Levothyroxine or L-thyroxine (brand names Synthroid, Levothroid, Levoxyl) is a synthetic form of thyroxine (thyroid hormone).Levothyroxine is a replacement for a hormone that is normally produced by your thyroid gland to regulate the body's energy and metabolism. Levothyroxine is given when the thyroid does not produce enough of this hormone on its own. Levothyroxine is used to replace the hormone that is normally produced by the thyroid gland for a condition known as hypothyroidism.
Thyroid hormone controls the rate of metabolism. When the thyroid is under active, all body processes slow down and symptoms such as weight gain, fatigue, and decreased body temperature are experienced. Through
supplementation of thyroid hormones, basal metabolic rate will be increased.