Levothyroxine

Levothyroxine, also -thyroxine or T₄, is a synthetic form of the thyroid hormone thyroxine, which is normally secreted by the follicular cells of the thyroid gland. Levothyroxine is used to treat thyroid hormone deficiency, and occasionally to prevent the recurrence of thyroid cancer. Like its naturally secreted counterpart, levothyroxine is chemically in the chiral L-form. The related drug dextrothyroxine (-thyroxine) was used in the past as a treatment for hypercholesterolemia (elevated cholesterol levels) but was withdrawn due to cardiac side-effects.