thinned' by extreme or abrupt body lengthening. The meaning of a change in skinfold in a growing child must now be questioned. Improvement in measurement technology is recommended. Section B. Age at puberty onset (PA) was defined as the age at which there was a positive shift in growth rate of biiliocristal breadth (BIIL) in girls and biacromial breadth (BIAC) in boys (SASK, Kormend). In SASK, PA occurs at the same mean ANin both genders, even though in boys average PA is two years delayed (ps.001) and mean NATV at PA is greater (ps.001) than in girls. Regression analysis showing mean ATV and %ANto be unchanged at all levels of PA while mean NANrises linearly with increasing PA (ps.05 (girls); pr.001 (boys)) identifies An/ and %AN as having a possible association with puberty onset, exclusive of NATV. Absence of a drop in coefficient of variation (CV) of AN, %ANand NANin the year of PA, except for a slight drop in CV of thigh An/ (girls and boys), indicates no 'critical' level of ANnecessary to trigger puberty. In Kormend, cross-decade differences in AN(ps.001) match the observed secular trend in PA, exclusive of NATV. Cross-decade NAN differences match the secular trend in age at menarche (MA), exclusive of ATV. In SASK girls, AN, %An/ and NANshow unchanging means at all levels of MA, with no evidence of a 'critical' effect by either, given unchanging CVs at MA. 6 The time interval 6om PA to MA has an inverse, linear relationship with NAN velocity (p1.005), but not with ANvelocity. In SASK boys, all tissue volumes are linearly related to SA (ps.001), suggesting nothing more than a general relationship between SA and largeness. In conclusion, ATV is not associated with menarche. That it does have an association with puberty onset cannot be ruled out. The relationship between adiposity and gonadarche requires closer examination with longitudinal investigation involving both anthropometric and hormonal assessment of growing children. Dedication

To my husband, Stanford Blade, whose unfailing love sustained my efforts.

To my parents, Hank and Ila Spenst, whose interest in my affairs inspired me to reach higher than I otherwise might have.

To Dan and Betty Blade, whose logistical support, understanding and encouragement made my load lighter. Foreword

Curiosity prompted me, in February, 1990, to begin monthly anthropometric assessment of a (biological) sister who had recently discovered

she was pregnant. Through fourteen months of her pregnancy and lactation I , became increasingly intrigued by the behavior of adipose tissue, both its fluctuating abundance and its shifting distribution about the body, seemingly in response to changes in hormonal status. The experience left an indelible impression that the anatomical component, adipose tissue, tells a contemporary and dynamic tale about internal physiology. Yet, who amongst us really understands this tale? Our vision is blurred by crude measurement and faulty, all be they necessary, assumpti~ns concerning the relationship between external measures of the body and internal composition and function. To understand the connection will, clearly, preoccupy a good many anthropometrists of the next generation as measurement technology improves. 6 Since it is my keen interest to participate in the advancement of this kind of knowledge, it is not by coincidence that when a vast quantity of anthropometric data on growing children was made available to me, I chose to investigate a proposed connection between adipose tissue and a physiological phenomenon (in this case, puberty). I trust that the experience has not only provided the methodological and theoretical awareness necessary to collaborate with colleagues across a wide range of human biological disciplines, which is required of anybody who seeks to understand the links between human form and function, but also that ideas expressed in this document will promote interest in the search. Acknowledgements

If I could indict two individuals for outrageous courage, skill and foresight in auxological research, I would subpoena Dr. Donald Bailey (University of Saskatchewan) and Dr. Otto Eiben (Eotvost Lorand University, Hungary), and then I would thank them for their generosity. Next, I would cite the following individuals for thought provocation: Dr. William D. Ross (my effervescent supervisor), Dr. Alan Martin, Dr. Susan Crawford, Dr. lgor Mekjavic, Dr. Richard Ward and authors Rose Frisch and Solomon Katz. Drs. Crawford and Martin (University of British Columbia) would deserve extra sentences for exceeding normal output of time and effort to guide me through the rigors of thesis development.

Let the record show that Dr. Robert Malina (University of Texas) betrayed conscientious attention to detail in his thorough and instructive examination of the contents herein. His presence was my reward and I thank him sincerely.

Colleagues, friends and family who stand accused of assisting the candidate with technical advice, constructive dialogue and/or just plain loving care span the Atlantic. For the record, they are:

In Canada: Don Drinkwater, Joi Belyk and Jochen Bochsnick, Fran Williams, Rod Rempel, Robin Carr, Lindsay Carter, Stephan Riek, Sanja Savic, Greg Anderson, Ian Wood, Shona Mclean, Sheila and Sharon Manhas, Anand Nithyanand, Gavril Morariu, Barb Cameron, Len Brownlie, Mike Walsh, Yves Roy, Bonnie Sawatsky, Thanasis Passias, Dale Parkyn, Rob Taylor, Ted Milner, Francois Bellavance (Statistical Consulting), Mary Ross, Dr. Parveen Bawa, Dr. Eric Banister, Randy and Sandra Kolarci Joe and Carolyn Nichols, Darrel and Margrete Spenst, Nancy Spenst, h ank and Ila Spenst, Carsten and Sherri Blade, Dan and Betty Blade, Vic and Gloria Spenst, Trish Glanfield and Vivian Rossner.

Jn Spain: Dr. Maria Teresa Aragones Clemente and Jordi Porta.

In Niaeria: Dr. Latif 0. Amusa, Dr. Ayo Agbonjinmi and Grace Akintunde (University of Ibadan); Dr. B.B. Singh, Les and Francis Macdonald and Andrew and Trixie Middleton-Mohr (IITA).

Of course, these assertions would have been much longer in coming had I not received financial assistance from the government of Canada (NSERC) and Simon Fraser University (NSERC top-ups, graduate studies scholarship and T.A.ships). So, I must thank the taxpayers of this fine country.

Dad, Mom, what else did you expect would result from giving a small girl soccer cleats and a microscope? I love you for it, even though it engendered this arduous journey. And, Stan, my best buddy, you will live to remit your decision to show me the world and cultivate my independence. If I can help it, yours will be a harvest of happiness. vii Table of Contents

.. Approval ...... 11 ... Abstract ...... 11 Dedication ...... v Foreword ...... vi .. Acknowledgements ...... I ... List of Tables ...... XIII ... List of Figures ...... XVIII ... Definitions ...... XXIII

Chapter 1. Introduction ...... 1 Endocrinology of Puberty ...... 2 The Frisch Hypothesis ...... 4

/ The 'Katz' Hypothesis ...... 9 Methodological Considerations ...... 15 Inadequate sampling ...... 15 Failure to correct for body size ...... 16 Physical thinning of adipose tissue with growth in segment length ...... 16 Prospectus ...... Ji ...... 19 Statement of Purpose ...... 21 Thesis Overview...... 22

SECTION A . Description of Adipose Tissue Volume Growth...... 23

Chapter 2 . Photogrammetric Derivation of Segment Lengths: Saskatchewan Girls ...... 24 Measurement Procedure...... -24 Measurement Strategy ...... 25 Reliability ...... 29 Accuracy ...... 32 Conversion of Photogrammetric Lengths to Life-size Equivalents...... 33 Conclusion ...... 34

viii Chapter 3. Growth of Adipose Tissue Volumes in Cross.sectional. Longitudinal and Secular Trend Studies ...... 35 Calculation of Segmental ANs...... 38 The Coquitlam Growth Study (COGRO) ...... 41 The lbadan Growth Study ...... 42 The Saskatchewan Growth Study (SASK) ...... 43 The Kormend Growth Study ...... 45 Description of the Growth of Adipose Tissue Volume ...... 46 A Mathematical Model of ANGrowth ...... 53 The Relationship Between ANand Skinfolds ...... 60

Chapter 4. Section A: Discussion ...... 75 Adipose Tissue Growth...... 75 Adipose Tissue Volume versus Skinfold Thickness ...... 78 Summary and Conclusion ...... 82

SECTION B. Investigation of the Relationship Between Adipose Tissue Volume and Maturity ...... 83

Chapter 5 . ANand Age at Puberty Onset in Saskatchewan Children...... 84 Methods ...... 87 Results and Diseussion ...... 91

Chapter 6 . Adiposity and Age at Puberty: a Secular Trend Analysis ...... 104 Methods ...... 06 Description of the Kormend Growth Study...... 106 Identification of change points in BlAC and BllL breadth ...... 107 Analysis of Relative Adiposity ...... 07 Comparison of ATV and NANeffects ...... 108 Results ...... 108 Discussion...... 22 Chapter 7. Adipose Tissue Volumes and Age at Menarche in Saskatchewan Girls ...... 127 Methods ...... 129 Results and Discussion ...... 132

Chapter 8 . ANversus Skeletal Age in Saskatchewan Boys ...... 138 Methods...... 139 Results and Discussion ...... 141

Chapter 9 . Section B:Discussion ...... 147 Adiposity and Puberty Onset ...... 147 Adiposity and Menarche...... 152 Conclusion ...... 154

Chapter 10. Summary. Conclusions and Recommendations...... 156 Summary of Results ...... 156

SECTION A . Description of Adipose Tissue Volume (Am) Growth...... 156

SECTION B. Investigation of the Relationship Between AN and Maturity ...... 158 6 General Conclusions ...... 161 Recommendations...... 163

APPENDIX 1. Abbreviations ...... 165

APPENDIX 2 . Description of Data Bases ...... 166 The Coquitlam Growth Study (COGRO) ...... 166 The lbadan Growth Study (Ibadan) ...... 166 The Saskatchewan Growth and Development Study (SASK) ...... 167 The Kormend Growth Study (Kormend '68. '78. '88) ...... 168

APPENDIX 3 . Nomenclature for Anthropometric Abbreviations ...... ,169

APPENDIX 4 . Age Summaries: all data bases ...... 175

APPENDIX 5. Height Summaries: all data bases...... 1 77 APPENDIX 6 . ATV Summaries:The Coquitlam Growth Study (COGRO)...... 179

APPENDIX 7 . ATV Summaries: the lbadan Growth Study ...... 181

APPENDIX 8 . ATV Summaries: The Saskatchewan Growth and Development Study (SASK)...... 82

APPENDIX 9 . ANSummaries: The Kormend Growth Study. 1968 ...... 184

APPENDIX 10 . ATV Summaries: The Kormend Growth Study. 1978 ...... 185

APPENDIX 1 1 . ATV Summaries: The Kormend Growth Study. 1988 ...... 187

APPENDIX 12 . Growth Curves of Regional Variables: Ibadan...... 199

APPENDIX 13 . Growth Curves of Regional Variables: SASK ...... 192

APPENDIX 14 . Growth Curves of Regional Variables: Kormend. 1968...... 195

APPENDIX 15 . Growth Curves of Regional Variables: Kormend. 1978...... 198

APPENDIX 16 . Growth Curves of Regional Variables: Kormend. 1988...... 201

APPENDIX 17. Skinfold Summaries: COGRO ...... 204

APPENDIX 18 . Skinfold Summaries: lbadan ...... 206 d APPENDIX 19. Skinfold Summaries: SASK ...... 207

APPENDIX 20 . Skinfold Summaries: Kormendy. 1968 ...... 209

APPENDIX 21 . Skinfold Summaries: Kormend. 1978...... 211

APPENDIX 22 . Skinfold Summaries: Kormend. 1988...... 23

APPENDIX 23 . Scatter Plots of Arm Tissue Volumes versus PA: SASK Children ...... 215

APPENDIX 24 . Scatter Plots of Trunk Tissue Volumes versus PA: SASK Children ...... 218

APPENDIX 25 . Scatter Plots of Thigh Tissue Volumes versus PA: SASK Children ...... 221 APPENDIX 26. Scatter Plots of Arm Tissue Volumes versus MA: SASK Girls ...... 224

APPENDIX 27. Scatter Plots of Trunk Tissue Volumes versus MA: SASK Girls ...... 225

APPENDIX 28. Scatter Plots of Thigh Tissue Volumes versus MA: SASK Girls ...... 226

APPENDIX 29. Scatter Plots of Change in Arm Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls...... 227

APPENDIX 30. Scatter Plots of Change in Trunk Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls...... :...... 228

APPENDIX 31. Scatter Plots of Change in Thigh Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls...... 229

APPENDIX 32. Scatter Plots of Growth Velocity of Arm Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls...... 230

APPENDIX 33. Scatter Plots of Growth Velocity of Trunk Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls...... 231

APPENDIX 34. Scatter Plots of Growth Velocity of Thigh Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls...... 232

REFERENCES ...... 233 List of Tables

Table 2.1. Landmarks used for photogrammetry of segmental lengths: SASK girls...... 26

Table 2.2. Frequency chart of comments made during data entry...... 28

Table 2.3. The technical error of measurement (TEM), percent TEM (%TEM) and coefficient of variation (CV) for three repeated photogrammetric estimates of segmental lengths of the Saskatchewan girls ...... 30

Table 2.4. Standard error of measurement for photogrammetry of segmental lengths: SASK girls ...... 32

Table 2.5. Regression equations for the prediction of life-size lengths (Y) from photogrammetric lengths (X) according to the model Y=mX+b...... 33

Table 3.1. Subject numbers by age (boyslgirls) for the four growth studies...... 4 1

Table 3.2. Variables used to calculate ATVs in the Coquitlam Growth Study (COG RO) ...... 42

Table 3.3. Variables used to calculate ATVs in the lbadan Growth Study ...... 42

Table 3.4. Variables used to calculate ANs in the Saskatchewan Growth Study (SASK)...... t 44

Table 3.5. Maximum/minimum comparisons of derived lengths common to COGRO and SASK data bases ...... 44

Table 3.6. Variables used to calculate ATVs in the Kormend Growth Study (K68, K78, K88)...... 45

Table 3.7. Summary of residual sum of squares when equations #1 and #2 were applied to boys and girls Kormend An/ data with the given maximum values fixed...... 56

Table 5.1. Summary statistics (mean, SD and N) for PA and tissue . volumes, AN, %ANand NATV: SASK girls and boys ...... 90

Table 5.2. Summary of probabilities resulting from regression analyses of PA versus ATV, %ATV and NATV (total and regional): SASK girls and boys ...... 91 Table 5.3. Assessment of the variability in An/ and NANat PA with respect to the variability over the entire growth period in SASK girls (ages 8 to 16 years) ...... 96

Table 5.4. Assessment of the variability in ANand NATV at PA with respect to the variability over the entire growth period in SASK boys (ages 8 to 16 years)...... 97

Table 6.1. Summary of p-values from cross-decade comparisons of total and regional ATV controlling for the effects of corresponding NANs by Analysis of Covariance (ANCOVA): Kormend girls ...... 1 1 1

Table 6.2. Summary of p-values from cross-decade comparisons of total and regional ATV controlling for the effects of corresponding NANs by Analysis of Covariance (ANCOVA): Kormend boys ...... 11 2

Table 6.3. Scheffe's pairwise comparison probabilities corresponding to ANCOVAs in Tables 6.1 and 6.2: total ATV ...... 1 13

Table 6.4. Scheffe's pairwise comparison probabilities corresponding to ANCOVAs in Tables 6.1 and 6.2: upper extremity ATV ...... 1 14

Table 6.5. Scheffe's pairwise comparison probabilities corresponding to ANCOVAs in Tables 6.1 and 6.2: trunk AN...... 11 5

Table 6.6. Pairwise differences of adjusted total ATV means given by the ANCOVA procedure...... 11 6

Table 6.7. Pairwise diffetences of adjusted upper extremity ANmeans given by the ANCOVA procedure...... 116

Table 6.8. Pairwise differences of adjusted trunk ANmeans given by the ANCOVA procedure...... 11 7

Table 6.9. Summary of t-tests of column differences in Tables 6, 7 and 8...... 117

Table 6.1 0. Summary of probabilities given by ANOVA and Scheffe's post hoc procedures in cross-decade comparisons of total ATV: Kormend girls ...... 118

Table 6.1 1. Summary of probabilities given by ANOVA and Scheffe's post hoc procedures in cross-decade comparisons of total NATV: Kormend girls ...... 1 19

Table 6.1 2. Summary of probabilities given by ANOVA and Scheffe's post hoc procedures in cross-decade comparisons of total ATV: Kormend boys ...... 120 Table 6.13. Summary of probabilities given by ANOVA and Scheffe's post hoc procedures in cross-decade comparisons of total NATV: Kormend Boys ...... 12 1

Table 7.1. Summary statistics (mean and standard deviation) of age at menarche (MA) and tissue volumes at this age in SASK girls (N=20 ...... 3 1

Table 7.2. Summary statistics of tissue volume changes over the PA-MA time interval in SASK Girls (N=14)...... 131

Table 8.1. Means and standard deviations of variables used to study the relationship between SA and adiposity in SASK boys (N=115) ...... 140

Table 9.1. Summary of all known investigations which have focused on the relationship between adiposity and gonadarche ...... 151

Table A4i. Girls summary of average age and standard deviation (SD) by age category for all data bases...... 175

Table A4ii. Boys summary of average age and standard deviation (SD) by age category for all data bases...... 176

Table A5i. Girls summary of average height and standard deviation (SD) by age category for all data bases...... 1 77

Table A5ii. Boys summafy of average height and standard deviation (SD) by age category for all data bases...... 178

Table A6i. Means and standard deviations (SD) of regional and total ATVs by age: COG RO girls ...... 1 79

Table A6ii. Means and standard deviations (SD) of regional and total ATVs by age COGRO boys ...... 1 80

Table A7i. Means and standard deviations (SD) of regional and total ATVs by age: lbadan girls ...... 181

Table A7ii. Means and standard deviations (SD) of regional and total ATVs by age: lbadan boys ...... 18 1

Table A8i. Means and standard deviations (SD) of regional and total AlVs by age: SASK girls ...... 1 82 Table A8ii. Means and standard deviations (SD) of regional and total ANs by age: SASK boys ...... 1 83

Table A9. Means and standard deviations (SD) of regional and total ANs by age: Kormend '68 girls and boys ...... I84

Table A1 Oi. Means and standard deviations (SD) of regional and total ANs by age: Kormend '78 girls ...... I85

Table AlOii. Means and standard deviations (SD) of regional and total ANs by age: Kormend '78 boys ...... 186

Table A1 1i. Means and standard deviations (SD) of regional and total ANs by age: Kormend '88 girls ...... I87

Table A1 1ii. Means and standard deviations (SD) of regional and total ANs by age: Kormend '88 boys...... I 88

Table A1 7i. Means and standard deviations (SD) of regional and total skinfolds by age: COGRO girls ...... 204

Table A1 7ii. Means and standard deviations (SD) of regional and total skinfolds by age: COGRO boys ...... 205

Table A1 8i. Means and standard deviations (SD) of regional and total skinfolds by age: lbadan girls ...... -...... -.206

Table A18ii. Means and standard deviations (SD) of regional and total skinfolds by age: lbadan boys ...... 206

Table A1 9i. Means and standard deviations (SD) of regional and total skinfolds by age: SASK girls ...... 207

Table A19ii. Means and standard deviations (SD) of regional and total skinfolds by age: SASK boys ...... 208

Table A20i. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '68 girls ...... 209

Table A20ii. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '68 boys ...... 210

Table A21 i. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '78 girls ...... 2 1 Table A2lii . Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '78 boys ...... 21 2 Table A22i . Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '88 girls ...... 21 3

Table A22ii . Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '88 boys ...... 21 4

xvii List of Figures

Figure 1.I. Feedback by which the level of spontaneously produced luteinizing hormone releasing factor (LRF) is regulated ...... 3

Figure 1.2. Simplified schemata of the sequential rise of various hormone species during human growth, with three distinct maturity events, adrenarche (A), gonadarche (G) and menarche (M) indicated ...... 11

Figure 1.3. The rate of growth of 'subcutaneous fat' diameter in arm, calf, and thigh, estimated by radiography...... 18

Figure 1.4. The rate of growth of muscle in arm, calf, and thigh, estimated by radiography...... 18

Figure 3.1 . Illustration of the strategy used to calculate ATV ...... 39

Figure 3.2. Growth of ANof COGRO children ...... 47

Figure 3.3. Growth of ANof lbadan children...... 48

Figure 3.4. Growth of ANof SASK children ...... 49

Figure 3.5. Growth of ANof Kormend '68 children ...... 50

Figure 3.6. Growth of ANof Kormend '78 children ...... 51 C Figure 3.7. Growth of ATV of Kormend '88 children ...... 52

Figure 3.8. The basic shapes being described by the two mathematical models ...... 55

Figure 3.9. Distance and velocity curves of ATV growth smoothed by the Preece-Baines mathematical model (Preece and Baines, 1978) using data of Kormend children (1968, 1978 and 1988 combined) ...... 57

Figure 3.1 0. The generalized curve of ANgrowth expressed as a percentage of its final value to facilitate comparison of adipose tissue growth with that of other tissues, particularly Tanner's 'four curves of human growth' ...... 58

Figure 3.1 1. Growth velocities of ATV and NANsmoothed by Equation #2 ...... 59 Figure 3.1 2. Growth of total AW, total length (L), total girth (G) and sum of skinfolds (SF) in COGRO girls and boys expressed as a percentage of total growth according to the 'standardized growth index'...... 6 1

Figure 3.1 3. Growth of total AW, total length (L), total girth (G) and sum of skinfolds (SF) in lbadan girls and boys expressed as a percentage of total growth according to the 'standardized growth index' ...... 62

Figure 3.1 4. Growth of total An/, total length (L), total girth (G) and sum of skinfolds (SF) in SASK girls and boys expressed as a percentage of total growth according to the 'standardized growth index' ...... 63

Figure 3.1 5. Growth of total AN, total length (L), total girth (G) and sum of skinfolds (SF) in Kormend168girls and boys expressed as a percentage of total growth according to the 'standardized growth index'...... 64

Figure 3.1 6. Growth of total AW, total length (L), total girth (G) and sum of skinfolds (SF) in Kormend178girls and boys expressed as a percentage of total growth according to the 'standardized growth index'...... 65

Figure 3.1 7. Growth of total An/, total length (L), total girth (G) and sum of skinfolds (SF) in Kormend188girls and boys expressed as a percentage of total growth according to the 'standardized growth index'...... 66

C Figure 3.1 8. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm, calf, thigh and trunk: COGRO girls ...... 68

Figure 3.1 9. Growth of segmental An/, length (L), girth (G) and skinfold (SF) of the arm, calf, thigh and trunk: COGRO boys ...... 69

Figure 3.20. Growth of total AW, total length (L), total girth (G) and sum of skinfolds (SF) for individual SASK Girls...... 71

Figure 3.21. Growth of total ATV, total length (L), total girth (G) and sum of skinfolds (SF) for individual SASK Boys ...... 72

Figure 5.1. Example of a typical change point in BlAC in a SASK boy (Subject #25)...... 88

Figure 5.2. Example of a change point observation with respect to BllL during growth in a SASK girl (Subject #607) for whom only two data points exist beyond the observed shift in slope...... 89 Figure 5.3. Scatterplots of PA versus transformed tissue volumes, Log Total AN, Log Y~TotalAN and Log Total NANin SASK girls ...... 94

Figure 5.4. Scatterplots of PA versus transformed tissue volumes, Log Total AN, Log %Total ANand Log Total NANin SASK boys...... 95

Figure 5.5. Coefficients of variation of total and regional tissue volumes, ATV, %ATV and NANversus time from PA: SASK girls ...... 99

Figure 5.6. Coefficients of variation of total and regional tissue volumes, ATV (a), %AN(b) and NAN(c) versus time from PA (+ 3 years): SASK boys...... 1 00

Figure 5.7. Total ATV as a percentage of combined volume of all segments (%Total An/) by age at puberty onset (PA)...... 103

Figure 6.1 . Growth of Total ATV: Kormend children ('68, '78, '88) ...... 105

Figure 6.2. Velocity curves for 1968, 1978 and I988 of biiliocristal breadth and biacromial breadth of Kormend children ...... 110

Figure 7.1. Scatter plots of MA versus totals of tissue volumes (ml), An/, %An/ and NATV in SASK girls ...... 133

Figure 7.2. Coefficients of variation of total and regional tissue volumes, ATV, %ANand NATV versus time from MA ...... 134

Figure 7.3. Changes in total ATV and total NANvolumes (ml) over the time interval from PA to MA ...... 136

Figure 7.4. Growth velocities of total ANand total NATV (mllyr) over the time interval from PA to MA ...... 137

Figure 8.1. Scatterplots of SA (expressed as MI) versus tissue volumes, Total ATV, %Total ANand Total NANin SASK boys...... 142

Figure 8.2. Scatterplots of SA (expressed as MI) versus tissue volumes, Arm AN, %Arm ANand Arm NANin SASK boys...... 143

Figure 8.3. Scatterplots of SA (expressed as MI) versus tissue volumes, Trunk ATV, %Trunk ANand Trunk NANin SASK boys ...... ; ...... 144

Figure 8.4. Scatterplots of SA (expressed as MI) versus tissue volumes, Thigh ATV, %Thigh ANand Thigh NATV in SASK boys...... 145 Figure A12i. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm, calf, thigh and trunk: lbadan girls ...... 190

Figure A12ii. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm, calf, thigh and trunk: lbadan boys ...... 19 1

Figure A1 3i. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm, thigh and trunk: SASK girls ...... 193

Figure A1 3ii. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm, thigh and trunk: SASK boys...... 194

Figure A1 4i. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the upper extremity and trunk: Kormend '68 girls...... 196 b Figure A14ii. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the upper extremity and trunk: Kormend '68 boys...... 197

Figure A1 5i. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the upper extremity, lower extremity and trunk: Kormend '78 girls ...... 199

Figure A1 5ii Growth of segmental ATV, length (L), girth (G) and skinfold (SF) of the upper extremity, lower extremity and trunk: Kormend '78 boys ...... 200

Figure A1 6i. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the upper extremity, lower extremity and trunk: Kormend '88 girls ...... 202

Figure A16ii. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the upper extremity, lower extremity and trunk: Kormend '88 boys ...... 203

Figure A23i. Scatterplots of PA versus transformed tissue volumes, Log Arm AN, Log %Arm ANand Log Arm NATV, in SASK girls ...... 21 6

Figure A23ii. Scatterplots of PA versus transformed tissue volumes, Log Arm AN, Log %Arm ANand Log Arm NAN, in SASK boys...... 21 7

Figure A24i. Scatterplots of PA versus transformed tissue volumes, Log Trunk ATV, Log %Trunk ANand Log Trunk NAN, in SASK girls ...... 219

Figure A24ii. Scatterplots of PA versus transformed tissue volumes, Log Trunk ATV, Log %Trunk ANand Log Trunk NAN, in SASK boys...... 220 Figure A25i. Scatterplots of PA versus transformed tissue volumes, Log Thigh ATV, Log 70Thigh ATV and Log Thigh NAN, in SASK girls ...... 222

Figure A25ii. Scatterplots of PA versus transformed tissue volumes, Log Thigh ATV, Log %Thigh ATV and Log Thigh NANin SASK boys...... 223

Figure A26. Scatter plots of MA versus arm volumes (ml), An/, %ATV and NATV in SASK girls...... 224

Figure A27. Scatter plots of MA versus trunk volumes (ml), ATV, %AN and NAW, in SASK girls ...... 225

Figure A28. Scatter plots of MA versus thigh volumes (ml), AW, %An/ and NAW in SASK girls...... 226

C Figure A29. Changes in arm ATV and arm NATV over the time interval from PA to MA ...... 227

Figure A30. Changes in trunk ATV and trunk NATV over the time interval from PA to MA ...... 228

Figure A31. Changes in thigh ANand thigh NANover the time interval from PA to MA ...... 229

Figure A32. Growth velocities of arm ANand arm NAN(mllyr) over the time interval from PA to MA ...... 230

Figure A33. Growth velocities of trunk ANand trunk NAN(mllyr) over the time interval from PA to MA ...... 231

Figure A34. Growth velocities of thigh ATV and thigh NAN(mllyr) over the time interval from PA to MA ...... 232 Definitions

Since the words used in discussions of both body fatness and the physical transition from childhood to adulthood are often ambiguous, the following definitions will help to clarify the ideas presented in this thesis:

pdipose tissue - A discrete tissue of the human body whose cells store fat and are capable of metabolizing hormones (e.g. adrenal androgens).

adi~osetissue distribution - The physical, phenotypical manifestation of adipose tissue being deposited in different amounts from one region of the body to the next.

adiposity - The total amount of adipose tissue present within a given individual. (from Drinkwater, 1984)

adolescence - The period of transition from childhood to adulthood (Malina, 1978) during which there are ..."changes in reproductive organs and the secondary sex characteristics; in body size and shape; in the relative proportions of muscle, fat and bone; and in a variety of physiological functions" (Tanner, 1978). adrenarck - The physiological event during mid-childhood when the adrenal cortex matures and adrenal androgen secretion begins to rise. It precedes gonadarche by about two years (Grumbach and Kaplan, 1990) anthropometric terms - taken from Ross and Marfell-Jones, 1991

$ioloaical maturitv - The degree to which a biological system approximates the mature, adult state. development - The concomitant advancement of growth and maturation. (adapted from Crawford, 1990) - Ether extractable lipid.

aonadarche - The physiological event in late childhood when sex steroid secretions from the gonads begin to rise as a result of the reactivation of the hypothalamic-pituitary gonadotropin-gonadal unit (adapted from Grumbach and Kaplan, 1990). It is the initiation of puberty. [In the current investigation gonadarche is roughly approximated as the age at which there is a widening of biiliocristal 'hip' breadth (BIIL) in girls and biacromial 'shoulder' breadth (BIAC) -- in boys.] mh- The increase in size of a variable with time. (adapted from Crawford, 1990)

index of bioloaical maturity - Any variable or set of variables within a biological system whose measurable quantity or quality represents the degree of differentiation or specialization in the direction of the adult form.

maturation - The increase in complexity of an organism in the direction of the adult form. (adapted from Crawford, 1990) o-scale - A physique assessment system which rates an individual's size- adjusted anthropometric measurements on a stanine scale representing the normal range of values for the same age and sex population (explained in Ross and Marfell-Jones, 1991). gubertv - The biological event which initiates adolescence. (adapted from Malina, 1978) secular trend - 1) An increase or decrease in the average age at which a particular value of an anthropometric variable is attained, a particular characteristic of maturation is developed or a variable reaches its adult value within a given population; and 2) an increase or decrease in the average adult size of any anthropometric variable for a given population. (adapted from Eiben, 1987) Standardized Growth Index - An index created in this thesis for convenience, allowing a single scale to be used to graphically display growth curves of a number of variables which differ in dimension andlor size. It is calculated in the following way: 100 x [(value of a variable at any given time - initial value in the series)/final value in the series]. skinfold - A double layer of skin plus entrapped adipose tissue resulting from a fold raised and encompassed with full tension on the pressure plates of a skinfold caliper applied to a specific site on the body. (adapted from Daniel, 1990) skinfold patterning - The pattern of the skinfold measurements at different anatomical sites: often used to represent adipose tissue distribution. Chapter 1. Introduction

Children in Western countries have experienced both menarche (girls) and the adolescent growth spurt in height (boys and girls) earlier with each decade since the industrial revolution in conjunction with improvement in living conditions (Tanner, 1990; Roche, 1979). Remarkably, age at menarche dropped by about four months per decade from 1840 to 1960 among European and American girls (Tanner, 1990). Delay of maturation associated with low social class can be eliminated by nation-wide improvement in living conditions, as has been shown in progressive countries such as Norway (Bruntland, Liestol and Walloe, 1980). But a difference in age at puberty continues to be detected across economic boundaries, with children of the economically disadvantaged lagging in physical development relative to children of the well-off, whether those boundaries are drawn between nations, races or societies (Cameron, Mitchell, Meyer, Moodie, Bowie, Mann and Hansen, 1990; Tanner, 1990; Eveleth and Tanner, 1990; Adadevoh, Agble, Hobbs and Elkins, 1989; Cameron et al., 1988; Singh and Malhotra, 1988; Eiben, 1987; Mavoungou, Gass, Emane, Cooper and Roth-Meyer, 1986; Worthman, 1986; Kulin, Bwibo, Mutie, Med and Santner, 1982). Whether earlier maturation arises'specificaliy from improvement in nutrition, sanitation or health care (as suggested in Tanner, 1990; Ellison, 1981 ; Malina, 1979 and Roche, 1979) or from easing of daily physical demands (as suggested in Eiben, 1987 and Ellison, 1981), what interests students of human biology are the physical mediator(s) and mechanism(s) that increase the pace of physical change towards adult biological status. Two authors, Rose Frisch, initially, (in Frisch, 1984; and Frisch, Revelle and Cook, 1973) and, more recently, Solomon Katz (in Katz, Hediger, Zemel and Parks, 1985) have proposed that increased adiposity or 'fatness', which generally accompanies improvement in standard of living,

1 accelerates sexual maturation in growing children. However, they suggest different mechanisms by which adiposity exerts its influence. In the pages that follow, a rationale is developed for acceptance of the 'Katz' hypothesis as the more plausible of the two. The statement of purpose for the thesis is then given, based on the premise that anthropometric variables in longitudinal, cross-sectional and secular trend studies can be used in specific ways to test this hypothesis. At the outset, however, a brief overview of the endocrinological control of puberty is given, as the ideas of Frisch and Katz pertain somewhat to this subject matter.

Endocrinology of Puberty Gonadarche, the event that triggers puberty, occurs between 8.5 and 13 years of age in 95% of girls and between ages 9.5 and 13.5 in 95% of boys (Kaplan and Grumbach, 1990). It is characterized by a sudden increase in sex steroid output from the gonads, estrogen from the ovaries and testosterone from the testes, in response to a surge in gonadotropins (LH and FSH) from the anterior pituitary. Prior to this event, pituitary output of LH and FSH is kept at a low level, because negative feedback at the level bf medial basal hypothalamus by both circulating sex steroids and neural inputs of unknown origins in the CNS inhibits the pulsatile release of luteinizing hormone releasing factor (LRF) in quantities or frequencies necessary for stimulation of the pituitary (Grumbach and Kaplan, 1990). Illustration of this feedback loop is provided in Figure 1.l. CNS

(+ Anterior 4 Hypothalamus Pituitary LRF (LRF Pulse Generator)

Gonadotropins (LH,FSH) Sex Steroids (Estrogen,Testosterone)

Gonads/

Figure 1.I. Feedback by which the level of spontaneously produced luteinizing hormone releasing factor (LRF) is regulated. Circulating sex steroids and neural inputs inhibit the hypothalamic LRF pulse generator, which results in low LH and FSH levels throughout childhood. Disinhibition of the hypothalamus in late childhood causes LH and FSH levels to rise and, hence, stimulates full gonadal output of sex steroids ('gonadarche').

The mystery of puberty is that for unknown reasons, the hypothalamus gradually becomes disinhibited in late childhood, allowing progressively more stimulation of the anterior pituitary by LRF and, therefore, the rise in LH and FSH output necessary for the onset of full gonadal function. As Kaplan and Grumbach (1990) imply, the components of the system - hypothalamus, pituitary and gonads - do not require maturation themselves. They have the capacity to function in an adult manner from the time of birth. Premature activation of the hypothalamic LRF pulse generator, either by the presence of tumors in the CNS or by other dysfunctions, has been seen to cause puberty in a child as early as age one year (Kaplan and Grumbach, 1990), the remarkable consequence in one case being the birth of a son to a five-year-old girl (Grumbach and Kaplan, 1990). The event of importance to puberty onset, therefore, is disinhibition of the hypothalamic LRF pulse generator to negative feedback by circulating sex steroids. If adiposity is hypothesized to accelerates puberty a plausible mechanism must be given whereby increased adiposity alters hypothalamic function.

