Thyroglobulin (Tg) is a 660 kDa, dimeric protein produced by the follicular cells of the thyroid and used entirely within the thyroid gland. Thyroglobulin protein accounts for approximately half of the protein content of the thyroid gland.Human TG is a homodimer of subunits each containing 2768 amino acids as synthesized (a short signal peptide may be removed from the N-terminus in the mature protein)
The protein is a precursor of the thyroid hormones; these are produced when thyroglobulin’s tyrosine residues are combined with iodine and the protein is subsequently cleaved
Each thyroglobulin molecule contains approximately 100-120 tyrosine residues, but only a small number (20) of these are subject to iodination by thyroperoxidase in the follicular colloid. Therefore, each Tg molecule forms only approximately 10 thyroid hormone molecules.