Tirosint is a replacement for a hormone which is normally produced by the thyroid gland in order to regulate the body's energy and metabolism. Tirosint is given when thyroid does not produce enough of the hormone by its own. Tirosint (levothyroxine) is a drug used to treat low thyroid hormone level. It is also widely used in the treatment of goiters, a condition that is caused by thyroid hormone deficiency. Tirosint works by providing or replacing the thyroid hormone when the body (thyroid gland) cannot produce enough. Low thyroid levels can occur naturally, but sometimes, the thyroid gland might be injured and fail to produce the hormone. It is also important to note the low thyroid levels can cause severe mental and physical disorders. Some of the medical conditions that Tirosint can be used to treat includes goiters and thyroid cancer. The drug is supplied in the form of capsules and should be administered orally. Hair loss is one of the side effects that will occur during the first few months.