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 ?
The effect of endurance training on serum triiodothyronine kinetics in man: physical conditioning marked by enhanced thyroid hormone metabolism.
Since endogenous production of antibodies directed against these hormones is a rare cause of elevated serum T4 and T3 level, we examined antibodies directed to triiodothyronine and thyroxine with radioimmunoassay (RIA) (Pasteur Cerba Lab.
Israeli patients treated with sertraline (Zoloft) and triiodothyronine ([T.
Its long half-life keeps the bioavailability of the drug on a much more even keel, compared with the roller-coaster effect of synthetic triiodothyronine, or [T.
Included in the Practice Guidelines are an overview of pre-analytic factors, a discussion of the importance of the laboratory-physician interface, and a detailed look at the range of thyroid tests available, including measurement of total and free thyroxine (T4) and triiodothyronine (T3), thyroid stimulating hormone, thyroid autoantibodies (thyroid peroxidase, thyroglobulin, and thyrotrophin receptor antibodies), thyroglobulin, calcitonin, the ret proto-oncogene, and urinary iodide.
Misleadingly low free thyroxine index and usefulness of reverse triiodothyronine measurement in nonthyroidal illnesses.
BDEs 47, 99, and 100 were significantly and positively associated with free and total thyroxine levels, and with total triiodothyronine levels above the normal range.
Triiodothyronine stimulation of in vitro growth and maturation of embryonic chick cartilage.
In such cases, (131)I gets accumulated in the thyroid, and is released in the form of radioiodinated triiodothyronine (T3) and tetraiodothronine (T4).
Total triiodothyronine was unaffected, according to Dr.