CYP19A1 and polycystic ovary syndrome: In PCOS, increased LH secretion stimulates theca cells to synthesize testosterone, but the concomitant decrease in aromatase activity leads to disorder in the aromatization process: granulosa cells are unable to aromatize androgen into estrogen, there is insufficient estrogen for oocyte maturation, and therefore chronic anovulation results, which is the major feature of PCOS [53].