In humans, it has been reported previously that the increased progesterone, 11-deoxycorticosterone and corticosterone, which accumulated upstream of the product catalyzed by Cyp17a1, can be seen due to the 17α-hydroxylase/17, 20-lyase deficiency caused by the cyp17a1 mutation (1). The gene discussed is CYP17A1; the disease is hyperinsulinemic hypoglycemia, familial, 4.