The Frisch Hypothesis Some twenty years ago, Frisch and Revelle (1 970; 1971 ) hypothesized that a critical weight was required for the onset of puberty, because comparison of early- and late-maturing groups of boys and girls showed no group differences in the average weight at onset of the adolescent growth spurt. Additionally, no significant difference was found in the average weight of early- and late-maturing girls at menarche (Frisch and Revelle, 1970). The observation that total body mass in rodents increased metabolic rate at estrus led Frisch and Revelle (1970) to envision a mechanism whereby the attainment of a critical body weight in children altered the sensitivity of the hypothalamus to estrogen by increasing metabolic rate and core temperature, thus setting off the cascade of events leading to puberty. Given that the coefficient of variation (CV) was higher for weight at age of menarche (14.4%) than at the onset of the growth spurt (7.5%), suggesting that other factors might complicate the relationship once the growth spurt had started (Frisch and Revelle, 1970), these authors attempted to identify which component of body weight was most closely associated with initiation of pubertal events. Lean body weight (LBW) and body fat (BF) were derived from weight and height regressed on total body water (TBW) using the equation of Mellits and Cheek (1970). Both LBW and BF showed no significant change with increasing age at menarche (Frisch et al., 1973),suggesting that critical levels of both are necessary for menarche to occur. But, since there was a 125% increase in BF from initiation of the growth spurt to menarche and only a 42% increase in LBW during the same

4 period, these authors concluded that it was most likely a critical amount of BF that dictated the timing of menarche, given enough LBW to afford structural support for a pregnancy. The hypothesis henceforth has been called the 'critical fat' hypothesis. Frisch and McArthur (1974) later postulated that a critical value of 17% BF was necessary for menarche to occur and 22% BF was the amount required to regain menstrual function lost from excessive dieting or exercise. The discovery that adrenal androgens are converted into estrogens in adipose tissue (e.g. Nimrod and Ryan, 1975) appeared to strengthen Frisch's argument, since, presumably, a greater amount of body fat could augment circulating levels of estrogens and, thus, precipitate gonadal maturation. Hence, Frisch (1984) proposed a dual mechanism for the influence of body components on maturity: while total body mass desensitizes the hypothalamus to negative feedback by increasing metabolic rate and core temperature, a certain, critical level of adiposity has a direct impact on the gonads by providing an extraglandular source of estrogens. This hypothesis was popular in medical circles, as it explained the disruption of gonadal function seen to occur in both males and females with environmental circumstances involving excessive fat loss (Frisch, 1984). Indeed, such a role for body fat seemed to be biologically adapthe in that the mean BF that Frisch et al. (1 973) observed at menarche amounted to about the same caloric content estimated by the FA0 to be necessary to sustain a pregnancy (as explained in Frisch, 1984). The proposal that a critical weight or %BF triggers menarche, however, has attracted much criticism amongst investigators. Many have argued that for a physical variable to be 'critical' to a physiological event, it must display a small variation at the time of the event (Johnston, Roche, Schell and Wettenhall, 1975; Cameron, 1976; Scott and Johnston, 1982). Yet, virtually all investigations into this

5 matter have found the CV of weight at menarche to be as large as at any other time during adolescence (Johnston et al., 1975; Billewicz, Fellowes and Hytten, 1976; Ellison, 1982). Also, Billewicz et al. (1976) found that a number of girls experienced menarche over one year after they had surpassed the weight threshold proposed by Frisch. Both observations call into doubt the existence of a single, critical weight. While Ellison (1982) did find weight and relative weight to have an influence on menarcheal age, he failed to find a threshold effect and added that skeletal maturation seemed to have a stronger impact on the timing of menarche. Focusing on the estimated components of body weight, Johnston,et al. (1975) showed that the lower CV calculated for TBW (hence, for LBW and BF) compared to the CV for weight at menarche reported by Frisch et al. (1973) was a mathematical artifact resulting from failure to include an appropriate error term in the regression equation used to predict these values. Other studies involving %BF estimation in girls offer little evidence to support the 'critical fat' hypothesis. In some cases, menarche occurred at %BF lower than the proposed threshold and in others it occurred only after the threshold was surpassed (Scott and Johnston, 1982). In another study, LBW rather than BF had a close relationship with the initiation and progress of pubertal events (Parra, Cervantes, Sanchez, Fletes, Garcia-Bulnes, Argote, Sojo, Carranco, Arias and Cortes-Gallegos, 1981). Use of the term, 'fat', by Frisch to mean 'adipose tissue' contributes to error in the testing of her hypothesis. Meaning 'oil' or 'lipid', fat is merely a constituent of a cell with no metabolism of its own. Physiological consequence ascribed to 'fatness' or 'adiposity' pertains to the metabolism of adipose tissue which contains fat. That Frisch meant 'adipose tissue' when she used the word 'fat' is revealed in the following statement: "Fat is the most labile body tissue: it therefore reflects environmental changes more rapidly than other tissues of the body." (Frisch, 1984, p. 184). Yet the test of her hypothesis involved the estimation of percent body lipid, not adipose tissue. To measure %BF is an exercise fraught with inaccuracy (Martin and Drinkwater, 1991 ), especially during childhood when, apart from the problem of subject cooperation, there is a high inter- and intra-individual variability in the relative abundance and density of non-fat components (Forbes, 1978; Holliday, 1978). While a large portion of body lipid is stored in adipose tissue, this is not the only tissue where lipid resides in the human body (Martin, 1984). Since the fraction of body lipid contained within adipose tissue varies from one individual to 3 the next (Martin, Daniel, Drinkwater and Clarys, 1993; Forbes, 1986), it is a rough approximation, at best, of the amount of adipose tissue available. An equally valid, if not better, determination of adiposity is the measurement of adipose tissue thickness by skinfold caliper. Cameron (1976, p.281) states that, "If body fat really is critical for the occurrence of menarche then skinfolds ought to demonstrate this critically by a reduction in their variability (at menarche)...". As with observations of weight at menarche, however, no reduction in CV was observed when skinfolds were involved in tests of the Frisch hypothesis (Billewicz et al., 1976; Cameron, 1976). This contributes to the evidence that the hypothesis is untenable. Special attention must be given to a recent longitudinal investigation of Dutch adolescent girls, since the protocol included measurement of plasma hormone concentrations, along with maturity assessment by breast stage and adiposity assessment by skinfold thickness (deRidder, Bruning, Zonderland, Thijssen, Bonfrer, Blankenstein, Huisveld and Erich, 1990; deRidder, Thijssen, Bruning, van der Brande, Zonderland and Erich, 1992). At the earliest stage of puberty (breast stage 2 - using the standards of Tanner, 1962), the level of 'fatness' (sum of four skinfolds - triceps, biceps, subscapular and suprailiac) was not

7 statistically related to plasma concentrations of sex steroids (estrone, estradiol and testosterone) or gonadotropins (LH and FSH) (de Ridder et al., 1990). Furthermore, with respect to longitudinal progress through maturational events, there was no significant relationship between level of 'fatness' and age at any of three stages: (1) onset of puberty (breast stage 2), (2) onset of breast stage 3 and (3) menarche; nor was there a relationship between sum of skinfolds and sex steroid or gonadotropin concentrations at any of these stages (de Ridder et al., 1992). Girls in the highest quartile for sum of skinfold, however, did experience a shorter interval between puberty onset and menarche than girls in the lowest quartile. Therefore, the results of deRidder generally do not support the concept of a 'critical' level of adiposity serving as the trigger for any maturational event during adolescence, although there may be an association between adiposity and rate of progress towards menarche once puberty has begun. Furthermore, there is contradictory evidence concerning the dual mechanism proposed by Frisch (1984). Core temperature, for example, does not increase significantly during puberty. Frisch et al. (1 973) themselves reported that metabolic rate actually decreases during adolescence, from 35 cal.kg-I -day-' at initiation of the growth spurt to 28 cal-kg-Asday-1at menarche, a decrease caused primarily by concurrent increases in body weight during this interval. Also, Frisch (1 984) did not explain how estrogens arising from adipose tissue could cause sexual maturation in boys. The 'Katz' Hypothesis Katz et al. (1985) have recently offered a more comprehensive explanation for a role adipose tissue might play in the onset of puberty in both girls and boys. They argue that body fat dictates the timing of gonadarche indirectly in the way it interacts with adrenal androgens following an event in mid-childhood now known as 'adrenarche'. Only in the past decade or two has adrenarche been established as a distinct hormonal milestone during growth and development (Cutler, Schiebinger, Albertson, Cassorla, Chrousos, Comite, Booth, Levine, Hobson and Loriaux, 1990; Hopper and Yen, 1975; Parker, Sack, Fisher and Odell, 1978; Sklar, Kaplan and Grumbach, 1981; Brook, 1981). It is characterized by the sudden maturation of the adrenal cortex sometime between the ages of five to eight years in both boys and girls, at which point the adrenal androgen species, dehydroepiandrosterone (DHEA) and its sulfate (DHEAS), are seen to rise (Shapiro, 1985; Brook, 1981; Parker et al., 1978; Bing, Xu,Zhang and Wang, 1988; Sizonenko, Paunier and Carmignac, 1976). Adrenal androgens continue to rise through late childhood and early adolescence, usually reaching a plateau at adult levels from ages fourteen to fifteen in both sexes (Sizonenko et al., 1976;'~eeand Migeon, 1975; Lee, Xenakis, Weiner and Matsenbaugh, 1976; Hopper and Yen, 1975; Genazzani, Facchinetti, Petraglia, Pintor and Bagnoli, 1983; Genazzani, Pintor, Facchinetti, Corboni, Pelosi and Corda, 1978; Zemel and Katz, 1986; Bing et al., 1988). Studies of twins and family groups reveal that maturation and function of the adrenal cortex have a strong genetic component (Akamine, Kato and Ibayashi, 1980; Rotter, Wong, Lifrak and Parks, 1985; Sklar et al., 1981). Adrenal androgen levels in mid-childhood, for example, showed a significantly higher intrapair similarity in monozygotic twins than in age-matched dizygotic twins (Akamine et al., 1980). Furthermore, it appears that adrenarche is under stricter genetic control than gonadarche, given the extent to which both are influenced by environmental conditions such as undernutrition. For example, African children from Kenya (Worthman, 1986) and Gabon (Mavoungou et al., 1986) who had a distinct delay in puberty of up to two or three years compared to Western averages, showed little difference in age of adrenarche. The time line for maturity events during growth, then, is illustrated in Figure 1.2. In both boys and girls, circulating levels of adrenal androgens (DHEA and PHEAS) begin to rise at around age seven years, representing adrenarche ('A' on the chart), while the steroid hormones related to the hypothalamic-pituitary-gonadal axis, Estrogen (E) and Testosterone (T), increase around ten or eleven years of age representing gonadarche ('G' on the chart). For girls, menarche ('M') generally happens about two years after gonadarche (Tanner, 1990). The lateral arrows represent the range over which adrenarche, gonadarche and menarche normally happen for 95% of children (Shapiro, 1985; Brook, 1981 ; Parker et al., 1978; Bing et al., 1988; Sizonenko et al., 1976; Kaplan and Grumbach, 1990; Tanner, 1990). With respect to Figure 1.2, Katz, et al. (1985) hypothesize that adipose tissue gained in the interval between 'A' and 'GI, labelled the 'K-zone' for convenience, dictates when in the 'G' range gonadarche will occur for any given individual and, consequently, when 'M' will occur. The proposal is thus: "that increased production of adrenal androgens in the presence of early increased adiposity (prepubertal) leads to earlier gonadarche." (Katz, et al., 1985, p. 402) b Sex Steroids

Adrenal Androgens

Figure 1.2. Simplified schemata of the sequential rise of various hormone species during human growth, with three distinct maturity events, adrenarche (A), gonadarche (G) and menarche (M), indicated by vertical arrows. Lateral arrows represent the range within which these events occur for 95% of children in Western populations. The 'K-zone' represents the period during which the accumulation of adiposity is proposed to influence when, in the 'G' range, gonadarche actually occurs for any given individual. [Curves-of adrenal androgens and sex steroids were estimated roughly from information given in Winter (1 978)]

In spite of the fact that the adrenal steroid, DHEAS, has been found to be highly associated with breast stage (Bing et al., 1988), pubic hair development

(Korth-Shultz, Levine and New, 1976; Lee and Migeon, 1975; Forest, 1983; Apter, I 1980; Brook, 1981 ; Bing et al., 1988), menarche (Bing et al., 1988) and bone age I (Zemel and Katz, 1986; Akamine et al., 1980; Katz, et al., 1985; Bing et al., 1988;

d l I Apter, 1980; Tanner, 1990; Sizonenko et al., 1976), Katz, et al. (1 985) argue that I high levels of DHEAS alone do not necessarily influence gonadal maturation. Neither premature adrenarche nor administration of excess DHEAS in mid- childhood, for example, have been shown to significantly accelerate gonadal development (Cutler et al., 1990; Genazzani, lnaudi and Kicovic, 1980; Sklar et al., 1980). Rather, it appears that adipose tissue must be present concurrently, as circumstances under which DHEAS is found to correlate significantly with gonadal maturation are invariably those in which DHEAS also has a significant correlation with adiposity (Bing et al., 1988; Katz, et al., 1985). As with the Frisch hypothesis, the 'Katz' hypothesis relies heavily on the fact that the adrenal androgen, DHEA, is metabolized into more active steroids, particularly androstenedione (A-dione) and estrone (El), within adipose tissue (Cleland, Mendelson and Simpson, 1985; Forney, Milewich, Grace, Garlock, Schwarz, Edman and MacBonald, 1981; Hemsell, Grodin, Brenner, Siiteri and MacDonald, 1974; Longcope, Pratt, Schneider and Fineberg, 1978; Schindler, Ebert and Friedrich, 1972; Perel and Killinger, 1979; Nimrod and Ryan, 1975). In contrast to Frisch (1984), however, who suggested that these active species, particularly the estrogens, act predominantly at the level of the gonads, Katz, et al. (1 985) propose that the by-products of aromatization, A-dione and/or El, act directly at the level of the hypothalamus, gradually shifting the sensitivity of the LRF pulse generator to sex steroids and, thereby, resulting in earlier onset of gonadal maturation. Evidence for such a mechanism comes, indirectly, from observations that, as stated in Katz, et al. :

"The hypothalamic regions controlling the onset of gonadarche have themselves a high concentration of aromatase (Naftoline and Maclusky, l982), and implantation + of androstenedione in the hypothalamus specifically has been shown to alter the sensitivity of gonadostatic control of pituitary gonadotropins in experimental animals (Febres, Seron, Weiner and Siiteri, 1977)". (Katz, et al., 1985, p. 402) As the level of adiposity rises in the human body, a preferential uptake of DHEA by the peripheral tissue coincides with increased secretion of both DHEA and DHEAS by the adrenal cortex, to the extent that in cases of obesity there is enormous over-production of these adrenal androgens (Feher and Halmy, 1975a; Feher and Halmy, 1975b). While the exact nature of this feedback mechanism remains a mystery (Wild, 1992; Tanner, 1990; Parker and Odell, 1979), it does explain both why obese children are observed to have high concentration of serum DHEAS (Pintor et al., 1980; Pintor, Loche, Faedda, Fanni, Nurchi and Corda, 1984). It also explains, given the metabolism of sequestered DHEA into active hormones, why they are observed to have advanced maturational characteristics (Beunen, Malina, Ostyn, Renson, Simons and van Gerven, 1982; Garn, Clark and Guire, 1974; Laron, Ben-Dan, Shrem, Kickerrnan and Lilos, 1978). Pintor et al. (1980, 1984) have found that DHEA levels return to normal with weight loss in both prepubertal and pubertal boys and girls. In summary, one can envision two ways in which increased adiposity might affect hypothalamic function: (a) by making more of the active by-products of DHEA aromatization available for transport to the hypothalamus and/or (b) by promoting the production of DHEA and DHEAS in the adrenal cortex via feedback, thereby making more DHEA available for aromatization to A-dione and El within the hypothalamus itself. Although it is true that aromatization of adrenal androgens can occur in a variety of other tissues, including muscle, skin, bone, neural tissue, hair and kidneys (Longcope, Pratt, Schneider and Fineberg, 1978; Forney, Milewich, Grace, Garlock, Schwarz, Edrnan and MacDonald, 1981), adipose tissue and muscle account for most of it. Since adipose tissue increases more than muscle during the pre-adolescent years, its contribution to the large increase in adrenal androgen aromatization during this phase of life is probably greater than the contribution of muscle tissue. Concerning the role increased adiposity might play in the advancement of maturation with improvement in lifestyle, then, it must be concluded that the 'Katz' hypothesis appears to surpass that of Frisch both in the clarity and specificity by which it delimits the influence of the physical mediator, adipose tissue, and in the \' plausibility of the mechanism by which this mediator is proposed to alter hypothalamic function. Katz et al. (1985) invite confirmation of their hypothesis with more-extensive longitudinal data bases on growing children. While the data available for the current investigation do not include hormonal measurements or assessment of hypothalamic function, anthropometric indicators of the general maturational events can be employed to test whether there is a relationship between adiposity and the age at which these events occur in a fashion which is consistent with the Katz hypothesis.

Methodological Considerations A concern of this investigation involves the measurement of adiposity itself. Total body lipid estimation in children, expressed as %BF, is not only inaccurate (Martin and Drinkwater, 1991); it is also somewhat irrelevant to the issue of extraglandular aromatization, since the conversions take place within stromal cells of the adipose tissue organ (Killinger, Perel, Danillescu, Kharlip and Lindsay, 1987; Cleland et al., 1985; Forney et al., 1981 ; Roncari, 1984). The only connection total body lipid has to hormonal metabolism is that, on average, 60% of it resides within the tissue of interest, although this value varies largely from one individual to the next (Forbes, 1986; Martin, Daniel, Drinkwater and Clarys, 1993; Martin, 1984). A more valid approximation of this anatomical tissue would appear to be the measurement of its thickness by skinfold caliper or by radiograph. But errors can also arise from the way in which adipose tissue thickness is handled conceptually. These are discussed in point form below.

1. Inadequate sampling Growth studies which include few skinfolds fail to sample adiposity on all regions of the body and risk miscalculation of over-all adiposity. This could lead to misinterpretation of metabolic consequence. The only two investigations that have explored the adiposity-maturity relationship with measurement of both skinfolds and plasma hormone concentrations, only sampled upper body adiposity: Katz et al. (1985) - triceps and subscapular skinfolds; and deRidder (1 991) - triceps, biceps, subscapular and suprailiac skinfolds. Given evidence that a large proportion of adrenal androgen aromatization takes place in the thigh and buttocks (Killinger et al., 1987), these two investigations might have missed an important part of the story by not sampling thigh adipose tissue. In deRidder (1 991), MRI analysis revealed that a preponderance of adipose tissue resided in the femoral region of their adolescent female subjects. Yet, the variable, (inappropriately) termed 'fat mass', was the sum of the four upper body skinfolds. What, then, is to be made of the conclusion that there appeared to be no difference in breast stage or hormonal status between girls of the lowest and highest sum of skinfolds quartile (deRidder et al., 1990; 19% ; l992)? The 'low' girls may have had as much adiposity or more in the hips and thighs. 2. Failure to correct for bodv size In any group of children, those with large skinfolds may simply be genetically big in all respects, rather than them being more mature, even if adiposity is related to maturity. Therefore, if children are grouped into 'low' and 'high' sum of skinfolds categories, it is possible that there are small children who are more mature in the 'low' category and, likewise, large children who are less mature in the 'high' category. In neither deRidder (1991) nor Katz et al. (1985) are group means for stature reported. Therefore, whether group differences in largeness might have influenced interpretation of results cannot be surmised. While it is important to consider adiposity relative to body size, this is difficult to achieve using skinfolds. There is no skinfold equivalent to %BF. To express relative adiposity as a ratio of skinfold to weight or to height is inappropriate, as skinfolds differ allometrically with these measures of body size during growth. The problem of allometric and dimensional differences among variables is discussed extensively in Gould (1966), Packard and Boardman (1987) and Ross, Grand, Marshall and Martin (1984). How it is resolved in the current investigation is stated under the heading 'Prospectu$ below.

3. Phvsical thinnina of adipose tissue with arowth in seament lenm Investigation of the rate of growth of adipose tissue thickness by a number of authors (Tanner, 1990; Forbes, 1986; Cronk, Mukherjee and Roche, 1983; Johnston, Hamill and Lemeshow, 1974; Malina and Johnston, 1967b) suggests that there might be a thinning of adipose tissue concomitant with each growth spurt in body length. This can be observed most dramatically in Figure 1.3, a plot of longitudinal adipose tissue growth, with both boys' and girls' curves being aligned for peak height velocity (PHV). At the same time, growth in muscle cross-sectional area is also reaching its peak (Figure 1.4). It is clear from these figures that at a

16 time when growth in both body length and underlying musculature is at its highest there is a sharp decline in skinfold thickness. Forbes (1986) suggested that this phenomenon might be indicative of a common hormonal influence being responsible for growth of both height and adipose tissue. Alternatively, it might mean that fat is being metabolized to fuel growth (Johnston, 1982). A third possibility, alluded to by a few authors (Tanner, 1962; Johnston et al., 1974; Frisancho, 1981), is that this thinning might simply be a physical 'spreading' or 'stretching' of adipose tissue with growth in length and/or underlying muscle girth of the particular region under consideration. For example, when thigh length is at its peak rate of growth a decrease in thigh skinfold might be expected merely because the tissue is being stretched to accommodate the enlargement of this region. This possibility has never been fully explored. What it means is that even though a skinfold may decrease as a child grows in length and girth, it does not necessarily mean that the volume of adipose tissue in that region has decreased. When Tanner (1 978) reports that the subscapular skinfold of a one-year-old boy is 3 mm thicker than that of an eight-year-old, surely this does not mean that the one-year-old has more adipose tissue on the trunk. And if it is the total mass (or volume) of adipose tissue that correlates with the degree of aromatization of hormones (Forney et al., 1981), some consideration must be given to the length and girth components when measuring skinfolds in growing children, particularly if the relationship between total adiposity and maturational events is being investigated. I Girls

\ \ f "\ Boys

-40 1 I I I I I I I I I 1 u?cyqyyoy--y 7 Y 9 I 9 0 Age (years)

Figure 1.3. The rate of growth of 'subcutaneous fat' diameter in arm, calf, and thigh, estimated by radiography. Adapted from Tanner (1974).

P.H.V

Boys

\ Girls

I I 1 I I I I $ Cy $ r; y 0 q -I& 7 0 7 Y I ?

Age (years)

Figure 1.4. The rate of growth of muscle in arm, calf, and thigh, estimated by radiography. Adapted from Tanner (1974). In longitudinal studies of adults, where segment lengths are not changing, this issue is of little consequence and changes in skinfolds really do mean that the amount of adipose tissue is changing in the observed direction (unless, perhaps, there is a large concomitant increase in muscularity). But for children, growth of adipose tissue must involve some approximation of mass or volume, since there is a great deal of variability in segment lengths and girths even within the same child from one year to the next. Physical 'spreading' of adipose tissue during growth in length might explain why some girls in deRidderts study (deRidder, et al., 1992) had a low sum of skinfolds at menarche, since menarche is known to happen shortly after PHV (Tanner, 1990). It would be of interest to know if deRidder, et al. (1992) found any of the girls to have shown a decrease in sum of skinfolds over the longitudinal measurement period. By expressing skinfold thickness as a standard deviation score from the norm, Katz et al. (1 985) probably avoided this problem - if one can assume all boys in a given population experience the same degree of 'spreading'.

Prospectus In the current investigation, adipose tissue volume (AN) is estimated from a length, a girth and a skinfold from a given segment of the body. It is used subsequently as the measure of adiposity in exploration of the relationship between adiposity and maturity. With respect to the methodological issues above, it should be emphasized that for every data base examined in the current investigation, ATV for arm, trunk and leg is included, such that no region of the body is completely over-looked. Furthermore, as is shown in Chapter 3, the calculation of An/ provides a covariate, non-adipose tissue volume (NATV), from each region, which affords dimensionally appropriate correction for body size when

19 ATV and maturity are considered. Finally, inclusion of length and girth in the ATV estimate is shown to make a difference in the expression of over-all adiposity than that offered by the one-dimensional skinfold thickness. Multiple data bases on growing children are used in order to bring as much evidence as possible to bear on the nature of An/ growth and on the association between An/ and various maturity indicators. Tests of the relationship between adiposity and maturity in this investigation accompany three general expectations. Firstly, if ATV is to be considered to have a distinct relationship with any maturity event, the volume of the remaining tissues (i.e. NATV) must be shown not to have a relationship. If NANis related, the maturity event can only be surmised to have a general association with overall body size, rather than with An/, exclusively. Secondly, if the 'Katz' hypothesis is more accurate than that of Frisch, the relationship between An/ and indicators of gonadarche will be stronger than that between ANand indicators of menarche. Once disinhibition of the hypothalamus has occurred, gonadal sex steroid output should have a greater impact than adiposity on the development of menstruation. Thirdly, given the observation that peripheral aromatization of adrenal androgens is much greater in the limbs than in abdominal adipose tissue (Killinger et al., 1987; Nimrod and Ryan, 1975), ATV of the limbs should demonstrate a stronger relationship to maturity events than ATV of the trunk. Statement of Purpose As previous investigations concerning the relationship between adiposity and maturity have employed skinfold measurements, it was desirable to re- examine this relationship using a novel measure of adiposity - adipose tissue volume (AN). Therefore, the purpose of this thesis is two-fold:

1. to document the growth of ANaccordingly: (a) to estimate ATVs of the arms, trunk and legs from anthropometric measurements; (b) to describe how these volumes and total ANchange in growing children using cross-sectional, longitudinal and secular trend data bases; and (c) to explore whether changes in skinfold values during growth truly represent changes that take place in An/

2. to test the hypothesis that ATV is related to maturity by testing the following sub- hypotheses: Sub-hypothesis 2a - ATV is related to the onset of puberty in both boys and girls,exclusive of NATV; Sub-hypothesis 2b - ANis related to menarche in girls, exclusive of NAN; Sub-hypothesis 2c - ANis related to the time interval between puberty onset and menarche in girls, exclusive of NAN; and Sub-hypothesis 2d - ATV is related to skeletal maturation, exclusive of NATV. .I Thesis Overview

This thesis is divided into two sections: SECTION A focuses on the problem of ANcalculation and on the description of ANgrowth and its relationship to skinfold changes. SECTION B then describes the specific tests of the hypothesis. SECTION A. Description of Adipose Tissue Volume Growth

This section of the thesis is a necessary first step toward the testing of the relationship between adiposity and maturity (see SECTION B), because it involves the creation of a variable to be used in the test - namely, adipose tissue volume (ATV). It will be shown in Chapter 3 that at least three anthropometric measurements are needed to calculate ATV of any body segment - a length, a girth and a skinfold. All of the data bases used in this study contained the full complement of variables required to calculate ANs of the arm, trunk and leg, except the mixed-longitudinal study of the Saskatchewan (SASK) girls. In this sample, life-size segmental length values had to be derived from negatives of somatotype photographs, taken of each girl at each measurement occasion, using a photogrammetric procedure developed by Crawford (1 990). Therefore, SECTION A begins with a description of the photogrammetric derivation of segment lengths of the SASK girls (Chapter 2). With data bases complete, it was then possible to address purpose #1 of the thesis in Chapter 3, which details the calculation of AN, a description of its growth and a determination of how its growth relates to changes in skinfold values over the same time period. The results of SECTION A are discussed in Chapter 4. At the outset is should be mentioned that a brief description of each data base used in the thesis is given in Appendix 2. A break-down of subject numbers by age category can be found in Chapter 3 (Table 3.1) Chapter 2. Photogrammetric Derivation of Segment Lengths: Saskatchewan Girls

In order to assess adipose tissue volume (ATV) of body segments from anthropometry, it is necessary that a data base contain at least one skinfold, one girth and one length for a given segment or region of the body. While skinfolds and girths are commonly measured, lengths are not always included in the protocol. Of the various data bases to be used in this study, only one, the Saskatchewan Growth Study (described in Appendix 2a), lacked length measurements. Standard somatotype photographs of each Saskatchewan subject were taken, however, allowing for the derivation of segment lengths from the negatives by a photogrammetric procedure developed by Crawford (1 990) for the Saskatchewan boys. Measurement Procedure Measurement of lengths from the 55mm negatives was achieved by mounting the negative transparency into a metal frame, which was then fitted onto an Omega Dichoric II photographic copy stand and magnified onto an even white surface to approximately 4.75X (0.1 2X life-size) with an f/4,0-80mm Rodenstock Rodagon lens. Each negative transparency (representing one measurement occasion) depicted a girl, with minimal clothing and without shoes and socks, in three different poses - anterior view, right lateral view and posterior view - accomplished by having the child stand on a swiveling pedestal which was maintained at standard distances from the floor, backdrop and camera throughout the duration of the study (Bailey, 1968). Subjects generally maintained a 'straight' posture with arms abducted 30-45" and hands held as straight as possible either in the anatomical position, with palms facing towards the camera (1 964-1967), or in the somatotype position, with palms facing towards the body (1968-1 973). In all cases, a 6x8 foot background grid, composed of three inch squares and positioned at a standard distance (1 8 inches) behind the subject, offered a suitable way to standardize the magnification of a negative on the Dichoric II enlarger. At the beginning of each photogrammetry session, magnification was set such that a central square of the background grid on the negative measured precisely 9.20 mm. This distance, plus the distance between anatomical landmarks of the subject, was measured with a 15 cm Mitutoyo Digimatic caliper to the nearest .Ol mm. Each time measurements commenced on another subject, the caliper was re-calibrated to zero. Data was key-punched directly into the Microsoft ExcelTM 3.0 spreadsheet on a Macintosh microcomputer.

Measurement Strategy The photographs were measured in ascending order by subject number and by year. (Across the entire data set, each subject was measured 5 years, on average, making this a mixed-longitudinal sample.) Triplicate measures of seven variables were taken in the following order for all girls (n=139):

Anterior Pose (sequence repeated 3X before switching negative to the lateral pose) 1. Upper Arm Length 2. Forearm Length 3. Hand Length 4. Calf Length *5. Sternale-Vertex Length (*see next page)

Right Lateral Pose (sequence repeated 3X) 6. Foot Length, '7. Lateral Maleolar Height (*see next page) Landmarks for these measurements are given in Table 2.1, portions of which are copied verbatim from Crawford (1 990).

Table 2.1. Landmarks used for photogrammetry of segmental lengths: Saskatchewan girls. Exposure Segment Photogrammetric Landmarks

Anterior upper arm - from the apex of the shoulder curvature to the mid-arm crease lower arm - mid-arm crease to base of the thenar eminence hand - base of the thenar eminence to tip of most extended digit calf - distal point of patellar fold, equivalent to the point of inflexion of the curve of the medial femoral epicondyle to the tip of the medial maleolus *head&neck - superior border of the sternal notch to the vertex Right Lateral foot - mid point of heel (calcaneous) curvature to tip of longest toe *maleolar ht - height from pedestal to the tip of the lateral maleolus

*[These variables were not measured by Crawford. They were added to the current protocol in anticipation of the need to estimate four adipose tissue volumes - upper arm, trunk, thigh and calf. A sternale-vertex estimate permits the derivation of trunk length from sitting height and a maleolar height correction is necessary to calculated thigh length when calf length and total leg length are the only other variables available. Since calf length is measured from medial landmarks (see Table 2.1), it would have been preferable to measure medial maleolar height on the negatives, especially since the majeoli are not in the same transverse plane. But, it was impossible to determine the point on the pedestal directly below the medial maleolus in the anterior pose, whereas the lateral maleolus was very easy to identify in the lateral pose. To maximize precision, it was decided that lateral maleolus would be measured. At the very least, it was hoped that these two additional measurements would offer assistance in the development of a "correction factor" for sternale-vertex and maleolar distances to be applied to various data bases which require such corrections.] Technical difficulties encountered during photogrammetry were often the same as those described in Crawford: namely, variations in posture, orientation of body segment or lighting making it difficult to identify landmarks. The sternum, the base of the thenar eminence, the tips of the maleoli, the calcaneous and the tips of the digits where generally quite easy to identify, while the landmarks on curvaceous or soft tissue areas such as the vertex, shoulder, elbow and knee were more problematic. A frequency chart of comments made on the Microsoft ExcelTM 3.0 spreadsheet as data were being entered data (Table 2.2) indicates that, as with Crawford, there were far more problems with hand measurement than anything else, with flexion of the metacarpophalangeal joints being the most common annoyance. In the case where hand flexion was limited to only the metacarpophalangeal joints, with all other joints (radiocarpal, carpometacarpal and interphalangeal) being unbent, hand length was determined by summing two distances: thenar eminence to tip of the most visible knuckle and tip of knuckle to tip of the most extended finger. Problems with the identification of the vertex were probably more frequent amongst the girls than would have been observed with the boys, since girls tend to have more variations in hair style. However, the upper-most point of the skull (referred to as the 'vertex' throughout this report, even though there is no guarantee that the girls held their heads in the Frankfort plane) was often surprisingly easy to see if hair was parted in the middle, as was (apparently) the style of choice for girls during this time period (1965-1973), regardless of hair length. Even when hair was not parted in the middle, the vertex could sometimes be inferred from the natural curvature of the head. Another common problem was the wearing of body suits or shirts which completely covered landmarks on the arm (and, occasionally, the sternum). For the most part, there were few problems with girls wearing shoes or socks, but it should be noted here that a new pedestal appeared in 1968 and occasionally this seemed to be the cause of the right foot rotating slightly outward toward the camera.

Table 2.2. Frequency chart of comments made during data entry.

General Problem Frequency Area

Arm elbow bent 3 elbow hyper extended 1 elbow crease difficult to see 1 clothing makes it difficult to see acromiale 21 clothing makes it difficult to see suprasternale 9 long-sleeve shirt makes it difficult to see radiale 4 long-sleeve shirt makes it difficult to see thenar 1 eminence

Hands hands curved, cupped, bent or flexed 47 hands pointing away from the camera 19 hands hyper extended 2

Foot foot turned out on pedestal (toward the camera on 3 right lateral exposure) shoes and socks on 1

Head hair style hides vertex 10

General film over-exposed picture is blurry Reliability Reliability of measures in the entire data set could be achieved, since triple measures were made throughout (n=4670 X3). Technical error of measurement (TEM) was used to judge reliability, as suggested by Dahlberg (1940) and Johnston (1979), where: TEM=(M~I~~).~ and, Zd is the sum of the difference between the measurements of any two sets. Therefore, three TEMs for each of the seven variables could be determined: TEMsl vs. s2, TEMsl vs. s3 and TEMs2 vs. s3, where sl=first measures, s2=second measures and s3=third measures. The meaning of this difference (TEM) between sets, however, depends upon the size of the variable being measured. Therefore, it is often useful to consider relative reliability by expressing TEM as a percentage of the mean of the first set in the pair (e.g. %TEM=TEM/meansl for the first comparison (TEMsl vs. s2).

According to Crawford (1 990), the overall relative error (the coefficient of variation or 'CV') for a variable is the mean of the three technical errors calculated as a percentage of the overall mean of the variable under consideration. Table 2.3 summarizes TEMs, %TEMs and CVs of the Saskatchewan girls' lengths measurements. One-way analysis of variance (ANOVA) tests carried out using the SystatTM 5.2 statistical program to determine if YoTEM varied significantly by trial or by variable indicated that, while there was no trial effect there was a significant variable effect. Tukey's post hoc test revealed that the significance was due entirely to the large %TEM of the lateral maleolus measurements. Since the tip of the maleolus seemed to be easy to identify, the high TEM of this measure is surprising and would suggest that the shadow cast by the foot onto the pedestal made it much more difficult than perceived to determine the point on that surface from which the measurement should be taken.

Table 2.3. The technical error of measurement (TEM), percent TEM (%TEM) and coefficient of variation (CV) for three repeated photogrammetric estimates of segmental lengths of the Saskatchewan girls.

Measurement upper lower stern- lat. sets arm arm hand calf vertex foot maleolus

.37 1.41 671

.36 1.36 671

.29 1.09 671 mean TEM (mm) .36 .34 cv 1.12 1.28 n (Total) 1992 2013

The intent of measuring lateral maleolus height was to improve the estimation of thigh length (thigh length = leg length - (calf + lat.maleolus)). Its low reliability, however, clearly limits its usefulness towards this end. For this thesis, then, thigh length of the Saskatchewan Girls will be derived in the same way as it was derived . for the Saskatchewan boys (thigh length = leg length - calf length), with the assumption that the inter-individual variation in lateral maleolar height is a negligible portion of the variation in total leg length. The general trend of upper limb measurements being less reliable than lower limb measurements agrees with previous reports (Crawford, 1990; Harrison and Marshall, 1970). The current measurements appear to be much more reliable than those of Crawford (1 990), but this can probably be attributed to the fact that in the current study, measurements were guided to a large extent by landmarks penciled- in at the commencement of each measurement round (i.e. each time a new transparency was inserted into the Dichoric II enlarger). All of the measurements except for lateral maleolus height hover around the 1% reliability tolerance established for anthropometric lengths by Borms, Hebbelinck, Carter, Ross and Lariviere (1979). That the suprasternale-vertex should do so suggests a heavy reliance upon the vertex landmark once that point had been established, since a greater %TEM would have been expected given the problem of hair styles.

Accuracy As noted by Crawford (1990), since the Saskatchewan somatotype photographs were not taken with photogrammetry in mind, variable conditions of lighting, posing and picture quality within the negatives themselves contribute to inaccuracies in the estimates of segmeni lengths. One measure of accuracy employed by Crawford (1 990), originally recommended by Tanner and Weiner (1949), was the standard error of measurement (smeas) which is purported to estimate how close to the first measure subsequent measures are likely to be and is given by the equation: smeas = s(1-r)5 where, r = (r1,2 + r1,3 + r2,3)/3 s = (s(set1) + s(set2) + s(set3))/3 Note: 'r' is the pearson correlation coefficient and 's' is the variance.

Following the precedent of Crawford, relative accuracy is, then, expressed as the coefficient of variation (CV), where, CV = 1OO(smeas/overalI-mean) The standard errors of measurement and CVs for segmental lengths of the Saskatchewan girls are given in Table 2.4.

Table 2.4. Standard error of measurement for photogrammetry of segmental lengths: Saskatchewan girls.

upper arm 664 1.233 3.696 forearm 671 .923 3.350 hand 661 .512 2.603 calf 672 1.31 5 3.309 stern-vert length 663 .719 1.934 foot 671 .544 1.81 5 lat. maleolus 670 .382 . 4.81 4

The CVs in Table 2.4 are remarkably consistent with Crawford's for the upper limb measurements, but are higher for the lower limb. Since r for adjacent set comparisons of both calf and foot never dropped below .992, these large Smeas values can only result from a large variance for these measures in the population at hand. That the girls had a higher variance in the lower limb than the boys indicates that the current investigator had more difficulty making consistent assessment of the lower limb than did Crawford. Once, again, lateral maleolus distinguished itself, this time being low in accuracy.

