BCH 4123 Lecture Notes - Lecture 7: Thyroxine-Binding Globulin, Anti-Thyroid Autoantibodies, Thyroid Storm
8 Feb 2017
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Regulation: classic negative feedback system from the hormone itself, trh from hypothalamus, tsh from anterior pit, t4 and t3 produced by thyroid gland, liver activates thyroid hormones or conjugates them for excretion. Anatomy: composed of follicles surrounded by cuboidal cells. Filled with colloid where hormones are produced from thyroglobulin. Synthesis and conversion: synthesized from tyrosine residues of thyroglobulin, requires tsh and iodine, t4 (thyroxin) is prohormone and converted to t3 by peripheral metabolism. Only some affinity for thyroid receptor: t3 (triiodothyronine) is active hormone. 80% derived from diodination of t4: reverse t3 is inactive. Peripheral conversion: activating and deactivating deiodinases. Above three transport >99% of the hormone: concentration of binding proteins affects total hormone but not free hormone concentrations (because of so much regulation) increased binding proteins during pregnancy, acute hepatitis, oral contraceptives (increased total hormone) Decreased binding protein during chronic liver disease, malnutrition, acromegaly, glucocorticoids, etc (decreased total hormone)
