Diurnal variation in blood 17-hydroxyprogesterone concentrations in untreated congenital adrenal hyperplasia

Blood spot 17-hydroxyprogesterone concentrations were measured serially over 24 hours in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency before they started treatment with glucocorticoids, and the development of diurnal rhythm in pituitary-adrenal activity was studied. Five infants aged 2 to 26 days showed an intradiem variation of 17-hydroxyprogesterone concentrations within the diagnostic range but without a characteristic diurnal pattern. Blood spot 17-hydroxyprogesterone values in a further eight patients aged 3 months to 6.5 years showed a diurnal rhythm, with high concentrations in the morning and a nadir in the evening. The results suggest that a diurnal rhythm in pituitary-adrenal activity may develop as early as the third month of life in those infants with an increased endogenous concentration of adrenocorticotrophic hormone.