Hence, all these data indicate that despite high intra-follicular concentrations of androstenedione and bioactive FSH in PCOS follicles, 5α-reduced androgens together with other factors such as AMH, EGF, and/or IL-6, may decrease aromatase activity within GC to down-regulate E2 production in vivo. The gene discussed is CYP19A1; the disease is polycystic ovary syndrome.