Conversion of Photogrammetric Lengths to Life-size Equivalents Once the data collection was complete, medians were selected from the triple measures and converted to life-size values using regression equations developed by Crawford (Table 2.5). Those variables not measured by Crawford (1 990) were transformed into life-size values by the regression corresponding to the variable of nearest proximity on the negative. In other words, the regression equation for Upper Arm Length was used to convert Sternale-Vertex Length to its life-size equivalent while the one for Foot Length was used to transform Lateral Maleolar Height.

Table 2.5. Regression equations for the prediction of life-size lengths (Y) from photogrammetric (phgrm) lengths (X) according to the model Y=mX+b. [Equations from Crawford, 19901

Arm Length .772 arm phgrm Forearm Length .644 forearm phgrrn Hand Length .723 hand phgrm Calf Length .679 calf phgrm Head&Neck Length .772 sternale-vertex phgrrn Foot Length -685 foot phgrm Maleolar Height .685 lateral maleolus height phgrm Conclusion Both the reliability and accuracy of Saskatchewan Girls' segment length measurement by photogrammetry are comparable to those of Crawford (1 990), with the accuracy being slightly lower for lower limb measurements. Since values for lateral maleolus height were highly unreliable and inaccurate, this variable must be rejected as a true measure of that length. Life-size equivalents of the remaining lengths were added to the Saskatchewan Girls data base for use in the calculation of regional adipose tissue volumes. Chapter 3. Growth of Adipose Tissue Volumes in Cross-sectional, Longitudinal and Secular Trend Studies.

To date, all studies into the relationship between adiposity ('fatness') and maturity in growing children have utilized either height and weight (Frisch and Revelle, 1970; Frisch and Revelle, 1971 ; Ellison, 1982; Johnston, Roche, Schell and Wettenhall, 1975; Billewicz et al., 1976), percent body fat (%BF) derived from height and weight (Frisch et al., 1973; Frisch and McArthur, 1974) or skinfold measurements (deRidder et al., 1992; Billewicz et al., 1976; Cameron, 1976; Katz et al., 1985) as the indicators of adiposity. Invariant mean weight for age at a specific maturity event, if observable, offers little information concerning anatomical mediation of the maturation process, as weight is comprised of various components (adipose tissue, muscle, bone, organs, etc.) differing in relative abundance from one person to the next (Martin, 1984) and from one age to the next in the same child (Forbes, 1986; Holliday, 1986). Frisch and colleagues (1 973, 1974) attempted to resolve this problem by estimating percent body fat (%BF) from height and weight using a regression equation developed by Mellits and Cheek (1970) to predict total body water (TBW) from which lean body mass (LBW) and body fat could be inferred. Criticism about the way this equation was used to draw connections between body composition and the control of puberty are well documented (Billewicz et al., 1976; Johnston et al., 1975; Scott and Johnston, 1982). In fact, any estimate of %BF in children is questionable, even if obtained by underwater densitometry. It has been shown that an error as small as 0.01 glml in fat free density, something that can easily happen given the large variability of fat free components in children, can result in a 7% difference in estimated %BF (Martin and Drinkwater, 1991). More importantly, it must be kept in mind that total body lipid, the inert chemical component which %BF estimates, is somewhat irrelevant to the issue of extraglandular aromatization, since the reactions take place within stromal cells of adipose tissue itself (Killinger et al., 1987; Cleland et al., 1985; Forney et al., 1981; Roncari, 1984). The only connection total body lipid has to hormonal metabolism is that, on average, 60% of it resides within the tissue of interest, although this value also varies largely from one individual to the next (Forbes, 1986; Martin, 1984; Martin, Daniel, Drinkwater and Clarys, 1993). A more valid expression of anatomical 'fatness' is a measure of the subcutaneous adipose tissue thickness by skinfold caliper, as some investigators have done to test and, subsequently, to refute Frisch's hypothesis (Cameron, 1976; Billewicz et al., 1976; deRidder et al., 1992). Yet, it is also possible that skinfold measurements alone also do not give a reliable account of changing adiposity during growth. Of particular concern is the sharp decline in the growth rate of subcutaneous adipose tissue thickness which coincides exactly with peak height velocity (Figure 1.3), and often leads to the statement that children, particularly boys, "lose fat" during the adolescent growth spurt (Tanner, 1990; Forbes, 1986; Cronk, Mukherjee and Roche, 1983; Johnston et

al., 1974; Malina and Johnston, 1967b). ' Forbes (1986) suggested that this phenomenon might be indicative of a common hormonal influence being responsible for growth of both height and adipose tissue. Alternatively, it might mean that fat is being metabolized to fuel growth (Johnston, 1982). A third possibility, alluded to by a few authors (Tanner, 1962; Johnston et 1 al., 1974; Frisancho, 1981), is that growth in body length and/or underlying P muscle tissue forces adipose tissue to be spread over a broader area, resulting Rik been no change or even an increase in adipose tissue volume. Such a phenomenon could have important implications in the interpretation of apparent links between 'body fatness' and physiological status, as, for example, in attempts to assess in growing children the etiology of diabetes and cardiovascular disease, the extent of malnutrition or the timing of sexual maturation. In keeping with purpose #1, stated in the thesis introduction, the purpose of this chapter is to estimate adipose tissue volume (AN) for various segments of the body in cross-sectional, longitudinal and secular trend data bases (each described generally in Appendix 2), to give a general description of how An/ grows and , finally, to compare AW growth with changes in skinfold values of corresponding segments in order to determine if there is a dissociation between these two adiposity variables during growth. This chapter begins with a description of how ATVs were calculated in each data base (Coquitlam, Ibadan, Saskatchewan and Kormend), including lists of which variables were used in the calculations. Next, is a description of how ANis observed to grow using a generalized mathematical model and a discussion of the extent to which ANgrowth appears to be distinct from that of non-adipose tissues. Finally, how ANg'rowth, both total and regional, relates to skinfold growth will be assessed. While most of the discussion will focus on group summaries, a small portion near the end of the chapter will deal with individual peculiarities in adipose tissue growth. Calculation of Segmental ATVs At the outset of this investigation, careful consideration was given to the type of geometrical model that would best represent a segment of the body. While the truncated cone used by Drinkwater's (1984) is more anatomically correct, particularly for limb segments, it was concluded that the types of variables contained in each data base limited this study to the cylinder. While this model tends to over-estimate limb volumes (personal observation, making a comparison between anthropometrically estimated ATV and ATV assessed by MRI), it probably does so systematically and, therefore, should not confound the relationships under investigation to an appreciable degree. At the same time, it should be kept in mind that this is only a first glimpse at the growth of ATV, whose resolution should improve with advances in measurement techniques. In general, the ANof each body segment was estimated by subtracting the volume of an inner cylinder (composed of muscle, bone and, in the case of the trunk, viscera) from total volume as shown in Figure 3.1 and as described in the mathematical progression below using arm anthropometry as an example: Adipose - Tissue - - Volume

--+- ---

Figure 3.1. lllustration of the strategy used to calculate An/. Non-adipose tissue volume (NAN) is subtracted from total volume to obtain a cylindrical volume of adipose tissue (ATV).

General Equation: AW = TV - NAN where, An/ = arm adipose tissue volume TV = total arm volume NAN= volume of arm muscle and bone (volume of the 'inner' cylinder)

Step 1. Calculation of N N= [(AG)~/~x]x AL where, AG = arm girth (at the level of triceps skinfold) AL = arm length n =3.14

Step 2. Calculation of NAW NAN= [(cAG)~/~x]x AL where, CAG = arm girth corrected for triceps skinfold according to the equation: CAG = AG - n(TSFI10) Step 3. Calculation of ATV AW=W-NAN What was necessary for this procedure were three basic anthropometric measurements from each region: a girth, a length and a skinfold. Since forearm skinfold is rarely taken, adipose tissue volume of this region was not estimated. Nor were the volumes of head, hands and feet included in this investigation, because the contribution of these regions to the total pool of adipose tissue is minimal and because it is difficult to measure such volumes. Therefore, it is an assumption of this thesis that monitoring the growth of ATVs of the upper arm, trunk, thigh and calf provides an adequate assessment of the changes in over- all adiposity that take place in growing children. The volumes that could be calculated, specifically, in each data base and the variables that were used for this purpose are tabulated in the following sections, with only a few outstanding features explained where necessary. Since the general form of the steps involved in An/ calculation are outlined above, merely the girth, length and skinfold variables that were used are listed for each segmental AN. The variables in the tables are abbreviated according to the strategy of Nomenclature for Standard Anthro~ometricAbbreviations detailed in Appendix 3. A summary of the sample sizes and age ranges corresponding to each data base is given in Table 3.1. Appendix 4 summarizes the average age and its standard deviation by age category for each of the data bases used in the current investigation. Similar summaries for height are given in Appendix 5, in case the issue of overall body size difference arises in the comparison of different groups. Age categories for all data bases except for the lbadan study are standardized, such that a six-year-old is any child of decimal age between 5.500 and 6.499 years. Table 3.1. Subject numbers by age (boyslgirls) for the four growth studies: Coquitlam (COGRO), Ibadan, Saskatchewan (SASK) and Kormend (K'68, K'78 and- K'88).

Age COGRO lbadan SASK K168

The Coauitlam Growth Studv (COGRO) A general description of the Coquitlam Growth Study is given in Appendix 2. The number of variables included in the COGRO data base were sufficient to allow ANcalculation of four body segments - arm, trunk, thigh and calf. The specific variables that went into the calculation are listed in Table 3.2. Summaries of total and segmental An/ by age for COGRO girls and boys are given in Appendix 6. It should be noted that in both lbadan and COGRO samples, ankle girth was taken into account in the calculation of corrected calf girth in a unique way. Since there is virtually no adipose tissue at the ankle and since it is also desirable to include this circumference in the estimation of the average circumference of the lower leg 'cylinder', corrected calf girth was calculated as follows: Corrected Calf Girth = [(G:CA-3.14(mF:CAIlO)) + G:AN]/2. It is really the average of calf girth corrected for calf skinfold and ankle girth.

Table 3.2. Variables used to calculate ATVs in the Coquitlam Growth Study (COGRO).

Girth Length Skinfold Arm AN rG:A(Pa-Pr)m L:Pa-Pr F2ri Calf ATV [G:CA+G:AN]/2 L:Rl mF:CA Thigh AN G:T L:H-sH-Ptl fF:T Trunk ATV [G:CHmst+G:W]/2 L:sH-(H-H:Pa) [F:ssc+F:isp+F:AB]/3

J he Ibadan Growth Studv A general description of the lbadan Growth Study is given in Appendix 2. As with COGRO, variables included in the lbadan Growth Study allowed for the calculation of ATV for all four segments - arm, trunk, thigh and calf. These are listed in Table 3.3.

Table 3.3. Variables used to calculate ATVs in the lbadan Growth Study.

Girth Length Skinfold Arm ATV G:A(a-r)m L:a-r FAri Calf ATV [G:CA+G:AN]/2 H:Rl mF:CA Trunk ATV [G:CHmst+G:W)]12 (sH:)x(1-.38*) [F:ssc+F:isp+F:AB]/3 Thigh ATV G:T L:H-sH-Ptl fF:T

'where, .38 is the proportion of sitting height occupied by head and neck, derived from COGRO children.

Trunk An/ in this sample includes a derived variable for length. Due to the absence of a measure for acromiale height, it was not possible to calculate the distance from the shoulder to the vertex which is necessary to determine trunk length. Since averages of [(H-Pa)/sH] for each COGRO age group in the same age range (6-12 years) showed little variation around the fraction of .38, suggesting that the vertex-shoulder distance is relatively constant, it was decided that this proportionality value could be imported from the COGRO sample for the derivation of trunk length in the lbadan sample. While this approach might be acceptable for general group observations of trunk An/ growth, it should not be used to assess individuals, as it has clearly been shown that there are proportionality differences between children of different ethnic origins (Blade, Amusa, Agbonjinmi and Ross, 1991; Malina, Hamill and Lemeshow, 1974; Eveleth and Tanner, 1990; Martorell, Mendoza, Castillo, Pawson and Budge, 1987; Martorell, Malina, Castillo, Mendoza and Pawson, 1988; Malina, Brown and Zavaleta, 1987). Summaries of regional and total ATV by age for lbadan children are given in Appendix 7.

The Saskatchewan Growth Studv (SASK) A general description of the Saskatchewan Growth and Development Study is given in Appendix 2. Since calf skinfold values were derived for the SASK data base by regression equations and since this measurement tends to have a high variability from one individual to the next, it was decided at the outset that calf ATV for SASK would not be included in the current investigation. Trunk length, however, for the SASK boys did include the derived fraction, .38, in the same manner explained above for the lbadan children, since the distance from sternum to vertex was not measured in the photogrammetry of the boys as it was in the SASK girls. What this means, then, is that trunk ANis not calculated in the same way for SASK boys and girls. This fact should be kept in mind whenever a comparison of these boys and girls is made. Variables included in the calculations of Arm, Trunk and Thigh are given in Table 3.4.

Table 3.4. Variables used to calculate ANs in the Saskatchewan Growth Study (SASK).

Girth Length Skinfold Arm ATV rG :A(a-r)m L:a-r F 2 ri Trunk AN(boys) exG:CHmst (sH)x(1-.38) [F:ssc+F:sic+F:AB]/3 Trunk AN(girls) exG:CHmst (sH)-(L:v-sst) [F:ssc+F:sic+F:AB]/3 Thigh AN [G:T+G:knee]/2 L:H-sH-(L:tm-sph) fF:T

A cursory check of maximum and minimum lengths for 7- to 16-year-old children (Table 3.5) indicates that the derivations within the SASK data base are about what should be expected, given the similarity of actual length measurements taken on COGRO children.

Table 3.5. Maxirnum/minimum comparisons of derived lengths common to COGRO and SASK data bases: boys and girls from 7- to 16-years of age.

MaxIMin SASK COGRO SASK COGRO boys boys girls girls Arm Max 37.6 40:1 34.4 36.1 Mi n 19.0 20.1 18.9 19.3 Trunk Max 61 :3 70.8 58.7 60.4 Min 36.6 35.1 31.7 36.1 Thigh Max 45.2 44.2 46.0 39.3 Mi n 23.0 20.6 23.9 19.3

Summaries of total and segmental ANby age for SASK girls and boys are given in Appendix 8. T9 A general description of the Kormend Growth Study is given in Appendix 2. Given that the only projected heights measured in the Kormend Growth Study were acromiale height, dactylion height and spinale height, An/ volume estimates in these samples were reduced to the following three segments: Upper Extremity AN, Trunk ANand Lower Extremity An/. Obviously, these limitations in the data make it invalid to directly compare Kormend ANvolumes with the ANs so far described in other data bases, although the nature of AN growth can still be compared qualitatively with that observed in the other studies. The variables that were used to calculate the volumes are listed in Table 3.6. In the Kormend Growth Study no skinfolds were measured at all in 1958 and no lower extremity skinfolds were measured in 1968. Therefore, upper extremity ANand trunk ATV calculations exist for 1968, 1978 and 1988, while lower extremity ANs only exist in the 1978 and 1988 data. This is also indicated in Table 3.6.

Table 3.6. Variables used to calculate ATVs in the Kormend Growth Study

Year Girth Length Skinfold

Upper Extremity '68, '78 & '88 G:A L:Pa-Pdac [F:bi+FAri]l2 AN Trunk AN '68, '78 & '88

Lower Extremity '78 & '88 AN Summaries of total and segmental ATV by age for Kormend girls and boys are given in Appendix 9 (1968), Appendix 10 (1978) and Appendix 11 (1988).

Description of the Growth of Adipose Tissue Volume Graphical exploration of ANgrowth using a number of data bases offers an overview of common features of An/ growth underlying the 'noise' commonly associated with measurement of adiposity. Each data base has a different age range (see Table 3.1). While COGRO data extend from age six to age twenty-one, the Kormend data offer a glimpse of growth from age three to age eighteen. Although the SASK data have a narrower range, the longitudinal design allows for an exploration of individual behavior patterns in ANgrowth over time and will be critical for insight into the relationship between ATV and maturity events. Both the narrow range and the low subject numbers in the lbadan study limit its usefulness, but these data provide a rough indication of racial similarities and/or differences in ATV growth. Group summary plots of total ATV for each data base are given in Figures 3.2 to 3.7, including the SASK data, which were treated cross-sectionally in the search for general characteristics of ATV growth. [Total ANrepresents the sum of regional AWs described in Tables 3.2 to 3.6 above.] Age (years)

Figure 3.2. Growth of ATV of COGRO children expressed on a single scale (+/- 1 se) to display gender differences (a) and with maximum and minimum values aligned using separate scales for girls and boys to illustrate the extent to which characteristics of ATV growth are common to both sexes (b). lbadan Children

Age (years)

Age (years)

Figure 3.3. Growth of ANof lbadan children expressed on a single scale (+/- 1 se) to display gender differences (a) and with maximum and minimum values aligned using separate scales for girls and boys to illustrate the extent to which characteristics of ATV growth are common to both sexes (b). SASK Children

Age (years)

7 8 9 10 11 12 '13 14 15 16 Age (years)

Figure 3.4. Growth of ANof SASK children expressed on a single scale (+I- 1 se) to display gender differences (a) and with maximum and minimum values aligned using separate scales for girls and boys to illustrate the extent to which characteristics of ATV growth are common to both sexes (b). Kormend '68 Children

- 3500 - 5 3000 -

5 2000 5 - I- 1500-

Age (years)

-- 2100.0 -F a- 1900.0 , u -- 1700.0 - "a 0 -- 1500.0 ah -- 1300.0 $ m .-1100.0 ; e -- 900.0 ! X (b) --700.0

IIIIIIIIIIII 500.0 r!!!...... r ~~~mc~~-rnu~o-~rnsmrnbm --r,-r-.--- Age (years)

Figure 3.5. Growth of ATV of Kormend '68 children expressed on a single scale (+I- 1 se) to display gender differences (a) and with maximum and minimum values aligned using separate scales for girls and boys to illustrate the extent to which characteristics of ATV growth are common to both sexes (b). Kormend '78 Children

Age (years)

morow,.m~o'NmProw~'w ,-,-r-,-.--77 Age (years)

Figure 3.6. Growth of ATV of Kormend '78 children expressed on a single scale (+/- 1 se) to display gender differences (a) and with maximum and minimum values aligned using separate scales for girls and boys to illustrate the extent to which characteristics of An/ growth are common to both sexes (b). Kormend '88 Children

SOOO - - E 4000 - 2 3 3000- :4-

I:::::::::::::::! mfPw~m0~--J~f"'~'-"'.-,------Age (years)

Figure 3.7. Growth of ATV of Kormend '88 children expressed on a single scale (+I- 1 se) to display gender differences (a) and with maximum and minimum values aligned using separate scales for girls and boys to illustrate the extent to which characteristics of ATV growth are common to both sexes (b). Initial inspection of all plots of total ANversus age shown above creates several immediate impressions about the manner in which adipose tissue appears to grow. While there is generally little difference in adiposity of boys and girls before age eight, girls acquire a much greater volume of adipose tissue thereafter. In COGRO (Figure 3.2), SASK (Figure 3.4), Kormend'68 (Figure 3.5) and Kormend '88 (Figure 3.7), the boys, but not the girls, demonstrated a surge in ANaround 11 to 12 years of age. Both the surge in boys and the higher adiposity in girls that coincides with the onset of puberty have been noted often in studies using skinfolds (Tanner, 1990; Malina and Bouchard, 1991; Evelith and Tanner, 1990; Forbes, 1986). In two cases, COGRO (Figure 3.2) and Kormend '78 (Figure 3.6), ATV appears to have taken off a year later in girls (at age 8) than in boys (at age 7). There are also some characteristics shared by both sexes. ATV growth appears to be sigmoidal in both cases, having a marked take-off in growth between the ages of 7 and 8 years and a semblance of a plateau from about 14 to 16 years of age in the data bases where measurements were taken at these age ranges (Figures 3.2, 3.4, 3.5, 3.6 and 3.7). Exceptions are the apparent ATV take-off at age five in the Kormend '88 boys (Figure 3.7) and additional increases in ATV after age 17 in COGRO children, which may simply reflect the fact that individuals from 17 to 21 years of age in the COGRO data base are a well-off sub-group of the local population that went on to attend university.

Mathematical Smoothing of ATV Growth The relatively common sigmoidal shape of the growth curves noted above prompted rudimentary mathematical smoothing of ATV growth in order to distill from these various data bases a generalized curve of adipose tissue growth that could be compared with growth curves of other body tissues, such as Scammon's well-known 'four curves of human growth' (Scammon, 1930). As the best over-all view of An/ growth is afforded by the age ranges included in the Kormend Growth Study, the curves of total ATV for 1968, 1978 and 1988 (boys and girls) were aligned at take off and ATVs at each age were averaged to get the most representative picture of how these volumes change with time. No alignment was necessary for the girls' An/ curves, but for the boys it was necessary to shift 1988 values forward by two years. Girls' ATV in 1988 appeared to be different enough (as will be discussed in the Chapter on Secular Trend) that it should have required an adjustment. However, the exact age at take-off was difficult to determine, so the Girls' values were simply averaged at each age as given in the An/ summaries in Appendix 9,10i and Ili. Two different mathematical models characterizing the sigmoidal shape were selected for application to the aligned Kormend averages:

Equation#l (an adaptation of an equation for a sigmoidal-shaped curve developed by Dr. T. Milner, Kinesiology, S.F.U.)

Y=[M+me-aX]/(b + ce-ax), where, M = maximum m = minimum a, b & c are constants

Equation#2 (from Preece and Baines, 1978)

where, Y =the value of the given variable at time, t MI = final (or adult) size of the given variable me = value of the variable at time 8 8 = a time constant so and sl are rate constants Equation #1 represents a true symmetrical sigmoid, with zero velocity before take-off and after the plateau, points of take-off and plateau being equidistant from the inflection point. Equation #2, the 'Preece-Baines' curve (Preece and Baines, 1978), is the modified sigmoid most commonly used to describe growth of stature. It allows for a small positive gain before take-off and plateaus relatively abruptly after inflection. These two shapes are illustrated in Figure 3.8.

::::::::::::::I "t",OL000.-Nn.1m~m -.---.----- Tina batrt)

100.0 - Sample Curve: -- Equation #2 .

80.0 .. B - 70.0 -- 0 . 60.0 -- 0

OI",OLO~DrNn.oODO C.-.--C.-.-.--

Figure 3.8. The basic shapes being described by the two mathematical models: Equation#l (a) and Equation#2 (b) When each equation was applied to the data, residual sum of squares was minimized by iteration on Microsoft Excel spreadsheet program such that the equation which best fit the total ANcurve could be identified. Parameters of each equation were allowed to vary while the end-point (maximum) value was held constant. This approach indicated that for both girls and boys, Equation#2 fit An/ growth slightly better than the true sigmoid (Equation#l). The results are given in Table 3.7.

Table 3.7. Summary of residual sum of squares when equations #1 and #2 were applied to boys and girls Kormend ANdata with the given maximum values fixed. Residual Sum of Squares Maximum (adult) value Girls Equation#l 5.43~105 4700ml Equation#2 4.41 XI05 4700ml Boys Equation#l 1.13~105 3600ml Equation#2 1.06~105 3600ml

Distance and velocity curves for ANgrowth given by the model of best fit, Equation #2, are shown in Figure 3.9. While Kormend girls demonstrate a more extreme peak in ANgrowth than boys, the age at which peak ANgrowth is attained is approximately the same in both sexes. Age (years)

Age (years)

Figure 3.9. Distance (a) and velocity (b) curves of ANgrowth smoothed by the Preece-Baines mathematical model (Preece and Baines, 1978) using data of Kormend children (1968, 1978 and I988 combined).

To express An/ growth in a form that is consistent with that of Scammon's 'four curves of human growth' (Scammon, 1930), percentage of total ANwas averaged for boys and girls. The result is given in Figure 3.1 0. Since the Preece-Baines model (Equation#2) tends to impose the shape of the 'general' curve of growth on any data series, the curve of ANgrowth given in the figure resembles that of somatic growth of the body as a whole.

Age (years)

Figure 3.1 0. The generalized curve of ANgrowth expressed as a percentage of its final value to facilitate comparison of adipose tissue growth with that of other tissues, particularly Tanner's 'four curves of human growth' (Tanner, 1990, p. 16), displayed similarly on a percentage scale.

Growth characteristics of ATV and NANwere then considered in tandem. Best fit predictions of the Preece;Baines curve on NANof combined Kormend data (1968, 1978 and 1988), show that, while there is almost a perfect alignment of An/ and NANcurves for girls (Figure 3.1 1a), for boys AW growth has a much different temporal dynamic relative to NATV growth. Peak ATV happens earlier and over a longer period of time than NATV in boys as shown in Figure 3.1 1b, which suggests that mechanisms controlling the growth of these two body components, ATV and NAN, might also be distinct. AGE (years)

AGE (years)

Figure 3.1 1. Growth velocities of ATV and NATV smoothed by Equation #2: Kormend girls (a) and boys(b) (1 968, 1978 and 1988 samples combined). The Relationship Between ATV and Skinfolds In the introduction it was explained that the drop in skinfold values which is often observed at peak height velocity may simply reflect a physical spreading of adipose tissue over a larger subcutaneous surface that accompanies growth in length and girth, rather than a utilization of fat for growth. To investigate this possibility, total ATV for girls and boys in each data base was plotted on the same chart as the three components from which it was derived (see Figures 3.1 2 to 3.1 7). On these charts, total An/ (AN), total length (L), total girth (G) and sum of skinfolds (SF) represent column totals of the variables described in Tables 3.2, 3.3, 3.4 and 3.6, respectively. To be consistent with the Kormend '68 data, ATV totals for Kormend '78 and Kormend '88 only included upper extremity and trunk ATVs, even though lower extremity ANwas available for those two years. As individual variables differ in dimension and size, their comparison using a single scale required a mathematical transformation common to all which would, at the same time, preserve the shape characteristics of each curve. This was accomplished by creating a 'standardized growth index' calculated as follows: 100x[(vaIue of the variable at any given time - initial value in the series)/final value in the series]. The set of graphs (Figure 3.12 to 3.17) indicates clearly that while fluctuations in skinfolds are largely responsible for fluctuations in ANin both sexes, there is a divergence in relative levels of the two adiposity variables in boys. Figures 3.12b, 3.14b, 3.16b, and 3.18b all show that this occurs during adolescence, although something similar also appears to have taken place at age three in Kormend '68 boys (Figure 3.15b) and at age 8.5 in lbadan boys (Figure 3.1 3b). While ATV continues to increase after the pre-adolescent surge, w~aaoT~~m~~~~o--.- v- CU CU Age (years) 70 - Total ATV:

Figure 3.12. Growth of total An/, total length (L), total girth (G) and sum of skinfolds (SF) in COGRO girls (a) and boys (b) expressed as a percentage of total growth according to the 'standardized growth index', which is determined in the following way; [((value of the variable - initial va1ue)lfinal value) x 1001. Total AN: lbadan Girls

I I I I I I 7.5 8.5 9.5 10.5 11.5 Age (years)

I Tota 5 lbadan Boys

9) -2

6.5 7.5 8.5 9.5 10.5 11.5 Age (years)

Figure 3.13. Growth of total AN, total length (L), total girth (G) and sum of skinfolds (SF) in lbadan girls (a) and boys (b) expressed as a percentage of total growth according to the 'standardized growth index', which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. Total ATV: SASK Glrls

Age (years) 801 -- 70- Total AN: $ SASK Boys 60- u, E 50- c 3 40- 8u 30- Q, ;20- 10- 0 5 0-

-10 1, I I I I I I I I I 1 7 8 9 10 11 12 13 14 15 16 Age (years)

Figure 3.1 4. Growth of total ATV, total length (L), total girth (G) and sum of skinfolds (SF) in SASK girls (a) and boys (b) expressed as a percentage of total growth according to the 'standardized growth index', which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. 'O01 Total ATV: -3 80jKormend168 Girls

11111111111111111 m~~wbal~~F'Nm*mwba rrrrrrrr Age (years)

- 80 Kormend'68 Boys -8 loo]

Figure 3.1 5. Growth of total An/, total length (L), total girth (G) and sum of skinfolds (SF) in Kormend168girls (a) and boys (b) expressed as a percentage of total growth according to the 'standardized growth index', which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. Total Am: Kormend'78 Girls X ua, C 60

- ATV - L

C=- G - -- SF

-20(11111,11111,1111 OtV)(ObQ)~O'ruO-?$$cO$ rrrr Age (years)

Figure 3.1 6. Growth of total An/, total length (L), total girth (G) and sum of skinfolds (SF) in Kormend'78 girls (a) and boys (b) expressed as a percentage of total growth according to the 'standardized growth index', which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. Total ATV: KormendW88Girls

Age (years) Total ATV: Kormend'88 Boys 60 f

Figure 3.1 7. Growth of total AN, total length (L), total girth (G) and sum of skinfolds (SF) in Kormend188girls (a) and boys (b) expressed as a percentage of total growth according to the 'standardized growth index', which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. skinfolds decrease absolutely as has so often been shown across all racial groups in the literature (Gasser, et al., 1993; Malina and Bouchard, 1991; Evelith and Tanner, 1990; Tanner, 1990). Since the divergence happens at a time when growth in body length is much more extreme in boys than it is in girls (Tanner, 1990), this observation strongly suggests that it is the physical growth dynamic rather than any direct metabolic or hormonal influence that causes the thinning of adipose tissue on the male during puberty. If a 'spreading' or 'stretching' phenomenon occurs in adipose tissue with a change in length and/or girth, a greater divergence between ATV and SF should be observed for body segments in which growth in length is more extreme; namely, in the limbs more so than in the trunk. Plots of regional AN growth show in dramatic fashion that this is, indeed, the case. The COGRO children are shown in Figure 3.1 8 and 3.1 9 for convenience. The rest of the regional graphs can be found in Appendices 12 through 16. [Skinfold summaries are also given in Appendices 17 to 22.1 In virtually every instance, girls as well as boys, the skinfold time course is much more representative of ATV growth on the trunk than it is on the limbs. Even though limb skinfolds continue to rise in girls during the adolescent years, a small divergence is detectable. In boys, however, the divergence is striking, presumably because growth continues and is generally more extreme than in girls. Standardized Growth lndex (%) Standardized Growth lndex (X) Standardized Gmwth index (%) Standardbed Growth lndex (%) A d oSggZ8 rkaSS8S8 70 1 ARM: COGRO

Boys

THIGH: .

TRUNK: COGRO Boys

1 -10 I 'W1b'W1~'z1=eN'91r12 lIS1g'e'~v1 N N Age (Y-1 Figure 3.1 9. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm (a), calf (b), thigh (c) and trunk (d): COGRO boys. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. Clearly, skinfolds do not always represent changes in ANvery well in growing children - particularly limb skinfolds. With respect to comments made by some concerning the drop in boys' skinfolds at puberty (Tanner, 1990; Forbes, 1986),it appears not that fat is being 'lost', but that it is probably being 'stretched'. Giving consideration to longitudinal changes in adiposity that might influence maturity events, the questions must be asked: Does the extreme divergence between ANand skinfolds always and only happen in boys?

Individual Considerations Longitudinal graphs of ANgrowth for individuals are as numerous as the number of SASK children. Therefore, graphs are shown of three girls and three boys, representing the range of divergence characteristics found in the data base. In Figures 3.20 and 3.21, plots (a), (b) and (c) correspond to individuals having high, medium and low associations, respectively, between total ATV and sum of skinfolds. SASK Girl

SASK Girl

Figure 3.20. Growth of total An/, total length (L), total girth (G) and sum of skinfolds (SF) for individual SASK Girls, representing different levels of association between ANand SF during growth: high (a), medium (b) and low (c). At each age, values are expressed as a percentage of total growth according to the 'standardized growth index', which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. A -ATV --- SF *- G C C- L t

Age (years)

SASK Boy #I30

-s 50- SASK Boy X #I48 uQ) r= 5 * *-.-.*' d 10 2 N E '-cc-- $ -10- ;\ r r, aa (a -30 11111Illll mbmaJ==~~~~~ Age (years) Figure 3.21. Growth of total AN, total length (L), total girth (G) and sum-of skinfolds (SF) for individual SASK Boys, representing different levels of association between ATV and SF during growth: high (a), medium (b) and low (c). At each age, values are expressed as a percentage of total growth according to the 'standardized growth index', which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. Apparently, a large divergence can happen in a girl, too (Figure 3.20(c). This supports the contention that the divergence reflects the degree of growth in other dimensions, since some individuals will experience more extreme growth than others, regardless of sex. By the same token, it is possible for a boy's skinfolds to have a very close relationship to ANgrowth (Figure 3.21 (a)). The fact that the divergence is more apparent in a group of boys than in a group of girls indicates that it happens more frequently in individual boys. Therefore, the best that can be said about a skinfold is that while it is likely to reflect a change in adiposity in a growing girl, it probably does not in a growing boy. In either case, one cannot be certain. Thus, ANrather than skinfolds will be used to study the relationship between adiposity and maturity in the remainder of this thesis. While An/ growth in individuals is not as smooth as might be suggested by the curves of group averages (compare figures 3.20 and 3.21, for example, with Figures 3.4 and 3.14), it should be a better indicator of adiposity, because included in its calculation are measures that represent changes in over-all body size which are likely to alter the amount of adipose tissue present. Indeed, given that measurement errors in length, girth and skinfold are independent and that technical errors of measurement for lengths and girths are typically less than one fifth that of skinfold measurements (Ross and Marfell-Jones, 1991; Lohman, Roche and Martorell, 1988), ATV will inevitably have a smaller technical error than a skinfold. To illustrate, the following formula from Topping (1962) yields technical error resulting from the product of three variables, whose errors are independent: Error of product ~1x2~3= [(el /x1)2+(e2/x2)2+(e3/x3)2]-5 where, xl =girth x2 = length x3 = skinfold el = technical error of girth measurement e2 = technical error of length measurement e3 = technical error of skinfold measurement While technical error of measurement (TEM) for most of these archival data is not known specifically, TEMs for girths, lengths and skinfolds are generally found to be in the range of I%, .5% and 5%, respectively (Ross and Marfell-Jones, 1991; Ross and Eiben, 1991; Lohman et al., 1988). Using average arm measurements of Coquit lam 13-yr-old boys to illustrate (girth =

24.1 cm; length = 29.6 cm; skinfold = 11.6 mm), TEM of arm ANis 4.3% based on the errors listed above. While skinfold error represents the major contribution of error to the An/ estimate, ANis more reliable. Information obtained by combining the three variables increases faster than the error propagated by each independent source. Thus, ATV appears to offer a better estimate of adiposity than a skinfold for two reasons: (a) it has a lower technical error and (b) it is dimensionally consistent with the tissue mass. The accuracy of the cylindrical model in growing children, however, requires further investigation. Chapter 4. SECTION A: DISCUSSION The purpose of this chapter is, firstly, to discuss issues arising from the empirical description of ANgrowth and, secondly, to explore implications of the divergence between changes in ATV and skinfold values observed in Chapter 3. Adipose Tissue Growth Skinfold curves in the current investigation were no different than previously reported. Across all racial groups, skinfolds have been observed to rise in girls throughout the growing years and peak in boys at age eleven or twelve, followed by a decrease during adolescence (Gasser, Ziegler, Kneip, Prader, Molinari and Largo, 1993; Malina and Bouchard, 1991; Tanner, 1990; Eveleth and Tanner, 1990; Johnston, 1982; Tanner, Hughes and Whitehouse, 1981 ; Cronk, Mukherjee and Roche, 1983; Zavaleta and Malina, 1980; Johnston, Hamill and Lemeshow, 1974; van Venrooij-IJsselmuiden, 1978; Malina and Johnston, 1967(a); 1967(b)). Thus, adipose tissue growth has generally been considered to be different in girls and boys. Perhaps this is one reason why discussion about adipose tissue growth in the literature often stops at description, with little further speculation about its function or control. That a general curve for ANgrowth, common to both sexes, could be elucidated from the current data at least provides a basis for speculation about a common ontogeny of the adipose tissue organ. Only in the past four decades has adipose tissue even been viewed as an organ with its own distinct array of metabolic characteristics (Cahill and Renold, 1983). Information about its growth at the cellular level is scant relative to what is known about other tissues of the human body. What currently appears to be known is that the pre- adolescent adipocyte size is attained by one year of age (Bonnet and Rocour- Brumioul, 1981; Knittle, Timmers, Ginsberg-Feller, Brown and Katz, 1979;

7 5 Hager, Sjostrom, Arvidsson, Bjortorp and Smith, 1977) and that the remainder of adipose tissue growth during childhood results primarily from hyperplasia (Poissonnet, LaVelle and Burdi, 1988). From puberty onward, increases in adiposity represent the combined effects of fat cell hypertrophy and hyperplasia (Bonnet, Rocour-Brumioul and Heuskin, 1979). Given that peak ATV velocity of boys and girls is temporally aligned (Figure 3.9),that ANtake-off happens around the same age in both sexes and that ATV growth is distinct from NANgrowth, at least in boys, it would seem that there could be a basic mechanism controlling adipose tissue growth common to both girls and boys which is distinct from biological mechanisms that control growth of other tissues in the NATV compartment, such as muscle. Other factors which influence adiposity (e.g. diet, hormonal status and exercise) might then be viewed as effects that are super-imposed upon this basic curve. Since over-all adiposity can only increase in one of two ways, by adipocyte hyperplasia or hypertrophy, it is logical to assume that if there is one characteristic of ATV that is controlled separately and has a strong genetic component, it would be one primarily involving hyperplasia, while environmental and physiological super-impositions upon the basic curve would be those which primarily promote changes in adipocyte size. If one considers the pre-adolescent ATV surge in boys, for example, it is easier to imagine that there is a filling and unfilling of adipocytes with lipid than it is to propose that adipocytes are gained and lost. -9-Sexual dimorphism in adiposity at puberty is thought to arise from an increase in both adipocyte size and number induced by estrogen and progesterone in girls (Vague, Meignen, Negrin, Thomas, Tramoni and Jubelin, 1984; Bonnet and Rocour-Brumioul, 1981). If this hormonal influence is extreme, it could create the impression that An/ growth matches the curve of other tissues influenced by gonadal maturation. Hence, An/ and NATV curves coincide in girls (Figure 3.1 1(a)) in spite of the fact that growth of the two tissue types is distinct in boys (Figure 3.1 1(b)). If gender-independent commonality observed in An/ growth, as depicted in Figure 3.1 0, represents a common change primarily in adipocyte cell number, a departure in adiposity from that basic sigmoidal curve for any given individual might have dual significance. Not only might it be indicative of a separate factor influencing fat cell size, but it might also be suggestive of a physiological function that is distinct from that controlling adipose tissue growth in general. Therefore, if one wishes to understand the physiological origin and significance of a change in adiposity, such as the pre-adolescent surge in ATV in boys, one might study the characteristics of the surge as departures from the basic AN curve and then look to the physiology for cellular, hormonal or neurological peculiarities that occur at the same time and have similar time-course parameters. The point is, a simple, empirical description of the growth pattern of a tissue, as has been done in Chapter 3, is important in that it could change the way in which that tissue is investigated and it certainly can alter the direction of thought concerning which physiological factors it is related to. Take, for example, Forbes' speculation that the coincidental nadir of triceps skinfold velocity and peak of height velocity points to, '...a single hormonal influence being responsible for both phenomena' (Forbes, 1986, p. 134). Having now seen that this appears to be a mechanical artifact, as ANcontinues to rise on a separate time-course from height even though triceps skinfolds decline around the time of the growth spurt (see Figure 3.1 9(a) and Appendices 12ii(a), 13ii(a), l4ii(a) and 15ii(a)), exactly the opposite explanation might be given: that growth of the two variables is mediated by two distinct hormonal influences. The timing of ANtake-off, at around 7 to 8 years of age, also begs physiological interpretation. That it appears to coincide precisely with the maturation of the adrenal cortex (i.e. adrenarche) is provocative. If the two . events are related, either directly or indirectly, and if it is true that ANgrowth consists almost entirely of adipocyte hyperplasia at this age, the question is: What neurological or hormonal signal prompts the adipose tissue control mechanism to stimulate adipocyte hyperplasia at adrenarche? Are the adrenal androgens, themselves, involved in this process or do the coincidental curves of ATV and DHEAS merely reflect a feedback mechanism (as suggested in Katz, et al., 1985) by which adrenal output of DHEAS is augmented as DHEA is continually being sequestered by ever greater numbers of adipocytes? [It would be interesting to know if any by-product of adrenal cortex metabolism has an effect on adipose tissue in situ. So far in my search of the literature I have found no reports of such an experiment.]

