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Triiodothyronine, also known as T3, is a thyroid hormone. It affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate. [ 1]
Reverse T 3 is the third-most common iodothyronine the thyroid gland releases into the bloodstream, at 0.9%; tetraiodothyronine (levothyroxine, T 4) constitutes 90% and T 3 is 9%. However, 95% of rT 3 in human blood is made elsewhere in the body, as enzymes remove a particular iodine atom from T 4. [ 1]
The major form of thyroid hormone in the blood is thyroxine (T 4), whose half-life of around one week [4] is longer than that of T 3. [5] In humans, the ratio of T 4 to T 3 released into the blood is approximately 14:1. [6] T 4 is converted to the active T 3 (three to four times more potent than T 4) within cells by deiodinases (5′-deiodinase).
Iodothyronine deiodinase. Iodothyronine deiodinases ( EC 1.21.99.4 and EC 1.21.99.3) are a subfamily of deiodinase enzymes important in the activation and deactivation of thyroid hormones. Thyroxine (T 4 ), the precursor of 3,5,3'- triiodothyronine (T 3) is transformed into T 3 by deiodinase activity. T 3, through binding a nuclear thyroid ...
Euthyroid sick syndrome ( ESS) is a state of adaptation or dysregulation of thyrotropic feedback control [ 1] wherein the levels of T3 and/or T4 are abnormal, but the thyroid gland does not appear to be dysfunctional. This condition may result from allostatic responses of hypothalamus-pituitary-thyroid feedback control, dyshomeostatic disorders ...
Intuitively, if plasma levels of T3 fall, there would be a compensatory rise in TSH, the secretion of which is inhibited by T3. However, because type 2 deiodinase mediates the conversion of T4 to T3 within the pituitary and CNS, and because caloric restriction does not affect this enzyme, local T3 levels in the pituitary are normal.Thus, the ...
003444. [ edit on Wikidata] 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 ...
The hypothalamic–pituitary–thyroid axis ( HPT axis for short, a.k.a. thyroid homeostasis or thyrotropic feedback control) is part of the neuroendocrine system responsible for the regulation of metabolism and also responds to stress. As its name suggests, it depends upon the hypothalamus, the pituitary gland, and the thyroid gland .