(S)-2-(2-Amino-3-(4-(3,5-diiodo-4-methoxyphenoxy)-3,5-diiodophenyl)propanamido)acetic Acid is a Levothyroxine impurity of Thyroxine (T425600), which is one of the thyroid hormones involved in the maintenance of metabolic homeostasis. Thyroxine is deiodinated in peripheral tissues to the active metabolite, liothyronine, which has been used to treat hyperlipidemia. Molecular Formula: C18H16I4N2O5 Molecular Weight: 847.95