Importância da prova de Synacthen no diagnóstico diferencial de pubarca precoce

Abstract

IntroductionIn patients with precocious pubarche (PP), the gold standard for the differential diagnosis between idiopathic PP (IPP) and nonclassical congenital adrenal hyperplasia (NCCAH) is the ACTH stimulation test (ST); this test also estimates the adrenal cortisol reserve in NCCAH patients. ObjectivesTo 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. MethodsCross‐sectonal study of patients with PP who underwent ST. Results43 patients were included; median age at diagnosis was 7.5 years [range: 3.5‐9.4], 37 (86.0%) were female. 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±3.70ng/ml [0.80‐10.50]; stimulated: 35.41±24.87ng/ml [12.0–80.2]) than IPP patients (basal: 1.04±0.77ng/ml [0.22–3.80]; stimulated: 4.18±1.71ng/ml [1.0–8.96]). Nevertheless, the proposed basal cut‐off level (<2.0ng/ml) for the distinction between the groups, did not allow for this in 2 NCCAH patients that were only diagnosed after ST. Two NCCAH patients (33.3%) had stimulated cortisol levels <18μg/dl, showing the need for glucocorticoid stress therapy. NCCAH patients with higher initial 17‐OHP value had lower cortisol after stimulation (p=0.004; r=‐0.43). ConclusionThe 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.