Circadian Variation in Plasma 17-Hydroxyprogesterone in Patients with Congenital Adrenal Hyperplasia

Plasma 17-hydroxyprogesterone (17-OHP) levels in 4 patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency were greatly raised and showed a marked circadian variation, with high morning levels and much lower values during the late evening. This finding indicates that patients with CAH may require relatively little adrenal suppression during the late evening and early hours of sleep, and suggests that the main suppressive dose of steroid should be reserved for the period between 3.00 a.m. and 3.00 p.m.