Background Liothyronine is a T3 thyroid hormone that is normally produced by the thyroid gland in a ratio of 4:1 to T4:T3. liothyronine sodium is the active form of thyroxine that is composed in a basic chemical structure of a tyrosine with bound iodine. The exogenous product liothyronine was developed by King Pharmaceuticals and approved by the FDA in 1956. Indication Liothyronine is...