Adipose Tissue Volume versus Skinfold Thickness Evidence in the current investigation that a change in a segment length and/or girth can alter the relationship of a skinfold to its regional adiposity may have important methodological implications in the interpretation of apparent links between 'body fatness' and physiological status, as, for example, in attempts to assess in growing children the etiology of diabetes and -. cardiovascular disease, the extent of malnutrition or the timing of sexual maturation. For example, the fact that adults with a centralized distribution of fat (i.e. on the trunk) tend to have higher incidences of non-insulin dependent diabetes and cardiovascular diseases (Vague, 1956; Bjorntorp, 1988; Kannel, 1983) has prompted some to focus on the dynamics of fat distribution in growing children in attempts to elucidate the etiology of these diseases. Since

7 8 measures of visceral adiposity are not often available for children, skinfold ratios (e.g. extremity-to-trunk or trunk-to-total) are often considered to reflect the degree to which fat is localized within and around the trunk (Westrate, Deurenberg and Tinteren, 1989). Invariably, boys are found to develop a higher ratio of trunk-to-extremity skinfolds than girls (Frisancho and Flegel, 1982; Baumgartner, Siervogel, Chumlea and Roche, 1989; Mueller, 1982; Malina and Bouchard, 1991; Katz et al., 1986; Westrate et at., 1989; Eveleth and Tanner, 1990). In view of the fact that extremity skinfolds decrease partly due to a stretching phenomenon during linear growth at adolescence, the meaning of trunk-to-extremity ratios may have to be re-examined. The 'stretching' phenomenon might explain one puzzling result in a study on the etiology of hypertension by Katz, et al. (1 986). It was observed that, for the most part, high levels of both DHEAS and 'body fat' (expressed as the BMI) were accompanied by high blood pressure. Yet, a small sub-group of adolescent boys had a high level of DHEAS and high blood pressure, while having a low BMI (read 'low adiposity'). The boys were described by the authors as being, "tall for their maturational status and thin, but not advanced in skeletal age." (Katz, et al., 1986, p. 282). Physical immaturity ruled out the possibility that a high testosterone level caused the high blood pressure. In the absence of an explanation, the authors concluded that there might be a second, independent effect, other than through its association with adiposity (BMI), by which DHEAS might exert its influence on blood pressure. Given the current results, however, a second explanation might at least be considered - that these tall 'thin' boys had actually acquired a higher adiposity (An/) with their growth in length (height) that was masked by the weightlheight ratio as well as the appearance of thinness created by the spreading of adipose tissue over the increased surface area. , ( That the 'spreading' or 'stretching' effect is more extreme in boys might also explain why Baumgartner et al. (1 989) found change in 'fat pattern' (expressed as subscapular-to-limb skinfold ratio) at adolescence to be associated with changes in both fat free mass and lipoprotein cholesterols differently in boys and girls. A need for improvement in the definition and assessment of childhood obesity has been expressed (Westrate et al., 1989). It is proposed here that the ATV estimate might be an attractive alternative both because it is dimensionally consistent with the tissue of interest and because it can be expressed in quantities relative to NATV - probably a much more pertinent covariate than height or weight. In assessing nutritional status, it has been observed that protein supplementation can cause a decrease in skinfold thickness in undernourished children (Lampl, Johnston and Malcolm, 1978). If the decrease merely reflects catch-up growth in length rather than a true loss of ATV, subsequent nutritional screening could be erroneous. Assisted children might be deemed 'high risk' and targeted for further supplementation to the detriment (exclusion) of children whose skinfolds remained unchanged due to growth failure from inadequate protein intake. Therefore, it seems prudent that adiposity status be expressed as a volume. Proportionality differences in segment length, aside from the issue of-- -- linear growth, could also alter the meaning of a skinfold value. It has been shown, for example, that there are distinct proportional length differences between black and white children, with black children having proportionally longer limbs and a shorter trunk length (Blade et al., 1991 ; Malina et al., 1974; Eveleth and Tanner, 1990; Martorell, Mendoza, Castillo, Pawson and Budge, 1987; Martorell, Malina, Castillo, Mendoza and Pawson, 1988; Malina, Brown

8 0 and Zavaleta, 1987). Hence the same subscapular skinfold value in black and white children would probably correspond to a higher ATV in whites, while equal triceps skinfolds would correspond to a lower ANin whites, since the differences in length would cause these differences in volume. This possibility is currently under investigation. Interestingly, there are many reports in the literature that black children have a centripetal dysplasia of adiposity by virtue of the fact that their trunk skinfolds are higher than those of white children, while their limb skinfolds are lower (Zillikens and Conway, 1990; Harsha, Voors and Berenson, 1980; Johnston, Hamill and Lemeshow, 1972; Malina, 1971). Might the fact that segment length differences counter-balance this trend indicate a drive in Homo sapiens towards a standard adipocyte cellularity at each region? If the control mechanism speculated upon earlier were to dictate the development of adipocyte number of a standard size in each segmental region of the body, it would stand to reason that similar numbers, occupying a similar volume would be represented by smaller skinfold values in children with proportionally longer segments and vice-versa. This issue could certainly be clarified with additional histological information on adipose tissue cellularity in growing children of different ethnic groups. Finally, the dissociation of skinfolds from ATV growth around the time of the growth spurt could have an impact on the observed relationship between skinfolds and maturity status. For example, given the requirement that a variable should demonstrate a lowered variability at the time of a maturity event if it is to be considered critical to that event, Cameron (1976) concluded that there was no 'critical' adiposity necessary for menarche because skinfolds showed no drop in variability in the year when the event happened. But, menarche generally occurs shortly after peak height velocity (Tanner, 1990).

8 1 Depending on the individual length characteristics of each girl in the study, some skinfolds might have been low and others high merely due to the degree to which each person was experiencing linear growth, even if ATV in all girls had been confined to a smaller range. The relationship between An/ and a number of maturity indicators will be investigated further in the next section to determine the nature of the relationship between adiposity and maturity when ATV is employed as the measure of adiposity.

Summary and Conclusion In summary, the current investigation suggests that adipose tissue growth is sigmoidal in behavior, showing a marked increase at ages 7 to 8 years and a slowing of growth at 15 to 16 years of age. This behavior sets it apart from muscle growth and even from observed changes in skinfold thickness, which raises a number of questions not only about the physiological control of its development, but also about the meaning of apparent links between adiposity and physiological status based on studies using skinfolds. More information about the ontogeny of the adipose tissue organ is required. That two measures of adiposity can disagree to the extent that they do in these results highlights the need for improvement in instrumentation and measurement technique. While accuracy of ATV remains to be assessed, it is a more reliable measurement than a skinfold, it is dimensionally consistent with the tissue of interest and its calculation provides a useful covariate, NAN, that can be used to make corrections for body size during growth. It is recommended that skinfold caliper assessment of adiposity be replaced by a more accurate, non-invasive technique. In the interim, error in the assessment of adiposity in growing children can be minimized by the incorporation of length and girth measures into the assessment.

8 2 SECTION B. Investigation of the Relationship Between Adipose Tissue Volume and Maturity

While SECTION A of this thesis dealt with purpose #I, which involved the calculation of ANand the description of its growth, particularly in comparison to skinfold changes, SECTION B documents the testing of the hypothesis that AN is related to maturity status in SASK and Kormend children by examining how An/ is related to a variety of maturity indicators (purpose #2). To test sub- hypothesis 2a, that An/ is related to puberty onset, Chapter 5 focuses on the relationship between ATV (total and regional) and the age at which puberty begins (PA) in the Saskatchewan Growth and Development Study. PA in this thesis is defined as the age in which there is an increase in the widening of biiliocristal 'hip' breadth (BIIL) in girls and biacromial 'shoulder' breadth (BIAC) in boys in the circumpubertal years. The rationale behind this particular PA detection strategy is given in Chapter 5. Additional information on the An/ versus PA relationship is drawn from cross-decade inspection of these two variables using the Kormend secular trend data (Chapter 6). Both Chapter 6 (Kormend girls) and Chapter 7 (SASK girls) offer information on the relationship between ATV and menarche (sub-hypothesis 2b), while Chapter 7 additionally tests the hypothesis that An/ is significantly related to the time interval between PA and menarche (sub-hypothesis 2c). Finally, Chapter 8 addresses sub- hypothesis 2d, that ANis related to skeletal age (SA), amongst 11-year-old Saskatchewan boys (the only skeletal age data available in the data bases used for this thesis). An over-all assessment of evidence gained in these four chapters is then given in Chapter 9. Chapter 5. ATV and Age at Puberty Onset in Saskatchewan Girls and Boys.

It is the hypothesis of Katz et al. (1985), inspired by disputes in the literature about the nature of the relationship between adiposity and earlier maturation (Frisch et al., 1973; Frisch and McArthur, 1974; Ellison, 1981, 1982; Scott and Johnston, 1982; Garn, 1974; Beunen et. al., 1982; Mueller, 1983), that the degree of adipose tissue accumulation in the years following adrenarche, but preceding puberty, influences when gonadarche will occur. Conversion of adrenal androgens to active sex steroids within adipose tissue is thought to alter hypothalamic function which, in turn, stimulates the gonads to produce sex steroids earlier than when adipose tissue accumulation is less (Katz et al., 1985). A true test of this hypothesis would require longitudinal data not only on adiposity, but also on sex steroid changes with age. In the current investigation, longitudinal anthropometric records contain sufficient measures to assess adiposity by the estimation of AN. However, to determine age at gonadarche when hormonal data are lacking is problematic. Generally, age at take-off of the height spurt, assessed retrospectively, is used as a rough estimate of the age at which puberty began for a given child (e.g. Frisch and Revelle, 1970; 1971; Parra et al., 1981). Derivation of age at puberty onset from height growth in a study of ANversus the age of puberty onset is inappropriate, however, as ATV includes a length component that contributes to height. Biacromial breadth (BIAC) in boys and biiliocristal breadth (BIIL) in girls are considered in the current investigation to be better indicators of adiposity than height for two reasons. Firstly, a sudden increase in breadth (of the shoulders in boys and of the hips in girls) in late childhood is strongly suggestive of an increase in sex steroids originating from the gonads, as it is thought that : r ''...cartilage cells in the hip joint are specialized to respond to female sex hormone (oestrogen) and cartilage cells in the shoulder region are specialized to respond to male sex hormone (androgens, primarily testosterone)." (Tanner, 1990, p.68)

The shoulder-hip-width characteristic has long been considered a key measure of sexual dimorphism that occurs with the onset of gonadal function or 'puberty' (Olivier, 1969; Malina and Bouchard, 1991). In studies of the relationships between anthropometric characteristics and hormone levels in adults, breadths show consistently significant correlations with hormone levels to a greater extent than with other body measurements (Knussman and Sperwien, 1988; Winkler and Christiansen, 1991; Kirchengast, 1993). Furthermore, Crawford (1 990) found that, while biacromial breadth in the SASK boys did not account for much of the variance in body shape characteristics thought to represent skeletal maturity, it did emerge as a distinct principal component of shape in the circumpubertal years. Thus a late childhood increase in BlAC growth is probably at least as adequate as height as a rough indicator of the change in gonadal sex steroid output coincidental with the onset of puberty or 'gonadarche' in boys. The same will be assumed for BllL in girls. Secondly, shoulder and hip breadth are probably as independent of factors affecting adiposity and of the variables used to estimate ANas can be found amongst anthropometric measurements. Therefore, their use as maturity indicators of the age of puberty onset (PA) affords a statistical assessment of the PA versus ANrelationship that is minimally encumbered by complications involving autocorrelation of predictor and predicted variables. The purpose of this chapter is to test sub-hypothesis 2a, that An/ is related to PA, exclusive of NATV in both SASK girls and SASK boys. This can be accomplished by satisfying the following three objectives: Objective 1. to determine if there is a relationship between ATV (both total and regional, absolute and size-adjusted) and PA in Saskatchewan girls and boys, Obiective 3. to determine if this relationship is exclusive or different from the relationship of PA with other tissues, represented by NATV measures, and

Objective 3. to determine whether there is any evidence that a 'critical' level of ATV or NANtriggers PA. Testing of the ATV versus PA relationship accompanies the expectation that, on the whole, ANof the limbs will appear to have a stronger association with PA than trunk ATV. This expectation arises from the reports that aromatization of adrenal androgens, which is thought to influence hypothalamic disinhibition leading to puberty onset, is greater in limbs than in the trunk (Killinger et al., 1987; Nimrod and Ryan, 1975). It is important to note at the outset that any variable which would influence PA or have any connection to it should appear to have a non- significant ('flat line') relationship in the regression of that variable on the age at which this maturity event took place in each individual. The 'flat-line' relationship would suggest that regardless of the age when it happened, PA generally occurred at a given level of ATV, NATV or whatever variable is being investigated. Conversely, a significant linear relationship (negative or positive) will be interpreted as the variable not having an influence on, or a relationship with the maturity event, as a slope in the linear relationship would suggest that growth in the tissue is on-going irrespective of the specific physiological incident. In other words, a significant linear relationship suggests that PA can occur at different levels of the variable depending on the age of occurrence of the maturity event. Whether a 'critical' level of a variable is necessary to trigger PA will be determined in the manner proposed by Cameron (1976), namely, that a decrease in variability (given by the coefficient of variation (CV)) of the variable should be observed at PA or immediately before it if the variable is to be considered a trigger.

Methods A general description of the SASK growth study is given in Appendix 2. In order to assess the ATV versus PA relationship in the SASK children, measures of these two variables had to exist. While ATV estimates (total and regional) for each child were readily available from the calculations described in Chapter 3, the PA estimate required inspection of each individual, longitudinal record (N=124 (boys) and N=74 (girls)) for a change in the slope of BlAC or BllL with age. Whenever it was possible, PA was determined as the age at intersection of two least squares regression lines fitted to data points before and after the age range in which the slope change was clearly evident on the longitudinal scatter plot (e.g. Figure 5.1). Records in which intersection of the two lines fell outside the range of the entire data set (i.e. slopes not being substantially different) or no obvious change point in BlAC (boys) or BllL (girls) could be seen were excluded from this particular investigation. Twenty-eight boys and sixteen girls were eliminated for this reason. An additional ten girls were dropped from the study because the number of measurement occasions were simply too few to submit to such inspection. Thus, the actual number of girls and boys included in the study were 48 and 96, respectively. 8 7 PAz13.445 years

8.000 10.000 12.000 14.000 16.000 18.000 AGE (years)

Figure 5.1. Example of a typical change point in BlAC in a SASK boy (Subject #25).

Due to the mixed-longitudinal nature of the SASK girls' data, virtually all of the records, except for eight, had insufficient data points for two-phase regression analysis (i.e. less than three) beyond the age at which a clear increase in BllL width was observed. Thus, the age at which the change point was visibly obvious was considered to be the PA. Figure 5.2 is an example of using this approach to identify PA of SASK girl #607. 1 SASK girl #607 0

6 8 10 12 14 Age (years)

Figure 5.2. Example of a change point observation with respect to BllL during growth in a SASK girl (Subject #607) for whom only two data points exist beyond the observed shift in slope.

When PA was detected by two-phase regression to occur between two measurement occasions, a second problem had to be resolved: what was the value of the anthropometric variable at that moment in time? To deal with this problem it was decided that for PAS estimated to occur within 2.25 years of a measurement occasion, the value of anthropometric variables measured at that occasion would be the ones associated with PA for that particular individual. For PAS estimated to occur from .250 to .749 of a decimal year between anthropometric measurement occasions, the average of the values of each anthropometric variable measured before and after that point in time was given as the value of the variable at PA. In total, PAS with corresponding anthropometry were obtained for 96 SASK boys and 48 SASK girls. These were the records included in the regression analysis to be described below. A summary of descriptive statistics about these records is given in Table 5.1. Group comparisons by one-way ANOVA, with resulting p-values included in the last column in Table 5.1.

Table 5.1. Summary statistics (mean, SD and N) for PA and tissue volumes, ATV, %ANand NATV: SASK girls and boys, with p-values shown for girls versus boys group comparisons by one-way ANOVA.

GIRL (N=48) BOY (N=96) Girls vs. Boys MEAN MEAN p-values PA (years) 10.2 12.3 p<.001 ATVs (ml) Arm 299.1 297.8 p=.958 Trunk 1124.3 1276.7 p=.281 Thigh 1062.4 947.0 p=.109 Total 2485.8 2521.5 p=.874 %ATVs Arm 31.8 26.1 p<.oo1 Trunk 7.6 6.5 p=.079 Thigh 28.1 20.8 pc.001 Total 12.8 10.1 p<.o01 NATVs (ml) Arm 623.8 81 9.0 p<.001 Trunk 13178.2 17398.4 p<.001 Thigh 2647.7 3524.9 p<.o01 Total 16449.7 21 742.3 p<.o01

In keeping with objectives #1 and #2 stated in the introduction to this chapter, regression analysis of AN(both ,absolute and relative amounts) and NANon PA were carried out using the analysis tools on Microsoft ExcelTM 4.0 spreadsheet. Relative (or 'size-adjusted') adiposity was expressed as the percentage of An/ relative to over-all volume of the region under consideration (e.g. %ArmAN=lOOx(Arm ANItotal volume of the Arm). For all variables, examination of residual behavior of the intial regression runs, as suggested in Draper and Smith (1981), indicated that the homoscedasticity assumption was being violated. [Apparently, this represents the normal state of affairs in growth studies, for, as children age, the range of body size possibilities increases such that the variance in any population of children is larger at higher ages.] Logarithmic transformation of variables as suggested in both Kleinbaum, Kupper and Muller (1988) and Draper and Smith (1 981) was successful in stabilizing the variance. Hence, the regression results in this chapter will show measures of both ATV, %ANand NATV expressed in logarithmic form. With respect to objective #3 stated in the chapter introduction, coefficients of variation (CVs) were plotted versus time from PA in order to determine if there was evidence of a 'critical' ATV, %An/ or NANnecessary for the onset of puberty. Results and Discussion Results of the regression analysis for girls and boys are summarized in Table 5.2. Scatterplots are given in Figures 5.3 and 5.4 for Total AN, %Total ATV and Total NATV (girls and boys) to allow for observations of the strength of the linear relationships observed in the tables. Equivalent plots of the regional ATV and NATV analyses are provided in Appendices 23 to 25.

Table 5.2. Summary of probabilities resulting from regression analyses of PA versus An/, %An/ and NAN(total and regional): SASK girls and boys [p- values are: ns = not significant; * = p1.05; ** = ps.01; *** = p1.0011.

TOTAL ARM TRUNK THIGH Girls ATV ns ns ns ns %ATV ns ns ns ns NATV t ns t Boys AN ns ns ns ns %AN ns *(-) ns ns NATV *** *** ***

In all regions of the body, except for the arm in boys, there is an absence of a linear trend suggesting that mean ATV and %An/ at PA is unchanging in both girls and boys regardless of the age when PA takes place (non-significant least-squares regression). Consistent linear trends of NATV with increasing PA in both girls and boys across regions rules out NANas playing any particular role in the onset of puberty. In girls, the distinction between ANand NATV was greatest in the thigh. Based on the regression analysis, the possibility that puberty onset might be influenced in some way by both relative and absolute adiposity cannot be rejected. Given the large variance of the non-linear ANclusters, however, the exact nature of the relationship between adiposity and puberty also remains uncertain. It is clear from these results, however, that whatever influence adiposity might have on puberty onset, it does so in a manner that is exclusive of the NANcomponent. Further evidence that ANmight be associated with puberty onset in some way is given in the summary figures in Table 5.1. Even though PA happened a two years later in boys (at age 12.3 years) than in girls (at 10.2 years), mean ATV of each region appeared to be almost identical in girls and boys at the onset of puberty, while sex differences in NATV were significant (Pc.001). It would appear, then, that puberty commenced in both SASK girls and boys when a certain mean level of estimated adiposity was achieved regardless of NATV and that this is particularly true for ANof the thigh in girls. Thus, if puberty onset is mediated by a tissue, ATV appears to be a contender, at least to a greater extent than NATV. These results, however, pertain to the group. Large variance and low correlation coefficients clearly preclude extrapolation to the individual case. One strategy for judging the potential usefulness of ANas a predictor of PA in individual children is to assess the magnitude of the variance at PA relative to the total variance that exists throughout the growth period (i.e. from 8 to 16 years of age). Presumably, if the ANstandard deviation (SD) at PA is 9 2 small relative to the An/ SD in the total pool of growing children, ranging from the most immature to the most mature, the average An/ at PA might have practical meaning. If, on the other hand, the SD of ANat PA is not much smaller than the total (8 to 16 year old) SD, it would suggest that the spectrum of possible ATV values at PA is almost as large as that which exists in all pre- to post-pubescent children. In the latter instance, the mean ANat PA might be found with almost equal probability in individuals on both extremes of the maturity continuum and, thus, the measure would have negligible meaning with respect to maturity status. This strategy for the assessment of variability is accommodated by the figures given for SASK girls and boys in Tables 5.3 and 5.4, respectively. Along with mean, SD, and % coefficient of variation (CV), the fourth column in these tables represents the value of SD at PA as a percentage of the over-all SD (i.e. SD for the total pool of all 8- to 16-year-olds). In both SASK girls (Table 5.3) and SASK boys (Table 5.4), SD of ATV at PA exceeds 80% of the pooled SD. Clearly, then, for an individual child more information than ANalone would be necessary to predict maturity status or to assess when PA might commence. SASK Girls

Multiple R = .224 p = .I27

r r PA (years)

1.4

Multiple R = .I21 p =: All

1-65- 1.55 - i= lA5- 3 1.35- 0. ..: - Multiple R = .318 -S 1.25- . - .%- SEE .06!57 .. 8 - = 1.1 . . CI) ------.I-.r . . .. Fz5.16 5 1.05- p = .0278 0.95- y=.025x+.954

PA (years)

Figure 5.3. Scatterplots of PA versus transformed tissue volumes, Log Total ATV (a), Log %Total An/ (b) and Log Total NAN(c) in SASK girls with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. SASK Boys

=.

. I =. rrg C I =. = :#. = = = Multiple R = .I76 =-.a= .. :! =...... = = p = .0829 .= .= .Pr'. =I- =I = 8 =:- . =-

PA (years)

= - = = = % - *;-=- = = 5v=4. == Multiple R = .061 =.== -- -2: G ' - p = .551 = .-.r =& -= - .= = -'

OS- (b) 0.5 I I I 1 1 I i 8 9 10 11 12 13 14 15 PA (years)

z 1.45- 2 1.35- - 1.25- Multiple R = .577 SEE = .0581 m 1.15- F = 47.88 3 1.05- p = 5.07E-10 :,I :,I (,) , ,.035x+.905

0.75 8 9 10 11 12 13 14 15 PA (years)

Figure 5.4. Scatterplots of PA versus transformed tissue volumes, Log Total AN(a), Log %Total AN(b) and Log Total NAN(c) in SASK boys with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. Table 5.3. Assessment of the variability in ANand NATV at PA with respect to the variability over the entire growth period in SASK girls (ages 8 to 16 years).

MEAN SD: PAJALL (%) ATV (ml) Arm(8-16) Arm(@PA) Thigh(8-16) Thigh(@PA) Trunk(8-16) Trunk(@PA) Total(8-16) Total(@PA) Grand Mean(8-16) Grand Mean(@PA)

NATV (ml) Arm(8-16) Arm(@PA) Thigh(8-16) Thigh(@PA) Trunk(8-16) Trunk(@PA) Total(8-16) Total(@PA) Grand Mean(8-16) Grand Mean(@PA) Table 5.4. Assessment of the variability in ATV and NANat PA with respect to the variability over the entire growth period in SASK boys (ages 8 to 16 years).

MEAN (CM) SD: PAI8-16 (%I ATV (ml) Arm(8-16) Arm(@PA) 85.5 Thigh(8-16) Thigh(@PA) 89.0 Trunk(8-16) Trunk(@PA) 88.9 Total(8-16) Total(@PA) 89.2 Grand Mean(8-16) Grand Mean(@PA) 88.17

NATV (ml) Arm(8-16) 895.69 Arm(@PA) 81 9.01 47.3 Thigh(8-16) 3656.70 Thigh(@PA) 3524.90 48.9 Trunk(8-1 6) 18754.30 Trunk(@PA) 17398.41 42.7 Total(8-16) 23304.43 Total(@PA) 21 742.31 43.1 Grand Mean(8-16) 1 1652.78 Grand Mean(@PA) 1 0 871 .16 45.52 In view of the above and with respect to objective #3, it must be said that even though PA may occur at an unchanging mean of ATV and %ATV, it is clearly untenable to suggest that PA, as defined, happens at a 'critical' level of adiposity. The fact that there is no identifiable drop in CV for most of the volume measurements (ANor NATV) in girls or boys in the year that PA occurred, as shown in Figures 5.5 and 5.6, supports this conclusion. It is interesting to note, however, that there is a drop in CVs of thigh ATV and %thigh ATV in both girls and boys, with the drop occurring in the year of PA in girls and in the year preceding PA in the boys. A discrepancy between ATV and NATV versus PA that is greater in the thigh than in other regions is consistent with the hypothesis that ANinfluences onset of puberty by its aromatization capacity, as conversion of adrenal androgens was observed to be 6- to 30-fold higher in fat stores of the upper thigh, flank and buttocks compared to those of the abdomen (Killinger et al., 1987). It is also known that this metabolic activity is limited to stromal cells within adipose tissue (Roncari, 1984; Killinger et al., 1987). But An/ includes the combined bulk of both non-aromatizing and active adipocytes. Thus, while expressing adiposity as a volume of adipose tissue is dimensionally preferable to a simple skinfold assessment, it is possible that ATV assessment continues to obscure the specific relationship between the aggregate of active adipocytes and PA. ATV might be influenced as much by changing bulk of the non- aromatizing, lipid-ladened cellular mass (or volume) as by alterations in the active adipose tissue component. If this scenario reflects the true nature of adipose tissue metabolism, current anthropometric strategies will be + Thigh & Trunk

1 Time from PA (years)

50 Time from PA (years)

0 tij 35

5 -

0 (c) I I I 3 -3 -2 -1 0 1 I2 3 Time from PA (years) N = 52 46 49 48 47 36 23 Fiaure 5.5. Coefficients of variation of total and regional tiss~ volumes, A~V(a), %ATV (b) and NAN(c) versus time from PA (k 3 years): SASK girls. [N is given at each year from PA, as the mixed-longitudinal design of the study resulted in changing subject numbers across the study period.]

99 4- Thigh + Trunk

60 1 Time from PA (years)

1 Time from PA (years)

5- 0 (a I I I 1 I I i -3 -2 -1 0 1 2 3 Time from PA (years)

Figure 5.6. Coefficients of variation of total and regional tissue volumes, AN (a), %ATV (b) and NAN(c) versus time from PA (+ 3 years): SASK boys (N=98). inadequate in elucidating predictive relationships between pertinent adipose tissue deposits and gonadarche. Clearly, the large variance of ATV at PA in the current investigation is attributable, in part, to crudeness in the estimation of both An/ and PA. While measurement error of ATV is smaller than that for a skinfold (as discussed in Chapter 3), the ATV also lacks validity. To what extent a cylindrical ATV estimate approximates the true volume of adipose tissue in any given region has yet to be determined. There are at least two sources of error in the estimation of PA. The first involves measurement error of biacromial and biiliocristal breadth which is relatively small (about 1%) (Ross and Marfell-Jones, 1991). Of much greater importance is the fact that estimated PA will always be later than the true PA. Theoretically, PA is the exact age when sex steroid levels begin to rise. A time lag necessary for bone breadths to respond to the hormones results in the detected PA being later than the true PA. Moreover, the age at intercept in the two-phase regression strategy will always be slightly higher than the age when the tissue begins to respond, as the first regression line is drawn through the point of initial increase. Given that the PA detection strategy differed depending on the number of points in the data series, error in the detection of PA cannot be considered systematic. Since the same PA for each coordinate is used in the regression analyses of both ATV and NATV, however, distinction in the behavior of the two tissue types could be identified in spite of the error associated with PA detection. Thus, although error in both ATV calculation and PA detection makes it difficult to determine the exact nature of the relationship between ANand puberty onset, it is clear that An/ behaves in a manner that is distinct from NAW. Scant evidence, based on the curves in Figures 5.5 and 5.6, that a certain ATV triggers PA, does not rule out the possibility that ATV plays a permissive role such that the human body may require a certain baseline level of adiposity before puberty can commence. If one considers the plot of %Total ATV for SASK girls and boys (Figure 5.7), for example, there does appear to be a baseline level at about (5%) of total AN. Variables contained not only in this data base, but in most anthropometric studies on growing children, are insufficient to allow for an adequate test of such a threshold effect. Longitudinal studies are necessary, requiring both accurate assessment of An/ and careful monitoring of gonadal function by hormone assays. In summary, these results offer circumstantial evidence in favor of propositions by both Frisch (1984) and Katz et al. (1985) that there is a physiological connection between adiposity and puberty onset. Given non- linear clustering of ANand %ANat PA and nearly identical mean volumes of An/ at PA in both girls and boys, the possibility that adiposity (both absolute and relative) is associated with puberty onset cannot be rejected. However, large variance of adiposity at PA, due in part to crudeness in the estimation of both An/ and PA, also does not permit resolution of the true nature of a relationship between ANand PA. Clearly, NATV does not influence puberty onset. A larger discrepancy between ATV and NANversus PA in the thigh and a drop in CV of thigh ATV around the time of PA, identifies thigh ATV specifically as having a potential role in the onset of puberty. The relationship between PA and thigh ANshould be inspected more carefully with a better marker of gonadarche. While there is no way to test (and, therefore, to rule in or out) that a certain baseline or 'threshold' level of adiposity acts in a permissive way to allow gonadarche (expressed as 'PA') to occur, it is clear from this analysis that An/, to the extent that it can 102 currently be measured, does not have a triggering effect with respect to the onset of puberty even though it is associated with it.

PA (years)

0 I 1 I I 1 6 6 lb 11 12 13 14 15 PA (years)

Figure 5.7. Total ANas a percentage of combined volume of all segments (%Total AN) by age at puberty onset (PA): Sask girls (a) and boys (b). Chapter 6. Adiposity and Age at Puberty: a Secular Trend Analysis

Frequent observation that a secular trend towards earlier maturation accompanies a trend of increases in adiposity has been cited often to support the proposition that adipose tissue somehow influences the rate of maturation in growing children (Frisch, 1984; Katz et al., 1985; Malina, 1979). Interestingly, with respect to the Kormend Secular Trend Study, Dr. Eiben reports that menarche happened progressively later in Hungarian girls from 1968 to 1988, in spite of the fact that these children became progressively more endomorphic over the same time frame (Eiben, 1988). Compilation of total ATV curves given in Chapter 3, shown here in Figure 6.1, appears to indicate that there was, indeed, a secular increase in total adiposity, although the extent to which decade differences in ANwere statistically significant will be explained below. Means and standard deviations for menarche were: 12.75~0.04(Kormend, 1968); 12.80&0.04 (Kormend, 1978) and 12.93~0.20(Kormend, 1988). Assuming that changes in biacromial (BIAC) breadth in boys and biiliocristal (BIIL) breadth in girls are somewhat reflective of changes in sex hormone levels, as explained in Chapter 5, such that take-off growth in these two measures might roughly represent age at gonadarche, it is of interest to know whether there was a secular trend in this maturity estimate and to what extent this trend matched the changes in adiposity from one decade to the next. A distinction must be drawn, however, between changes in adiposity that result from over-all increases in body frame size, something that realistically might have occurred in the Kormend children based on the observed secular increase in standing height (Eiben, 1988), and changes in adiposity relative to body size. Figure 6.1. Growth of Total ATV: Kormend girls (a) and boys (b), 1968, 1978, 1988.

If adipose tissue does play a role in maturity events by virtue of its aromatization capacity, its amount relative to other body constituents involved in the over-all metabolic process would probably have as much or more to do with its impact on maturity than its absolute amount. Thus, any attempt to relate 'fatness' to maturity must explore the effects of adiposity corrected for body size. Finally, if one is to assert that it is adipose tissue that influences maturity, one must also demonstrate that it does so to a greater extent than do other tissues. In view of the above considerations, sub-hypotheses 2a and 2b (Chapter I), that ATV is related to puberty onset in both boys and girls and to menarche in girls, can be tested deductively with these secular trend data. Accordingly, the purpose of this chapter is threefold: 1. to determine if there is a secular trend in the age of onset of puberty, 2. to determine if the secular trends in both relative and absolute ATV match the secular trend in puberty onset, exclusive of the trend in NATV, and 3. to determine if the secular trend in ANmatches that that given for menarche by Eiben (1988).

