Age of appearance of circadian rhythm in blood 17-hydroxyprogesterone in 21-hydroxylase deficiency.

Sixty-one daily profiles of blood-spot 17-hydroxyprogesterone derived from patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency were analysed to determine the age of appearance of circadian rhythm in hypothalamo-pituitary-adrenal activity. The results revealed that typical circadian adrenocortical rhythm is established at approximately three months after birth. In conclusion, the maturation of supra-hypothalamic brain structure proceeds normally also in humans with constant low level of cortisol in blood.