Diabetologia (1999) 42: 336±342 Ó Springer-Verlag 1999 Finger and penile tactile sensitivity in sexually functional and dysfunctional diabetic men D.L. Morrissette1, M.K.Goldstein2, D.B.Raskin1, D.L. Rowland3 1 Department of Molecular and Cellular Physiology, Stanford University, Stanford, California, USA 2 Veterans Affairs Palo Alto Health Care System (182B), Palo Alto, California, USA 3 Department of Psychology, Valparaiso University, Valparaiso, Indiana, USA Summary Tactile sensitivity of the penis is related to threshold for the sexually dysfunctional group was sexual functioning, however its role in diabetic erec- also marginally higher compared with the functional tile problems is unclear. We evaluated penile sensitiv- diabetic group (p < 0.052) but did not differ from con- ity in 10 diabetic men with erectile dysfunction, 17 trol subjects (p = 0.09). Diabetic men with erectile sexually functional diabetic men and 14 control sub- dysfunction exhibited different response patterns jects. Finger and penile thresholds and ratings of in- than sexually functional men on dimensions of inten- tensity and pleasantness for finger and penis were as- sity and pleasantness to penile stimulation. Although sessed using vibrotactile stimulation. Glycosylated these data do not directly implicate subjective re- haemoglobin and total and bioavailable testosterone sponse to penile stimulation in diabetic erectile measurements were determined and subjects comple- problems, they suggest such anomalous response ted self-reports on sexual function. Diabetic men with could be one contributing factor. [Diabetologia erectile problems had higher values of glycosylated (1999) 42: 336±342] haemoglobin than sexually functional diabetic men (p = 0.02) and both groups had lower bioavailable Keywords Diabetic erectile dysfunction, penile sensi- testosterone than control subjects (p K 0.05). Sexual- tivity, penile threshold, glycosylated haemoglobin, ly dysfunctional diabetic men had a higher finger testosterone. threshold than the other two groups (p < 0.01). Penile Although not all men with diabetes mellitus report not presumed to be the primary cause of erectile difficulty achieving and maintaining erections, fac- problems, such diminished sensitivity could com- tors that differentiate sexually functional from dys- pound the ischaemic, metabolic and other effects of functional diabetic men have not been explored ex- various pathophysiological states such as diabetes. tensively. Previous research has shown that penile vi- Diabetic men with erectile dysfunction have been bratory thresholds are related to male sexual func- shown to have higher penile thresholds (i.e., de- tioning [1]. Furthermore, ageing and pathophysiology creased sensitivity) than young non-diabetic men [3]. related to vascular function have been associated Subjective cutaneous thresholds, however, represent with decreased penile sensitivity and diminished abil- only the most basic of sensory processes. Equally im- ity to achieve and maintain erections [2]. Although portant to sexual functioning is the perceived intensi- ty and pleasantness of penile stimulation. Endocrine factors could also be involved in diabet- Received: 28 April 1998 and in final revised form: 30 October ic erectile dysfunction. Varying methodologies have 1998 yielded conflicting results regarding the association between testosterone concentrations and diabetic Corresponding author: D.Morrissette, Ph.D., Department of Molecular and Cellular Physiology, Stanford University, Stan- erectile capacity [4±7], with at least one study indicat- ford, CA 94305-5426, USA ing lower testosterone in men with diabetes. Because Abbreviations: NPT, Nocturnal penile tumescence. testosterone concentrations have been implicated in D.L.Morrissette et al.: Tactile sensitivity in diabetic men 337 penile thresholds, with testosterone deficiency associ- values above 13% or self-reports of erectile function- ated with penile hypersensitivity [8], perception of pe- ing not confirmed by nocturnal penile tumescence nile stimulation in both diabetic and non-diabetic men (NPT) testing; 18 other subjects declined after learn- might be modulated by circulating testosterone. ing more about the study or failed to appear for the In this study we 1) determined penile and finger vi- screening. Two control subjects dropped out for per- brotactile thresholds, 2) assessed finger and penile in- sonal reasons unrelated to the study. tensity and pleasantness to seven suprathreshold vi- We interviewed diabetic subjects to obtain details bratory levels of stimulation, and 3) determined total of the diabetic history and to look for causes of erec- and bioavailable testosterone concentrations. We ex- tile dysfunction other than diabetes. History of anxi- amined these variables