Pediat. Res. 12: 1057-1061 (1978) Adrenal gland cortisol adrenocorticotropin test dehydroepiandrosterone sulfate corticosteroid premature infant Serum Cortisol and Dehydroepiandrosterone Sulfate Responses to Adrenocorticotropin Stimulation in Premature Infants AKIHIKO NOGUCH1'25' AND JOHN W. REYNOLDS Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA Summary cortisol and DHAS levels in early life. There are few studies of these steroids in the first months of life (2,6,8,12,13,16,20). The ACTH stimulation tests were performed in 15 premature infants present study was designed to investigate changes in the basal in a serial fashion at the ages of 5-10 days and 27-31 days. Six of levels of these steroids, and their responsiveness to exogenous the 15 had subsequent ACTH stimulation tests at 6-8 weeks ACTH in premature infants studied in a serial fashion. and/or 12-13 weeks. The pre- and post-ACTH serum cortisol and dehydroepiandrosterone sulfate (DHAS) levels were determined by radioimmunoassay. The mean basal levels of cortisol, 55 ng/ml, MATERIALS AND METHODS and DHAS, 4108 ng/ml, were significantly higher (P< 0.05 and P < 0.025, respectively) at 5-10 days than those of 24 ng/rnl and PATIENTS 1858 ng/ml, respectively, at 27-31 days. The mean net change The premature infants studied were patients on the Newborn (A) of cortisol after ACTH at 5-10 days, 95 ng/ml, increased Intensive Care Unit of the University of Minnesota Hospitals. significantly to 148 ng/ml at 27-31 days. However, ADHAS did Fifteen premature infants were studied on at least two occasions not differ significantly between the two periods (1514 ng/ml vs. by blood sampling before and after ACTH administration, and 972 ng/ml). Therefore, ADHAS/Acortisol was lower (P< 0.05) their clinical features are presented in Table 1. All of the infants at 27-31 days than at 5-10 days. No further significant changes were appropriate for gestational age in weight, defined as a birth were observed after 4 weeks of age in the levels of the two steroids. weight between the 10th and 90th percentile of normal weight for There was little correlation of basal levels between cortisol and gestational age using the intrauterine growth chart of Lubchenco DHAS, nor between Acortisol and ADHAS at any age period we et al. (15). This test was performed only when the infants were studied. There were four infants whose mothers had prenatal clinically well or suffering only from periodic apnea of prematurity steroid treatment for the prevention of hyaline membrane disease or occasional seizure episodes. None of the infants were receiving and their values were notdifferent from the other infants. an FiOz more than 25% at the time of the study and all grew satisfactorily in weight and length during the investi ation. ACTH Speculation was administered as Cosyntropin, the synthetic (a1-'5ACTh prep- aration. 0.25 rng in 1 ml normal saline was given iv over 4 rnin at Increased responsiveness of cortisol to ACTH at 1 month of age 5-10 days and at 27-31 days. Six of the 15 infants stayed in age may suggest that there is increasing 3/3-hydroxysteroid dehy- the hospital long enough to have the ACTH administration re- drogenase in the neonatal adrenal gland in this period. The well peated at 6-8 weeks and/or 12-13 weeks (Table 1). On each maintained DHAS responsiveness to ACTH until 3 months of age, occasion 0.5 ml blood was drawn by venipuncture or through however, implies that there is a persistence of fetal cortico- umbilical catheters immediately before and 1 hr after ACTH steroidogenic pathways through the first months of life. injection. The blood was centrifuged after a minimal delay for clotting and the serum was kept frozen until the time of assay. All the samples obtained from any one infant were assayed simulta- At birth, the fetal zone makes up 78% of the adrenal cortex in neously. The study was approved by the Committee on Human premature infants (19). Histochemical (1 1) and biochemical stud- Volunteers of the University of Minnesota and a parent of each ies (5, 18) have shown that 3P-hydroxysteroid dehydrogenase (3P- patient gave full and informed consent before the study was HSD) enzyme activity, which is essential for the production of started. cortisol and other A4-3-ketosteroids,is almost exclusively localized in the permanent zone of the adrenal cortex, and the neonatal PROCEDURE FOR SERUM STEROID ASSAYS adrenal gland as a whole, studied in vitro (21), has lower 3P-HSD activity than does the adult adrenal gland. This enzymatic pattern