Name	Levothyroxine sodium
Synonyms	Sodium 4-O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-L-tyrosine
Molecular Formula	C15H10I4NNaO4
Molecular Weight	798.86
CAS Registry Number	55-03-8 (50809-32-0)

Light yellow to buff-colored

Specific rotation: -5° to -6°

Loss on drying≤11.0％

Iodides content≤0.08％

Liothyronine≤2.0％

Levothyroxine Sodium:97-103.0%

One of the thyroid hormones involved in the maintenance of metabolic homeostasis. Synthesized and stored as amino acid residues of thyroglobulin, the major protein component of the thyroid follicular colloid. Synthesis and secretion are regulated by the pituitary hormone (TSH). Deiodinated in peripheral tissues to the active metabolite, liothyronine. The D-form has very little activity as a thyroid hormone, but has been used to treat hyperlipidemia.