PHGY 214 Lecture Notes - Lecture 2: Catecholamine, Catabolism, Heat Intolerance
11 May 2016
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Thyroid gland, describe the synthesis of thyroid hormones. Thyroglobulin is produced and transported inside lumen by exocytosis, where the cells actively take up iodide. The iodide is inactive thus through tpo is activated. Activated iodide diffuses into colloid (follicle) and tpo incorporates iodide onto tyrosine to form two different forms (t1 and t2) T1 and t2 then form t3 and also make t4. * t3 and t4 are stored in colloid, which is mostly water, thus both are hydrophilic. * the binding to thyrogloubin is what makes t3 and t4 hydrophilic. * t3 (tri-iodotyronine) and t4 (tetra-iodotyronine) are amine hormones. When there is a signal for secretion, the follicular cell engulfs some of the colloid (which contains t1- Lysosome attack the thyroglobulin and the substituents are freed. Free t3 and t4 is no longer hydrophilic but lipophilic, which allows it to diffuse through the membrane into the blood (circulation)
