Endocrine Abstracts

Introduction: Nonclassical congenital adrenal hyperplasia (NCCAH) is caused by reduced 21-hydroxylase activity, leading to excessive adrenal androgens and premature pubarche (PP); idiopathic PP (IPP) is its main differential diagnosis. The gold standard for the differential diagnosis is ACTH stimulation test (ST); this test also estimates the adrenal cortisol reserve in NCCAH patients.

Objectives: To compare the clinical characteristics and baseline hormonal profile of patients with PP; to determine the importance of ST in the differential diagnosis between IPP and NCCAH and in the evaluation of the adrenal production of cortisol.

Methods: Retrospective study of patients with PP starting after 2 years of age who underwent ST.

Results: 43 patients were included; median age at diagnosis was 7.5 years (range: 3.5–9.4), 37 (86.0%) were females. After ST, 37 (86.0%) were classified as IPP and 6 (14.0%) as NCCAH. No significant differences could be found in the clinical characteristics and baseline determination of ACTH, cortisol, and adrenal androgens between the groups. Both basal and stimulated 17-OHP levels were significantly higher (P=0.001 and P<0.001 respectively) in NCCAH patients (basal: 4.62±3.70 ng/ml (0.80–10.50); stimulated: 35.41±24.87 ng/ml (12.0–80.2)) than IPP patients (basal: 1.04±0.77 ng/ml (0.22–3.80); stimulated: 4.18±1.71 ng/ml (1.0–8.96)). Nevertheless, the proposed cut-off level (<2.0 ng/ml) for the distinction between the groups, did not allow for this in two NCCAH patients that were only diagnosed after ST. Two NCCAH patients (33.3%) had stimulated cortisol levels <18 μg/dl, showing the need for glucocorticoid stress therapy. NCCAH patients with higher initial 17-OHP value had a lower cortisol after stimulation (P=0.004, r=−0.43).

Conclusion: The ST was useful to distinguish between patients with NCCAH and IPP, for no basal 17-OHP level could allow for a definitive differential diagnosis in the individual patient. In some NCCAH cases, it also showed inappropriate cortisol secretion under stress, contributing to the therapeutic decision.