T3 25

Liothyronine sodium (T3) is a synthetic form of triiodothyronine, a biologically active thyroid hormone that plays a central role in regulating metabolic rate, thermogenesis, and cellular energy turnover. T3 acts on nuclear thyroid hormone receptors to modulate gene expression involved in oxygen consumption, lipid and carbohydrate metabolism, and protein synthesis. Clinically, it is used in the treatment of hypothyroidism, especially in cases requiring rapid onset of action or in patients unresponsive to levothyroxine (T4) monotherapy. Due to its rapid absorption and short half-life, liothyronine reaches peak plasma levels quickly, making it suitable for situations requiring prompt metabolic stimulation. It has also been used off-label for depression augmentation and in endocrinological testing (e.g. T3 suppression test). Adverse effects are dose-dependent and may include tachycardia, anxiety, heat intolerance, and muscle wasting with excessive use. Monitoring of thyroid function and cardiovascular status is essential during therapy.