46,XY DSD with low testosterone and increased precursors can be caused by several variants of CAH, namely by 17α-hydroxylase (CYP17A1) deficiency, ORD and 3βHSD2 deficiency, caused by inactivating mutations in the corresponding genes CYP17A1, POR and HSD3B2, respectively. The gene discussed is CYP17A1; the disease is hyperinsulinemic hypoglycemia, familial, 4.