Correct option is C
Explanation-
Organification refers to the iodination of tyrosine residues in the thyroglobulin (Tg) protein in the thyroid follicular cells. This is an essential step in the synthesis of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine).
Steps in Thyroid Hormone Biosynthesis:
1. Iodide (I⁻) is actively transported into thyroid follicular cells from the blood.
2. It is then oxidized to iodine (I₂) by thyroid peroxidase (TPO) in the presence of H₂O₂.
3. This oxidized iodine (I⁺ or I₂) iodinates tyrosine residues in the thyroglobulin to form Monoiodotyrosine (MIT) and Diiodotyrosine (DIT)
Coupling of MIT + DIT → T3, and DIT + DIT → T4
Organification step uses oxidized iodine to bind iodine covalently to tyrosine.
Incorrect option -
Option a - Iodine (I₂) - Without oxidation (activation), iodine can't react with tyrosine.
Option b - Reduced iodine (I⁻) - This is the form transported into the thyroid cell, not used directly in organification.
Option d - Hydrogen iodide (HI) - Not involved in thyroid hormone biosynthesis. It is an acid, not a reactive iodine source here.
Final Answer: Option c – Oxidized iodine
