Overview General thyroid hormone synthesis two forms (T3 and T4) T3 is more potent than T4 rT3 is inactive contain iodine transported in blood bound to thyroxine-binding globulin (TBG) Function bone growth CNS maturation recall cretinism involves short stature and mental retardation increase the basal metabolic rate via ↑ Na+/K+-ATPase activity results in ↑ O2 consumption, RR, and body temperature ↑ β1 receptors in heart results in ↑ CO, HR, SV, and contractility recall the importance of treating hyperthyroidism with β-blockers ↑ glycogenolysis, gluconeogenesis, and lipolysis Synthesis created in the thyroid gland stored in thyroid follicles thyroid peroxidase responsible for oxidation, organification, and coupling forms I2 via oxidation of I- forms thyroglobulin via organification of I2 T4 converted to T3 in peripheral tissues by outer ring deiodinase T4 converted to rT3 by inner ring deiodinase Regulation TRH released from the hypothalamus to stimulates TSH release from the pituitary TSH stimulates follicular cells to produce T3 and T4