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Sensitivity of TSH-producing pituitary cells to thyroid hormones; also a marker for the set point of thyroid homeostasis The Thyrotroph Thyroid Hormone Sensitivity Index (abbreviated TTSI , also referred to as Thyrotroph T4 Resistance Index or TT4RI ) is a calculated structure parameter of thyroid homeostasis .
The final step in thyroxine synthesis involves the free radical mediated coupling of two DIT residues, catalyzed by TPO, to form T 4 while still attached to the Tg backbone. [5] [6] When thyroid hormone is needed, Tg is internalized by thyrocytes, and proteolytic enzymes in lysosomes cleave the T 4 from Tg, allowing for its release into the ...
Thyroid function tests (TFTs) is a collective term for blood tests used to check the function of the thyroid. [1] TFTs may be requested if a patient is thought to suffer from hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid), or to monitor the effectiveness of either thyroid-suppression or hormone replacement therapy.
Thyroid's secretory capacity (G T, also referred to as thyroid's incretory capacity, maximum thyroid hormone output, T4 output or, if calculated from serum levels of thyrotropin and thyroxine, as SPINA-GT [a]) is the maximum stimulated amount of thyroxine that the thyroid can produce in a given time-unit (e.g. one second).
Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine (T 4), and then triiodothyronine (T 3) which stimulates the metabolism of almost every tissue in the body. [1]
The pituitary gland secretes thyrotropin (TSH; Thyroid Stimulating Hormone) that stimulates the thyroid to secrete thyroxine (T4) and, to a lesser degree, triiodothyronine (T3). The major portion of T3, however, is produced in peripheral organs, e.g. liver, adipose tissue, glia and skeletal muscle by deiodination from
Thyroid-stimulating hormone (TSH) released from the anterior pituitary (also known as the adenohypophysis) 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.
TSH levels are determined by a classic negative feedback system in which high levels of T3 and T4 suppress the production of TSH, and low levels of T3 and T4 increase the production of TSH. TSH levels are thus often used by doctors as a screening test, where the first approach is to determine whether TSH is elevated, suppressed, or normal. [25]