What is T3?
T3 (liothyronine) is the synthetic form of triiodothyronine, the active thyroid hormone. While the thyroid mainly produces the storage hormone T4 that the body must first convert to T3, liothyronine acts immediately and directly. It raises basal metabolic rate and speeds up metabolism - used in research contexts for fat burning.
This information is for research and educational purposes only. No medical advice.
How it works
T3 binds thyroid hormone receptors in virtually every cell and raises the metabolic rate - cells burn more energy. That markedly increases calorie consumption at rest. The catch: T3 is not selective for fat. At too high a dose the body also burns muscle tissue, and the body's own thyroid production is suppressed.
Dosing
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What the research shows
The Celi study (J Clin Endocrinol Metab, 2011) compared liothyronine directly with levothyroxine (T4) and showed that T3, at an equivalent dose, led to greater weight loss and a better lipid profile, with no differences in cardiac function or insulin sensitivity. That confirms the direct metabolic effect.
Side effects
- Muscle loss: at too high a dose T3 also burns muscle - so in research it is often combined with anabolics to protect muscle.
- Heart: palpitations, raised pulse, arrhythmia risk on overdose.
- Thyroid suppression: your own production winds down - hence the slow taper.
- Sweating, nervousness, feeling hot.
Storage
Store dry and protected from light. Out of reach of children.