This study utilizes infusions of kisspeptin in healthy women to isolate the impact of kisspeptin on beta-cell responsivity assessed by the mixed meal tolerance test.

Assignment: each study subject serves as their own control, and will come in timed to their cycle. The order in which they undergo the kisspeptin or placebo arms is randomized and separated by greater than two weeks to minimize variability and study-specific effects. Delivery of Interventions: Prior to each visit, study subjects will be asked to: * eat at least 150 gm carbohydrates per day * refrain from strenuous exercise On the day of the visit, study subjects will: * eat a standardized meal prepared by the metabolic kitchen in the clinical research center * be observed overnight to ensure a 12-hour fast * have an IV placed, for a 16 hour kisspeptin or placebo infusion * after the 12 hour fast, starting at 8 am in the morning will undergo a mixed meal tolerance test