Methods Description of the Kormend Growth Studv The Kormend Growth Study represents a series of cross-sectional growth studies on all 3- to 18-year-old children in the small town of Kormend, Hungary carried out by Dr. Otto Eiben at ten-year intervals over a forty year period: in 1958 (N=l656), 1968 (N=l736), 1978 (N=2420) and 1988 (N=2867). Detailed anthropometric measurements were taken using the techniques specified in the International Biological Program handbook (Weiner and Lourie, 1969). Since skinfolds were not measured in 1958, investigation of adiposity is limited in the current study to three decade groups: 1968, 1978 and 1988. Upper extremity, trunk and lower extremity ANs were calculated as described in Chapter 3. In 1968, no skinfolds were measured on the lower extremity. Therefore, 'total AN' is the sum of trunk and upper extremity ATVs for all three decade groups, although lower extremity ANin 1978 and 1988 will also be examined. BlAC and BllL breadth were measured in each of the three decade groups. Identification of chanae ~ointsin BlAC and BllL breadth Both the cross-sectional nature of the study and the sheer number of subjects at each decade dictated against the two-phase regression approach to the identification of age at change-point in BlAC breadth (boys) and BllL breadth (girls) as was described in Chapter 4. Rather, 112-year means were smoothed by the Preece-Baines mathematical function (Preece and Baines, 1978), using an iteration procedure on Microsoft ExcelTM 4.0 spreadsheet to minimize residual sum of squares, in order to distill from the scattered plots the basic growth time-course characteristics of BlAC and BllL breadths for each decade. Since decade differences are difficult to see on distance curves, breadth growth velocities will be shown in the results over the age ranges which allow for the observation of breadth take-off and peak velocity. Analvsis of Relative Adi~osity Corrections for body size are often accomplished by ratios - ANlweight would be one example. Given the problems associated with variance and allometric differences between numerator and denominator variables, as explained by Packard and Boardman (1987), cross-decade comparisons of relative adiposity (total and regional) were accomplished by analysis of covariance (ANCOVA), using NANcorresponding to each ATV measure as the control variable (or 'covariate'). SystatTM 5.2 statistical software was used for this procedure. Decade effects were analyzed for each age category, from ages 3 to 18. When significant decade effects were found, post hoc, pairwise comparisons of adjusted An/ least squares means were carried out using Scheffe's statistic, as recommended for analyses in which sample sizes differ (Kleinbaum, Kupper and Muller, 1987). Comparison of ANand NANeffects To determine to what extent secular changes in adiposity were distinct from changes in other tissues, cross-decade comparisons of AWand NATV by analysis of variance (ANOVA) using SystatTM 5.2 were conducted in parallel without controlling for body size, since, presumably, body size characteristics for any given individual should affect both AWand NATV of the same region to the same extent. Decade to decade changes in least squares means of An/ and NANfor each age category indicated whether one tissue type was changing to a greater extent than the other. Since NATV means and standard errors (SEs) are generally much larger than the corresponding AWparameters of a given region, graphical comparison of changes in the two variables from one decade to the next required a transformation such that both could be viewed on a single scale. This was accomplished by taking the average SE for a given variable across the three decades and expressing individual decade summaries (mean and SE) in SE units given by that average. For convenience in viewing the results, all values were then adjusted such' that the 1968 means fall on zero. Results Velocity charts in Figure 6.2 indicate that there was a secular trend in the widening of the BllL breadth (hips) in the girls (Figure 6.2a) and of the BlAC breadth (shoulders) in boys (Figure 6.2b), with the event happening earlier in each successive decade as indicated by a leftward shift in the velocity curves. With respect to the girls, it appears that the onset of the velocity increase in BllL (BIIL) breadth did not differ much between 1978 and 1988 samples. For the boys, the distinction is clearer between decade groups in the onset of growth velocity of BlAC (BIAC) breadth, but the temporal shift happens over a smaller range of time than it did for the girls. In the absence of a statistical procedure to establish significance of these observed shifts, it is only safe to proclaim with some degree of certainty that, in both Kormend girls and boys, the age of puberty onset was earlier in 1988 than it was in 1968. The best that can be said regarding 1978 curves is that for the girls, the age of onset of BllL widening appears to resemble that of 1988 girls, whereas for the boys, age of onset of BlAC widening seems to happen more closely to that of 1968 boys. 1.4- A L 3 g 1.2- V *I = 1- -8 3 0.8- 1 8 0.6- h 3r 0.4- -V) -% 0.2- 5 (a) Girls 0 I1I

Age (years)

2 0.2 rn' 4 (b) Boys

Figure 6.2. Velocity curves for 1968, 1978 and 1988 of biiliocristal breadth (a) and biacromial breadth (b) of Kormend girls and boys, respectively, smoothed by the Preece-Baines procedure.

Results of the ANCOVA analysis, summarized in Tables 6.1 and 6.2, indicate unequivocally that there was a statistically significant secular trend of increased adiposity relative to body size. Except for 3-year-old girls, p-values for total ANwere all less than or equal to .001. Significant differences in both upper extremity and trunk adiposity accounted for the significance in total An/. Interestingly, cross-decade effects were significant much less frequently for lower extremity AN, which suggests that secular increases in adiposity might involve preferential deposition of adipose tissue in the upper body.

Table 6.1. Summary of p-values from cross-decade comparisons of total and regional ANcontrolling for the effects of corresponding NANs by Analysis of Covariance (ANCOVA): Kormend Girls. [p-values are: ns = not significant; = ps.05; ** = ps.01; *** - ps.O01]

Upper Lower AGE Total ATV Extremity Trunk ATV Extremity ATV ATV (78-88 only) *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***' *** *** *** *** *** *** *** Table 6.2. Summary of p-values from cross-decade comparisons of total and regional ATV controlling for the effects of corresponding NATVs by Analysis of Covariance (ANCOVA): Kormend Boys. [p-values are: ns = not significant; = ~1.05;** = ~1.01;"* = p~.OO1]

Upper Lower AGE Total ATV Extremity Trunk ATV Extremity ATV ATV (78-88 only) 3 *** *** *** ns 4 *** *** *** ns 5 *** *** *** ns 6 *** *** *** ns 7 *** *** *** ns 8 *** *** ** ns 9 *** *** *** ns 10 *** *** *** ns 11 *** *** *** ns 12 *** *** *** 13 *** *** *** ns 14 *** *** *** ns 15 *** *** *** ns 16 *** *** *** * 17 *** *** *** ns 18 *** *** *** ns

Scheffe's pairwise comparison probabilities shown in Tables 6.3, 6.4 and 6.5 indicate that for prepubertal ages, overall cross-decade ANCOVA significance for total and trunk AN(both girls and boys) can be attributed largely to the change in adiposity that took place from 1978 to 1988. It stands to reason that this increase over the last decade results in highly significant differences in adiposity being observed between 1968 and 1988 groups. Highly significant increases in upper extremity ANare observed to have happened both from 1968 to 1978 and from 1978 to 1988. Table 6.3. Scheffe's pairwise comparison probabilities corresponding to ANCOVAs in Tables 6.1 and 6.2: total ATV. [p-values are: ns = not significant; = ~1.05;** = ~1.01;*** = p1.001]

GIRLS BOYS AGE '68:'78 '68:'78 3 * ns 4 ns ns 5 ns * * 6 ns 7 * ns 8 ns ns 9 * ns 10 ns ** 11 ** 12 *** * 13 *** 14 *** * * 15 * *** 16 * ** 17 *** ** 18 ns Table 6.4. Scheffe's painnrise comparison probabilities corresponding to ANCOVAs in Tables 6.1 and 6.2: upper extremity An/. [p-values are: ns = not significant; * = p1.05; ** = ps.01; *** = p1.0011

GIRLS BOYS AGE '68:'78 '68:'78 3 * * ns 4 * * * 5 *** ** 6 *** *** 7 *** * 8 * * * 9 *** *** 10 *** *** 11 * *** 12 *** *** 13 *** *** 14 *** *** 15 * * *** 16 *** *** 17 *** *** 18 ns * Table 6.5. Scheffe's pairwise comparison probabilities corresponding to ANCOVAs in Tables 6.1 and 6.2: trunk An/. [p-values are: ns = not significant; = ps.05; ** = ps.01; *** = ps.0011

GIRLS BOYS AGE '68:'78 '68:'78 3 ns ns 4 ns ns 5 ns 6 ns ns 7 ns ns 8 ns ns 9 ns ns 10 ns 11

Pairwise differences in adjusted least square means for total AN, upper extremity An/ and trunk An/ (girls and boys) are given in Tables 6.6, 6.7 and 6.8. Positive values indicate that the mean of the later decade was larger than that of the earlier decade. T-tests of the 68:78 and 78:88 columns (summarized in Table 6.9) indicate that for no region was the increase in relative adiposity from 1968 to 1978 greater than it was from 1978 to 1988. [For the t-test, negative mean differences between the columns indicate that the 68:78 change was smaller than the 78:88 increase.] The greater increase in total ANover the last decade interval of 1978 to 1988 is attributable to a greater second interval increase in trunk An/ in the girls and in upper extremity ANin the boys. Table 6.6. Pairwise differences of adjusted total ANmeans given by the ANCOVA procedure.

Girls Boys AGE '68:'78 '78:'88 '68:'78 '78:'88 3 171.6 54.9 17.0 362.3 4 40.7 372.7 89.6 309.0 5 163.8 284.7 166.0 246.6 6 293.7 271.4 123.0 310.6 7 309.0 518.2 65.6 545.7 8 53.3 687.7 186.0 452.8 9 352.4 621.1 347.7 583.5 10 341.6 920.8 558.0 435.0 11 569.9 986.5 607.7 731.2 12 1125.0 920.8 644.2 1159.0 13 1029.8 1233.0 71 8.7 507.3 14 1037.5 1330.3 667.2 833.2 15 736.7 1796.7 655.6 1544.8 16 964.8 1454.6 754.3 1435.9 17 1508.0 836.3 685.0 1086.9 18 228.0 1434.4 960.5 1420.6

Table 6.7. Pairwise differences of adjusted upper extremity ANmeans given by the ANCOVA procedure.

Girls Boys AGE '68:'78 '78:'88 '68:'78 '78:'88 Table 6.8. Paiwise differences of adjusted trunk ATV means given by the ANCOVA procedure.

Girls Boys AGE '68:'78 '68:*78 3 94.6 -34.6 4 -1 .o 43.7 5 73.7 98.1 6 148.1 86.0 7 204.3 22.8 8 21.2 130.2 9 253.1 224.4 10 208.6 421.1 11 438.3 442.5 12 876.9 41 4.6 13 732.1 535.3 14 731.5 51 9.2 15 433.2 502.5 16 577.0 626.2 17 1036.4 495.8 18 29.7 823.0

Table 6.9. Summary of t-tests of column differences in Tables 6, 7 and 8. [p- values are: ns = not significant; * = p5.05; ** = ps.01; *** = ps.0011

T-test Total Upper Trunk Summary AN Extremity AN AN Girls Mean Difference (68:78- 78:88)= -299.9 -30.8 -212.8 T= -2.611 -0.858 -2.143 df= 15 15 15 Probability= 0.02 (*) 0.405 (ns) 0.049 (*)

Boys Mean Difference (68:78 - 78188)~ -1 02.4 T= -1.950 df= 15 Probability= 0.07 (ns) Cross-decade ANOVA comparisons of both ANand NATV, conducted in order to ascertain the extent to which musculo-skeletal growth (the NATV compartment) might play a role in earlier maturation are summarized in Tables 6.10, 6.11, 6.12 and 6.13.

Table 6.1 0. Summary of probabilities given by ANOVA and Scheffe's post hoc procedures in cross-decade comparisons of total An/: Kormend Girls. [p-values are: ns = not significant; = p1.05; ** = ps.01; *** - ps.0011 Scheffe's Probabilities AGE ANOVA '68:'78 '68:'88 '78:'88 3 ns * ns 4 *** ns *** *** *** *** 5 *** ns 6 *** ns *** *** 7 *** ns *** *** 8 *** ns *** *** *** *** 9 *** ns 10 *** ns *** *** 11 *** ns *** *** 12 *** ns *** *** *** *** 13 *** ns 14 *** ns *** *** *** *** 15 *** ns *** *** 16 *** ns 17 *** *** ** 18 *** ns *** Table 6.1 1. Summary of probabilities given by ANOVA and Scheffe's post hoc procedures in cross-decade comparisons of total NAN: Kormerid Girls. [p- values are: ns = not significant; * = p5.05; ** = ps.01; *** = ps.0011

Scheffe's Probabilities AGE ANOVA '68:'78 '68:'88 '78:'88 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Table 6.1 2. Summary of probabilities given by ANOVA and Scheffe's post hoc procedures in cross-decade comparisons of total AN: Kormend Boys. [p- values are: ns = not significant; = ps.05; ** = ps.01; *** = ps.0011 Scheffe's Probabilities AGE ANOVA '68:'78 3 *** ns 4 *** ns 5 *** ns 6 * ** ns 7 *** ns 8 *** ns 9 *** * 10 *** 11 *** ns 12 *** * 13 *** * 14 *** *** 15 *** ** 16 *** * * 17 *** ns 18 *** Table 6.1 3. Summary of probabilities given by ANOVA and Scheffe's post hoc procedures in cross-decade comparisons of total NAN: Kormend Boys. [p- values are: ns = not significant; = ps.05; ** = ps.01; *** = pr.001]

Scheffe's Probabilities AGE N ANOVA '68:'78 '68:'88 '78:'88 3 46 * ns ns * 4 120 ns ns ns ns 5 131 *** * ns *** 6 141 ** ns * * * 7 198 *** ns * * * 8 182 * ns ns 9 21 0 ** ns ** ns 10 209 * ns ns 11 252 ns ns * 12 264 ns ns ns ns 13 284 *** ns ** ** 14 281 *** ns ns *** 15 31 9 *** ns *** *** 16 278 *** ns *** ** 17 236 *** ns *** *** 18 136 ns ns ns ns

From both the tables and the figures it is clear that for Kormend girls, highly significant ANOVAs at every age represent a positive secular trend in total AN, most of which took place from 1978 to 1988, such that 1988 girls had a much greater total ANthan 1968 girls. At the same time, there was virtually no change in NATV values from one decade to the next during the pre-pubertal years and, in fact, significant NATV ANOVAs listed for 13- to 18-year-old girls (Table 6.1 1) represent a negative secular trend in total NATV such that in 1988 Kormend girls had an absolutely smaller total NATV than did the 1968 group. Thus, for girls, the secular trend in ATV occurred in a direction concordant with the secular trend in puberty onset and contrary to the secular trend in menarche. The secular trend in NATV matched that of menarche better than did the secular trend in AN. For Kormend boys, the distinction in secular trend between ATV and NATV was not as dramatic. But, over the age range where body composition could influence maturation there were instances in which a highly significant increase in total An/ from 1978 to 1988 accompanied non-significant change in total NATV (ages 8, 9, 10 and 12 in Tables 6.12 and 6.13; see also Figures 6.8, 6.9, 6.1 0 and 6.1 2). In no case was the inverse observed, with total NAN showing a significant, positive secular trend while total ANdid not. As with the girls, the bulk of the pre-pubescent secular increase in total adiposity in boys can be attributed largely to increases between 1978 and 1988. From the ages of 6 to 10 years, slight increases in total NANfrom one decade to the next were not in themselves significant, but were enough, additively, to result in 1988 boys having a significantly greater total NATV than 1968 boys. The increase in ATV from 1968 to 1988, however, was both more consistent (from one age to the next) and much greater relative to 1968 values (for every age group) than that of total NATV. Discussion In the current investigation significant increases in both absolute ATV and ATV relative to body size from 1968 to 1988 occurred concomitantly with decade to decade advancement in the age'of puberty onset in both boys and girls. This observation is interpreted as offering circumstantial evidence in favor of the contention that there is a relationship between adiposity and puberty onset. That ANis likely to play more of a role in this maturity event than musculo-skeletal tissue is suggested by the fact that in many instances, NATV did not increase significantly in concert with the secular trends of ATV and maturity. Certainly, at particular ages in Kormend boys, the secular trend in NATV was similar to that of ATV, but this did not occur consistently across all age categories. In the Kormend girls, NANchanges during pubertal years actually showed a significant, negative secular trend - exactly the opposite behavior expected if NATV is to play a role in the onset of puberty. Given the manner in which tissue constituents are proposed by Katz et al. (1985) to influence gonadarche, the event which promotes production of hormones necessary for shoulder and hip widening, there is no reason to believe that the tissue mediation should operate differently in boys than in girls. Therefore, since NANappears to have nothing to do with the secular trend of this particular maturity indicator in girls, it is unlikely to be involved in the mediation of puberty onset in boys, either. Positive secular NATV trends in boys, if observed, are probably incidental rather than causal with respect to secular trends in onset of puberty. It is interesting to note that during the decade interval over which the most dramatic change in ANoccurred, 1978 to 1988, there was no significant increase at most ages in lower extremity ANfor boys and for girls in the prepubertal years. At face value this appears to refute evidence that lower body adiposity has a particularly strong association with PA, as observed in the SASK children (Chapter 5). Care must be taken in making such a comparison, however, as it was the calf skinfold that was used to calculate lower extremity An/ in Kormend data rather than the thigh skinfold used in SASK. Hence, these results may imply that thigh adipose tissue plays a greater role in pubertal events than calf adipose tissue. In the current study, then, the secular increase in ATV appears to have been largely confined to the upper body. Given that upper body adiposity has been implicated as a risk factor in the development of cardiovascular disease and diabetes (Malina and Bouchard, 1991 ; Westrate et al., 1989; Eveleth and Tanner, 1990; Vague, 1956; Bjorntorp, 1988; Kannel, l983), the above observation suggests that after a point, secular increases in adiposity might be unhealthy. This possibility has been suggested previously (Tanner, 1990; Malina, 1979), but, to date, approaches to determine how adiposity in each region changes relative to both An/ in other regions and non-AN of the same region have been inadequate. Hence, the definition of a 'healthy' increase in adiposity has been difficult to express. Adipose and non-adipose volumes implemented for the first time in this investigation appear to offer a means by which this type of inspection can be performed with ease. A secular trend in adiposity might then be considered to be 'unhealthy', for example, when the increase in size-adjusted upper body AN exceeds that of lower body An/ by a certain amount. It is recommended that this approach be considered in future secular trend studies. Finally, a positive secular trend in adiposity concomitant with a negative secular trend in menarche does not support the proposal of Frisch and colleagues (Frisch and Revelle, 1970; Frisch et al., 1973; Frisch and McArthur, 1974) that fatness dictates the timing of menarche. Rather, these results indicate that the non-adipose tissue components might be more closely associated with menarche, as decreases in total NATV from ages 13 to 16 years matched the lag in menarche. Many authors have observed that a relationship between menarche and musculo-skeletal status is equally, if not more, significant than the observed relationship between menarche and body fatness by virtue of its high correlation with height velocity prior to menarche (Ellison, 1982; Elizondo, 1992; Scott and Johnston, 1982; Forbes, 1992; Parra et al., 1981). Ellison (1 982) refers to this as the first, more traditional view of the relationship between physical growth and menarche in humans, since close correlations between rate of skeletal maturation and menarcheal age have been observed since the 1930s. Scott and Johnston (1982) cite studies in which bone age was found to be much more closely related to menarche than was weight. More recently, in a cross-sectional study of perimenarchal girls by Forbes (1 992), urine analysis revealed a significant rise in hydroxyproline excretion (a measure of bone turnover) a year in advance of menarche after which hydroxyproline fell to well below prepubertal levels. Forbes (1992) also noted a greater absolute increase in lean body mass (estimated by potassium 40 counting) than in body fat in the years preceding menarche. He thus concluded that:

"...those features generally associated with androgen effects, such as increases in lean body mass and hand grip strength, exhibit perimenarchal changes fully as great as those ascribed to estrogen effects, such as abdomen-hip ratio, body fat acquisition, and breast development." (Forbes, 1992, p.66) Ellison (1982) considered this to be biologically adaptive, since an 'appropriate structural status' would seem to be desirable before reproduction begins. Frisch (1984) also alluded to this requirement in order to explain why in her results there appeared to be, along with body fat, a relationship between lean body mass and menarche. Ellison (1982) suggested that the link between structural maturation and menarcheal age may be mediated by 'adrenocortical secretion of anabolic androgens' (p. 277). Indeed, Zemel and Katz (1986) showed that in addition to testosterone, the adrenal androgen DHEAS, through its interaction with skeletal age, had a significant impact on height velocity in adolescent boys. Yet, DHEAS production is also considered to be augmented by increases in adipose tissue stores (Parker and Odell, 1979; Katz et al., 1985). If such a feedback mechanism exists and if DHEAS does contribute to musculo- skeletal robustness, how NATV in the Kormend girls could drop from one decade to the next while ANrises dramatically is a difficult to explain. In conclusion, what this study suggests is that if there is tissue mediation of maturity events, that which mediates the onset of puberty is distinct from that which mediates the onset of menstruation. An/ appears to have a much closer relationship to the first event while NATV seems to be related to the second. Chapter 7. Adipose Tissue Volumes and Age at Menarche in Saskatchewan Girls

There has been great controversy in the literature as to whether adiposity influences menstruation or is in any way related to it (Forbes, 1992;Elizondo, 1992;Bronson and Manning, 1991 ; Frisch and Revelle, 1970;1971;Frisch, Revelle and Cook, 1973;Frisch and McArthur, 1974; Frisch, 1984;Cameron, 1976;Johnton et al., 1975;Malina, Spirduso, Tate and Baylor, 1978;Scott and Johnston, 1982; Billewicz, Fellows and Hytten, 1976;Ellison, 1981 ; 1982;Parra et al., 1981,deRidder et al, 1990;deRidder et al., 1992). Those who adhere to the Frisch hypothesis consider adiposity to have a triggering effect, such that 18% BF triggers menarche and 22% BF restores menstruation in adult women after a bout of amenorrhea. Others have argued that apparent relationships between estimates of body fat and menarche have either been spurious due to the way in which %body fat was derived or too general to merit the designation of adiposity as the tissue of importance in this maturity event (Forbes, 1992; Elizondo, 1992; Bronson and Manning, 1991 ; Cameron, 1976;Johnton et a]., 1975;Scott and Johnston, 1982; Billewicz et a]., 1976; Ellison, 1981 ; 1982; Parra et al., 1981,deRidder et al, 1990;deRidder et al., 1992). Some studies have shown lean body weight (LBW) to have an equally strong relationship, if not stronger, with menarche as that of adiposity (Frisch and Revelle, 1970;Parra et al., 1981 ; Ellison, 1982). Oddly, Frisch's early results are among them, yet she still emphasized the role of adiposity in menstrual dynamics (Frisch and Revelle, 1 97O;l97l).As Ellison points out, the notion that LBW or some measure of it, such as the rate of skeletal growth, somehow influences the age at which menarche occurs is the more traditional or 'classical' view (Ellison, 1981 ; 1982). Recently, in a cross-sectional sample 127 of adolescent girls, Forbes (1 992) has observed much greater increases in variables that are associated with lean body weight (both anthropometric and biochemical) than those associated with adiposity in the trans-menarcheal years. In the current investigation, measures of both adipose and non-adipose tissue volumes exist in a longitudinal sample of pubescent girls from the Saskatchewan Growth Study for whom ages at menarche are known (~20). The purpose of this chapter, then, is to test sub-hypotheses 2b and 2c, namely, that ATV is significantly related both to menarche (2b) and to the time interval between puberty onset and menarche (2c). This is done by investigating the relationship between various tissue volumes, ATV, %An/ and NAN, and age at menarche (MA) in order to determine whether one type of tissue, in particular, has a significant and exclusive relationship to MA. With respect to sub-hypothesis 2b, regressions of AN, %ANand NAN on MA can be carried out and, as was the case for PA in Chapter 5, any component that appears to have an unchanging range of values regardless of a girl's MA, can at least be considered to have some association with this maturity event. With respect to sub-hypothesis 2c, linear relationships between changes in tissue volumes and the amount of time it took for each girl to get from PA to MA (the 'PA-MA interval') can be explored. Presumably, if a tissue volume does have an influence on the timing of menarche or is in any way related to MA, its relationship to the PA-MA interval should be significant and negative, such that girls who have a higher amount of the tissue experience MA earlier after PA than those who have low tissue volumes. Methods A general description of SASK is given in Appendix 2. There were 20 SASK girls for whom tissue volumes of ATV and NATV could be determined during the time when they experienced menarche. ANand NANfor the arm, trunk and thigh were calculated according to the procedure described in Chapter 3. Age of menarche was determined retrospectively by a follow-up survey conducted by Dr. Bailey in 1975 (personal communication). Bailey's questionnaire requesting a recall, to the closest month, of the age of menarche by the subjects who had participated in the SASK study included a 'certainty' rating from 1 to 4, representing the following levels of certainty:

1 = certain of date 2 = fairly certain 3 = only approximate 4 = best estimate, but uncertain

Only those subjects who were able to recall their MA with a certainty of '1' or '2' were included in the current investigation. In total, there were 58 respondents who qualified for this sub-category. Unfortunately, 34 had to be dropped because their age of menarche fell outside the time frame over which they were measured and 4 were left out because they had insufficient anthropometric data to evaluate ATV. Thus, 20 girls remained to be examined in the current study As in Chapter 5, for girls who experienced MA within + .25 years of an anthropometric measurement occasion, the values of tissue volumes at that measurement occasion were used in the analysis without any attempt to interpolate what the volume might have been at the actual MA. For MAS estimated to occur from .250 to .749 of a decimal year between two 129 anthropometric measurement occasions, the averages of tissue volumes measured immediately before and after that event were used in the analysis. A descriptive statistical summary of the age at menarche and of the component tissue volumes is provided in Table 7.1. Regression analysis of ATV (both absolute and relative amounts) and NATV on MA were carried out using the analysis function on the Microsoft ExcelTM 4.0 spreadsheet. Relative adiposity was expressed as the percentage of ANrelative to over-all volume of the region under consideration (e.g. %Arm ATV = 1OO*(ArmATVItotal volume of the Arm). For all variables, regression diagnostics of initial analyses (as recommended by Draper and Smith (1981 ) revealed residual behavior that appeared to violate the assumption of homoscedasticity. Logarithmic transformation of variables, as suggested in both Kleinbaum, Kupper and Muller (1988) and Draper and Smith (1981), was successful in stabilizing the variance. Hence, the regression results in the first part of this analysis will show measures of An/ and NANin logarithmic form. To determine whether there was a 'critical' ATV, %ANor NATV necessary for the onset of menstruation, coefficients of variation (CVs) were plotted versus time from MA in years (-5 to +1 years). The second part of the analysis involved examination of the linear relationship between a change in a tissue volume (ANor NAN) and the PA- MA interval. Values of ANand NATV (total and regional) were available at both PA and MA only in a sub-group of 14 SASK girls. The change in ATV and NANfrom PA to MA was simply expressed as the difference of the variable at MA and PA by subtraction. Velocities of ATV and NATV versus the PA-MA interval were also examined - velocity (in units of mllyear) being calculated as the change in a variable from PA to MA divided by the time interval (e.g. Arm ATV velocity = (ArmAN@MA - ArmATV@PA)/PA-MA interval). A descriptive 130 statistical summary of the changes in tissue volumes over the PA-MA time interval is given in Table 7.2. The time interval, itself, had a mean and standard deviation of 2.323 and 1.078 years, respectively.

Table 7.1. Summary statistics (mean and standard deviation) of age at menarche (MA) and tissue volumes at this age in SASK girls (N=20).

Mean SD

Age at Menarche ATVs(ml) Arm ATV Trunk ATV Thigh ATV Total ATV %ATVs %Arm ATV %Trunk ATV %Thigh ATV %Total ATV NATVs(ml) Arm NATV Trunk NATV Thigh NATV Total NATV

Table 7.2. Summary statistics of tissue volume changes over the PA-MA time interval in SASK Girls (N=14).

Change of Volume Velocity of Volume (ml) Change (mllyr) Mean SD Mean SD ATV Arm 72.6 93.1 Trunk 634.3 779.6 Thigh 352.0 351 .O Total 1058.9 1171.5 NATV Arm 256.5 116.8 Trunk 3765.6 1304.1 Thigh 1279.6 542.1 Total 5301.7 1656.1 Results and Discussion Scatter plots of the linear relationship between MA and logarithmically transformed tissue volumes with least squares regression lines and related statistics are shown in Figure 7.1 for Total AN, %Total ATV and Total NAN and in Appendices 26,27 and 28 for equivalent measures of the arm, trunk and thigh, respectively. All variables examined in this manner have no significant linear relationship with MA, which seems to indicate that MA occurs within a certain range of both ANand NATV and, therefore, that neither can be said to have an exclusive effect on menarche. The chart of CV versus time from MA in Figure 7.2, however, offers little evidence that a particular value of ATV or NATV triggers MA. All variables except %arm AN, thigh ANand %thigh ANseem to undergo a drop in CV. No one tissue, then, can be designated the 'trigger'. More likely, the CV drop reflects either the drop in subject number around that time or an emergence of .I - . - Multiple R = .0741 , - p = .756

MA (years) 1.6, - I

s- I , - I Multiple R = .0341 p = .887 -- r

MA (years)

Multiple R p = .570

Figure 7.1. Scatter plots of MA versus totals of tissue volumes (ml), An/ (a), %AN (b) and NAN(c) in SASK girls, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. -cc Thigh -b Trunk -+- Total

Time from Menarche

60 %AN

Time from Menarche

NAN

Time from Menarche N= 25 45 44 52 39 18 9 Figure 7.2. Coefficients of variation of total and regional tissue volumes, ATV (a), %ATV (b) and NATV (c) versus time from MA: -5 to +I years. [N is given at each year from MA, as the mixed-longitudinal design of the study resulted in changing subject numbers across the study period.] all girls from the height spurt phase, which is a time of great variability, to the stable, adult-size endpoint of height growth. Results of the second part of the analysis are shown graphically in Figure 7.3, Figure 7.4 and Appendices 29 to 34. Figure 7.3. focuses on changes in total tissue volumes, ANand NAN, over the PA-MA interval, while changes in regional tissue volumes over the same time period are shown in Appendices 29 to 31. Figure 7.4 shows velocity of change in total tissue volumes, ATV and NAN, versus the PA-MA interval. Equivalent velocity relationships for regional ATV and NATV of the arm, trunk and thigh are shown in Appendices 32,33 and 34, respectively. In Figures 7.3 and 7.4, it is clear that the only variable which behaves in a manner to be expected of one that is related to the pace of maturation from PA to MA is total NANvelocity (Figure 7.4~).Interestingly, this is primarily attributable to trunk NANvelocity (Appendix 33). Van't Hof and Roede (1977) also found sitting height, along with bone age, to be related to menarche. What meaning trunk NANgrowth might have with respect to menarche is unclear, but these results tend to concur with the observation that menarche is related to height velocity (Elizondo, 1992; Forbes, 1992; Ellison, 1982; Parra et al., 1981; Malina et al., 1978), since the trunk grows during this time (i.e. after leg lengthening) (Malina and Bouchard, 1991). Hence, the current results support those observed in Chapter 6 and others in the literature that menarche is more highly associated with musculo-skeletal development than is adiposity. Sub- hypotheses 2b and 2c are rejected. = 2000- uE P 2 1000- m (II C 0 C- .-C 0- Q) Multiple R = 591 CI) c SEE = 983.6 (II F = 6.442 4 -1000- p = ,0260 ~~642.5~-433.7 (a) - -2000 I 1 I I I I I i 0 0.5 1 1.5 2 2.5 3 3.5 4 PA-MA Interval (years) 9000, 8000 - A

YE 7000 - > 6000 - Z -m 5000- C 8 4000 - C .- s Multiple R = .709 g, 3000 - r SEE = 1216.4 g 2000- F = 12.1 00 0 p = ,00456 1000 - y=1 089.0~+2771.9

0 (b) I I 1 0 0.~5 1:5 d 2.5 3 3.5 4 PA-MA Interval (years)

Figure 7.3. Changes in total An/ (a) and total NATV (b) volumes (mi) over the time interval from PA to MA, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. Multiple p = ,300

PA-MA Interval (years) 6000 - -*L -E5000 - az z 4000- -s 0 t 3000- 0 ). -g 2000- Multiple R = .737 >" = 1000- p = .00264 z0 y=-799.9~+4511.7 (b) 8 0 I 1 I 1 I I I i 0 0.5 1 1.5 2 2.5 3 3.5 4 PA-MA Interval (years)

Figure 7.4. Growth velocities of total An/ (a) and total NATV (b) (mllyr) over the time interval from PA to MA, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. Chapter 8. ATV versus Skeletal Age in Saskatchewan Boys

It is possible to infer a link between adiposity and skeletal development during growth by the apparent connection of both to adrenal androgen levels in circulation. Observations of significant positive associations between DHEAS and skeletal age in growing children (Raisz and Kream, 1981; Bing et al., 1988; Katz et al., 1985), DHEA and vertebral density in post-menopausal women (Meikle, Daynes and Araneo, 1991) and DHEAS and acceleration of bone maturation in rodents (Howard, 1963, cited in Katz et al., 1985; Wirman et al., 1986) has been seen to accelerate bone maturation in mice (Howard, 1963, cited by Katz et. al., 1985) suggest that adrenal androgens, particularly DHEAS, may have a direct impact on bone. At the same time, it has been observed that obesity in children results in high levels of DHEAS in circulation (Feher and Halmy, 1975a; 1975b; Pintor et al., 1980; Pintor et al., 1984), presumably by some feedback mechanism whereby the adrenal cortex is stimulated to increase production of DHEAS as adrenal androgens are sequestered by increasing amounts of adipose tissue (suggested by Katz et al., 1985). If adiposity promotes DHEAS secretion and DHEAS, in turn, promotes bone developme,nt, it is reasonable to infer that adiposity might influence skeletal maturation. On the other hand, skeletal growth is known to be influenced by a host of other factors, including parathyroid hormone, vitamin D, calcitonin, growth hormone, insulin, thyroid hormone, glucocorticoids, sex hormones, somatomedins and prostaglandins (Raisz and Kream, 1981). Prader (1990) discussed an intriguing possibility that some peripheral expression of a genetic code on a sex chromosome, that operates independently of any known hormonal mediation, could also contribute to bone development. 138 Whether or not adipose tissue has a relationship to skeletal maturation that is exclusive of the relationship between skeletal age and other tissues can be investigated in a general way using the Saskatchewan Growth Study data on 11-year-old boys for whom skeletal age was assessed. In order to test sub- hypothesis 2d (Chapter I), then, the purpose of this chapter is to analyze the linear relationships between skeletal age (SA) and tissue volumes, ATV, %ATV and NATV, by regression analysis in order to determine if ANhas a distinct impact on skeletal maturation. Since there is a range of skeletal ages amongst these 11-year-old boys, a tissue volume will be deemed to have an association with the advancement of SA if its regression on SA results in a significant, positive relationship. Methods A general description of the SASK growth study is provided in Appendix 2. There were 115 Sask Boys (all between the decimal ages of 10.58 and 12.75) for whom skeletal age was assessed from a radiograph of the left hand and wrist according to the Greulich Pyle Atlas method (see Bailey, 1968, and Crawford, 1990). Three experienced raters from the Department of Diagnostic Radiology, University Hospital, University of Saskatchewan independently estimated SA corresponding to each radiograph. Chronological age was revealed to each rater only after the x-ray had been evaluated. SA at exposure for each child was determined as the mean of the three ratings. Ratings differing by 12 months were re-analysed by all three raters. Intra-observer reliability for radiograph assessment was r=.92 (Bailey, 1968). Regional and total tissue volumes, ATV and NATV, were calculated as described in Chapter 3. Since the skeletal age assessment occurred mid-year between anthropometric measurement occasions, the average of each tissue volume from the measurement occasions immediately before and after the 139 skeletal age assessment were considered as the volumes existing at SA. A descriptive statistical summary of SA and volume measures included in this analysis is provided in Table 8.1.

Table 8.1. Means and standard deviations of variables used to study the relationship between SA and adiposity in SASK boys (N=115).

MEAN Maturity Index(=Skeletal 0.96 age1Decimal age) ATVs (ml) Arm ATV Trunk ATV Thigh ATV Total ATV %ATVs (%) %Arm ATV %Trunk ATV %Thigh ATV YoTotal ATV NATVs (rnl) Arm NATV Trunk NATV Thigh NATV Total NATV

It is recommended that a better indicator of relative maturity than SA by itself is the expression of SA relative to chronological age of a child (Crawford, 1990; Katz et al., 1985). Since all of the boys in this particular sample had chronological ages within one year of each other, the distinction between actual SA and relative SA hardly matters. To remain consistent with convention, however, the maturity index (MI), a ratio of skeletal age to chronological age, will be used instead of SA in the regression analyses below. Regression analysis of ATV (both absolute and relative amounts) and NANon MI were carried out using Microsoft ExcelTM 4.0 spreadsheet. Relative adiposity was expressed as the percentage of ATV relative to over-all volume of 140 the region under consideration (e.g. %Arm ATV=100*(Arm AlV/Total Volume of the Arm). For all variables, examination of residual behavior resulting from the initial regression runs, as suggested in Draper and Smith (1981), indicated that the homoscedasticity assumption was being violated. Logarithmic transformation of volume variables, as suggested in both Kleinbaum, Kupper and Muller (1988) and Draper and Smith (1981), was successful in stabilizing the variance. Hence, the regression results in this chapter will show measures of both ANand NATV in logarithmic form. Results and Discussion Results of the regression analysis are displayed in Figures 8.1 to 8.4. These are scatter plots of total and regional tissue volumes versus MI, which include the least squares best fit regression line and related statistical summaries. In a word, everything, AN, %An/ and NAN(total and regional), is related to skeletal age. Therefore, adiposity cannot be considered to have an exclusive impact on bone age even if the two might be linked by DHEAS dynamics and adrenal function. Since it has been observed that early skeletal maturers tend to have a bigger over-all body size than their peers (Crawford, 1990), it is not surprising that the boys in this study who had a greater SA also tended to have higher volumes of both tissue types, ANand NATV, as these volumes are influenced by body size. Multiple R = A37 SEE = .I86 F = 26.697 p = 1.035E-06 yz.83~-.473

Maturity lndex

Multiple R = .320 SEE = .I41 I... = I . I F 42.877

0.4 I I I I 1 0.'6 0 0.8 0.9 1 1.1 1.2 Maturity lndex

Z I= Multiple R = .600 SEE = .0504

0.6 I(c) I I I I I 1 0.6 0.7 0.8 0.9 1 1 1.2 Maturity lndex

Figure 8.1. Scatterplots of SA (expressed as MI) versus tissue volumes, Total ATV (a), %Total ATV (b) and Total NATV (c) in SASK boys, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. Multiple R = .456 SEE = .I70 F = 29.645 p = 3.059E-07 yz.80~-1.34

Maturity lndex

E -.- 3 1.4 Multiple R = .252 rn . . . - SEE = .0976 ,o 1.2 F = 7.684 p = .00652

1 (b) 0.8 , I I I I I i 0.6 0.7 0.8 0.9 1 1.1 1.2 Maturity lndex

-0.2 Multiple R = .558 a - r SEE = .On9 9 -0.4 . F = 51.150

-0.8 I,(c) I I I I I i 0.6 0.7 0.8 0.9 1 1.1 1.2 Maturity lndex

Figure 8.2. Scatterplots of SA (expressed as MI) versus tissue volumes, Arm ATV (a), %Arm ATV (b) and Arm NATV (c) in SASK boys, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. Log Trunk NATV Log %Trunk ATV Log Trunk ATV A-L-L-L gg-riubbb ggg 4 A L' g , 0 w 1. Multiple R = SEE = .I74 F = 32.811

(a) -0.8 I , I I I I I I 0.6 0.7 0.8 0.9 1 1.1 1.2 Maturity lndex

a I. . C I . Multiple R = ,271 C SEE = .I22

0.6 1 (b) , I I I I I 1 0.6 0.7 0.8 0.9 1 1.1 1.2 Maturity index

4' I 0.~6I -.a . : r * . :.= = cn 0.4 .- *-= Is . Multiple R = -595 E = - -- SEE .0678 = I . .- = C

-0.2 I, (c) I I I I i 0.6 0.7 0.8 0.9 1 1.1 1.2 Maturity lndex

Figure 8.4. Scatterplots of SA (expressed as MI) versus tissue volumes, Thigh ATV (a), %Thigh An/ (b) and Thigh NATV (c) in SASK boys, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. It can be concluded, then, that while the results of this study are in agreement with those of others, which showed that measures of adiposity are significantly associated with skeletal age (Bing et al., 1988; Katz et al. 1985), the current results offer little information beyond that point, as all tissue volumes appear to be related to SA, without distinction. Chapter 9. Section B: Discussion

Tests in Section B of the hypothesis that adiposity is related to maturity involved three different maturity indicators: 1. age at the onset of puberty (PA), identified by changes in biiliocristal breadth and biacromial breadth in girls and boys, respectively, 2. age at menarche (MA) in girls and 3. skeletal age (SA) in a group of 11 -year-old boys. Since the observed relationship between ATV and SA (Chapter 8) offers little insight beyond the fact that SA appears to be related to over-all body size, in general, no further importance will be ascribed to this particular association. Results of interest pertain to the examination of tissue volumes versus PA and MA.

