thyroxine


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Related to thyroxine: Levothyroxine

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.
free thyroxine the fraction of thyroxine in the serum that is not bound to a binding protein.

thy·rox·ine (T4),

, thyroxin (thī-rok'sēn, -sin),
The l-isomer is the active iodine compound existing normally in the thyroid gland and extracted therefrom in crystalline form for therapeutic use; also prepared synthetically; used for the relief of hypothyroidism, cretinism, and myxedema.

thyroxine

(thī-rŏk′sēn′, -sĭn) also

thyroxin

(-rŏk′sĭn)
n.
An iodine-containing hormone, C15H11I4NO4, produced by the thyroid gland, that increases the rate of cell metabolism and regulates growth and that is made synthetically for treatment of thyroid disorders.

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.

thy·rox·ine

, thyroxin (thī-rok'sēn, -sin)
The active iodine compound existing normally in the thyroid gland and extracted therefrom in crystalline form for therapeutic use; also prepared synthetically; used for the relief of hypothyroidism, congenital hypothyroidism, and myxedema.

thyroxine

The principal thyroid hormone. Thyroxine has four iodine atoms in the molecule and is often known as T4. The sodium salt of thyroxide (levothyroxine) is sold as a drug used to treat thyroid deficiency disorders (hypothyroidism) under the brand name Eltroxin.

thyroxine

a complex organic compound containing iodine which is the main hormone produced by the THYROID GLAND.

Thyroxine (T 4 )

Thyroid hormone that regulates many essential body processes.
Mentioned in: Hypothyroidism

thy·rox·ine

, thyroxin (thī-rok'sēn, -sin)
The active iodine compound existing normally in the thyroid gland and extracted therefrom in crystalline form for therapeutic use; also prepared synthetically; used for the relief of congenital hypothyroidism, and myxedema.
References in periodicals archive ?
The most common causes of non-responders to thyroxine treatment are non-compliance or insufficient or varying degrees of absorption.
He writes: "There are only two published reports that give details of the patients' clinical assessment when the dose of thyroxine has been titrated [carefully adjusted] to return the TSH to the reference range."
Patients who are treated with thyroxine should be followed for possible side effects of the medication, including arrhythmia and osteopenia, particularly in elderly patients and those who take the medication for long periods.
"Thyroxine in goiter, Helicobacter pylori infection, and chronic gastritis," NEJM, April 27, 2006.
By the 1970s, thyroxine was the only acceptable treatment modality for hypothyroidism because, of course, the iodophobic domino effect of the 1948 Wolff-Chaikoff publication prevented physicians from supplementing their patients with iodine.
If the thyroid gland produces too much thyroxine (also known as hyperthyroidism or thyrotoxicosis), the body goes into overdrive producing symptoms such as: l Intolerance of hot conditions and excessive sweating l Rapid heart rate and pulse l Increase in energy levels l Weight loss Insomnia l Anxiety, irritability, nervousness, or even panic attacks l Difficulty concentrating l Tremors and diarrhoea Tiredness l Dry skin, eye problems, fine hair and erratic periods.
The University of Aberdeen has already identified that mice with a higher metabolic rate live longer, and greater thyroxine in the body helps this.
The horse was successfully treated with thyroxine and is now, of course, the most winning equine in southern England.
Thyroxine, which is used to treat thyroid deficiency, as well as amphetamine-based diet pills, were found to be strongly linked to homosexuality in female offspring: the mothers of lesbians were up to eight times more likely to have taken such drugs (especially in the first trimester).
Effects of thyroxine as compared with thyroxine plus triiodothyronine in patients with hypothyroidism.
Prof Lazarus, a clinical endocrinologist at Llandough Hospital, and his team will screen mothers-to-be for low levels of thyroxine or high levels of thyroid stimulating hormone in their blood before their 16th week of pregnancy.
During the following week, the patient was noted to have rising levels of serum free thyroxine ([T.sub.4]) and triiodothyronine ([T.sub.3]) and a corresponding reduction in the level of serum thyroid-stimulating hormone (TSH) (figure).

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