Synthroid, with the generic name Levothyroxine Sodium, is a synthetic form of the T4 thyroid hormone. Normally, the thyroid gland produces and releases these hormones to regulate the body’s metabolism. In cases of hypothyroidism, where the thyroid gland is underactive, it doesn’t produce enough hormone, leading to a slower metabolism. Synthroid T4 helps supplement this deficiency, restoring balance and supporting normal metabolic function.