Pharmacology · single question
What is the mechanism of action of levothyroxine (Synthroid)?
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Correct answer: A. Acts as a synthetic T4 (thyroxine) replacement
Levothyroxine is a synthetic form of thyroxine (T4), the primary secretory product of the thyroid gland. It acts as a direct hormone replacement in hypothyroidism. After absorption, T4 is converted peripherally to the more active T3 (triiodothyronine) by deiodinases in target tissues. Levothyroxine does not stimulate the thyroid or inhibit hormone production; it replaces the endogenous T4 that is deficient.