CYP19A1 and polycystic ovary syndrome: The decreased expression levels of “response to estrogen”-related genes may explain why patients with PCOS are less sensitive to estrogen and have increased T levels (Supplementary Table 1), supporting the increased androgen biosynthesis in PCOS theca cells and the inhibition of aromatase in granulosa cells (Nelson et al., 1999; Magoffin, 2006).