Levothyroxine

Mechanism of Action

Levothyroxine is a synthetic form of thyroxine (T4), the primary secretory product of the thyroid gland. T4 is a prohormone converted in peripheral tissues to the biologically active triiodothyronine (T3) by deiodinase enzymes (DIO1, DIO2). T3 binds to nuclear thyroid hormone receptors (TRα and TRβ), which function as ligand-activated transcription factors regulating genes involved in basal metabolic rate, thermogenesis, cardiac output, lipid metabolism, skeletal growth, and neurodevelopment. Thyroid hormones are critical for normal metabolic homeostasis, and exogenous T4 is used to replace deficient endogenous production.

Evidence Level

Clinical Trial - Human

6 studies published