SYNTHESIS OF THYROID HORMONES: STEP 1 - IODINATION

TYROSINE

THYROGLOBULIN

I

Tyr

THYROGLOBULIN

MONOIODOTYROSINE (MIT)

Approximately 10% of the tyrosine residues on the 550 amino acid residue Thyroglobulin molecule may become iodinated by the enzyme - thyroid peroxidase acting on the colloid at the luminal surface of the thyroid follicle. These reactions only occur in the thyroid at specific residues in “Hormonogenic” sites located at the extreme ends of the Thyroglobulin molecule.

TYROSINE  IODINATION

I

DIIODOTYROSINE (DIT)

Tyr

-

THYROGLOBULIN

NH2

I