The goal of this clinical trial to clarify the impact of changes in thyroid hormone levels on glucose and lipid metabolism.
Patients will be included in whom thyroid hormone levels are intentionally changed by treatment. In patients with Graves' disease, thyroid hormone levels will be lowered using medication, while in patients with thyroid cancer, thyroid hormone levels will be raised using medication. Oral glucose tolerance tests will be performed before treatment and at two time points after treatment begins to assess metabolic effects.