Adiposity and Puberty Onset Based on analysis involving both SASK and Kormend data, the possibility that there is an association between adiposity (both absolute and relative) and puberty onset cannot be ruled out. That ATV behaves in a manner that is exclusive of NATV (in both girls and boys) during this physiological transition is clear. A discrepancy between An/ and NANversus PA that is larger in the thigh than in other regions is consistent with the hypothesis that ANinfluences onset of puberty by its aromatization capacity, as conversion of adrenal androgens has been observed to be higher in fat stores of the upper thigh, flank and buttocks compared to those of the abdomen (Killinger et al., 1987; Nimrod, 1975). Although the variance of An/ at PA is high, casting doubt on ATV acting as a trigger of puberty onset, the variance must be considered with respect to ATV variance in the years preceding and following PA. A number of authors have argued that if a variable is to be considered 'critical to' or 'a trigger of' a physiological event, it must at least demonstrate a reduction of variability in a group of subjects at the time of the event or shortly before it. (Cameron, 1976; Ellison, 1981; Johnston et al., 1975). While coefficients of variation (CVs) of arm ATV and trunk ANwere unchanged at PA, a decrease in CV of the thigh adiposity (both ANand %ATV) in the year of PA in girls and in the year preceding PA in boys suggests that this regional ATV volume should be studied more closely for its effect on the gonadostatic control mechanism during the adrenarche-to-gonadarche time interval. While it is likely that neither PA nor AW were assessed accurately enough in the current investigation to provide definitive evidence of the tissue playing a 'critical' role in the onset of puberty, the possibility that ANof some region, such as the thigh or buttocks, might trigger the event cannot be ruled out by these results. Derivation of PA from changes in BILL (girls) and BlAC (boys) was intended to serve as an approximation of gonadarche, the event hypothesized by Katz et al. (1985) to be uniquely influenced by adiposity. Thus, the results of the current investigation must be considered in light of other studies which have focussed specifically on this transition. Surprisingly, in all of the discourse surrounding Frisch's hypothesis, only four such studies exist (Frisch, Revelle and Cook, 1973; Parra et al., 1981 ; Katz et al., 1985; deRidder et al., 1992). By far, most investigations have focused on menarche, for obvious reasons. Menarche is easy to define and identify, requiring no longitudinal hormonal assessment. Gonadarche, on the other hand, is more difficult to define and detect. While Grumbach and Kaplan (1990; p. 2) describe it mechanistically as the moment of 'reactivation (disinhibition) of the hypothalamic LRF-pulse generator' (p.2), they offer no specific endocrinological definition, in terms of hormonal concentrations to be normally expected at transition to puberty. With respect to boys, Katz et al. (1985) considered testosterone levels of less than 100 ngldl, between 100 and 280 ngldl and greater than 280 ngldl to represent 'pre- gonadarcheal', 'trans-gonadarcheal' and 'post-gonadarcheal' stages of development. In other studies, puberty onset was defined as Tanner's breast stage 2 (deRidder, et al., 1992), the change point in gonadotrophin and sex steroid concentrations (Parra et al., 1981) and the take-off of height growth at the time of the growth spurt (Frisch, Revelle and Cook, 1973). These investigations are summarized in Table 9.1. Adiposity was also measured differently from one study to the next. The derivation of %BF by the Mellits and Cheek (1970) equation used by both Frisch et al. (1973) and Parra et al. (1981) has been completely discredited in the literature for having statistical, methodological and conceptual flaws (Scott and Johnston, 1982), while skinfolds used in the other two studies (Katz et al., 1985; deRidder, 1992) are limited to the upper body and might have been influenced by changes in other body dimensions during the time of their measurement as shown in SECTI@NA of this thesis. Hence, none of these were exempt from methodological problems involving 'appropriate' representation of adiposity. The use of skinfolds in the more recent investigations, however, is certainly more appropriate than the derived %BF of the original two. So, the weight of the evidence on the relationship between adiposity and gonadarche rests on the two more recent studies (Katz et al., 1985; deRidder et all 1992). Indirect measures of both adiposity and gonadarche in all studies shown in Table 9.1 underscore the fact that evidence in favor of the hypothesis that adiposity is related to gonadarche can only be circumstantial. Conclusive or direct evidence would require both accurate measures of each variable and the ability to control or 'manipulate' the variables. The results are split. While Katz et al. (1985) considered adiposity to be related to maturity through its association with DHEAS in boys, deRidder et al. (1992) found that two groups of girls at the same stage of puberty had highly significant differences in sum of skinfolds with no differences in gonadotrophins or sex steroids. In isolation, these investigations might suggest a sex difference in the adipositylgonadarche relationship, but in the current investigation the manner in which An/ was related to PA was similar in both girls and boys. Given the paucity of information on the role of body tissues with respect to the onset of full gonadal function in children, the current evidence that there appears to be some association between adiposity and onset of puberty that is exclusive of the effects of other tissues in both longitudinal and secular trend data represents a substantial contribution to the area. For a definitive conclusion to be reached on this issue, however, further investigation must be conducted with improvement in research design and in the measurement of both adiposity and gonadarche. Additional consideration must be given to the possibility that the metabolic capacity to aromatize adrenal androgens applies to only a subset of adipocytes (Roncari, 1984; Killinger et al., 1987). If this is true, bulk AN assessment might never adequately explah the relationship between the aggregate of active adipocytes and puberty onset. The presence of non- aromatizing, lipid-ladened adipocytes will always obscure the specific effect. This possibility must be investigated further. Table 9.1. Summary of all known investigations which provided circumstantial evidence on the relationship between adiposity and gonadarche. (No study has demonstrated a causal relationship.)

Authors indicator of Gonadarche (G) Measure of Adiposity (A) Study Design (A appears to /Analytical Strategy be related to G3) Frisch, Revelle and Height at take-off %BF - derived from weight, Longitudinal YES Cook, 1973 (girls) height and TBW (Mellits and /regression of weight on age Cheek, 1970) at take-off

Parra et al., 1981 Change point in gonadotrophin and %BF - derived from weight, Cross-sectional sex steroid concentrations height and TBW (Mellits and /polynomial regression of (girls and boys) Cheek, 1970) hormones on weight

Katz et al., 1985 Testosterone levels (ngldl): Triceps SF Cross-sectional YES 'pre-gonadarcheal' (4OO), Subscapular SF /two-way ANOVA of 'trans-gonadarcheal' (100-280), and BMI testosterone and DHEAS 'post-gonadarcheal' (>280) effects predicting SF and BMI (boys) deRidder et al., 1992 Tanner's breast stage 2 (B2) Sum of four skinfolds (S): Longitudinal (treated cross- (girls) Triceps SF sectionally) Biceps SF /Mann Whitney test of Subscapular SF hormonal levels in high S and Suprailiac SF low S groups at 82

Blade, 1993 BllL change point (girls) ATV (arm, trunk and thigh) Longitudinal YES BlAC change point (boys) - calculated from length, girth /regression of ATV on age at and skinfold of a given body PA segment (cylindrical model) Secular Trend (i.e. serial cross- YES sectional) /one-way ANCOVA of cross- decade effects predicting ATV (controlling for body size using NATV) Adiposity and Menarche Interestingly, there is no evidence that ANis strongly or exclusively related to menarche (Chapters 6 and 7). If anything, it is the NANcomponent that appears to have an exclusive link with menarche. In particular, trunk NATV velocity showed a significant, inverse (ps.001) linear relationship with the time interval from PA to MA. Girls who had a high trunk NANvelocity experienced menarche shortly after puberty onset, while in girls who had a low trunk NAN velocity, menarche occurred later. These results agree with a number of reports in the literature linking menarche to musculo-skeletal development (Elizondo, 1992; Forbes, 1992; Ellison, 1982; Parra, et al., 1981; Malina et al., 1978; Van't Hof and Roede, 1977; Marshall and De Limongi, 1976; Frisch et al., 1973). It is interesting that Frisch et al. observed an association between LBW and menarche, but persisted in ascribing greater importance to relative body fatness. In a re- analysis of the same data (Berkely Growth Study), however, Ellison (1 981) found height velocity to be much more closely associated than any measure of weight with menarche, which he then interpreted as evidence of a 'significantly synchronized' attainment of menarche at an 'appropriate skeletal maturity' (p. 275). Ellison considered this synchronization to be biologically adaptive, as structural integrity is required to withstand the mechanical constraints of childbearing. Further evidence of a connection between skeletal status and menarche is given by observations that urinary hydroxyproline excretion (a measure of bone turnover), bone volume, bone age and metacarpal cross-sectional area all increase in the years immediately prior to menarche (Forbes, 1992). Inspection of CV changes in An/, %ATV and NATV over the perimenarchal years (Chapter 7) reveals that almost all variables have a drop in CV at or immediately before MA. In the words of Forbes (1992) who also found a large array of variables to be associated with menarche, "...it is impossible to designate any one of them as the 'trigger' " (p. 66). The decreases in CV in the current investigation more likely reflect either a decrease in variance which happened to accompany a decrease in subject numbers in the SASK sample over this period or a decrease in variance of all measurements having to do with the attainment of adult body size at MA, since MA is known to occur one year after peak height velocity (Tanner, 1990). All of these changes, along with menarche, probably reflect the same developmental process. That menarche appears to have more to do with musculo-skeletal development than adiposity prompts reconsideration of commonly cited evidence that makes the link between menstrual function and adiposity so intuitively appealing. To summarize, amenorrhea has been observed to result from endurance training (Baker, 1981), intensive training (Schwartz, Cumming, Riordon, Selye, Yen and Rebar, 1981 ; Feicht, Johnson, Martin, Sparks and Wagner, 1978), low caloric intake (Nelson, Fisher, Catsos, Meredith, Turksoy and Evans, 1986), psychological stress (dalle, Freeman, Galle, Huggins, and Sondheimer, 1983), low body weight (Feicht-Sanborn, Martin and Wagner, 1982) and vegetarianism (Brooks, Sanborn, Albreight and Wagner, 1984; Slavin, Lutter and Cushman, 1984). Certainly, a decrease in adiposity is the prominent feature of altered physical status in all of these situations, except for that involving psychological stress. But, nothing in these articles rules out the possibility that some accompanying alteration of the underlying musculo- skeletal component signals menstrual disruption in response to negative nitrogen balance. The relationship between musculo-skeletal status and menstrual status requires further investigation.

Conclusion The fact that ANis related to PA but not to MA supports deRidder's suggestion that the control of puberty onset is somewhat independent of the control of menarche (deRidder et al., 1992). It also supports the Katz hypothesis that the impact of adiposity on maturation is limited primarily to the time interval between adrenarche and gonadarche (see illustration in Figure 1.2). Katz et al. (1985) hypothesized that during this interval, levels of active steroids rise by peripheral conversion of adrenal androgens in ever increasing amounts of adipose tissue and serve to alter hypothalamic sensitivity. But it should be expected that once gonadarche has occurred, sex steroid output from functional gonads would completely overwhelm any peripheral contribution to the hormonal pool. Thus, once female puberty has commenced, changes in adiposity would have little impact on the drive towards menarche except, perhaps, in the extremely obese. According to this scheme, whether or not adiposity can be considered to have an impact on menarche really depends on focus. Specifically, it does not. Generally, however, it can be considered to have an influence, in that gonadarche must occur before menarche can. Thus, Frisch and colleagues might not have been entirely wrong in attributing earlier maturation of modern peoples to increases in energy stores. But, by delimiting the time frame of the adiposity influence on sexual maturation, Katz et al (1985) offer a superior explanation which reconciles the apparently conflicting evidence that adiposity is related to pubertal events in some instances and not in others. In keeping with the 'Katz' hypothesis, the current investigation suggests that An/ might, indeed, influence the timing of puberty onset, but that it has little to do with the progress of puberty thereafter. Chapter 10. Summary, Conclusions and Recommendations

The purpose of this thesis was to develop a new way to express adiposity ('fatness') and, then, to employ this new measure in an investigation of the relationship between adiposity and maturity in growing children using data from cross-sectional, longitudinal and secular trend studies. Therefore, the thesis has two parts: SECTION A, which deals with the calculation of adipose tissue volume (Am) as a measure of adiposity that is dimensionally and anatomically appropriate if the tissue is to be scrutinized for its metabolic influence, and SECTION B, which involves tests of the hypothesized relationships between ANand various maturity indicators.

Summary of Results

SECTION A. Description of Adipose Tissue Volume (ATV) Growth Pumose 1a - Calculation of ATV ANs of limb segments and trunk were calculated in Chapter 3 using a cylindrical model, which required at least one length, one girth and one skinfold from each region. The absence of segmental lengths in the SASK girls data required initial derivation of the following lengths by photogrammetry in Chapter

upper arm length forearm length hand length calf length foot length sternum-to-vertex length Accuracy and reliability checks of the photogrammetry led to a rejection of lateral malleolus height derivations (TEM>4.0; Cb4.0). Acceptance of the other six lengths in Chapter 2 was confirmed by them showing reasonable size ranges in same-age COGRO children in Chapter 3 (see Table 3.5).

Pur~ose1 Q - Description of ANGrowth An/ growth was described in Chapter 3. In both sexes, AN demonstrated a growth take-off around 7 to 8 years of age and began to slow towards a plateau at about 14 to 16 years of age. This curve of ANgrowth common to both girls and boys was derived by empirical curve-fitting of ATV using the Preece-Baines (1 978) function:

where, Y = the value of the given variable at time, t M1 = final (or adult) size of the given variable me = value of the variable at time 8 8 = a time constant so and sl are rate constants

Preece-Baines curves of both ATV and NANgrowth demonstrated that ATV growth has a time course that is distinct from NATV growth in boys. ATV and NATV curves coincided in girls. Peak ATV growth of boys and girls was temporally aligned. Therefore, there is no sexual dimorphism in the timing of ATV growth even though there is for the timing of NATV growth.

Purpose 1c - Comparison of Changes in An/ and Skinfolds During Growth Graphical analysis of An/ and skinfold changes during growth in Chapter 3 showed clearly that, while fluctuations in skinfolds largely accounted 157 for fluctuations about the curve of ANgrowth, a dramatic divergence between ANand skinfold curves can occur during adolescence. ANremained stable or continued to rise, while skinfold values dropped. That the divergence happened more often in boys than girls and in limbs than trunk, suggests that the divergence in the ATV-skinfold relationship results from exaggerated segmental lengthening. Thus, a change in a skinfold value during growth may not necessarily represent a change in adiposity.

SECTION B. Investigation of the Relationship Between ATV and Maturity Purpose 2 - Test of the general hypothesis that ANis related to maturity Sub-hv~othesis2a: ATV is related to the onset of puberty, exclusive of NAN. The relationship between An/ and age of onset of puberty (PA) in girls and boys was explored using the SASK data in Chapter 5 and the Kormend data in Chapter 6. In the SASK children both ANand %An/ (in logarithmic form) were observed to have unchanging means at all levels of PA, while NATV and PA had a positive, linear'relationship (pe.05 (girls); p<.001 (boys)). That PA can occur at different levels of NANdisqualifies NATV from being a potential mediator in onset of puberty and suggests that ANmight have a distinct (albeit general) association with this maturity event. A large variance of ANat PA, however, precludes the use of AN as a predictor of puberty onset in individual children. In girls, the discrepancy in the relationship of ATV and NANto PA was greatest at the thigh. CV of the thigh also demonstrated a slight drop at or just prior to PA (girls and boys). Thus, thigh ATV is recommended 158 as a candidate for further inspection in the search for the 'trigger' of gonadarche. In the Kormend children, decade-to-decade increases (ps.001) in ANand ANrelative to body size (determined by ANCOVA, with NATV as the covariate) matched a secular trend of earlier PA by the bone width criteria. NATV did not match the secular trend except in a few instances. A large portion of the secular trend in ATV can be attributed to increases in adiposity from 1978 to 1988, rather than from 1968 to 1978. Upper body adiposity showed a much stronger secular trend than lower body adiposity. Conclusion: Circumstantial evidence supports acceptance of the hypothesis that there is a general association between ATV and puberty onset that is exclusive of NATV. A causal relationship has not been demonstrated. Moreover, the large variance in ATV at PA precludes its use for individual prediction of maturity status.

Sub-hv~othesis2b - ANis related to menarche, exclusive of NAN. The relationship between age at menarche (MA) and An/, %AN and NATV was investigated using orm mend data in Chapter 6 and SASK data in Chapter 7. In the Kormend girls, MA was reported to be progressively delayed from 1968 to 1988 (Eiben, 1988). Ages at menarche were: 12.75+.04 (Kormend '68), l2.80+.04 (Kormend '78) and l2.93+.20 (Kormend '88). A negative trend in NAN matched the menarche trend, while a positive trend in ANcontrasted with it. In SASK girls, logarithmic values of tissue variables AN, %ATV and NATV all appeared to be associated with MA. MA occurred within 159 an unchanging range for all variables. A drop in CV at MA for all the variables negates the possibility that any one of them serves as the 'trigger' for menarche. Conclusion: The hypothesis is rejected.

Sub-hv~othesis2c - An/ is related to the time interval between PA and MA, exclusive of NATV. Regression of absolute change in ATV and NATV from PA to MA on the PA-MA time interval in Chapter 7 suggested that neither ATV nor NATV influence menarche. When the velocities of these variables were examined, however, a negative relationship (pg.01) was observed between total NATV velocity and the PA-MA interval. This was attributable to a negative relationship between trunk NATV and the time interval. Thus, trunk NATV velocity is related to progress towards menarche, while every other measure of ATV or NATV is not. Conclusion: The hypothesis is rejected.

Sub-hvpothesis ?d - ANis related to skeletal age (SA), exclusive of NATV. Regression analyses of ATV, %ATV and NATV (in logarithmic form) versus SA using SASK boys data (Chapter 8) demonstrated highly significant relationships between all tissue volumes and SA (Ps.001). This merely confirms previous observations that SA is generally related to body size (e.g. Crawford, 1990) and offers no insight into the role that specific tissues might play in maturity. Conclusion: The hypothesis is rejected. General Conclusions

1. Growth of adipose tissue is sigmoidal in behavior, showing a marked increase at ages 7 to 8 years and a slowing of growth from ages 15 to 16, onward, in both girls and boys.

2. Lengthening of body segments during growth can result in a 'spreading' or 'stretching' of the adipose tissue mantle in such a way that skinfolds decrease while ATV either remains constant or increases. The divergence in the An/- skinfold relationship occurs more often in boys than in girls and in limbs than in the trunk.

3. Skinfold measurements alone can no longer be considered to provide an adequate assessment of adiposity changes in growing children.

4. Circumstantial evidence supports acceptance of the hypothesis that there is a general association between ATV and puberty onset that is exclusive of NATV in both girls and boys. A causal relationship has not been demonstrated. No segmental AN, except thigh ATV, shows any sign of being a 'trigger' of gonadarche.

5. A large variance of ATV in all body segments at puberty onset precludes its use as a predictor of this physiological event in individual children.

6. There is no evidence that adiposity is strongly or exclusively related to menarche. Rather, the evidence points to a an association between menarche and rate of NATV growth. 16 1 7. ATV is only one of many variables associated with skeletal age in 11-yr-old boys, which merely confirms previous reports that skeletal maturity is associated with over-all body size.

8. In aggregate, the results of this thesis provide circumstantial evidence in general agreement with the 'Katz' hypothesis (Katz et al., 1985) that adiposity is associated with gonadarche. Recommendations

Given the results of this investigation, it is recommended that:

1. the validity of the cylindrical estimation of ANbe tested. This might involve a comparison of AWderived from MRI analysis and anthropometrically derived ATV in children of different ages.

2. new instrumentation and techniques be developed to improve the accuracy of non-invasive adipose tissue measurement.

3. more tests be conducted to quantify the extent to which changes in length and underlying muscularity alter skinfold values.

4. a new definition of obesity be developed based on ANmeasurement relative to NAW. This volumetric approach might be a convenient alternative to the use of skinfold ratios or ratios of skinfolds to other measures such as height and/or weight in the study of metabolic diseases known to be associated with obesity.

5. endocrinological investigation be carried out to determine the connection between growth take-off in adiposity and onset of adrenal cortex activity at adrenarche.

6. the statement by Tanner that cartilage cells in the hips and shoulders respond differently to estrogens and androgens (Tanner, 1990, p.68) be tested by histological investigation. 163 7. a study be done to identify the best anthropometric indicator of gonadarche. As part of this study, the degree to which changes in biiliocristal breadth in girls and biacromial breadth in boys reflect hormonal changes should be determined.

8. more longitudinal studies be conducted with a focus on the relationship between adiposity and gonadarche. Both anthropometric and hormonal measurements must be involved.

9. a closer examination be made of the link between musculo-skeletal development and menarche, with a view to expanding current information on the physiological dynamics of human fecundity.

10. a nutritional study be done to determine whether negative nitrogen balance causes amenorrhea in women. APPENDIX 1. Abbreviations

A-dione androstenedione ANCOVA analysis of covariance ANOVA analysis of variance An/ adipose tissue volume BF body fat BlAC biacromial breadth BllL biiliocristal breadth CNS central nervous system COGRO The Coquitlam Growth Study cv coefficient of variation DHEA dehydroepiandrosterone DHEAS dehydroepiandrosterone sulfate El estro ne E2 estradiol FA0 Food and Agriculture Organization FSH follicle stimulating hormone LBW lean body weight LH luteinizing hormone LRF luteinizing hormone releasing factor MA age at menarche MRI magnetic resonance imaging NATV non-adipose tissue volume PA age at the onset of puberty SASK The Saskatchewan Growth and Development Study SEE standard error of the estimate TBW total body water TEM technical error of measurement APPENDIX 2. Description of Data Bases

1. The Coquitlam Growth Studv COGROL The COGRO study was a cross-sectional anthropometric investigation of children in five different schools in Coquitlam, British Columbia, carried out in the late 1970's. Some of the older subjects were university students of the same region. Although children of different ethnic origins were probably included, this sample is generally considered to be representative of Caucasian Canadian children. Over 1200 boys and girls ranging in age from 5 to 21 years were subjected to complete anthropometry according to the methods described in Ross and Marfell-Jones (1 991). The study has been previously described in Ross, Drinkwater, Whittingham and Faulkner (1980).

2. The lbadan Growth Studv (Ibadan) The lbadan Growth Study was a cross-sectional anthropometric investigation of Yoruba children in three different 'fee-paying' schools in Ibadan, Nigeria, carried out in the Fall of 1989 by myself and three Nigerian colleagues: Dr. Latif 0. Amusa (Head of Department), Dr. Ayo Agbonjinmi and Grace Akintunde - at the time, all were members of the Department of Health and Physical Education, University of Ibadan. As attendance at these schools required a fee, it was assumed that the children represented physical status of the middle- to upper-class. [This was an important assumption, because the purpose of the investigation at that time was to test a specific statistical technique by which healthy, population-specific anthropometric norms could be constructed quickly and at low cost.] Age categories were set such that a six-year-old was any child between decimal age 6.000 and 6.999 years. The age range was 6 to 11 years (see Table 3.1). The N of 9 for each age group resulted from a research design consisting of two phases: Phase 1. Measurement of weight and height of a stratified, random sample (N=522) selected from the fee-paying school system in Ibadan. Phase 2. Selection of highest, lowest and median ponderosity child (boys and girls considered separately) from each age category at each of three schools to ensure selection of the widest range of body types for complete anthropometric assessment. The Benn Index (Benn, 1971) was used in the calculation of ponderosity. Thus, the means used in this analysis, listed in Appendix 7, represent a pooling of anthropometric data from three highly ponderous children, three minimally ponderous children and three children each of whom had a ponderosity which represented the median value for the given age group at each of three schools (therefore, N=9). It should be emphasized that the N of 9 selected in this fashion is probably more representative of the true range of body types in the Yoruba population than would be an N of 9 selected randomly.

3. Thc) The SASK Growth Study consisted of a complete anthropometric and physiological protocol being applied to the same 123 boys at yearly intervals over a ten-year period (from 1964-1973) by Dr. D. A. Bailey and colleagues at the College of Physical Education, University of Saskatchewan. The anthropometry is described in Bailey (1968). There was a small group of girls included in the study at the outset, with more being added each year as boys dropped out. Therefore, while the SASK boys data represent a true, longitudinal assessment of growth, SASK girls data comprise a mixed- longitudinal array, with small subject numbers in the teen years. 4. The Kormend Growth Studv (Kormend 1168. 78. '881 The Kormend Growth Study represents some of the best secular trend data ever compiled. It is a series of cross-sectional growth studies on 3- to 18- year-old children in the small town of Kormend, Hungary carried out by Dr. Otto Eiben at ten-year intervals over a forty-year period: in 1958 (N=1656), 1968 (N=l736), 1978 (N=2420) and 1988 (N=2867). Detailed anthropometric measurements were taken using the techniques of the International Biological Program (IBP) (Weiner and Lourie, 1969). A description of the transformation of Kormend from an agricultural village into a 'strong industrialized town' from 1958 to 1978 is given in Eiben (1987). Virtually every child in this town within the age range given was measured. Hence, these data are completely representative of the physical changes that took place in Hungarian children of this particular region throughout the mid- to late-twentieth century. APPENDIX 3. Nomenclature for Anthropometric Abbreviations

As full variable names are often cumbersome to use on spreadsheets, variable abbreviation is inevitable in the handling of large data bases. It is critical, however, that abbreviations be unequivocal and carry as much information about the variable as possible so as to maximize understanding and minimize faulty interpretation. What follows is the system of abbreviation created by Linda Blade, using the basic nomenclature proposed by the classical anthropometrist, Rudolph Martin (1 928), to describe variables included in adipose tissue volume estimation for her thesis. The basic feature of this abbreviation system is a colon which separates aenerd variable categories and characteristics (on the left) from s~ecific anatomical entities, characteristics and locations (on the right). Since we read from left to right, the item to the left of the colon should serve to direct the mind to the appropriate category of variables being referred to by the abbreviation. Once a person is clear on whether the variable is a length, breadth, girth, etc., and the nature of the measurement (inspired, expired, etc.), the portion to the left of the abbreviation can be forgotten and the mind can, then, focus on the specifics.

Rule 1. The first capital letter in an abbreviation denotes the variable category. Variable categories and their abbreviations are: Weight (W), Height (H), Arm Span (SP), Lengths (L), Breadths (B), Girths (G) and Skinfolds (F)

Rule 2. A small letter preceeding the first capital letter (variable category) in an abbreviation denotes a quality of the variable. Qualities and their abbreviations include: free standing (fs), proportional (p), tensed or flexed (t), relaxed (r), corrected (c) middle or medial (m), inspired (in), expired (ex), maximum or maximal (max), minimum or minimal (min), recumbant (rec), sitting (s), front (f), transverse (tr) and anterior/posterior (ap)

Rule 3. The 'p' for 'proportional' takes precedence at the front of an abbreviation above all other variable category descriptors. e.g. proportional sitting height is psH:

Rule 4. A colon (:) separates the variable category from the specific anatomical entity being measured.

Rule 5. Capital letters to the right of the colon represent anatomical entities. Anatomical entities and their abbreviations are given below: Crown (CR), Rump (R), Chest (CH), Arm (A), Forearm (F), Thigh (T), Calf (CA), Wrist (WR), Waist (W), Head (H), Neck (N), Abdominal (AB), Gluteal (G),Humerus (HUM), Femur (FEM), Knee (KN) and Ankle (AN) S~ecialCase: P = projected from the floor to the given landmark

Rule 6. Lower-case letters to the right of the colon represent specific points along the anatomical entity. Transverse olane~ Skinfold sites at the level of ... triceps (tri) ... mesosternale (ms) su bscapular (ssc) ...epigastrale (eg) biceps (bi) ...omphalion (om) iliac crest (sic) ...abdominal (ab) supra spinale (sisp) Rule 7. Specifications of transverse planes that require more than landmark abbreviations shall employ brackets around the landmark, followed by a descriptor: at the level...... mid-way between the acromiale and radiale is (a-r)m ... mid-way between the trocanterion and tibiale laterale is (tro-ti)m ...mid-way between the inguinal fold and proximal patella (i-pa)m .. .proxi ma1 styloids is (sty)p ...distal sty loids is (sty)d

Rule 8. A dash (-) means "to" [as in, acromiale to radiale (a-r)] or denotes a subtraction [as in, projected acromiale minus projected radiale (Pa-Pr)].

Conclusion An appropriate conclusion to this comment is a break-down of what I perceive to be the advantages and disadvantages of this system. These are listed below. Advantages: - abbreviation structure is consistent - creating abbreviations for new variables (future considerations) is predictable - the constancy of rules governing abbreviations could make it easier to write a computer program to convert abbreviations to full variable names, thereby saving time when transfering summary data from spreadsheets to word applications Disadvantages: - some abbreviations are lengthy - requires memorization of rules List of Anthropometric Abbreviations

Mass Inferred from Weight Weight W: Proportional weight pw:

Heights Height H: Height, free standing fsH: Sitting height sH: Cervicale height H :Pce Supra sternale height H:Pss lliospinale height H :Pisp Trochanterion height H:Ptr Pubis Symphysion height H :Psy Gluteale height H:Pgu Leg, tibiale laterale to floor H:Ptl

Lengths Recumbant Length recL: Crown-Rump Length L:CR-R Trunk length, derived L:H-SH Upper limb length, direct acromiale to dactylion L:a-dac Upper limb length from projected measures of L: Pa-Pdac acromiale and dactylion Upper limb minus hand, direct acromiale L:a-sty to stylion

Upper limb minus hand, projected measures of L:Pa-Psty acromiale to stylion Arm Length, acromiale to radiale L:a- r Forearm Length, radiale to stylion L:r-sty Hand Length, stylion to dactylion L:sty-dac Hand Length, mid-stylion line to dactylion L:(sty-dac) m Hand Length, projected measures of stylion L:Psty-Pdac to dactylion Thigh Length, direct trochanterion to tibiale L:tro-tl laterale Thigh Length, projected measures of trochanterion L:Ptro-Ptl to tibiale laterale Thigh Length, derived from sitting height L:H-sH-Ptl Tibia, tibiale mediale to sphyrion tibiale L:tm-sph Foot length L:ak-pte

Breadths Biacromial breadth Transverse chest breadth at mesosternale level AP chest depth at mesosternale level Biiliocristal breadth Bispinale breadth Humerus breadth, biepicondylar Wrist breadth, bistyloid radiale and ulnare Hand bread, metacarpal I to V Femur breadth, bicondylar Foot width, metatarsal I to V

Girths Head girth Neck girth Chest girth at mesosternale level Waist girth, at visually narrowest about epig astrale level Abdominal girth at omphalion level Abdominal girth, maximal

Hip or Gluteal girth Arm girth, maximal flexed Arm girth, relaxed at the mid acromiale- radiale level Forearm girth, maximal, relaxed maxG:F Wrist girth, proximal styloids G :WR(sty )P Wrist girth, distal styloids G:WR(sty)d Thigh girth, 1 cm distal to gluteal line G:T Thigh girth at mid tro-ti level G :T(t ro-t I) m

Thigh girth at mid inguinal-proximal patella level Calf girth, maximal standing Ankle girth, minimal

Skinfold Thicknesses Triceps F3ri Subscapular F:ssc Biceps F:bi Iliac Crest, Suprailiacus cresta F:sic Supraspinale, or supra iliospinale F:sisp Abdominal FAB Front Thigh ff:T Medial Calf mF:CA APPENDIX 4. Age Summaries: all data bases

Table A4i. Girls summary of average age and standard deviation (SD) by age category for all data bases.

AGE COGRO lbadan SASK Korrnend Kormend Korrnend ' 6 8 '78 '88 SD SD SD SD ED SD 3 3.100 3.266 3.243 0.202 0.160 0.180 4 4.1 63 3.985 4.035 0.273 0.255 0.275 5 5.017 5.018 4.955 0.34 1 0.29 1 0.285 6 6.132 6.028 6.077 0.263 0.270 0.287 7 7.035 6.965 7.01 9 0.271 0.288 0.305 8 8.056 8.021 8.01 5 0.288 0.316 0.307 9 9.050 8.905 9.056 0.265 0.269 0.301 10 9.952 9.996 10.042 0.322 0.316 0.299 11 10.993 11 .O45 11.016 0.308 0.283 0.313 12 12.028 12.021 12.025 0.223 0.319 0.277 13 13.023 12.975 13.01 1 0.267 0.258 0.299 14 13.975 14.006 13.956 0.306 0.253 0.286 15 14.990 14.965 14.996 0.262 0.273 0.310 16 16.051 16.029 15.986 0.329 0.314 0.299 17 17.034 16.944 16.904 0.238 0.270 0.274 18 17.778 17.945 17.870 0.21 0 0.307 0.220 19

2 0

2 1 Table A4ii. Boys summary of average age and standard deviation (SD) by age category for all data bases.

AGE lbadan SASK Kormend Kormend Kormend '68 ' 7 8 '88 SD SD SD SD SD 3 3.231 3.300 3.234 0.156 0.145 0.176 4 3.977 3.987 3.953 0.335 0.287 0.301 5 5.068 5.021 4.960 0.294 0.262 0.299 6 6.572 6.067 5.993 6.084 0.290 0.301 0.280 0.263 7 7.587 7.086 6.998 7.032 6.996 0.395 0.259 0.300 0.274 0.275 8 8.599 8.021 7.990 8.001 8.033 0.258 0.283 0.270 0.255 0.300 9 9.800 9.045 8.982 8.977 8.980 0.31 1 0.280 0.271 0.286 0.298 10 10.639 10.046 10.072 10.028 10.002 0.254 0.273 0.312 0.283 0.294 11 11.493 11.O32 10.986 51.001 10.974 0.304 0.289 0.278 0.254 0.304 12 12.020 12.024 12.008 11.989 0.285 0.252 0.269 0.308 13 13.007 13.018 13.009 13.064 0.276 0.297 0.260 0.285 14 14.009 14.030 14.019 13.999 0.29 1 0.295 0.272 0,302 15 15.01 2 15.021 15.009 15.000 0.297 0.296 0.272 0.273 16 16.01 8 16.01 2 15.967 15.947 0.275 0.271 0.270 0.288 17 16.980 16.988 16.955 0.305 0.270 0.299 18 17.877 17.902 17.909 0.245 0.289 0.230 19

2 0

2 1 APPENDIX 5. Height Summaries: all data bases

Table A5i. Girls summary of average height and standard deviation (SD) by age category for all data bases.

AGE lbadan SASK Kormend Kormend Korrnend '68 '78 '88 a SD SD a ED 3 94.6 97.3 97.4 3.9 1 2.86 3.42 4 103.3 101.9 105.2 4.19 5.35 3.74 5 109.4 109.2 110.2 5.43 4.9 1 5.06 6 114.3 114.6 117.8 5.53 4.82 5.35 7 121.9 120.7 123.4 5.69 5.33 5.49 8 125.7 126.2 127.8 5.56 5.77 6.25 9 130.0 132.5 133.8 4.52 6.90 6.45 10 137.3 137.3 140.6 6.58 6.79 6.9 7 11 141.7 144.4 147.0 6.30 5.44 7.40 12 149.6 148.7 152.0 6.79 6.30 7.60 13 154.3 155.9 157.6 6.82 6.39 6.72 14 156.3 158.2 159.7 4.89 5.84 6.53 15 158.7 160.5 160.4 5.03 6.28 6.19 16 160.1 159.6 161.9 6.35 4.87 6.50 17 158.2 161.O 161.6 9.04 5.27 6.26 18 159.5 159.9 160.2 5.27 5.18 6.4 1 19

2 0

2 1 Table A5ii. Boys summary of average height and standard deviation (SD) by age category for all data bases.

