PHSI2006 Lecture 8: lecture 8
14 Jan 2019
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Colloid (inactive precursor of t3 and t4: made up of glycoprotein (called thyroglobulin), made by epithelial cells, bound to iodine. **in hyperthyroidism: thyroid enlarged & hyperactive, so follicles would look smaller. Parathyroid gland = embedded in capsule of thyroid gland. 2 types of cells: chief (or principle) cells: small eosinophilic staining, secrete pth (resting has paler cytoplasm, children more active, oxyphil cells: (larger & lighter staining than chief) appear onset of puberty, no known function. *pth acts on osteoclasts & epithelial cells of renal tubule to increase plasma ca by promoting bone resorption & increase renal. Thyroid effects: t3 (4-5x) > t4 >> rt3 (inert) Too little th: impaired growth and development (in utero & neonates: impaired. Too much th nett tissue breakdown eg decreased bone. Sympathomimetic effects: some similar effects to relationship to catecholamines, t4/t3 increase adrenergic receptors (no. & affinity: some effects of t4/t3 can be treated with blockers.
