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Thyroid function testing often shows decreased thyroid stimulating hormone and increased serum levels of triiodothyronine and thyroxine during the acute phase. Thyroid scans show minimal uptake during the acute phase due to disrupted thyroid follicles, but increase during recovery due to the thyroid gland's enhanced iodine trapping capacity.
Thyroid follicular cells form a simple cuboidal epithelium and are arranged in spherical thyroid follicles surrounding a fluid filled space known as the colloid. The interior space formed by the follicular cells is known as the follicular lumen .
In small doses, when they are taken up by overactive thyroid follicular cells, they emit small amounts of beta radiation that destroys not all, but many thyroid follicular cells, thereby reducing thyroid hormone production. [15] This is a form of targeted therapy for hyperthyroidism.
Once inside the follicular cells, the iodide diffuses to the apical membrane, where it is metabolically oxidized through the action of thyroid peroxidase to iodinium (I +) which in turn iodinates tyrosine residues of the thyroglobulin proteins in the follicle colloid. Thus, NIS is essential for the synthesis of thyroid hormones (T 3 and T 4). [14]
Hashimoto's Thyroiditis is a T-lymphocyte mediated attack on the thyroid gland. [15] T helper 1 cells trigger macrophages and cytotoxic lymphocytes to destroy thyroid follicular cells, while T helper 2 cells stimulate the excessive production of B cells and plasma cells which generate antibodies against the thyroid antigens, leading to ...
The Wolff–Chaikoff effect is known as an autoregulatory phenomenon that inhibits organification in the thyroid gland, the formation of thyroid hormones inside the thyroid follicle, and the release of thyroid hormones into the bloodstream. [6] This becomes evident secondary to elevated levels of circulating iodide.
Thyroid-stimulating hormone (TSH) released from the anterior pituitary gland binds the TSH receptor (a G s protein-coupled receptor) on the basolateral membrane of the cell and stimulates the endocytosis of the colloid. The endocytosed vesicles fuse with the lysosomes of the follicular cell. The lysosomal enzymes cleave the T 4 from the ...
Thyroglobulin (Tg) is a 660 kDa, dimeric glycoprotein produced by the follicular cells of the thyroid and used entirely within the thyroid gland. Tg is secreted and accumulated at hundreds of grams per litre in the extracellular compartment of the thyroid follicles, accounting for approximately half of the protein content of the thyroid gland. [5]