ABSTRACT
I. Non-classical adult-onset adrenal hyperplasia is a differential diagnosis that can be distinguished from polycystic ovary syndrome by basal 17-hydroxyprogesterone measurement. The prevalence of non-classical CAH varies according to population from 1% to 19%. Most patients with either PCOS or non-classical CAH will have elevated DHEAS androstendione and testosterone. Basal 17-hydroxyprogesterone (17-OHP) levels <200 ng/dl (0.6 nmol/l) effectively rule out 21-OH-deficient CAH, whilst levels >500 ng/dl (15.1 nmol/l) confirm the diagnosis.
