In PCOS theca cells there is a coordinated increase in the expression of several steroidogenic enzymes, including CYP17A1, 3ß-HSDII, Aldoketoreductase 1C2, (AKR1C1, encoding 20α-HSD), and CYP11A1[20]. Here, CYP17A1 is linked to polycystic ovary syndrome.