Cortisol and DHAS were measured by radioimmunoassay. The correlates with the high plasma A5-3P-hydroxysteroids (lo) and radioimmunoassay of cortisol was based on that described by DHAS (8,20) levels in the first weeks of life. During this period, Abraham and Buster (1). We carried out an ether extraction, used cortisol is produced in physiologically adequate amounts, but at cortisol antibody (C-001) from Steranti Research, Ltd., St. Albans, the expense of a high production of physiologically inactive A5- Herts, England, and used saturated (NH4)'S04 solution to separate 3P-hydroxysteroids. By 1 month of age in premature and full term bound from free steroid. The cortisol antibody had the following infants the absolute weight of the adrenal gland decreases to about cross reactivities in our laboratory (cortisol, 100%): cortisone, half of the weight at birth because of the involution of the fetal 2.0%; corticosterone, 1%, 11-deoxycortisol, 15 %; progesterone, zone, which occupies 20% of the total gland at this time (19). In <l%, 17-OH-progesterone, 14%; prednisolone, 20%; all other ste- contrast, the permanent zone has increased its mass 2-3 times by roids tested, <I%. The interassay coefficient of variation (cv) = 1 month (4). 18.3% and the intraassay CV = 9.1%. The DHAS assay has been To study the changing function of the adrenal cortex over the described in full (20). The serum was extracted by ethanol, am- first few months of life, we carried out this investigation of serum monium sulfate was used to separate free from bound steroid, and c Table 1. Clinical summary of I5 premature infants 'dl0 Postnatal age at ACTH tests Clinical conditions Prenatal steroids to 03 Patient Sex Gestational age (wk) Birth wt (g) the mother 5-10 days 27-31 days 6-8 wk 12-13 wk 5-10 days 4 wk or later 1 M 29 1020 Dexarnetha- X X Apneic spells Apneic spells, sone, 4 mg im treated with theophylline q 8 x 4 days CPAP and 25% Rx till 6 wk FiO2 1580 None Stable Stable 1020 None X Apneic spells Apneic spells, treated with theophylline CPAP and 25% Rx until 8 wk; FiOs phenobarbital for seizures be- yond discharge 969 None X Apneic spells Apneic spells treated with treated with CPAP and 25% CPAP till 30 Fi02 days; pheno- barbital Rx for seizures be- yond discharge 1120 None X X Stable Stable 1620 None X X Stable Stable 1370 Betamethasone, X X Stable Stable 12 mg im 4 hr before 1340 Betamethasone, X X Transient apnea, Stable 12 mg im qd hypotension, X 4 days cultures non- significant 980 None X X Apneic spells Stable treated with CPAP and 25% FiOz 1250 Betamethasone, X Stable Stable 12 mg im qd x 4 days 1170 None X Stable ACTH STIMULATION IN PREMATURE INFANTS 1059 the antibody (S-1502 no. 7) was purchased from Dr. Guy Abra- ham. STATISTICAL ANALYSIS Two-tailed Student's t-test for paired samples was used to evaluate the significance of differences of values at each age period. RESULTS $ e zsw g6as In Figure 1 are presented the basal (pre-ACTH stimulation) h 5,s ,$ E ,? -., levels of cortisol and DHAS found in the infants studied. The a$ '5 !2 7, mean and SE of cortisol level at 5-10 days, 55 + 11 ng/ml, was p.5 e, 3 ", gas e, .22@@ significantly higher than at 27-31 days, 24 5 ng/ml (P < 0.05). sx%2d A ggsz + gcsua 8%2 , However, 4 of the 15 patients increased their basal cortisol levels d m 2 3 during this period. The DHAS level also was significantly higher at 5-10 days, 4108 + 948 ng/ml, than at 27-31 days, 1858 + 278 nglml (P < 0.025). Although DHAS further decreased to the mean and SE of 1328 + 138 ng/ml at 6-8 weeks, this decline was not significant. In Figure 2 are shown the net changes (A) of the levels of cortisol and DHAS in response to a standardized ACTH dose. The mean and SE for Acortisol of 95 + 11 ng/ml at 5-10 days significantly increased to 148 + 15 ng/ml at 27-31 days (P < 0.002). In contrast, the mean and SE for ADHAS, 1514 + 360 ng/ml at 5-10 days, was not significantly different from the value of 972 + 142 ng/ml found at 27-31 days (P > 0.05). In addition, the mean for ADHAS was not significantly different at 6-8 weeks of age from the value at 5-10 days. The ratio of ADHAS/Acortisol was significantly lower at 27-31 days than at 5-10 days of age (P < 0.05). There was no further significant change of this ratio in the 6- to 8-week-old group of infants (Fig. 3). The correlations of basal DHAS and cortisol values, and ADHAS and Acortisol values, at the various ages studies were examined. The results were as follows Basal DHAS vs.
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