Recent studies including a couple by our department have demonstrated that a significant percentage of female CYP21A2 heterozygous carriers can be at increased risk of developing hyperandrogenemia and that indeed there are discrepancies in hormonal levels among heterozygous carriers, non-carriers, and females with non-classic congenital hyperplasia [24–27]. The gene discussed is CYP21A2; the disease is polycystic ovary syndrome.