2937.90.40.00 - l-Thyroxine (Levothyroxine), sodium

This HTS category, 2937.90.40.00, specifically classifies l-Thyroxine (Levothyroxine) in its sodium salt form. l-Thyroxine is a synthetic thyroid hormone, identical to naturally occurring thyroxine produced by the thyroid gland. Its primary use is in medicine to treat hypothyroidism and other thyroid-related conditions. As a specific chemical entity, its classification hinges on its precise molecular structure and its identity as a derivative of amino acids used primarily as a hormone.

This subcategory is distinguished from its sibling category, 2937.90.45.00 ("Other"), by its singular focus on l-Thyroxine (Levothyroxine), sodium. While the "Other" category would encompass any remaining amino-acid derivatives used as hormones not specifically listed elsewhere, this node is dedicated to this particular, widely used pharmaceutical compound.

As this is a leaf node within the HTS structure, there are no further subcategories. Classification at this level is definitive for l-Thyroxine (Levothyroxine), sodium. The key criterion for classification here is the precise identification of the chemical substance as l-Thyroxine in its sodium salt form, irrespective of its specific pharmaceutical formulation or purity, provided it meets the general requirements of Chapter 29.