SERPINA7 encodes thyroxine-binding globulin (TBG), the major thyroid hormone transport protein in serum, carrying approximately 75% of circulating T4 and T3 1. As a serpin family member, SERPINA7 functions as a serine-type endopeptidase inhibitor and operates in the extracellular region [GO annotations]. The protein is synthesized in the liver and secreted into circulation where it binds thyroid hormones with high affinity 2. TBG deficiency results from SERPINA7 mutations causing amino acid substitutions, truncations, or alterations in protein stability and secretion 31. Mutations can produce complete or partial deficiency phenotypes, with compound hemizygous variants showing cumulative effects on protein folding and function 3. Clinically, TBG deficiency presents with abnormally low serum total T4 and T3 in euthyroid individuals with normal TSH, potentially leading to misdiagnosis as hypothyroidism if unrecognized 14. Genome-wide association studies identified SERPINA7 variants associated with free T3 levels, highlighting its role in thyroid function regulation 2. Beyond thyroid hormone transport, SERPINA7 levels are downregulated in primary open-angle glaucoma aqueous humor and serve as a prognostic biomarker in idiopathic pulmonary fibrosis 56, suggesting broader physiological significance in ocular and pulmonary pathologies.