Compared with the obese PCOS group, the lean PCOS group showed increased activity of P450c17 (17-OHP5/ pregnenolone) (P < 0.001), P450aro (E1/AD2) (P < 0.001), and 3βHSD2 (P/ pregnenolone and 17-OHP/17-OHP5, both P < 0.001), and decreased activity of P450c17 (AD2/17-OHP) (P < 0.001), P450c21 (DOC/P) (P = 0.001, see Supplementary Fig. S2A), and P450c21 (S/17-OHP) (P < 0.001, see Supplementary Fig. S2B). This evidence concerns the gene CYP17A1 and polycystic ovary syndrome.