The incidence of late-onset congenital adrenal hyperplasia due to 21-hydroxylase deficiency among hirsute women.

Late-onset congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is a cause of hirsutism in adult women. Its reported frequency of occurrence in hirsute women has varied from 0-30%, but the number of patients studied was small. To establish the incidence of CAH, 83 unselected hirsute women were studied prospectively with a standard ACTH stimulation test. On the basis of an exaggerated response of serum 17 alpha-hydroxyprogesterone to ACTH, 1 patient with CAH was found, for an incidence of 1.2%. The 95% confidence limits for the incidence of CAH among hirsute women were 0% and 3.4%. Five of seven hirsute women without CAH whose serum 17 alpha-hydroxyprogesterone levels rose above 3 ng/ml in response to ACTH had simultaneous serum progesterone values consistent with recent ovulation. Since routine screening of all hirsute women by means of ACTH stimulation does not appear to be cost effective, reported cases of CAH were reviewed in order to discern potentially helpful clinical clues. Severe hirsutism, virilization, early onset of symptoms, short stature, familial occurrence, and regular menses were identified as the clinical characteristics associated with late-onset CAH.