CYP19A1 and polycystic ovary syndrome: The pathophysiology of PCOS is however complex: although testosterone levels in small follicles from women with PCOS are increased and luteinized granulosa cells showed significantly increased transcripts of FSHR in PCOS, CYP19 expression is reduced, thus the follicular hyperandrogenism downregulates conversion to estrogen (5, 6); these alterations may impact on oocyte quality (7).