Thyroid Hormone

Main protein in the colloid is Thyroglobulin. This protein is rich in tyrosine residues. The iodine combines with these residues to form either monoiodotyrosine (MIT) - addition of one iodine atom to tyrosine residue or diiodotyrosine (DAT) - addition of two iodine molecules to a tyrosine residue. Two molecules of diiodotyrosine (DIT) combine within thyroglobulin to form L-thyroxine (T4) .

If one molecule of monoiodotyrosine (MIT) combines with one molecule of diiodotyrosine (DIT) to form T3.