Thyroid hormones exert their actions via intranuclear receptors Enter cells via membrane transporter proteins Bind to intranuclear receptors causing activation and conformation changes Allows binding of the complex to specific “thyroid responsive” sections...
<1% transported freely in plasma unbound to plasma proteins: Forms the active portion of the hormone Mostly transported by non-covalent binding to plasma proteins: Thyroid binding globulin (TBG) – predominant transport protein Transthyretin Albumin TBG has...
Can be considered in 4 steps: 1. Iodide Trapping 2. Iodide Oxidation & Organification 3. Storage in Colloid with Thyroglobulin 4. Secretion of Thyroid Hormones Iodine obtained in diet from dairy, grains and meat (150mg/day required)Reduced to the inorganic form...
T3 T4 Active form of thyroid hormone - 3x more potent than T420% of T3 secreted directly from the thyroid80% converted peripherally from T4 Often referred to as the prohormone due to low biological coactivityApproximately 90% is converted in peripheral tissues to more...
