Thyroid and Glucose and Energy Metabolism

This study will examine how two thyroid preparations-levothyroxine (T4) and liothyronine (T3)-affect fat and cholesterol metabolism, blood sugar regulation, and thyrotropin secretion in patients who have had their thyroid gland removed. Results of the study may help in the development of better therapies to optimize blood sugar and cholesterol levels in some patients. Patients 18 years of age or older who have had most or all of their thyroid gland removed and are taking long-term thyroid hormone medication may be eligible for this study after screening.