in men of similar age: sexually ety, depression and sexual function were also ob- functional diabetic men, diabetic men with erectile tained. The physical examination included heart, dysfunction and healthy control subjects. We hypo- lung, thyroid, skin, arterial pulses by palpation and thesized sexually dysfunctional diabetic men would auscultation, abdomen, deep tendon reflexes, pro- exhibit higher thresholds than men in the other two prioception, light touch, and capillary filling of toes. groups and give lower ratings of intensity and pleas- The genital examination included palpation of the antness. We also investigated the extent that total penis for plaques or fibrosis, palpation of the testes and bioavailable testosterone vary according to dia- for size and irregularity, sensory exam of the peri- betic status to explore their possible role in differen- neum, rectal sphincter tone, palpation of the prostate, ces to our response variables. and tests of anal wink and bulbocavernoses reflexes. Assignment to the diabetic erectile dysfunction group was based initially on self-reported inability to Subjects and methods achieve and maintain an erection in 75% or more of intercourse or masturbation or both in the preceding Subjects. We studied 41 men (Table 1): 10 diabetic month and a diagnosis of diabetes preceding erectile subjects with erectile dysfunction, 17 sexually func- dysfunction. Sexually functional diabetic and control tional diabetic subjects and 14 control subjects. The subjects were those reporting no erectile dysfunction protocol was approved by our institutional review in 25% or less of sexual activity in the preceding board. Selection criteria included: age range of month. To objectively confirm erectile functioning, 29±52 years and diagnosis of diabetes for a minimum NPT [11±12] was assessed for 1 to 3 nights using ei- of 4 years (diabetic subjects). Exclusion criteria were: ther the RigiScan or Penile Tumescence portable obesity (greater than 20% over ideal body weight for home monitors (Dacomed Corp., Minneapolis, Min- height according to the Metropolitan Life Insurance nesota, USA; Event Systems, Moorestown, New Jer- Tables); mild-moderate to severe depression scores sey, USA, respectively). Subjects were considered on the Beck Depression Inventory [9]; medication sexually functional when NPT data showed three or (prescription, over-the-counter and illicit), surgery or more erections a night with a 15 mm increase above history of medical conditions (except diabetes for the baseline for a minimum of 15 min and penile rigidity diabetic groups) that could affect sexual function: (RigiScan only) of 60% or greater. Subjects not both low total and bioavailable testosterone; glycosy- meeting these criteria were confirmed as sexually lated haemoglobin values above 13%; retarded or dysfunctional. No subject was reclassified into a dif- premature ejaculation; and substance abuse. ferent group because of NPT results. Men were recruited via media announcements, a diabetes newsletter, local diabetologists and word of Assays. Glycosylated haemoglobin was determined mouth. Over a 26-month period, 178 subjects volun- by affinity chromatography using the Isolab (Akron, teered. During a telephone screening, 75 subjects Ohio, USA) minicolumn method (normal range, failed to meet the criteria (e.g. age, obesity) and 16 4.0±8.0%; slightly increased, 8.1±10.5%; mildly declined to participate. We screened 87 subjects in increased, 10.6±13.0%; moderately increased, person: they gave informed consent and completed 13.0±15.5%; greatly increased, 15.6% and above). the Beck Depression Inventory, a demographics ques- Testosterone was measured by radioimmunoassay tionnaire, a health and sexual function questionnaire as described by Anderson et al. [13] (normal values: and a semistructured interview. One blood sample mean = 21.11 nmol/l; range = 12.24±38.1 nmol/l). was drawn to determine glycosylated haemoglobin Bioavailable testosterone was measured using the and two additional samples were drawn, approxi- method of Tremblay and Dube [14] (normal values: mately 1 week apart (between 0900 and 1700 hours), mean = 7.87 nmol/l; range = 3.4±12.93 nmol/l). In- to assess total and bioavailable [10] testosterone traassay coefficients of reliability for total testoster- concentrations. For gonadal hormones, the mean val- one and bioavailable testosterone were 3.0% and ue of the two samples was used for statistical analysis. 5.8%, respectively. Interassay coefficients of reliabil- Screenings resulted in the rejection of 26 volun- ity were total testosterone, 5.0% and bioavailable teers, mainly because of glycosylated haemoglobin testosterone, 6.0%. 338 D.L.Morrissette et al.: Tactile sensitivity in diabetic
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