thyroxine /thy·rox·ine/ (T4) (thi-rok´sin) an iodine-containing hormone secreted by the thyroid gland, occurring naturally as l-thyroxine; its chief function is to increase the rate of cell metabolism. It is deiodinated in peripheral tissues to form triiodothyronine, which has greater biological activity. A preparation of thyroxine, levothyroxine, is used pharmaceutically.
Thyroxine (T 4 )
thyroxine (T4)
thyroxine (T4) [thi-rok´sin]
thyroxine (thīrok´sin),
thyroxine
thy·rox·ine (th -r k s n , -s n) or thy·rox·in (-rksn)n. Abbr. T4 An iodine-containing hormone that is produced by the thyroid gland, increases the rate of cell metabolism, regulates growth, and is made synthetically for treatment of thyroid disorders. |
Thyroxine (T 4 )
Thyroid hormone that regulates many essential body processes.
Mentioned in: Hypothyroidism
thyroxine (T4)
[thīrok′sēn]
a hormone of the thyroid gland, derived from tyrosine and deiodinated in the periphery to T3 (triiodothyronine) that stimulates metabolic rate. Also called tetraiodothyronine.
thyroxine (T4) [thi-rok´sin]
a thyroid hormone that contains iodine and is a derivative of the amino acid tyrosine, occurring naturally as l-thyroxine; its chemical name is tetraiodothyronine. It is formed and stored in the thyroid follicles as thyroglobulin and released from the gland by the action of a proteolytic enzyme. It is deiodinated in peripheral tissues to form triiodothyronine (T3), which has a greater biological activity.
Thyroxine acts as a catalyst in the body and influences a great variety of effects, including metabolic rate (oxygen consumption); growth and development; metabolism of carbohydrates, fats, proteins, electrolytes, and water; vitamin requirements; reproduction; and resistance to infection. Pharmaceutical preparations of thyroxine, extracted from animals or made synthetically, are called levothyroxine.
Thyroxine acts as a catalyst in the body and influences a great variety of effects, including metabolic rate (oxygen consumption); growth and development; metabolism of carbohydrates, fats, proteins, electrolytes, and water; vitamin requirements; reproduction; and resistance to infection. Pharmaceutical preparations of thyroxine, extracted from animals or made synthetically, are called levothyroxine.
free thyroxine the fraction of thyroxine in the serum that is not bound to a binding protein.
thyroxine (thīrok´sin),
n the hormone secretion of the thyroid gland, L-3,5,3´,5´-tetraiodothyronine.
thyroxine, thyroxin
a hormone of the thyroid gland that contains iodine and is a derivative of the amino acid tyrosine. The chemical name for thyroxine is tetraiodothyronine (symbol, T4); it is formed and stored in the thyroid follicles as thyroglobulin, the storage form. Thyroxine is released from the gland by the action of a proteolytic enzyme. T4 is deiodinated in peripheral tissues to form tri-iodothyronine (T3), which has a greater biological activity.
Thyroxine acts as a catalyst in the body and influences a great variety of effects, including metabolic rate (oxygen consumption); growth and development; metabolism of carbohydrates, fats, proteins, electrolytes and water; vitamin requirements; reproduction; and resistance to infection.
Thyroxine can be extracted from animals or made synthetically; it is used in the treatment of hypothyroidism and some types of goiter.
free thyroxine
the metabolically active fraction of thyroxine; abbreviated FT4, Tf. T4 = Tf + TBG. The amount is very small and difficult to estimate so that the amount present in serum is not used as a more accurate indicator of thyroxine status than T4.
thyroxine-binding globulin (TBG)
most (99.95%) of the thyroxine in plasma is bound to globulin and a small amount bound to prealbumin.
thyroxine-binding prealbumin
bound to a small fraction of circulating T4. This is the only known function of prealbumins.
L-thyroxine
see levothyroxine.
thyroxine
T4, 3,5,3',5'-Tetraiodothyronine A hormone that stimulates metabolism and O2 consumption, which is secreted by the thyroid gland in response to TSH–thyrotropin produced in the
adenohypophysis–anterior pituitary gland ↑ in Hyperthyroidism, acute thyroiditis, myasthenia gravis, preeclampsia, pregnancy, viral hepatitis, therapy with clofibrate, OCs, estrogens, perphenazine ↓ in Hypothyroidism, malnutrition,
vigorous exercise, hypofunction of adenohypophysis–anterior pituitary gland, renal failure, therapy with corticosteroids, chlorpromazine, heparin, lithium, phenytoin, propranolol, reserpine, salicylates, sulfonamides, testosterone,
tolbutamide. See Triiodothyronine–T3, Thyroxine-binding globulin.
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