Thyroglobulin (Tg)

Thyroglobulin is a very large, dimeric glycoprotein (approximately 660 kDa) produced by and secreted from thyroid follicular cells. It serves as the essential precursor and storage scaffold for thyroid hormone biosynthesis, containing multiple tyrosine residues that are iodinated and then enzymatically coupled to form thyroxine (T4) and triiodothyronine (T3) within the thyroid follicle lumen. Thyroglobulin is glycosylated, rich in disulfide bonds, and unusually abundant, accounting for almost half of thyroid gland protein content. After iodination and hormone synthesis, it is reabsorbed into thyrocytes and proteolytically degraded in lysosomes, releasing T3 and T4 into circulation and recycling iodine. Mutations in the TG gene can cause congenital hypothyroidism by impairing its synthesis, folding, or secretion. Serum thyroglobulin is widely used as a tumor marker to monitor differentiated thyroid cancer after thyroidectomy or ablation. Although critical for hormone biosynthesis, thyroglobulin is not a classic drug target; rather, its measurement aids in diagnosis, monitoring, and risk stratification of thyroid diseases.

Other names

TGhTGThyroglobulin protein

Not applicable (Thyroglobulin is a substrate and not itself the mechanistic target of drugs. Its functions are altered by autoimmune reactions and thyroid tissue pathology, not by classic inhibitory/agonistic interaction)