Understanding Cytomel (T3) and Fat Loss: Physiology, Promises, and Results In fitness forums and bodybuilding communities, Cytomel—the brand name for liothyronine sodium, a synthetic version of the thyroid hormone triiodothyronine (T3)—is often discussed as a potent “fat burner.” Advocates praise its ability to ramp up metabolism and melt off body fat rapidly. What Is Cytomel (T3)? Your thyroid gland naturally …