At the 2nd (baseline) visit, patients will undergo a euglycemic-hyperinsulinemic clamp (a procedure to measure insulin sensitivity by continuous intravenous infusion of insulin, and variable infusion of glucose). Blood samples will be drawn throughout the procedure. At completion, the insulin infusion will be stopped, participants will be fed, and the glucose infusion continued for at least 15 minutes to ensure stability of the blood glucose concentration. After the procedure, participants will be randomized to receive either metformin plus leuprolide placebo, leuprolide plus metformin placebo, or metformin placebo plus leuprolide placebo. The leuprolide or leuprolide placebo will be administered as an injection by a nurse. The metformin or metformin placebo will be dispensed to the participant in the form of pills, with instructions for titrating the dose. Participants will be contacted by telephone once weekly during the titration period to assess drug tolerability and adverse events (AEs). Participants will be maintained at their maximum tolerated dose for the duration of the study intervention period.