KINESIOL 1AA3 Lecture Notes - Lecture 20: Aldosterone, Adrenergic, Cortisone
18 Apr 2016
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Contains 2 cells: follicular cells contains colloid, parafollicular cells secretes calcitonin. Colloid: contains thyroglobulin, stores thyroid hormones. Triiodothyronine t3: the active form, target tissue all cells. Tetraiodothyronine (thyroxine) t4: the precursor to t3, target tissue all cells. Thyroglobulin: synthesized in the follicular cell. Iodates the tyrosine molecules: thyroglobulin is exocytosed into the lumen. 2 iodinated tyrosine molecules come together: forms t3 and t4, stored in thyroglobulin. Thyroid stimulating hormone: stimulates t3 and t4 secretion, thyroglobulin is endocytosed back into the cell. Lysosomal degradation: digests the thyroglobulin, forms amino acid and t3 and t4. T3 and t4 diffuse out of the cell. Increasing secretion: secrete thyroid releasing hormone, secretes thyroid stimulating hormone. Increases metabolic rate: results in heat production. Thyroid hormones are bound: 75% bound to thyroxine-binding globulin, 25% bound to other proteins. Forms large reservoirs of circulating thyroid hormones: also increases the half life. Some of t4 is converted into t3 (40%: has a higher affinity for the nuclear receptor.
