Acute Adrenocorticotropin-(1–24) (ACTH) Adrenal Stimulation in Eumenorrheic Women: Reproducibility and Effect of ACTH Dose, Subject Weight, and Sampling Time*

Abstract

Assessment of adrenal reserve and the diagnosis of adrenal insufficiency by acute adrenocortical stimulation with ACTH-(1-24) has been well established. Alternatively, estimation of adrenocortical enzymatic activities by this method for the detection of inherited or acquired biosynthetic abnormalities has been less well characterized. Some of the discrepancies between studies estimating adrenocortical enzymatic activities in different pathological conditions (e.g. hyperandrogenism) may result from the different stimulation protocols used. The objective of this prospective study was to establish the inherent variability of the adrenal response to acute ACTH-(1-24) stimulation and to determine the effect of sampling time, stimulation dose, and subject weight on the same. Forty-one normal female volunteers were recruited (mean age, 29.1 yr), 30 within 90-110% ideal body weight and 11 weighing more than 120% ideal body weight. Three protocols were designed to study 1) the effects of sampling time, ACTH-(1-24) dose, and subject weight on adrenal response; 2) the effect of time of the day on the variability of basal steroid levels and the adrenal response to stimulation; and 3) the long term reproducibility of the adrenal response to ACTH-(1-24). Androstenedione, 17-hydroxyprogesterone, 11-deoxycortisol, dehydroepiandrosterone, and cortisol were measured in serum under basal and stimulated conditions. All subjects had normal basal levels of testosterone, androstenedione, dehydroepiandrosterone sulfate, and PRL. The acute iv administration of 0.10, 0.25, and 1.0 mg ACTH-(1-24) elicited similar and maximal steroid responses, with all steroid levels reaching a plateau 60-90 min poststimulation regardless of subject weight. Sampling of basal steroid levels every 5 min in the morning (AM; beginning 0700-0900 h) or evening (PM; 1500-1700 h) did not reveal any difference in steroid variability. Only the mean basal cortisol level was higher in AM than PM testing (P less than 0.03). Although the mean levels of dehydroepiandrosterone and 17-hydroxyprogesterone 60 min after stimulation were significantly higher in AM than PM studies, these differences were minimal. Ten volunteers underwent an average of four (range, 2-6) adrenal stimulation studies using 1.0 mg ACTH-(1-24) over a 1-yr period. The long term coefficient of variation (CV) for basal steroid levels ranged from 15-28%. Calculations of net adrenal response (delta steroid O-T and area delta steroid O-T) were less reproducible (CV, 0-82%) than measures of absolute response (steroid T, area steroid T, and %steroid T; CV, 7-32%). This difference in CV between the measures of net and absolute adrenal responses was significant for all steroids except androstenedione.(ABSTRACT TRUNCATED AT 400 WORDS)