CYP19A1 and polycystic ovary syndrome: Because aromatase catalyzes the rate-determining step during the biosynthesis of estrogens from androgens, decreased activity of this enzyme could be expected to result in hormonal imbalance, circulating hyperandrogenism and intraovarian androgen excess, resulting in polycystic ovaries (Kafali et al., 2004; Caldwell et al., 2014).