FSU BIOL 610 - Thyroid Notes (21 pages)

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Phayrngeal Region Endocrine Glands Thyroid Phayrngeal Region Endocrine Glands Thyroid Follicular cell with a space for hormone storage Produce T4 and T3 calcitonin Iodine based Present in all vertebrates Chemistry T4 tetraiodothyroxine T3 Triiodothyroxine Thyroglobulin Phayrngeal Region Endocrine Glands Thyroid Synthesis of thyroid hormone Iodine uptake Iodination of tyrosine Coupling of iodinated tyrosines Proteolysis of thyroglobulin Phayrngeal Region Endocrine Glands Thyroid Synthesis of thyroid hormone Iodine uptake Iodine reduced to iodide follicular cells actively uptake iodine next the iodide diffuses in to the thyroglobulin Iodination of tyrosine Iodine and tyrosine come in contact and form monoiodotyrosine MIT and diiodotyrosine DIT Coupling Two DIT T4 MIT DIT T3 Proteolysis Cells bite off part of thyroglobulin take it into the cell lysosomal action released MIT DIT T3 T4 Conversion of T4 to T3 T4 in blood and tissue is converted by 5 monodiodinase to form T3 Circulation Bound to TBG Thyroxine binding globulins Long life 6 7 days T4 binds T3 Metabolism of T4 Diodinated to form T3 Deaminated to form propionic acids Decarboxylated to in cells All generate biologically active products Thyroid Hormone Pharmacology Effects on iodination coupling or conversion Inhibition of TRF hyp or TSH pit by long loop feedback Inhibition of T4 to T3 conversion causes hypertrophy goiter Goiter over production of TSH because long loop feedback is absent Thyroid Hormone Pharmacology goiterogens Chemical agents affecting T4 T3 Propylthiouracil Methimazole Iodine Ionic inhibitors Thyroid Hormone Function T4 is a prohormone T3 is the active form of the hormone 90 of effects caused by T3 Functions include Regulation of metabolism Metabolic biochemistry Growth and development Behavior Thyroid Hormone Function Is the thyroid essential for life Thyroid Hormone Function Metabolic effects Caloriogenesis Water and electrolyte balance Biochemical metabolism fat carbohydrate protein Growth