AGE COGRO lbadan SASK Korrnend Korrnend Korrnend '68 SD 3 98.6 3.37 4 101.9 4.50 5 109.6 5.15 6 115.3 5.10 7 120.6 4.71 8 125.9 5.0 1 9 131.1 6.06 10 137.2 6.88 11 141.4 7.44 12 145.5 6.66 13 152.0 7.35 14 156.7 8.19 15 164.6 8.41 16 167.6 7.15 17 171.3 6.63 18 170.8 7.13 19

2 0

2 1 APPENDIX 6. ATV Summaries: The Coquitlam Growth Study (COGRO)

Table A6i. Means and standard deviations (SD) of regional and total AWs by age: COGRO girls.

AGE Arm ATV Calf ATV Thigh ATV Trunk ATV Tot ATV (mi) (mi) (mi) (mi) (mi) SD SD SD SD SD 6 206.2 150.7 724.7 743.4 1825.0 77.0 60.8 337.0 324.4 746.9 7 226.6 150.9 750.0 856.9 1984.4 108.5 70.9 339.1 544.5 1012.4 8 225.4 159.4 729.0 710.0 1823.8 76.0 79.8 393.7 222.2 698.6 9 278.3 198.8 984.3 961.5 2422.9 100.7 72.7 439.9 482.0 1049.2 10 332.5 282.1 1407.8 1536.9 3559.3 1 77.0 195.2 917.7 1078.0 2305.0 11 401.2 306.1 1599.2 1773.5 4079.9 163.3 157.4 692.6 1034.8 1997.1 12 407.6 360.0 1759.8 1933.4 4460.9 175.9 147.5 851.0 1005.0 2082.9 13 428.7 364.0 1712.7 2309.9 4814.9 204.2 148.7 744.2 1497.2 2445.1 14 506.2 420.9 1993.1 2665.1 5588.2 201.9 178.7 775.3 1449.7 2465.1 15 530.8 433.3 2140.8 2621 .O 5725.9 193.9 168.4 688.9 1227.0 2126.9 16 522.7 433.2 2125.5 2555.5 5551 .O 207.9 188.7 741.3 1196.5 2039.3 17 589.8 472.2 2337.9 2566.6 5966.5 181.0 187.2 8 77.1 969.5 1985.1 18 684.1 512.8 2641.5 3149.8 6988.3 268.8 187.8 839.7 1401.9 2503.3 19 650.3 474.4 2492.8 2734.9 6352.4 190.6 196.5 848.7 958.3 1801.5 2 0 571.5 409.1 2383.3 2513.5 5877.5 136.9 113.8 690.1 765.7 154 7.2 2 1 61 8.7 376.7 2102.3 2456.7 5554.3 157.9 90.8 525.2 896.7 1474.0 Table A6ii. Means and standard deviations (SD) of regional and total ANs by age: COGRO boys.

AGE Arm ATV Calf ATV Thigh ATV Trunk Total ATV (mi) (mi) (mi) ATV(ml) (mi) SD SD SD 6 191.1 133.4 673.2 61.7 45.4 287.9 7 198.5 150.1 644.4 47.0 51 .O 253.5 8 230.3 165.8 761.O 108.2 84.0 498.4 9 21 9.3 176.3 806.7 102.8 98.4 507.7 10 254.9 208.1 1054.6 137.4 121.0 61 7.4 11 271.7 232.6 1037.8 124.1 11 1.1 425.3 12 410.6 337.2 1500.9 271.0 249.7 1052.8 13 388.4 318.9 1315.9 243.7 170.3 684.6 14 357.6 315.1 1264.7 173.9 151.2 636.0 15 388.0 323.2 1314.0 223.6 187.5 730.8 16 381.3 326.8 1275.8 174.2 184.3 752.9 17 436.4 31 1.9 1240.9 286.4 184.3 688.3 18 443.7 297.7 1304.6 135.3 108.7 530.5 19 452.4 279.4 1234.9 192.5 132.0 543.9 2 0 482.9 293.0 1361.7 251.2 164.4 723.6 2 1 51 0.0 276.0 1416.5 160.5 104.3 397.1 APPENDIX 7. ATV Summaries: the lbadan Growth Study

Table A7i. Means and standard deviations (SD) of regional and total ATVs by age: lbadan girls.

AGE N Arm ATV Calf ATV Thigh ATV Trunk ATV Total ATV (mi) (mi) (mi) (ml) (m1) SD SD SD SD SD 95.8 362.7 510.7 1074.1 35.7 150.8 149.3 366.8 127.9 451.4 563.9 1283.4 58.1 224.1 185.6 512.2 166.4 725.7 880.3 1965.8 69.0 348.9 531.3 987.9 171.5 776.9 747.8 1863.1 67.3 371.9 130.0 584.6 176.8 730.0 891.3 1974.0 57.2 362.5 442.8 924.3 282.5 1111.0 1295.0 2941 .O 1 77.2 681.9 641.6 1598.4

Table A7ii. Means and standard deviations (SD) of regional and total ATVs by age: lbadan boys.

AGE Arm ATV Ca If ATV Thigh ATV Trunk ATV Total ATV (mi) (ml) (mi) (m 1) (ml) SD SD SD SD 6.5 93.7 92.2 332.5 465.8 984.1 32.4 45.1 170.7 94.8 324.1 7.5 96.7 96.4 31 5.4 435.3 943.7 36.4 44.5 140.9 99.1 306.1 8.5 115.6 92.9 328.8 444.3 981.6 27.7 31.4 93.1 87.1 200.3 9.5 105.4 107.0 352.3 520.5 1085.1 23.7 28.9 9 7.3 99.3 213.3 10.5 11 4.5 117.2 362.2 558.2 1152.1 42.8 76.3 157.4 145.7 3 79.5 11.5 134.0 124.4 475.0 630.5 1363.8 34.9 51.7 207.3 130.6 361.2 APPENDIX 8. ATV Summaries: The Saskatchewan Growth and Development Study (SASK)

Table A8i. Means and standard deviations (SD) of regional and total ATVs by age: SASK girls.

AGE Arm ATV Thigh ATV Trunk ATV Total ATV (mi) (mi) (mi) (ml) SD SD SD SD 193.0 653.7 632.3 1480.8 71.5 245.0 259.4 541.7 217.6 731.1 778.6 1734.5 84.4 280.3 436.4 741.3 250.4 867.3 908.9 2037.6 99.9 312.6 471.4 839.6 28 8.3 1022.0 2435.4 123.7 413.9 1179.7 324.2 11 67.5 2906.3 131.8 460.5 1444.9 344.0 1268.3 3170.4 152.9 455.3 1597.9 387.2 1357.1 3517.1 155.0 41 1.4 1336.3 4407.2 1921.6 3913.9 1449.2 Table A8ii. Means and standard deviations (SD) of regional and total ANs by age: SASK boys.

AGE N Arm ATV Thigh ATV Trunk ATV Total ATV (mi) ( m1) (mi) (mi) m SD m SD 7 103 138.7 413.9 572.2 1124.0 40.3 158.4 185.7 350.9 8 120 160.9 531.9 624.2 1317.0 60.6 242.6 242.1 508.4 9 121 194.9 643.3 764.4 1604.4 81.7 291.5 391.6 71 0.9 10 119 219.1 767.2 829.3 1815.6 97.1 415.9 461.6 934.9 11 122 270.5 858.4 1057.0 2185.8 123.0 471.3 715.1 1242.2 12 120 327.9 994.8 1345.2 2667.8 161.3 4 70.2 9 72.5 1549.2 13 117 303.1 965.5 1411.1 2664.9 146.9 437.1 881.9 1382.2 14 119 335.4 1037.6 1615.8 2991.5 169.8 497.5 984.6 1586.6 15 114 365.8 1093.6 1942.3 3401.7 169.3 505.8 1203.2 1810.6 16 117 360.0 1078.5 2017.0 3455.5 1 92.0 490.0 1228.1 1818.3 APPENDIX 9. ATV Summaries: The Kormend Growth Study, 1968

Table A9. Means and standard deviations (SD) of regional and total AlVs by age: Kormend '68 girls and boys. GI RLS UPP Tr unk UPP Tr unk Tat al Extremity ATV(ml) ktrernity AN( ml) ATV ( ml) ATV ( ml) AN( ml) SD 706.6 221 -1 604.2 174.6 61 2.2 138.7 6 67.9 2042 692.4 273.8 823.6 3343 815.0 271 .1 943.2 3459 1 21 7.6 5453 1182.5 4803 1458.1 715.1 1580.8 5273 1720.9 594.9 1981.5 626.1 2224.8 728.8 21 87.2 539.7 APPENDIX 10. ATV Summaries: The Kormend Growth Study, 1978

Table A1 Oi. Means and standard deviations (SD) of regional and total ATVs by age: Kormend '78 girls.

AGE Upper Lower Trunk ATV Total ATV Extremity Extremity (ml) (mi) ATV (ml) ATV (ml) SD SJ m SD 3 267.7 598.5 474.9 742.6 69.5 175.1 2 13.2 271.1 4 266.6 640.4 479.6 744.8 73.8 156.3 158.9 215.6 5 293.1 740.3 551.6 842.7 79.7 243.3 195.3 256.5 6 31 4.1 798.5 638.8 957.5 110.1 302.0 3 14.6 410.4 7 362.6 955.3 776.9 1135.6 182.7 51 6.5 650.4 822.7 8 358.9 1049.9 796.2 1123.9 168.3 497.6 582.6 727.8 9 470.3 1346.0 1107.1 1566.4 193.9 648.0 709.1 878.6 10 503.1 1392.4 1200.5 1703.4 210.7 618.0 653.6 832.7 11 569.2 1666.7 1507.7 2088.0 280.8 708.6 1008.0 1264.5 12 649.1 1969.5 1999.3 2668.8 386.0 1034.3 1456.6 1804.8 13 722.1 2184.7 2194.5 2914.6

385.4 949.9 ' 1281.5 1631.1 14 822.2 2385.3 2651.8 3486.6 408.4 923.8 1382.0 1 756.3 15 874.8 261 4.4 2778.3 3692.9 348.8 1023.6 1221.0 1493.6 16 1020.3 2758.7 3076.5 4096.8 41 1.6 926.4 1566.0 1914.6 17 1052.5 3054.0 3462.1 4533.1 413.8 1102.8 1560.3 1912.9 18 880.9 2761.4 2880.6 3761.4 348.0 961.5 1039.0 1315.7 *Total ATV only includes Upper Extremity and Trunk ATVs in keeping with Kormend 1968 data.

185 Table A1 Oii. Means and standard deviations (SD) of regional and total ANs by age: Kormend '78 boys.

AGE Upper Lower Trunk ATV Total ATV Extremity Extremity (ml) (m1) ATV (ml) ATV (ml) m ED 3 393.6 656.8 86.8 144.5 4 421.4 671 .O 150.6 207.4 5 445.6 712.9 164.1 212.9 6 525.2 794.1 251.0 331.4 7 531.3 811.1 338.4 460.5 8 749.2 1085.8 727.2 914.5 9 957.6 1368.6 898.2 1093.9 10 1131.2 1550.8 1031.1 1261.1 11 1277.9 1776.0 1161.0 1481.5 12 1431.9 1980.6 1235.5 1555.8 13 1625.1 2207.6 1487.3 1 843.5 14 1902.0 2536.8

' 1463.8 1844.7 15 1795.3 2371.3 932.6 1136.9 16 2181.2 2786.7 1319.8 1592.3 17 2127.3 2717.8 1323.1 1661.1 18 2607.3 3234.9 1379.1 1630.5

*Total ANonly includes Upper Extremity and Trunk ATVs in keeping with Kormend 1968 data. APPENDIX 11. ANSummaries: The Kormend Growth Study, 1988

Table A1 1 i. Means and standard deviations (SD) of regional and total ANs by age: Kormend '88 girls.

AGE Upper Lower Trunk ATV Total ATV Extremity Extremity (mi) (ml) ATV (ml) ATV (ml) SD m SD 3 278.3 577.6 894.4 68.5 164.9 239.0 4 385.8 841 -0 1170.4 98.7 285.5 429.9 5 403.3 841 .O 1295.1 152.8 339.3 71 9.6 6 458.1 946.5 1452.7 1 72.8 425.9 642.5 7 529.2 11 19.0 1716.0 204.5 498.1 830.9 8 579.6 1345.9 1989.4 242.7 636.3 1 055.2 9 677.0 1527.0 2284.1 279.6 612.1 1250.9 10 820.2 1953.7 2844.9 361.3 903.9 1557.6 11 908.2 221 2.8 3330.5 392.0 1091.9 1657.1 12 964.9 2467.4 3742.5 4 95.0 1249.8 21 62.4 13 1049.8 2750.3 4034.5 494.3 1409.7 20 18.4 14 1145.4 3 0 0 7.8 4708.2 423.9 1284.6 191 1.8 15 1280.3 3346.0 5440.3 573.9 1629.8 2295.3 16 1306.1 3475.9 5909.3 541.1 1440.4 2064.9 17 1185.9 31 23.1 5413.4 379.7 1107.4 1586.3 18 1223.8 3319.5 5606.2 508.7 1419.9 2076.7

*Total ATV only includes Upper Extremity and Trunk ATVs in keeping with Kormend 1968 data. Table A1 1ii. Means and standard deviations (SD) of regional and total ANs by age: Kormend '88 boys.

AGE Upper Lower Trunk ATV Total ATV Extremity Extremity (ml) (mi) ATV (ml) ATV (ml) SD SD SD 37 3 372.3 644.2 664.4 1104.7 92.0 233.7 243.4 338.4 4 359.0 619.8 670.6 1025.8 138.8 242.0 305.3 471.9 5 370.9 671 .O 656.6 1036.5 101.0 222.0 235.5 343.6 6 406.0 737.9 768.4 1221.9 140.8 242.9 323.2 512.1 7 446.9 930.3 1004.5 1489.4 215.3 460.3 617.3 878.5 8 539.0 1107.7 1084.8 1707.7 244.7 542.1 603.9 902.4 9 645.2 1288.6 1345.1 1992.0 348.3 707.3 1021.9 1304.0 10 689.8 1386.7 1524.2 2304.8 351.4 808.7 1183.4 1566.5 11 810.3 1736.4 1897.6 2746.9 41 1.4 1108.9 1561.1 1700.9 12 91 5.2 20 9 8.5 2427.7 3306.2 473.0 1393.9 1768.5 1831.4 13 845.4 1943.5 2155.2 3067.5 427.8 1143.5 1536.1 1643.6 14 929.1 21 03.7 2538.9 3407.9 449.0 1115.8 1408.4 1462.9 15 1004.3 2230.8 3095.5 4149.5 477.5 1151.9 2092.1 2397.7 16 1065.5 2284.1 3366.1 4429.4 525.8 1098.9 2020.1 2209.5 17 1040.4 2142.5 3371.4 4644.3 552.9 1062.5 1647.1 2202.2 18 990.1 2022.9 3854.2 4854.9 433.2 1035.1 1604.1 1931.2

*Total ATV only includes Upper Extremity and Trunk ATVs in keeping with Kormend 1968 data. APPENDIX 12. Growth Curves of Regional Variables: The lbadan Growth Study. E 55 gk:" Girls -$45

654 THIGH: / lbadan Girls /

~5-TRUNK: E 55- lbadan Girls -$45- s 35- 0 25- Y0 2 15- 5 5- V) (a -5 I I t I 1 6.5 7.5 8.5 95 105 115 A* wars)

Figure A12i. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm (a), calf (b), thigh (c) and trunk (d): lbadan Girls. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. THIGH: Et lbadan Boys /

Figure A12ii. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm (a), calf (b), thigh (c) and trunk (d): lbadan Boys. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. APPENDIX 13. Growth Curves of Regional Variables: The Saskatchewan Growth and Development Study (SASK). SASK Girls

_ 70 THIGH: SASK GWIS

-08 E 50

-10 I , I I I I I I1 7 8 9 10 11 12 13 14 15 Age (years)

TRUNK: SASK Girls

-10 1 I I I I I I I I1 7 8 9 10 11 12 13 14 15 Age (years)

Figure A13i. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the arm (a), thigh (b) and trunk (c): SASK Girls. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)lfinal value) x 1001. Standardized Growth lndex (%) Standardized Growth lndex (%) Standardized Growth lndex (%) oo~gg$ulQ)-JQ)4 A -h)WPVIm.J 0000 000000000 111111III, I APPENDIX 14. Growth Curves of Regional Variables: The Kormend Growth Study, 1968. 100- - Upper Extremfty: - 80- KormendV68Girls uV S 60-

+-4. +-+

U

(a) -20 1111111111111111 mwwwbarn~=~g~~$k~ Age (years) 100, TRUNK: Kormend'68 Girls

Age (years)

Figure A1 4i. Growth of segmental An/, length (L), girth (G) and skinfold (SF) of the upper extremity (a), and trunk (b): Kormend '68 Girls. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. Figure A1 4ii. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the upper extremity (a), and trunk (b): Kormend '68 Boys. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. APPENDIX 15. Growth Curves of Regional Variables: The Kormend Growth Study, 1978. Upper Extremity: Kormend'78 Girls

Lower Extremity: Kormend'78 Girls r

100- - TRUNK: Kormend878Girls V '0 S 60-

(a -20 , , , , , , , , , , , , , , , COWmWbam~rtUmP~Wbm .-.-77777.- Age (years) Figure A1 5i. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the upper extremity (a), lower extremity (b) and trunk (c): Kormend '78 Girls. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. Upper Extremity:

Lower Extremity: ;s 80 1 Kormend78 Boys u S 60

TRUNK: Kormend78 Boys

Figure A15ii Growth of segmental ATV, length (L), girth (G) and skinfold (SF) of the upper extremity (a), lower extremity (b) and trunk (c): Kormend '78 Boys. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. APPENDIX 16. Growth Curves of Regional Variables: The Kormend Growth Study, 1988. Upper Extremity: Kormend'88 Girls fC

Lower Extremity: Kormend'88 Girls

- 90- TRUNK:Kormend'88 Girls -$ 3 70- 2

'0

m

Figure A16i. Growth of segmental ATV, length (L), girth (G) and skinfold (SF) of the upper extremity (a), lower extremity (b) and trunk (c): Kormend '88 Girls. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. Upper Extremity: Kormend'88 Boys /'

W1 Lower Extremity: -g so- Kormend188Boys x

-40 f , , , , , , , , , , , , , , , 1 m*tnlDba"$=$c~~$~z Age (years)

Figure A16ii. Growth of segmental AN, length (L), girth (G) and skinfold (SF) of the upper extremity (a), lower extremity (b) and trunk (c): Kormend '88 Boys. Percentage of growth is expressed as the standardized growth index, which is determined in the following way; [((value of the variable - initial value)/final value) x 1001. APPENDIX 17. Skinfold Summaries: The Coquitlam Growth Study (COGO)

Table A17i. Means and standard deviations (SD) of regional and total skinfolds by age: COGRO girls.

AGE Arm SF Calf SF Thigh SF Trunk SF Total SF SD SD SD SD m 6 11.5 10.2 17.9 6.6 4 6.2 3.2 3.4 7.3 2.5 15.6 7 11.8 9.4 16.9 7.4 45.5 4.4 3.7 6.3 4.0 17.3 8 11.2 9.2 16.0 5.9 42.3 2.7 3.9 6.5 1.6 13.0 9 12.5 10.4 18.7 7.2 48.9 3.4 3.0 6.7 2.8 14.5 10 12.5 12.5 22.2 9.8 57.0 4.6 6.4 10.3 5.2 25.6 11 14.3 12.9 23.5 11.1 61.8 4.2 5.4 8.2 5.1 21.8 12 13.4 14.2 23.6 11.2 62.5 4.6 4.8 9.2 5.0 21.7 13 13.0 13.2 21.4 12.3 60.0 4.8 4.8 7.8 6.7 21.9 14 14.6 14.8 23.2 13.6 66.2 4.8 5.6 7.6 6.2 22.4 15 15.1 15.2 24.7 13.3 68.3 4.7 5.3 7.3 5.6 20.8 16 14.5 15.0 24.3 13.1 66.6 4.4 5.9 7.2 5.6 21.0 17 16.3 16.4 25.9 12.5 71.2 4.6 5.4 7.5 4.2 19.0 18 18.4 17.7 28.7 14.5 79.3 6.5 6.9 9.2 5.4 23.8 19 18.1 16.7 27.5 12.9 75.2 5.3 7.1 8.8 4.3 20.6 2 0 16.3 14.5 26.9 11.8 69.6 4.3 4.0 7.7 3.5 17.2 2 1 16.2 12.7 23.1 11.2 63.1 3.8 2.8 5.2 3.9 12.9 Table A1 7ii. Means and standard deviations (SD) of regional and total skinfolds by age: COGRO boys.

AGE Arm SF Calf SF Thigh SF Trunk SF Total SF SD SD SD 6 9.5 8.3 12.9 2.0 2.0 4.8 7 10.4 9.4 15.2 2.2 2.8 4.7 8 10.4 9.1 15.3 3.4 3.9 7.9 9 9.8 9.1 15.2 3.2 4.1 6.9 10 9.9 9.7 17.7 3.6 4.4 7.9 11 10.0 10.0 17.0 3.4 3.6 5.8 12 13.2 13.5 21.5 7.2 8.5 12.3 13 11.6 11.2 16.4 6.2 5.6 7.6 14 10.0 10.5 14.6 4.4 4.6 6.3 15 9.6 10.4 14.5 4.6 5.3 7.6 16 8.9 10.0 13.1 3.8 5.5 7.3 17 9.5 9.5 12.1 5.2 5.0 5.7 18 9.3 8.6 12.4 2.5 2.9 4.2 19 9.6 8.2 12.4 3.9 3.8 5.4 2 0 10.1 8.7 13.5 4.8 4.5 6.5 2 1 10.6 8.0 14.3 3.2 3.1 4.7 APPENDIX 18. Skinfold Summaries: The lbadan Growth Study

Table A18i. Means and standard deviations (SD) of regional and total skinfolds by age: lbadan girls.

AGE N Arm SF Calf SF Thigh SF Trunk SF Total SF SD tz' SD SD ED 6 9 6.3 6.6 8.9 4.7 26.5 1.8 2.0 3.0 1.2 7.7 7 9 7.4 7.3 9.4 4.9 29.0 2.9 2.0 3.1 1.5 8.6 8 9 9.1 8.6 14.1 7.0 38.8 3.1 2.9 5.7 3.9 14.3 9 9 7.8 8.6 14.4 6.0 36.8 2.0 2.6 5.5 0.9 9.7 10 9 7.7 8.6 12.8 6.6 35.6 2.5 2.2 4.9 2.5 11.3 11 9 9.3 11.6 16.2 9.1 46.2 3.5 6.1 8.6 5.2 22.8

Table A18ii. Means and standard deviations (SD) of regional and total skinfolds by age: lbadan boys.

AGE N Arm SF Calf SF Thigh SF Trunk SF Total SF SD ED ED SD SD 6 9 5.3 5.9 7.3 4.5 23.0 1.5 2.5 2.5 1.0 7.1 7 9 5.4 5.9 7.5 4.0 22.9 1.4 2.3 2.5 0.6 6.6 8 9 6.2 5.3 7.5 4.2 23.2 1.3 1.2 1.6 0.7 3.8 9 9 4.9 5.4 6.8 4.4 21.6 1.0 1.4 1.7 0.8 4.2 10 9 5.1 5.4 6.6 4.5 21.6 1.4 2.2 2.1 1.1 6.1 11 9 5.9 5.8 8.2 5.0 24.9 1.6 2.0 3.3 1.0 6.6 APPENDIX 19. Skinfold Summaries: The Saskatchewan Growth and Development Study (SASK)

Table A19i. Means and standard deviations (SD) of regional and total skinfolds by age: SASK girls.

AGE Arm SF Thigh SF Trunk SF Total SF SD SD ED sl 7 10.0 15.1 5.7 30.9 2.8 4.6 1.9 8.7 8 10.2 15.3 6.4 31.9 3.0 5.0 2.8 9.9 9 10.6 16.1 7.0 33.7 3.2 4.6 3.0 9.9 10 11.2 17.2 8.3 36.7 3.6 5.4 4.7 12.6 11 11.7 17.8 9.5 3 9.0 3.6 5.5 5.1 13.4 12 11.7 18.0 10.0 39.7 3.7 4.9 4.9 12.5 13 11.8 18.0 10.7 40.5 3.8 4.4 4.2 11.5 14 12.5 21.4 12.0 45.9 4.8 6.6 6.6 16.7 15 12.1 18.9 10.3 41.3 4.1 4.8 4.5 12.4 Table A1 9ii. Means and standard deviations (SD) of regional and total skinfolds by age: SASK Boys.

AGE Arm SF Thigh SF Trunk SF Total SF SD SD a SD 7 8.0 10.3 4.8 23.1 1.9 3.5 1.3 5.9 8 7.9 11.6 4.8 24.3 2.3 4.6 1.6 7.8 9 8.6 12.5 5.5 26.6 2.7 4.8 2.3 8.9 10 8.9 13.5 5.6 28.0 3.0 6.3 2.6 11.3 11 9.8 13.6 6.7 30.1 3.3 6.5 3.9 12.8 12 11.0 14.4 8.0 33.3 4.1 5.6 5.1 14.0 13 9.3 12.7 7.9 29.9 3.5 4.8 4.2 11.6 14 9.4 12.3 8.1 29.7 3.7 4.9 4.0 11.8 15 9.2 11.8 8.8 29.9 3.5 4.7 4.5 11.9 16 8.4 11.3 8.5 28.2 3.6 4.5 4.3 11.5 APPENDIX 20. Skinfold Summaries: The Kormend Growth Study, 1968

Table A20i. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '68 girls.

AGE Arm SF Trunk SF Total SF SD SD SD 3 7.9 6.9 14.9 1.8 1.6 3.1 4 7.9 7.5 15.4 1.2 1.9 2.7 5 7.2 6.6 13.8 1 .o 1.7 2.3 6 6.9 6.8 13.8 1.5 2.5 3.7 7 6.9 6.3 13.2 1.5 1.7 3.0 8 7.4 7.9 15.3 1.7 2.9 4.3 9 7.5 7.8 15.3 2.0 2.4 4.2 10 8.2 9.3 17.5 2.4 2.8 4.8 11 8.9 9.8 18.8 3.7 3.9 6.6 12 8.1 10.3 18.4 1.8 2.8 4.4 13 8.9 12.3 21 .I 2.7 4.4 6.9 14 9.4 14.4 23.8 2.8 4.6 6.9 15 11.4 18.1 29.5 3.0 5.6 8.0 16 10.9 17.8 28.7 3.4 3.9 6.8 17 10.4 16.8 27.3 2.9 4.5 6.8 18 11.5 19.7 31.2 2.8 3.9 5.4 Table A20ii. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '68 boys.

AGE Arm SF Trunk SF Total SF Ev SD SD 3 8.1 6.8 15.1 1.4 2.2 3.4 4 7.4 5.6 13.0 1.3 1.5 2.6 5 6.5 5.2 11.7 1.0 1.2 1.8 6 6.5 5.4 11.9 1.3 1.3 2.4 7 5.9 5.4 11.3 1.3 2.6 3.5 8 6.2 6.0 12.2 1.6 2.3 3.8 9 6.0 5.5 11.4 2.3 1.8 3.4 10 6.0 5.9 12.0 1.8 1.9 3.5 11 6.7 7.1 13.8 2.0 2.8 4.6 12 5.9 6.7 12.6 1.7 2.3 3.6 13 6.4 7.5 13.8 2.3 3.0 5.1 14 6.0 7.7 13.7 1.6 2.2 3.5 15 5.5 7.7 13.2 1.3 2.1 3.1 16 5.7 8.3 14.0 1.5 2.0 3.3 17 5.5 9.0 14.5 1.3 2.6 3.7 18 5.4 8.8 14.2 1.3 2.1 3.1 APPENDIX 21. Skinfold Summaries: The Kormend Growth Study, 1978

Table A21 i. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '78 girls.

AGE Upper Lower Extremity Extremity Trunk SF Total SF

SD

3 17.7 4.3 4 16.7 4.0 5 17.1 4.2 6 17.2 5.3 7 18.0 8.6 8 17.4 8.3 9 2 0.7 9.0 10 21.1 8.5 11 22.2 10.2 12 25.3 13.0 13 25.8 11.4 14 28.3 10.9 15 29.4 10.1 16 32.6 11.4 17 34.1 11.0 18 29.8 9.1 Table A21 ii. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '78 boys.

AGE N Upper Lower Extremity Extremity Trunk SF Total SF SF SF APPENDIX 22. Skinfold Summaries: The Kormend Growth Study, 1988

Table A22i. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '88 girls.

AGE N Upper Lower Extremity Extremity Trunk SF Total SF SF SF

- -'\ i SD SD SD Table A22i. Means and standard deviations (SD) of regional and total skinfolds by age: Kormend '88 girls.

AGE Upper Lower Extremity Extremity Trunk SF Total SF SF a m

3 9.5 23.3 3.2 5.4 4 9.1 20.6 3.1 6.1 5 8.4 19.4 2.8 5.2 6 8.7 19.5 3.6 6.6 7 10.5 21.5 5.7 9.9 8 10.8 23.0 5.2 9.5 9 12.5 26.3 7.7 13.5 10 12.8 26.0 8.1 12.8 11 15.2 30.0 9.8 14.9 12 17.2 32.5 10.5 16.1 13 14.2 26.7 8.1 13.0 14 15.1 27.5 7.1 11.9 15 16.5 28.8 8.9 13.3 16 17.0 29.1 9.1 13.5 17 16.6 28.0 7.3 12.2 18 18.6 29.0 7.3 10.2 APPENDIX 23. Scatter Plots of Arm Tissue Volumes versus PA: SASK Children SASK Girls 01

-0.3 .-= -0.4 Multiple R = .211 . .-= p = ,150 -1 -0.6

PA (years)

PA (years)

I

Z Multiple R = .335 2 -0.35 = = = SEE = .0979

Figure A23i. Scatterplots of PA versus transformed tissue volumes, Log Arm AW (a), Log %Arm An/ (b) and Log Arm NATV (c) in SASK girls with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. SASK Boys

(a) -1.2 I I I I I I I 8 9 10 11 12 13 14 15 PA (years) 2- 1.9 - 1.8 - 1.7- 5 1.6- E a 1.5- Multiple R = .213 8-1.4- SEE = ,101 F = 5.412 9 1.3, p = .0221 1.2, I - y=-.020~+1.65 I - '-'- (b) 1 I I I I I I i 8 9 10 11 12 13 14 15 PA (years)

Multiple R = .522 SEE = .0895 F = 35.94 p = 3.57E-08 yz.046~-.670

PA (years)

Figure A23ii. Scatterplots of PA versus transformed tissue volumes, Log Arm ATV (a), Log %Arm ATV (b) and Log Arm NATV (c) in SASK boys with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 24. Scatter Plots of Trunk Tissue Volumes versus PA: SASK Children SASK Girls

. . Multiple R = .221 -= . - p= .I32 I I -.-

2 1.1 I Multiple R = .I55 p .294 I = CI) I I I I 5 0.8 --

OS- 9

0.5 (b)I I I I I I I I i eeqmy,oq=ygq w 0, 0 -F r! PA (years) 1.5

1.3

Multiple R = .272 p = -0614

O"- (c) 0.5 I I I I I I I 11 wL"my= g=*gz aD 0, F F F F PA (years)

Figure A24i. Scatterplots of PA versus transformed tissue volumes, Log Trunk ATV (a), Log %Trunk AN(b) and Log Trunk NATV (c) in SASK girls with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. SASK Boys

Multiple R = .I84 p = .069

-0.4 - (a) -0.6 I I I I I I 1 8 9 10 11 12 13 14 15 PA (years) 1.3- 1.2- 1.1 - . . . ez 1- Yc 0.9- .= I -= Multiple R .0006 t -. . r -. = 0.8- = .: = p .995 c, ..I. - = . = ' .* +=:. =. - 0.7- . = 0- # a==*.==-. +:. 0.6 - . = . I. = .I -

PA (years)

> 1.45- . C 3 1.35- z 5 1.25- Multiple R = .559 F_i.is- F = 43.53 3 1.05- p = 2.28E-09 0.95, y=.032x+.842 0e8=- (c) 0.75 I I I I I I I 8 9 10 11 12 13 14 15 PA (years)

Figure A24ii. Scatterplots of PA versus transformed tissue volumes, Log Trunk ATV (a), Log %Trunk ATV (b) and Log Trunk NATV (c) in SASK boys with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 25. Scatter Plots of Thigh Tissue Volumes versus PA: SASK Children SASK Glrls

Multiple R = .I98 p = ,177

PA (years) *l

Multiple R = .431 E SEE = .0784 F = 10.470 3 0.3 p = .00225

PA (years)

Figure A25 Scatterplots of PA versus transformed tissue volumes, Log Thigh ATV (a), Log %Thigh ATV (b) and Log Thigh NAN(c) in SASK girls with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. SASK Boys

-0.6 I (a) . . , I I I I I I i 8 9 10 11 12 13 14 15 PA (years)

51.3 E Multiple R = .I67 1.2 I . SEE .I16 = .= =' = r $1 .I .= F = 2.7601

O'- O'- (b) 0.8 I I I I I I i 8 9 10 11 12 13 14 15 PA (years)

.- Multiple R = .577 SEE = .077 = . F = 48.00 D = 4.87E-10

0 I I I I I I I 8 9 10 11 12 13 14 15 PA (years)

Figure A25ii. Scatterplots of PA versus transformed tissue volumes, Log Thigh ATV (a), Log %Thigh ATV (b) and Log Thigh NATV (c) in SASK boys with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 26. Scatter Plots of Arm Tissue Volumes versus MA: SASK Girls

Multiple R = .0562 I p= .814 I. - - .

l-l - 1 (b) I I I I I I I I I =~=~g"-?-"$?~"e F .r .r F .- MA (years) 1

Multiple R = .431 .I . - .- p = .0575

MA (years)

Figure A26. Scatter plots of MA versus arm volumes (ml), AN(a), %AN (b) and NATV (c) in SASK girls, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 27. Scatter Plots of Trunk Tissue Volumes versus MA: SASK Girls

-- ,, . - I I - , , - Multiple R = .0434 p .856

. MA (years) 1.5,

.I . Multiple R = ,0337 p = .888

. MA (years)

1.6

. Multiple R = .0586 --.= :Om . p = .806

MA (years)

Figure A27. Scatter plots of MA versus trunk volumes (ml), An/ (a), %ATV (b) and NATV (c) in SASK girls, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 28. Scatter Plots of Thigh Tissue Volumes versus MA: SASK Girls

Multiple R = .I66 p = .484

- --9. . - -- Multiple R = .0122 I p = .959

= .-. :- I. - Multiple R = .323

Figure A28. Scatter plots of MA versus thigh volumes (ml), ATV (a), %AN (b) and NAN(c) in SASK girls, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 29. Scatter Plots of Change in Arm Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls

I I I A- E 100- I Y I

z D I a I 0- .-C a Multiple R .422 W r p = .I33 r" -100- 0

PA-MA Interval (years) 500 I 450 4 I

Multiple R = SEE = 87.3 F = 11.288 p = .00567

PA-MA Interval (years)

Figure A29. Changes in arm An/ (a) and arm NAN(b) volumes (ml) over the time interval from PA to MA, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 30. Scatter Plots of Change in Trunk Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls

Multiple R = ,536 SEE = 684.9 F = 4.842

PA-MA Interval (years)

. . I . Multiple R = .473 p = .0876

(b) 0 I I I I I i 0 0:s 1.5 2 2.5 3 3.5 4 PA-MA Interval (years)

Figure A30. Changes in trunk AN(a) and trunk NAN(b) volumes (ml) over the time interval from PA to MA, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 31. Scatter Plots of Change in Thigh Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls

800, I

Multiple R = SEE = 271.3

- - I I I I I I I i 0 0:5 1 1.5 2 2.5 3 3.5 4 PA-MA Interval (years)

I

$2000- I Y E 1500- C EW .-c 1000- a Multiple R = .877 W SEE 271.5 E = 2 500- F = 39.842 O p = 3.877E-05 y=441 .Ox+255.1

0 (b) 1 I I 1 i 0 0 1.k 2 2.5 3 3.5 4 PA-MA Interval (years)

Figure A31. Changes in thigh ATV (a) and thigh NAN(b) volumes (ml) over the time interval from PA to MA, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 32. Scatter Plots of Growth Velocity of Arm Tissue Volumes versus the PA-to-MA Time interval: SASK Girls

s?AL E Y 100- a aE m C 0 0- I )r .-C 0 0 Multiple R = .I41 - p = .631 >" -100- C 3i 2 (3 (a) -200 I I I I 1 I I 1 0 0.5 1 1.5 2 2.5 3 3.5 4 PA-MA Interval (years) 2501

m m Multiple R = .374 looi I p = .I87

PA-MA Interval (years)

Figure A32. Growth velocities of arm An/ (a) and arm NATV (b) (mllyr) over the time interval from PA to MA, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. APPENDIX 33. Scatter Plots of Growth Velocity of Trunk Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls

.-5 -500- o Multiple R = .271 0 -a p = 348 = -1000- rP (a) -1500 I I I I I I I 1 0 0.5 1 1.5 2 2.5 3 3.5 4 PA-MA lnterval (years)

6 2000- m % C Multiple R = .722 g 1500- - SEE = 773.3 >" 1000- =-\ pF = .0035513.061 0

500 - y=-719.3~+3625.9 (b) 0 I I 1 I I 1 I 1 0 0.5 1 1.5 2 2.5 3 3.5 4 PA-MA lnterval (years)

Figure A33. Growth velocities of trunk ATV (a) and trunk NATV (b) (mllyr) over the time interval from PA to MA, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. i APPENDIX 34. Scatter Plots of rod Velocity of Thigh Tissue Volumes versus the PA-to-MA Time Interval: SASK Girls

PA-MA Interval (years)

I

). CI = Multiple R = .499 g 300- - p = ,0691 >" 200- C z 100- E (b) 00 I 1 I I I I I 3 0 0.5 1 1.5 2 2.5 3 3.5 4 PA-MA Interval (years)

Figure A34. Growth velocities of thigh ATV (a) and thigh NATV (b) (mllyr) over the time interval from PA to MA, with related statistical summaries and corresponding least squares regression line(s) shown where appropriate. REFERENCES

Adadevoh, S.W.K., T.K. Agble, C. Ho&s qdT.E. Elkins, "Menarcheal age in Ghanaian school girls", International Journal of Gvnecoloav and Obstetrics, 30, pp. 63-68, 1989.

