what is l-thyroxine means
Freebase(0.00 / 0 votes)Rate this definition: Levothyroxine. Levothyroxine, also L-thyroxine or T4, is a synthetic form of the thyroid hormone thyroxine, which is normally secreted by the follicular cells of the thyroid gland. It is also used to treat thyroid hormone deficiency, and occasionally to prevent the recurrence of thyroid cancer.