Precocious pubarche: distinguishing late-onset congenital adrenal hyperplasia from premature adrenarche.

CONTEXT Because precocious pubarche (PP) reveals late-onset congenital adrenal hyperplasia (LO-CAH) in 5 to 20% of cases, an adrenal stimulation test is recommended in all patients presenting with it. This test is stressful and expensive, and results are normal in more than 80% of cases. OBJECTIVE Our objective was to identify clinical and plasma predictors of LO-CAH among patients presenting with PP. DESIGN, SETTING, AND PATIENTS We conducted a retrospective cohort study that included all patients seen for PP at our hospital between 1999 and 2006 (n = 238). All had undergone an ACTH test. MAIN OUTCOME MEASURE LO-CAH was defined by a post-ACTH 17-hydroxyprogesterone (17-OHP) plasma level greater than 10 ng/ml and confirmed by mutational analysis of the CYP21 gene. The association of standard clinical and laboratory indicators with LO-CAH was assessed. RESULTS Ten (4%) of 238 patients had LO-CAH. Basal 17-OHP, Delta4-androstenedione, and testosterone plasma levels were significantly higher in these patients. A 2-ng/ml threshold for basal 17-OHP plasma levels offered 100% (95% CI, 69-100) sensitivity for the diagnosis of LO-CAH and 99% (95% CI, 96-100) specificity. CONCLUSION We identified three plasma predictors of LO-CAH in patients presenting with PP. A selective strategy based on a 2-ng/ml basal 17-OHP plasma level threshold would have safely avoided 99% of the unnecessary ACTH tests among our patients.