Akamine Y., K. Kato and H. Ibayashi, "Studies on changes in the concentration of serum adrenal androgens in pubertal twins", Acta Endocrin, 93, pp. 356-364,1980.

Apter D., "Serum steroids and pituitary hormones in female puberty: a partly longitudinal study", Clin. Endocrin., 12, pp. 107-120, 1980.

Bailey, D.A., Saskatchewan Growth and Development Study. (internal report), College of Physical Education, University of Saskatchewan, Saskatoon, 1968.

Baker, E.R., "Menstrual dysfunction and hormonal status in athletic women: a review", Fertilitv and Sterilitv, 36(6), pp. 691 -696, 1981.

Baumgartner, R. N., R.M. Siervogel, W.C. Chumlea and A.F. Roche, "Associations between plasma lipoprotein cholesterols, adiposity and adipose tissue distribution during adolescence," International Journal of Obesity, 13, pp. 31 -41, 1989. Benn, R.T., "Some mathematical properties of weight for height indices used as measures of adiposity", &-. J. Prev. Soc. Med,, 25, pp. 42-50, 1971. Beunen G., R.M. Malina, M. Ostyn, R. Renson, J. Simons and D. Van Gerven, "Fatness and skeletal maturity of Belgian boys: 12 through 17 years of age", Am. J. Phvs. Anthrop., 59, pp. 387-392, 1982.

Billewicz, W.Z., H.M. Fellowes and C.A. Hytten, "Comments on the critical metabolic mass and the age of menarche", Annals of Human Biology, 3, pp. 51 -59, 1976.

Bing C., S.E. Xu, G.D. Zhang and W.Y. Wang, "Serum dehydroepiandrosterone sulphate and pubertal development in Chinese girls", Annals of Human Biology, 15, pp. 421 -429, 1988.

Bjorntorp P., "The association between obesity, adipose tissue distribution and disease", Acta Medica Scandinavica (Suppl.) 723, pp. 121-1 34, 1988

Blade, L.F., L.O. Amusa, A.P. Agbonjinmi, and W.D. Ross,, "Ethnic dimorphism in prepubescent boys", Pnthropoloaiai Kozlemanyeka, 33, pp. 305-312, 1991.

Bonnet, F.P., and D Rocour-Brumioul, "Normal growth of human adipose tissue", In: Adipose Tissue in Childhood, F.P. Bonnet (Ed.), Boca Raton, FL.: CRC Press, pp. 81 -107, 1981. Bonnet, F.P., D Rocour-Brumioul and A. Heuskin, "Regional variations of adipose cell size and local cellularity in human subcutaneous fat during normal growth", Acta. Paediatr. Bela., 32, pp. 17-27, 1979.

Borms, J., M. Hebbelinck, J.E.L. Carter, W.D. Ross and G. Lariviere, "Standardization of basic anthropometry in Olympic athletes - The MOGAP procedure", In: Methods of Functional Anthropometry. Novotny and Titlabachova, (eds), Praha: Universitas Carolina Pragensis, 1979.

Bronson, F.H. and J.M. Manning, "The energetic regulation of ovulation: a realistic role for body fat", Bioloav of Reproduction, 44, pp. 945-950, 1991.

Brook C.G. D., "Endocrinological control of growth at puberty", British Medical Bulletin, 37, pp. 281 -285, 1981.

Brooks, S.M., C.F. Sanborn, B.H. Albreight and W.W. Wagner, "Diet in athletic amenorrhoea", Lancet, 1(8367-8380), pp. 559-560, 1984.

Brundtland, G.H., K. Liestol and Walloe, "Height, weight and menarcheal age of Oslo school children during the last sixty years", Annals of Human Bioloav, 7, pp. 307- 322,1980.

Cahill, G.F. and A.E. Renold, "Adipose tissue: a brief history", In: The Adipocyte and Obesity: Cellular and Molecular Mechanisms, A. Angel, C.H. Hollenberg and D.A.K. Roncari (Eds.), New York, Raven Press, pp. 1-7, 1983.

Cameron, N., J. Mitchell, D. Meyer, A. Moodie, M.D. Bowie, M.D. Mann and J.D.L. Hansen. "Secondary sexual development of 'Cape Coloured' girls following kwashiorkor", Annals,15, pp. 65-76, 1988.

Cameron, N., J. Mitchell, D. Meyer, A. Moodie, M.D. Bowie, M.D. Mann and J.D.L. Hansen. "Secondary sexual development of Cape Coloured boys following kwashiorkor1', Annals of Human Bioloav, 17, pp. 21 7-228, 1990.

Cameron, N., "Weight and skinfold variation at menarche and the critical body weight hypothesis", Annals of Human Bioloay, 3, pp. 279-282, 1976.

Cleland W.H., C.E. Mendelson and E.R. Simpson, "Effects of aging and obesity on aromatase activity of human adipose cells", J. Clin. Endocrinal. Metab., 60, pp. 174-177, 1985.

Crawford, S. M., Morphometric Models for the Assessment of Developmental Status of Boys Age 7 to 76.,PhD Thesis. School of Kinesiology, Simon Fraser University, Burnaby, 1990. Cronk, C. E., D. Mukherjee and A.F. Roche, "Changes in triceps and subscapular skinfold thickness during adolescence", j-luman Bioloay, 55, pp. 707-721, 1983.

Cutler, G.B., R.J. Schebinger, B.D. Albertson, F.G. Cassorla, G.P. Chrousos, F. Comite, J.D. Booth, J. Levine, W.C. Hobson and DL. Loriaux, "Chapter 23. The adrenarche (Human and Animal)", In: Controlof the Onset of Puberty, Grumbach M.M, Sizonenko P.C. and Aubert M.L. (eds), Williams and Wilkins. Baltimore, pp. 506-524, 1990.

Dahlberg , G., Statistical Methods for Medical and Biological Students, George Allen and Unwin, Ltd., London, 1940. ( deRidder, C. M., Sexual Maturation of Pubertal Girls: physical and hormonal development in relation to metabolic and nutritional factors, Doctoral Thesis, Department of Physiology and Sports Medicine, Utrecht, 1991. de Ridder, C.M., P.F. Bruning, M.L. Zonderland, J.H.H. Thijssen, J.M.G. Bonfrer, M.A. Blankenstein, I.A. Huisveld and W.B.M. Erich, "Body fat mass, body fat distribution and plasma hormones in early puberty in females", J. Clin. Endocrinol. Metab., 70, pp. 888-893, 1990. de Ridder, C.M., J.H.H. Thijssen, P.F. Bruning, J.L. vander Brande, M.L. Zonderland and W.B.M. Erich, "Body fat mass, body fat distribution and pubertal development: a longitudinal study of physical and hormonal sexual maturation of girls", J. Clin. Endocrinol. Metab,, 75(2), pp.442- 446,1992.

Draper N.R. and H. Smith, Applied Regression Analysis, second edition, John Wiley and Sons, Inc., New York, 1981.

Drinkwater D.T., "An anatomically derived method for the anthropometric estimation of human body composition8'. Ph.D. thesis. Simon Fraser University, Burnaby, 1984.

Eiben, O., "Szekularis novekedesvaltozasok Magyarorszagon", Humanbioloaia Budapestinensis, Supplementum 6, Budapest, 1988.

Eiben O.G., "Secular trend and its sociodemographic aspects in Hungary", In: Crescita, Adolescenza e Sport, Nicoletti, I. (ed.). Edizioni Cent ro Studi Auxologici. Firenze. pp. 15-32, 1987.

Elizondo, S., "Age at menarche: its relation to linear and ponderal growth", Annals of Human Bioloav, 19(2), pp. 197-199, 1992.

Ellison, P.T., "Skeletal growth, fatness, and menarcheal age: a comparison of two hypotheses", Human Bioloay, 54, pp. 269-281, 1982. Ellison, P.T., "Morbidity, mortality and menarche", Human Bioloay, 53, pp. 635-644, 1981.

Eveleth, P.B. and J.M. Tanner, Worldwide variation in human growth, second edition, Cambridge University Press, Cambridge, 1990.

Faust, I.M., "Chapter 3. Adipose Tissue Growth and Obesity", In: Human Growth, volume 2, second edition, F. Falkner and J. M. Tanner (eds.), Plenum Press, New York, pp. 61-72,1986. I Faust, I. M., "Signals from adipose tissue", In: The Body Weight Regulatory System: Normal and Disturbed Mechanisms, L. A. Cioffi et al. (Eds.) , New York, Raven Press, pp. 39-43,1981.

Febres, F., M. Seron, R. Weiner and P.K. Siiteri, "Androstenedione (A)-induced LH release in female rats: a new concept of gonadotropin regulation, Proc. Annu. Mta. Endocr. Soc., 149, pp. 131, 1977.

Feher T. and L. Halmy, "Dehydroepiandrosterone and dehydroepiandrosterone sulphate dynamics in obesity", Can,53, pp. 21 5-222, 1975a.

Feher T. and L. Halmy, "The production and fate of adrenal DHEA in normal and overweight subjects", J-lorm. Res,, 6, pp. 303-304, 1975b.

Feicht, C.B., T.S. Johnson, B.J. Martin, K.E. Sparks and W.W. Wagner, "Secondary amenorrhea in athletes", Lancet, 2, pp. 1 145-1146, 1978.

Feicht-Sanborn, C., B.J. Martin and W.W. Wagner, "Is athletic amenorrhea specific to runners?", Obstetrics and Gvnecoloav, 143, 859-861, 1982.

Forbes, G.B., "Body size and composition of perimenarchal girls", American Journal of Diseases of Children, 146, pp. 63-66, 1992.

Forbes, G.B., "Chapter 6. Body composition in adolescence", In: Human Growth, volume 2, second edition, F. Falkner and J.M. Tanner (eds.), Plenum Press, New York, pp. 119-1 45, 1986.

Forest M.G., "Role of androgens in fetal and pubertal development", Hormone Research, 18: 67-83, 1983.

Forney, J.P., L. Milewich, T.C. Grace, J.L. Gorlock, B.E. Schwarz, C.D. Edman and P.C. Macdonald, "Aromatization of androstenedione to estrone by human adipose tissue in vitro : correlation with adipose tissue mass, age and endometrial neoplasia", J. Clin. Endocrinal Metab., 53, pp. 192, 1981.

Frisancho, A. R. and P.N. Flegel, "Advanced maturation associated with centripetal fat pattern", Human Bioloay, 54, pp. 71 7-727, 1982. Frisancho, R. A., "New norms of upper limb fat and muscle areas for assessment of nutritional status", The American Journal of Clinical Nutrition, 34, pp. 2540-2545, 1981.

Frisch R.E., "Body fat, puberty and fertilityw,BioI. Rev%,59, pp. 161-1 88, 1984.

Frisch, R.E. and J. McArthur, "Menstrual cycles: fatness as a determinant of minimum weight for height necessary for their maintenance or onset", Science, 185, pp. 94?951,1974.

Frisch, R.E. and R. Revelle, "The height and weight of girls and boys at the time of initiation of the adolescent growth spurt in height and weight and the relationship to menarche", Human Bioloay, 41, pp. 140-159, 1971.

Frisch, R.E. and R. Revelle, "Height and weight at menarche and a hypothesis of critical body weights and adolescent eventsn, $cience. 169, pp. 397- 399,1970.

Frisch, R.E., R. Revelle and S. Cook, "Components of the critical weight at menarche and at initiation of the adolescent spurt: estimated total water, lean body mass, and fat", Human Bioloay, 45, pp. 469-483, 1973.

Galle, P.C., E.W. Freeman, M.G. Galle, G.R. Huggins and S.T. Sondheimer, "Physiologic and psychologic profiles in a survey of women runners", Fertilitv and Sterilitv, 39, pp. 633-639, 1983.

Garn S.M., D.C. Clark and K.E. Guire, "Level of fatness and size attainment", Am J. Phvs. Anthro~ol.,40, pp. 447-450, 1974.

Gasser, Th., P. Ziegler, A. Kneip, A. Prader, L. Molinari and R.H. Largo, "The dynamics of growth of weight, circumferences and skinfolds in distance, velocity and acceleration", Annals of Human Bioloav, 20(3), pp. 239-259, 1993.

Genazzani, A.R., V. De Leo, P. lnaudi and P. Kicovic, "Effects of DHAS treatment on the hypothalamus-pituitary-gonadal axis in delayed adrenarche", In: Adrenal Androgens, A.R. Genazzani, J.H.H. Thijssen and P.K. Siiteri (Eds.), Raven Press, New York, pp. 31 5-333, 1980.

Genazzini A.R., C. Pintor, F. Facchinetti, G. Carboni, U. Pelosi and R. Corda, "Adrenal and gonadal steroids in girls during sexual maturation", Clinical -, -, 8, pp. 15-25, 1978.

Gould, S.J., "Allometry and size in ontogeny and phylogeny", Biol. Rev., 41, pp. 587-640, 1966. Grumbach M.M. and Kaplan S.L., "Chapter 1. The neuroendocnnology of human puberty: an ontogenetic perspective", In: Control of the Onset of Puberty, Grumbach M.M, Sizonenko P.C. and Aubert M.L. (eds), Williams and Wilkins. Baltimore, pp. 1-62, 1990.

Hager, A., L. Sjostrom, B. Arvidsson, P. Bjorntorp and U. Smith, "Body fat and adipose tissue cellularity in infants: a longitudinal study", Metabolism: Clinical and Fxperimental, 26, pp. 607-614, 1977.

Harrison, J.M. and W.A. Marshall, "wormal standards for the relationship between the length of the limbs and limb segments in young British women: A photogrammetric study", Human Riol,, 42, pp. 90-104, 1970.

Harsha, D.W., A.W. Voors and G.S. Berenson, "Racial differences in subcutaneous fat patterns in children aged 7-1 5 years", Am. J. Phvs. Anthropol., 53, pp. 333-337, 1980.

Hemsell, D.L., J.M. Grodin, P.F. Brenner, P.K. Siiteri and P.C. MacDonald, "Plasma precursors of estrogen. II. Correlation of the extent of conversion of plasma androstenedione to estrone with age", J. Clin. Endocrinol. Metab., 38, pp. 476, 1974.

Holliday, M.A., "Body composition and energy needs during growth", In: Human Growth: 11. Postnatal Growth, F. Faulkner and J.M. Tanner (eds.), Plenum Press, New York, pp. 117-1 39, 1978. . Hopper B.R. and S.S.C. Yen , "Circulating concentrations of dehydroepiandrosterone and dehydroepiandrosterone sulphate during puberty", Journal of Clinical Endocrinoloav and Metabolism, 40, pp. 458- 461,1975.

Johnston, F. E., "Relationships between body composition and anthropometry", Human Biology, 54, 221-245, 1982.

Johnston, F.E., "Research design and sample selection in studies of growth and development", In: Johnston, F.E., A.F. Roche, and C. Susanne, (eds) Human Physical Growth and Maturation: Methodologies and Factors, N .Y. Plenum Press, 1979.

Johnston, F. E., P.V. Hamill and S. Lemeshow, "Skinfold thicknesses in a national probability sample of U. S. males and females aged 6 through 17 years", American Journal of Phvsical Anthropology, 40, pp. 321-324, 1974.

Johnston, F. E., P.V. Hamill and S. Lemeshow, "Skinfold thickness of children 6- 11 years, United States, National Center for Health Statistics, series1 1, no. 120, 1972. Johnston, F.E., A.F. Roche, L.M. Schell and N.E. Wettenhall, "Critical weight at menarche: critique of a hypothesis", Am J. Dis. Child., 129, pp. 19-23, 1975.

Kannel, W. B., "Obesity in man: a risk factor in metabolic and cardiovascular disease", In: The Adipocyte and Obesity: Cellular and Molecular Mechanisms, A. Angel, C. H. Hollenberg and D. A. K. Roncari (eds.), New York, Raven Press, pp. 9-18, 1983.

Kaplan, S.L. and M.M. Grumbach, "bhapter 28. Pathogenesis of sexual precocity", In: Control of the Onset of Puberly, Grumbach M. M, Sizonen ko P.C. and Au bert M.L. (eds), Williams and Wilkins. Baltimore, pp. 620-662, 1990.

Katz, S.H., M.L. Hediger, B.S. Zemel and J.S. Parks, "Blood pressure, body fat, and dehydroepiandrosterone sulfate variation in adolescence", Hvpertension, 8, pp. 27-284, 1986.

Katz S.H., Hediger M.L., Zemel B.S. and Parks J.S. , "Adrenal androgens, body fat and advanced skeletal age in puberty: new evidence for the relations of adrenarche and gonadarche in males", Human Bioloay, 57, pp.401- 41 3,1985.

Killinger D.W., E. Perel, D. Daniillescu, L. Kharlip and W.R.N. Lindsay, "The relationship between aromatic activity and body fat distribution", Steroids, 501, PP. 61 -72, 1987. Kirchengast, S., "Anthropometric-hormonal correlation patterns in fertile and post-menopausal women from Austria", Annals of Human Bioloav, 20(1), 47-65, 1993.

Kleinbaum D.G., L.L. Kupper and K.E. Muller, Applied Regression Analysis and other Multivariable Methods: second edition, PWS-Kent Publishing Company, Boston, 1988.

Knittle, J.L., K Timmers, F. ~insber~-~ellner,R.E. Brown and D.P. Katz, "The growth of adipose tissue in children and adolescents", Journal of Clinical Investiaation, 63, pp. 239-246, 1979.

Knussman, R. and A. Sperwien, "Relations between anthropometric characteristics and androgen hormone level in healthy young men", Annals of Human Bioloav, 15, pp. 131-1 42, 1988.

Korth-Schutz S., L.S. Levine and M.I. New, "Serum androgens in normal prepubertal and pubertal children and in children with precocious adrenarche", J. Clin. Endocrinol. Metab., 42, pp. 117-1 24, 1976.

Kulin, H.E., N. Bwibo, D. Mutie, M. Med and S.J. Santner, "The effect of chronic childhood malnutrition on pubertal growth and development", The American Journal of Clinical Nutrition, 36, pp. 527-536, 1982. Lampl, M., Johnston, F. E., and Malcolm, L. A., "The effects of protein supplementation on the growth and skeletal maturation of New Guinean school children", Annals of Human Bioloay, 5(3), pp. 21 9-227, 1978.

Laron, Z., I. Ben-Dan, M. shrem, Z. Dickerman and P. Lilos, "Puberty in simple obese boys and girls", In: Obesity in Childhood. Cacciari, Laron, Raiti (Eds.), Acqdemic Press, N.Y., pp. 29-40, 1978.

Lee P.A. a& C.& Migeon, "Puberty in boys: correlations of plasma levels of gonadotropins (LH, FSH), androgens (testosterone, androstenedione, dehydroepiandrosterone and its sulphate), estrogens (esterone and estradiol) and progestins (progesterone and 17-hydroxyprogeserone)", J. Clin. Endocrinol. Met&, 41, pp. 556-562, 1975.

Lee P.A., T. Xenakis, J. Winter and S. Matsenbaugh, "Puberty in girls: correlation of serum levels of gonadotropin, prolactin, androgen, estrogens and progestins with physical changes", Journal Clin. Endocnnol. Metab., 43, pp. 775-784, 1976.

Leibel, R. L., Berry, E. M., and Hirsch, J., "Biochemistry and development of adipose tissue in man", In: Health and Obesity, edited by H. L. Conn, Jr., E. A. DeFelice, and P. Kuo (Eds.), New York, Raven Press, pp. 21- 48, 1983.

Lohman, T.G., A.F. Roche and R. Martorell (eds.). Anthropometric Standardization Reference Manual, Champaign, Illinois, Human Kinetics Books, pp. 61 -71,1988.

Longcope C., L.H. Pratt, S.H. Schneider and S.E. Fineberg SE , "Aromatization of androgens by muscle and adipose tissue in vivo", J. Clin. Fndocrinol. Metab., 46, pp. 146-152, 1978.

Loucks, A. B. and S. M. Horvath, "Athletic amenorrhea: a review", Medicine and Science in S~ortsand Exercise, 17 (I), pp. 56-72, 1985.

Malina, R.M., "Secular changes in size and maturity: causes and effects", In: Secular trends in Human Growth, Maturation, and Development, Roche A. (ed.), University of Chicago Press for the Society for Research in Child Development, serial no. 179, vol. 44, num 3-4, pp. 59-102, 1979.

Malina, R.M., "Skinfolds in American Negro and White children", Journal.of the American Dietetic Association, 59, pp. 34-40, 1971.

Malina, R.M. and C. Bouchard, Growth, Maturation, and PhysicalActivity, Human Kinetics Books, Champaign, Illinois, pp. 133-149, 1991. Malina, R.M., K.H. Brown and A.N. Zavaleta, "Relative lower extremity length in Mexican American and in American Black and White youth", Am. J. Phvs. Anthropol., 72, pp. 89-94, 1987.

Malina, R.M., P.V. Hamill and S. Lemeshow, "Body Dimensions and Proportions, White and Negro children 6-1 1 years, United States, National Center for Health Statistics, series 11 , no. 143, 1974.

Malina, R.M. and F.E. Johnston, "Relations between bone, muscle and fat widths of the upper arms and calves of boys and girls studied cross- sectionally at ages 6 to 16 years", Human Bioloav, 39, pp. 21 1-223, 1967a.

Malina, R.M. and F.E. Johnston, "Significance of age, sex, and maturity differences in upper arm composition", Research Quarterlv, 38, pp. 21 9- 230,1967b.

Malina, R.M., W.W. Spirduso, C. Tate and A.M. Baylor, "Age at menarche and selected menstrual characteristics in athletes at different competitive levels and in different sports", Medicine and Science in Sports, 10, pp. 21 8-222,1978.

Marshall, W.A. and Y. De Limongi, "Skeletal maturity and the prediction of age at menarche", Ann. Human Biol., 3, pp. 235-243, 1976. Martin, A. D., An anatomical basis for assessing human body composition: evidence from 25 dissections, Ph.D. thesis, Simon Fraser University, Burnaby, 1984.

Martin, A.D., M.Z. Daniel, D.T. Drinkwater and J.P. Clarys, "Adipose tissue density, estimated adipose lipid fraction and whole body adiposity in male cadavers", jnternational Journal of Obesity, 5, pp. 1-5, 1993, in press.

Martin, A.D. and D.T. Drinkwater, "Variability in the measures of body fat: assumptions or technique?", Sports Medicine, 11(5), pp. 277-288, 1991.

Martin, A.D., W.D. Ross, D.T. Drinkwater and J.P. Clarys, "Prediction of body fat by skinfold caliper: assumptions and cadaver evidence", International Journal of Obesity, 9(suppl. I), pp. 31-39, 1985.

Martin, R., Lehurbuch der Anthropologie, Gustav Fischer Jena, Vol. 1., 1928.

Martorell, R., R.M. Malina, R.O. Castillo, F.S. Mendoza and L.G. Pawson, "Body proportions in three ethnic groups: children and youths 2-17 years in NHANESll and HHANES", Human Bioloav, 60(2), pp. 205-222,1988.

Martorell, R., F.S. Mendoza, R.O. Castillo, I.G. Pawson and C.C. Budge, "Short and plump physique of Mexican-American children", American Journal of Phvsical Anthropology, 73, pp. 475-487, 1987. Mavoungou D, Gass R, Emane MN, Cooper RW and Roth-Meyer C , "Plasma dehydroepiandrosterone, its sulphate, testosterone and FSH during puberty of African children,iqGabonl', Journal of Steroid Biochemistry, 24, pp. 645-651 , 1986.

Meikle, A.W., R.A. Daynes and B.A. Araneo, "Adrenal androgen secretion and biologic effects", Endocrinol. Metab. Clin. North Am., 20(2), pp. 381-400, 1991.

Mellits, E.D. and D. Cheek, "The assessment of body water and fatness from infancy to adulthood, In: Physical Growth and Body Composition (ed. J. Brozek). Monographs of the Society for Research in Child Development, 35, pp. 12-26, 1970. Mueller, W.H., "The genetics of human fatness", Yearbook of Phvsical Anthro~oloav,26, pp. 215-230, 1983.

Mueller, W.H., "The changes with age of the anatomical distribution of fat. Soc. Sci. Med., 16, pp. 191-1 96, 1982.

Naftolin, F. and N.J. MacLusky, "Aromatase in the Central Nervous System", Cancer Research (suDDI.), 42, pp. 3274s-3276s, 1982.

Nelson, M.E., E.C. Fisher, P.D. Catsos, C.N. Meredith, R.N. Turksoy and W.J. Evans, "Diet and bone status in amenorrheic runners", The American Journal of Clinical Nutrition, 43(6), pp. 910-91 6, 1986.

Nimrod, A. and K.J. Ryan, "Aromatization of androgens by human abdominal and breast fat tissue", J. Clin. Endocrinol. Metab., 40, pp. 367-372, 1975.

Packard G.C. and T.J. Boardman, "Chapterlo. The misuse of ratios to scale physiological data that vary allometrically with body size", In: New Directions in Ecological Physiology. Feder M .E., Bennett A. F., Burggren W.W. and Huey R.B. (eds), Cambridge University Press, pp. 21 6-239, 1987.

Parker, C.R. and V.V. Mehesh, "Dehydroepiandrosterone (DHA) induced precocious ovulation: correlative changes in blood steroids, gonadotropins and cytosol estradiol receptors of anterior pituitary gland and hypothalamus", J. Steroid Biochem., 8, p. 173, 1977.

Parker, L.N. and W.D. Odell, "Evidence for existence of cortical androgen-stimulating hormone", The American Journal of Phvsioloay, 236(6), pp. E616-E620, 1979.

Parker, L.H., J. Sack, D.A. Fisher and W.D. Odell, "The adrenarche: prolactin, gonadotropins, adrenal androgens and cortisol", J. Clin. Endocrinol. Metab., 46, pp. 396-401, 1978. Parra, A., C. Cervantes, M. Sanchez, L. Fletes, G. Garcia-Bulnes, R.M Argote, I. Sojo, A. Carranco, R. Arias and V. Cortes-Gallegos, "The relationship of plasma gonadotrophins and steroid concentrations to body growth in girls", Acta Endocrinoloaic& 98, pp. 161-1 70, 1981. - Perel E. and D.W. Killinger, "The inter-conversion and aromatization of androgens by human adipose tissue", J. Steroid Biochem., 10, pp. 623, 1979.

Pintor C., S. Loche, A. Faedda, V. Fanni, A.M. Nuchi and R. Corda, "Adrenal androgens in obese boys before and after weight loss", Human Metabol.

vRes 16, pp. 544-548, 1984.

Pintor, C., A.R. Genazzani, R. Puggioni, G. Carboni, A. Faedda, E. Pisano, S. Orani, T Fanni, G. D'Ambrogio and R. Corda, "Effect of weight loss on adrenal androgen plasma levels in obese prepubertal girls", In: Adrenal Androgens, A.R. Genazzani, J.H.H. Thijssen and P.K. Siiteri (Eds.), Raven Press, New York, pp. 259-266, 1980.

Poissonnet, C.M., M. LaVelle and A.R. Burdi, "Growth and development of adipose tissue", The Journal of Pediatrics, 11 3, pp.1-9, 1988.

Prader, A., "Chapter 24. Hormonal regulation of growth and the adolescent growth spurt", In: Control of the Onset of Puberty, Grumbach M.M, Sizonenko P.C. and Aubert M.L. (eds), Williams and Wilkins. Baltimore, pp. 534-553, 1990.

Preece, M.A. and M.J. Baines, "A new family of mathematical models describing the human growth curve", Annals of Human Biology, 5(1), pp. 1-24, 1978.

Raisz, L.G. and B.E. Kream, "Hormonal control of skeletal growth", h.Rev. Phvsiol., 43, pp. 225-238, 1981.

Roche A.F., "Secular trends in stature, weight and maturation". In: Secular trends in Human Growth, Maturation, and Development., Roche A. (ed.), University of Chicago Press for the Society for Research in Child Development, serial no. 179, vol. 44, num 3-4, pp. 3-27, 1979.

Roncari, D.A.K., "Pre-adipose cell replication and differentiation", Trends in Biochem. SCI., 9, pp. 486-489, 1984.

Ross, W. D., D.T. Drinkwater, N.O. Whittingham and R.A. Faulkner, The Coquitlam Growth Study, In: Children and Exercise IX, International Series on Sport Science, vol. 10, edited by K. Berg and B. 0. Eriksson (Baltimore: University Park Press), pp. 3-12, 1980.

Ross, W.D. and O.G. Eiben, "The sum of skinfolds and the 0-scale system for physique assessment rating of adiposity", Anthro~oloaiaiKozlemanveke, 33, pp. 299-303, 1991. Ross, W.D., T.I. Grand, G.R. Marshall and A.D. Martin, "On human and animal geometry", In: Proceedings of VII Commonwealth and International Conference on Sport, Physical Education, Recreation and Dance, Kinesiological Sciences, vol. 7, M.L. Howell and B.D. Wilson (Eds.), Department of Human Movement Studies, University of Queensland, Brisbane, pp.77-97, 1984.

Ross, W.D. and M. Marfell-Jones, "Kinanthropometry", In: Physiological Testing of the High-Performance Athlete, Second Edition, J.D. MacDougall, H.A. Wenger and H.J. Green (Eds.), Human Kinetics Books, Champaign, pp. 233-308, 1991.

Rotter J.I., L. Wong, E.T. Lifrak and L.N. Parker, "A genetic component to the variation of dehydroepiandrosterone sulfate", Metabolism, 34, pp. 731 - 736,1985.

Scammon, R.E., "The measurement of the body in childhood", In: The Measurement of Man, Harris, Jackson, Peterson and Scammon (eds.), Minneapolis, University of Minnesota Press, 1930.

Schindler A.E., A. Ebert and E. Friedrich, "Conversion of androstenedione to estrone in human fat tissue", J. Clin. Endocrinol. Metab., 35, pp. 627, 1972.

Schwartz, B., D.C. Cumming, E. Riordon, M. Selye, S.S.C. Yen and R.W. Rebar, "Exercise-associated amenorrhea: a distinct entity?", American Journal of Obstetrics and Gvnecoloay, 141 , pp. 662-670, 1981. Scott, E.C. and F.E. Johnston, "Critical fat, menarche, and the maintenancy of menstrual cycles", J. Adol. Health Care, 2, pp. 249-260, 1982.

Singh, S.P. and P. Malhotra, "Secular shift in menarcheal age of Patiala (India) schoolgirls between 1974 and 1986", Annals of Human Bioloay, 15, pp. 77-80, 1988. Sizonenko, P.C. and M.L. Aubert, "Chapter 22. Pituitary gonadotropins, prolactin, and sex steroids: secretion in prepuberty and puberty", In: Control of the Onset of Puberty, Grumbach M.M, Sizonenko P.C. and Aubert M.L. (eds), Williams and Wilkins. Baltimore, pp. 479-505, 1990.

Sizonenko PC., L. Painier and D. Carmingac, "Hormonal changes during puberty. IV. Longitudinal study of adrenal androgen secretion", J-lormonal Research, 7, pp. 288-320, 1976.

Sklar C.A., S.L. Kaplan and M.M. Grumbach, "Lack of effect of oestrogens on adrenal androgen secretion in children and adolescents with a comment on oestrogens and pubic hair growth", Clin. Endocnnol., 14, pp. 31 1- 320, 1981. Sklar C.A., S.L. Kaplan and M.M. Grumbach, "Evidence for dissociation between adrenarche and gonadarche: studies in patients with idiopathic precocious puberty, gonadal dysgenesis, isolated gonadotropin deficiency and constitutionally delayed growth and adolescence", L Clin. Endocrinol. Metab., 51, pp. 548-556, 1980.

Slavin, J., J. Lutter and S. Cushman, "Amenorrhea in vegetarian athletes", Lancet, 1(8381 -8392), pp. 1474-1475, 1984.

Tanner, J.M., Fetus into Man: Physical Growth from Conception to Maturity, second edition, Harvard University Press, Cambridge, 1990.

Tanner J. M., Fetus into Man: Physical Growth from Conception to Maturity, Harvard University Press, Cambridge, 1978.

Tanner, J.M., "Chapter 17. Sequence and tempo in the somatic changes in puberty", In: Control of the Onset of Puberty, Grumbach M.M., Grave G.D. and Mayer F.E. (eds), John Wiley and Sons. New York, pp. 448-470, 1974.

Tanner, J.M., Growth at adolescence, second edition, Blackwell Scientific Publications, Oxford, 1962.

Tanner, J. M., P.C.R. Hughes and R.H. Whitehouse, "Radiographically determined widths of bone muscle and fat in the upper arm and calf from age 3-18 years", Amof, 8(6), pp. 495-51 7, 1981. Tanner, J.M. and J.S. Weiner, "The reliability of the photogrammetric method of anthropometry, with a description of a miniature camera technique", Am. J. Phvs. Anthrop., 7, pp. 145-186, 1949.

Topping, J. Errors of Observation and their Treatment, The Institute of Physics and the Physical Society Monographs for Students, London, Chapman and Hall Limited, p. 82, 1962.

Vague J., "The degree of masculine differentiation of obesities", Am. J. Clin. m.4, pp. 20-34, 1956. Vague, J., J.M. Meignen, J.F. Negrin, M. Thomas, M. Tramoni and J. Jubelin, "Androgenes, oestrogenes et cortisol dans la physio-pathologie due tissu adipeux", Sem. HOD.Paris, 60, pp. 1465-1476, 1984. (cited in Poissnnet, LaVelle and Burdi, 1988). van Venrooij-IJsselmuiden, M.E., "Mixed longitudinal data on height, weight, limb circumferences and skinfold measurements of Dutch children", Human Bioloay, 50(3), pp. 369-384, 1978. Van't Hof, M.A. and M.J. Roede, "A Monte Carlo test of weight as a critical factor in menarche, compared with bone age and measures of height, weight, and sexual development. Ann. Human Biol., 4, pp. 581-585, 1977.

We ine r, J .S. and J. A. Lourie , Human Biology: A Guide to Field Methods. IBP Handbook No. 9, Oxford, Blackwell Scientific Publications, 1969.

Westrate, J. A., Deurenberg, P. and vanTinteren, H., "Indices of body fat distribution and adiposity in Dutch children from birth to 18 years of age", International Journal of Obesity, 13, pp. 465-477, 1989.

Wierman, M.E., D.E. Beardsworth, rawford, ford, J.F. Crigier, M.J. Mansfield, H.H. Bode, P.A. Boepple, D.C. Kushner, and W.F. Crowley, "Adrenarche and skeletal maturation during luteinizing hormone releasing hormone analogue suppression of gondadarche", J. Clin. Invest., 77, pp. 121-1 26, 1986.

Wild, R.A., "Hyperandrogenism in the adolescent", Obstetric and Gvnecoloav Clinics of North America, 19, pp. 71-89, 1992.

Winkler, E.-M. and K. Christiansen, "Anthropometric-hormonal correlation patterns in San and Kavango males from Namibia", Annals of Human Bioloav, 18(4), pp. 341-355, 1991.

Winter, J.S.D., "Chapter 7. Prepubertal and pubertal endocrinology", In: Human Growth: 11. Postnatal Growth, F. Faulkner and J. M. Tanner (eds.), Plenum Press, New York, pp. 183-213, 1978.

Wolff, O.H., "Obesity in childhood", Quarterlv Journal of Medicine, 24, pp. 109-123, 1955. Worthman C.M. "Later-maturing populations and control of the onset of puberty", Am. J. Phvs. Anthro~ol.,69, pp. 282, 1986. Zavaleta,A.N. and R.M. Malina, "Growth, fatness, and leanness in Mexican- American children", Am. J. Clin. Nutr., 33, pp. 2008-2020, 1980.

Zemel B.S. and S.H. Katz, "The contribution of adrenal and gonadal androgens to the growth in height of adolescent males", Am. J. Phvs. Anthropol., 71, pp. 459-466, 1986.

Zillikens, M.C. and J.M. Conway, "Anthropometry in blacks: applicability of generalized skinfold equations and differences in fat patterning between blacks and whites", Am. J. Clin. Nutr., 52, pp. 45-51, 1990.