free thyroxine


Also found in: Dictionary, Thesaurus, Encyclopedia.
Related to free thyroxine: free thyroxine index, Free Triiodothyronine

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.
References in periodicals archive ?
[2] Nonstandard abbreviations: ATA, American Thyroid Association; TSH, thyroid-stimulating hormone; FT4, free thyroxine; FT3, free triiodothyronine.
Table 1: Mean [+ or -] SD of Body Mass Index (BMI), Triiodothyronine (T3), Free thyroxine (FT4), Free Triiodothyronine, Thyrotropin (TSH), Thyroglobulin antibodies (Anti-TG) and Anti-thyroid peroxidase antibodies (Anti-TPO) in post-treatment breast, pre-treatment breast cancer patients, fibrocystic patients and healthy control subjects.
CRP: C-reactive protein; free T3: free triiodothyronine; free T4: free thyroxine; KI: potassium iodide; MPOANCA: myeloperoxidase-anti-neutrophil cytoplasmic antibody; MTX: methotrexate; PR3-ANCA: proteinase 3-anti-neutrophil cytoplasmic antibody; PSL: prednisolone; PTU: propylthiouracil; RI (13mCi): radioisotope (13mCi); TSH: thyroid-stimulating hormone.
Higher levels of free thyroxine (T4) were associated with an increased risk of SCD, with a hazard ratio of 1.87 for every 1-ng/dL increase in free T4.
Soldin, "Inverse log-linear relationship between thyroid-stimulating hormone and free thyroxine measured by direct analog immunoassay and tandem mass spectrometry," Clinical Chemistry, vol.
Two cases of antiruthenium antibody interference in modular free thyroxine assay.
Serum total thyroxine, total triidothyronine, free thyroxine, and thyrotropin concentrations in dogs with non thyroidal disease.
Pakarinen et al, (1988) showed nonbeing change of T3 and also significant decrease in thyroxine (T4) and free thyroxine (fT4) [8].
Even in cases of subclinical hyperthyroidism, which occurs when low thyroid-stimulating hormone (TSH) levels aren't accompanied by higher-than-normal free thyroxine, the risk of AF is increased.
The levels of thyrotropin, free thyroxine and triiodothyronine, dehydroepiandrosterone, its sulfate and its 7-hydroxyepimers were measured.
The researchers included all 10 prospective longitudinal cohorts in the literature that reported baseline thyrotropin and free thyroxine levels, included euthyroid control groups, and specifically tracked coronary heart disease (CHD) and mortality outcomes.