Women will begin E2 patches (0.1 mg/d per patch, 2 patches [delivering a total of 0.2 mg/d] placed on the abdomen and changed every 2 d) on the evening of day 4-8 of the study cycle (controls or PCOS) or >= 8 weeks post-menses (PCOS only). These patches will be continued for a total of 4 d, with GCRC admission occurring on day 3 of E2 administration. Exogenous E2 administration will standardize hypothalamic exposure to E2 and help ensure the presence of sufficient hypothalamic P receptors.