Synthesis of thyroid hormones

synthesis of thyroid hormones

1. SYNTHESIS OF THYROID HORMONES Ms.Anu Sebastian: B.Pharm ; M.Pharm Assistant Professor, Dept. Of Pharmacology Nirmala College Of Pharmacy Muvattupuzha,Ernakulam,Kerala

2. STEPS INVOLVED IODIDE TRAPPING SYNTHESIS OF THYROGLOBULIN(TGB) OXIDATION OF IODIDE IODINATION OF TYROSINE COUPLING OF T1 & T2 PINOCYTOSIS & DIGESTION OF COLLOIDS SECRETION OF THYROID HORMONES TRANSPORT IN THE BLOOD

3. IODIDE TRAPPING Follicular cells trap iodide ions by Na- Iodide transporter. SYNTHESIS OF THYROGLOBULIN(TGB) TGB is large glycoprotein synthesized in the rough endoplasmic reticulum of follicular cells. Modified & stored in secretory vesicles by Golgi apparatus. Then these are released into the lumen of thyroid follicles.

4. OXIDATION OF IODIDE For the synthesis of thyroid hormones, the aminoacids ( ie Tyrosine ) of TGB need to be iodinated. Negatively charged iodide ions cant iodinate tyrosine.So they undergo oxidation by the enzyme peroxidase to form iodine . IODINATION OF TYROSINE If one iodine react with tyrosine –forms monoiodotyrosine . If two iodine react with tyrosine – forms Diiodotyrosine , Colloid – The TGB with attached iodine atom is stored in the lumen of the thyroid follicle.

5. COUPLING T1 & T2 Two molecules of T2 join to form T4( Tetraiodotyronine ) One molecule of T2 & one molecule of T1 join to form T3( Triiodotyronine ) PINOCYTOSIS AND DIGESTION OF COLLOIDS Droplets of colloid re-enter follicular cells by pinocytosis . It will fuse with lysosome . The digestive enzyme protease in lysosome breakdown Thyroglobulin and release T3 & T4.

6. SECRETION OF THYROID HORMONES As T3 & T4 are lipid soluble,they diffuse through the plasma membrane and reaches blood circulation . TRANSPORT IN THE BLOOD T3 & T4 are transported in the blood by combining with transport proteins in blood ie Thyroxine binding proteins.

7. THANK YOU