5. Phlebotomy will be performed to measure circulating melatonin, plasma renin activity, and angiotensin II. These assays are markers of the systemic renin angiotensin system. Phlebotomy will also measure adiponectin, leptin, ghrelin, and HbA1c. These assays are markers of glucose homeostasis and insulin sensitivity. In addition, intravenous access will be placed to permit blood draws every 2 hours from 7 pm until 9 am the following morning (ie, the morning of day 1). These nocturnal blood draws will be used to measure nocturnal serum melatonin levels. In order for these blood draws to be completed without entering the subject's room and possibly waking the subject, a specialized circadian IV protocol will be used whereby an antecubital IV line will be secured with a kerlix wrap and connected to a 12 foot IV tubing that will traverse a metal window in the wall that was constructed especially for such purposes and that is present in patient rooms in the BWH CCI. Patency of the IV tubing during the night will be ensured by infusing a low dose of unfractionated heparin (approximately 200 units per hour). The heparin will be stopped and the IV converted to a standard IV at approximately 9 am on Day 1. This is standard protocol in the BWH CCI for measuring overnight melatonin concentrations.