Subjects will be admitted to the General Clinical Research Center at 1600 h after 4 hours of fasting. We will measure luteinizing hormone every 10 minutes from 1800 h to 0900 h; other hormones (e.g., testosterone) will be assessed as well. Measurements of insulin and glucose will occur before and after a standardized mixed meal (eaten at 1900 h) and while fasting the following morning. A standard hyperinsulinemic euglycemic clamp procedure will be performed from 0900-1100 h.