Which of the following iodinated compound is present in a maximum concentration in the thyroid?
THYROID HORMONE SYNTHESIS AND SECRETIONThyroid hormones are synthesized in the colloid, near the apical cell membrane of the follicular cells. Catalyzed by the enzyme thyroidal peroxidase, iodide in the thyroid cell is oxidized to iodine.The iodine enters the colloid and is rapidly bound at the 3 position to tyrosine molecules attached to thyroglobulin, forming monoiodotyrosine (MIT).MIT is next iodinated at the 5 position, forming diiodotyrosine (DIT).Two DIT molecules then condense in an oxidative process ("coupling reaction") to form one thyroxine (T4) molecule.Some T3 is probably formed within the thyroid gland by condensation of MIT with DIT. A small amount of reverse T3 (rT3) is also formed.In the normal thyroid, the average distribution of iodinated compounds is 23% MIT, 33% DIT, 35% T4, 7% T3, and 2% reverse T3.
Monoiodotyrosine (MIT)
Diiodotyrosine (DIT)
T3
Reverse T3
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