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Book

Physiology, Thyroid

Yasaman Pirahanchi  1 , Muhammad Ali Tariq  2 , Ishwarlal Jialal  3
In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan.
.
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Physiology, Thyroid

Yasaman Pirahanchi et al.
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Excerpt

The thyroid gland comprises thyroid follicles that synthesize and store thyroid hormone. The epithelial cells, referred to as follicular cells or thyrocytes, surround the colloid in the lumen. The ultimo-branchial cells or neural cells accompanying them are the origins of the C-cells in the thyroid gland, which secrete the hormone calcitonin. The hypothalamus releases thyroid-releasing hormone (TRH), which stimulates thyrotrophs of the anterior pituitary to secrete thyroid-stimulating hormone (TSH). The anterior pituitary releases TSH and stimulates the thyroid follicular cells to release thyroxine, T4 (80%), triiodothyronine, or T3 (20%). The synthesis of thyroid hormones depends on the availability of iodide, TSH stimulation, and tyrosine residues on thyroglobulin. When T4 is released into circulation, it can convert to T3 through deiodination. T4 and T3 can then exert negative feedback on TSH levels, with high levels of T3/T4 decreasing TSH and low levels of T3/T4 increasing TSH levels from the anterior pituitary. This topic reviews the physiology, biochemistry, and clinical relevance of thyroid hormones.

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Conflict of interest statement

Disclosure: Yasaman Pirahanchi declares no relevant financial relationships with ineligible companies.

Disclosure: Muhammad Ali Tariq declares no relevant financial relationships with ineligible companies.

Disclosure: Ishwarlal Jialal declares no relevant financial relationships with ineligible companies.

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