triiodothyronine


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triiodothyronine

 [tri″i-o″do-thi´ro-nēn]
a thyroid hormone that contains iodine and is liberated from thyroglobulin by hydrolysis. It has several times the biologic activity of thyroxine.
free triiodothyronine the fraction of triiodothyronine in the serum that is not bound to a binding protein.
triiodothyronine resin uptake test a thyroid function test, measuring how many sites on thyroxine-binding globulin (TBG) are occupied by endogenous triiodothyronine (T3) and how many sites remain available. An excess of radioactive exogenous triiodothyronine is added to the sample, followed by the addition of a resin that also binds T3. A portion of the radioactive T3 binds to sites on TBG not already occupied by endogenous thyroid hormones, and the remainder binds to the resin. The amount of labeled hormones bound to the resin (the triiodothyronine resin uptake) can be subtracted from the total that was added and the remainder is the amount that bound to the unoccupied binding sites on the thyroxine-binding globulin.

triiodothyronine

/tri·io·do·thy·ro·nine/ (tri″i-o″do-thi´ro-nēn) one of the thyroid hormones, an organic iodine-containing compound liberated from thyroglobulin by hydrolysis. It has several times the biological activity of thyroxine. Symbol T3.

triiodothyronine

(trī′ī-ō′dō-thī′rə-nēn′, -ī-ŏd′ō-)
n.
A thyroid hormone, C15H12I3NO4, similar to thyroxine but more potent, used in the treatment of hypothyroidism.

triiodothyronine (T3)

[trī′ī·ō′dōthī′rənēn]
a hormone that helps regulate growth and development, helps control metabolism and body temperature, and, by a negative-feedback system, acts to inhibit the secretion of thyrotropin by the pituitary gland. Triiodothyronine is produced mainly from the deiodination of thyroxine in the peripheral tissues but is also synthesized by and stored in the thyroid gland as an amino acid residue of the protein thyroglobulin. Triiodothyronine circulates in the plasma, where it is bound mainly to thyroxine-binding globulin and thyroxine-binding prealbumin, proteins that protect the hormone from metabolism and excretion during its half-life of 2 days or less before it is degraded in the liver. The hormone is the most active thyroid hormone and affects all body processes, including gene expressions. It is a component of various drugs, such as liotrix and liothyronine sodium, used in the treatment of hypothyroidism and simple goiter. Normal adult blood levels are 110 to 230 ng/dL. See also thyroid hormone.

triiodothyronine

T3, 3,5,3´,-´triiodothyronine A hormone formed by removing an iodine ion from the chemical parent thyroxine–T4, which occurs in the liver and kidney; in general, the T3 and T4 serum levels rise and fall together with certain exceptions–eg, T3 thyrotoxicosis, in which T4 and free T4 values are in the normal range; most T3 is not bound to a carrier protein in the circulation ↑ in Hyperthyroidism–T3 thyrotoxicosis, pregnancy, and therapy with clofibrate,–oral contraceptives–progestins, estrogens, methadone, perphenazine ↓ in Euthyroid sick syndrome, ↑ free fatty acids, hypothyroidism, malnutrition, or therapy with corticosteroids, ethionamide, heparin, iodides, lithium, methimazole, phenylbutazone, phenytoin, propranolol, propylthiouracil, reserpine, salicylates, sulfonamides, testosterone, tolbutamide; Pts with T3 thyrotoxicosis are clinically heterogeneous and lack distinctive signs and Sx, comprising 4% of hyperthyroid Pts due to Graves' disease, toxic nodular goiter and thyroid adenomas and a higher percentage of hyperthyroidism in regions with lower levels of iodine Ref value 0.92-2.46 nmol/L; 60-160 ng/dL. See Thyroxine–T4, Thyroxine-binding globulin, TSH.

triiodothyronine (trī´īō´dōthī´rə-nēn´),

n a hormone that helps regulate growth and development, control metabolism and body temperature, and by a negative-feedback system, inhibit the secretion of thyrotropin by the pituitary gland.
References in periodicals archive ?
Low ambient temperature elevates plasma triiodothyronine concentrations while reducing digesta mean retention time and methane yield in sheep.
Todisco, "Low triiodothyronine (T3) state: a predictor of outcome in respiratory failure?
Growth and plasma triiodothyronine concentrations are modified by selenium deficiency and repletion in second-generation selenium-deficient rats.
Further, since serotonin is known as an inhibitory neurotransmitter in the secretion of thyrotropin-releasing hormone, harmala seed extract, by increasing the rate of serotonin causes a decrease of secretion of thyrotropin-releasing hormone and subsequently thyroid stimulating hormone levels in plasma, so thyroxine and triiodothyronine would decrease [16].
Alterations of serum reverse triiodothyronine and thyroxine kinetics in chronic renal failure: role of nutritional status, chronic illness, uremia, and hemodialysis.
In recent years, attention has shifted towards milder forms of thyroid disease, such as the so-called "low T3 syndrome", which is characterized by an isolated reduction in circulating levels of the biologically active form of thyroid hormone, triiodothyronine (T3).
Triiodothyronine is an option in adjunctive depression treatment, even for patients with a normal thyroid; longer-term studies are needed to assess its efficacy and long-term safety.
Serum thyroxin (T4), free thyroxin (fT4), triiodothyronine (T3), free triiodothyronine (fT3), glucose, beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), triglyceride (TAG), cholesterol, very low density lipoproteins (VLDL-cholesterol), low density lipoproteins (LDL- cholesterol) and high density lipoproteins (HDL-cholesterol) were investigated.
The levels of thyrotropin, free thyroxine and triiodothyronine, dehydroepiandrosterone, its sulfate and its 7-hydroxyepimers were measured.
In experiments on adult rats have snown that relatively high doses of LCT lead to a marked decrease in the concentration of thyroxine (T4) and triiodothyronine (T3), which was accompanied by increase in thyroid-stimulating (TSH) hormone (Akhtar, Kayani, Ahmad, and Shahab, 1996).
Triiodothyronine modulates growth, secretory function and androgen receptor concentration in the prostatic carcinoma cell line LNCaP.
When the thyroid gland produces an excess of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), it essentially cranks up the furnace, thereby accelerating metabolic activity in your cat.