CYP21A2 and hyperandrogenism: Since differences in P450c17, P450c21 3βHSD2, and P450aro were observed between the lean and obese PCOS patients (Fig. 1) and the former three enzymes mainly function in the adrenals, we further sequenced their encoding genes including CYP17A1, CYP21A2 and HSD3B2 in 216 PCOS patients with hyperandrogenism [defined as patients with increased T or free testosterone (FT) levels measured using immunoassay based on the clinical reference intervals].