RecruitingPhase 1Drug trialLevothyroxine Supplementation for Heart Transplant RecipientsThis will be a prospective, randomized study performed at a single tertiary referral academic medical center (University of California San Francisco, CA), evaluating the survival benefits of levothyroxine compared with no levothyroxine for patients who have undergone heart transplant. It will be double-blinded and placebo-control; participants will be randomized to receive levothyroxine or receive no levothyroxine.