CYP19A1 and polycystic ovary syndrome: Insulin increases the expression of StAR but also of 17-α-hydroxylase/17,20-lyase, 3-β-hydroxysteroid dehydrogenase and aromatase, leading to the excessive production of progesterone, 17-α hydroxyprogesterone and testosterone in polycystic ovaries compared with healthy ovaries (Figure 2) [87].