PSL201Y1 Chapter : PSL201 – Feb 26 – Endocrine 3 Thyroid Hormones.docx
Document Summary
Thyroid gland and parathyroid glands thyroid gland: butterflyshaped structure on the ventral side of the trachea: secretes t3,/t4 (regulate metabolic rates), and calcitonin (regulates calcium levels in blood) Parathyroid glands: smaller structures on posterior surface of the thyroid: secrete parathyroid hormone (pth) Thymus close to the heart and secretes thymosin critical for normal immune function. Work to maintain rather than trigger little change in levels. Hormones produced from follicles: single outer layer of follicular cells surrounding a central protein rich colloid secreted by the follicular cells. C cells are located in the space between follicles: synthesize and secrete calcitonin. Throboglobulin (tg): primary substance found in colloid that functions as a precursor for thyroid hormones. Steps of thyrois hormone secretion and synthesis: tg residues are iodinated forming monoiodotyrosine (mit) Addition of a second iodide forms diiodotyrosine (dit: two mit or dit on the same tg molecule are coupled and two tyrosine are linked together by a double bond.
