Physiology
Thyroid Hormone Production
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Get access- TSH is a glycoprotein hormone produced by the anterior pituitary
- Actions
- Increases active transport of iodine ions into thyroid follicular cells
- Increases thyroglobulin production via peroxidase enzymes
- Increases iodinated tyrosine coupling to produce T3 and T4
- Thyroglobulin is produced in follicular cells
- T3 and T4 are transported back to the follicular cells in complex with thyroglobulin
Lysosomes cleave T3 and T4 from thyroglobulin before they are released into the circulation
Thyroid hormones
- T3:T4 is 1:100
- 99% are bound:
- 80% to thyroid binding globulin
- Thyroid binding prealbumin
- Albumin
- T3 is 2-3 times more potent
In circulation it mostly comes from deiodinated T4 rather than directly produced from the thyroid gland
- Functions
- Increase metabolic rate of tissues by increasing oxygen consumption
- Convert carotenes to vitamin A
- Decrease oxygen consumption of the anterior pituitary: negative feedback
- Sensitise myocardium to noradrenaline