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T 3 is the more metabolically active hormone produced from T 4.T 4 is deiodinated by three deiodinase enzymes to produce the more-active triiodothyronine: . Type I present in liver, kidney, thyroid, and (to a lesser extent) pituitary; it accounts for 80% of the deiodination of T 4.
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).
Hypothyroidism is common in pregnancy with an estimated prevalence of 2-3% and 0.3-0.5% for subclinical and overt hypothyroidism respectively. [8] Endemic iodine deficiency accounts for most hypothyroidism in pregnant women worldwide while chronic autoimmune thyroiditis is the most common cause of hypothyroidism in iodine sufficient parts of the world.
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] It is a glycoprotein hormone produced by thyrotrope cells ...
Low-T3 syndrome and high-T3 syndrome: Consequences of step-up hypodeiodination, e.g. in critical illness as an example for type 1 allostasis, [20] or hyperdeiodination, as in type 2 allostasis, including posttraumatic stress disorder. [12] Resistance to thyroid hormone: Feedback loop interrupted on the level of pituitary thyroid hormone receptors.
Thyroid disease is a medical condition that affects the function of the thyroid gland. The thyroid gland is located at the front of the neck and produces thyroid hormones [ 1] that travel through the blood to help regulate many other organs, meaning that it is an endocrine organ. These hormones normally act in the body to regulate energy use ...
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]
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 ...