Phayrngeal Region Endocrine GlandsThyroidPhayrngeal Region Endocrine Glands• Thyroid• Follicular cell with a space, for hormone storage• Produce T4and T3 ,calcitonin• Iodine based• Present in all vertebrates•Chemistry–T4-tetraiodothyroxine–T3-Triiodothyroxine– ThyroglobulinPhayrngeal Region Endocrine Glands• Thyroid• Synthesis of thyroid hormone– Iodine uptake– Iodination of tyrosine– Coupling of iodinated tyrosines– Proteolysis of thyroglobulinPhayrngeal 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,T4Conversion of T4to T3•T4in blood and tissue is converted by 5 monodiodinase to form T3• Circulation– Bound to TBG (Thyroxine binding globulins)– Long ½ life (6-7 days)– T4 binds >T3Metabolism 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 T4to T3conversion 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 inhibitorsThyroid Hormone Function•T4is a prohormone, T3is the active form of the hormone, 90 % of effects caused by T3• Functions include– Regulation of metabolism– Metabolic biochemistry– Growth and development– BehaviorThyroid Hormone Function• Is the thyroid essential for life?Thyroid Hormone Function• Metabolic effects– Caloriogenesis– Water and electrolyte balance– Biochemical metabolism (fat, carbohydrate, protein)– Growth and development• Maturity• Development of CNS• Mammary glandsThyroid Hormone Function• Other effects– Stimulation of CNS– Protein metabolism– Insomnia– Blood pressure– Body temperature– Molting–