CYP17A1 and polycystic ovary syndrome: PCOS manifestation often includes development of hypertrophied ovarian theca cells [135] that express steroidogenic enzymes for androgen biosynthesis: CYP11A1, CYP17, HSD3B2 [136] 5a-reductase, and 5a-androstane-3,17-dione [135,137].