Triiodothyronine (T3) And Thyroxine (T4) Triiodothyronine (T3) and Thyroxine (T4) are hormones produced by the thyroid and are primarily responsible for regulating metabolism. They predominately circulate bound to a carrier protein (e.g. thyroid-binding globulin, prealbumin, and albumin), rendering them biologically inactive. T4 is the major form of the hormone and is converted into active T3 by deiodinases (5’-deiodinase). Although circulating levels of T4 are much greater than T3 levels, 99% of T4 remains bound and inactive. Overall, T3 possess more biological activity than T4 (3-4 times more) and its effect are briefer due to its shorter half-life compared to T4. T3 and T4 diagnostic assays complement the TSH assay, and are used to confirm a thyroid disorder or to monitor the effectiveness of treatment. Blood tests can measure total T4, free T4, total T3, or free T3. The total hormone concentration is dependent on the concentration of thyroid transport proteins, therefore any conditions that affect levels of thyroid binding proteins will affect the total (but not the free) T4 hormone levels. For example, estrogens and acute liver disease will increase thyroid binding, while androgens, steroids, chronic liver disease and severe illness can decrease it. Overall, T3 levels are thought to be a more sensitive indicator of hyperthyroidism than total T4 and it is useful in monitoring both patients under treatment for hyperthyroidism, and in patients who have discontinued anti-thyroid drug therapy. It is especially valuable in distinguishing between euthyroid and hyperthyroid subjects. T3 levels are elevated in women who are pregnant, and in women receiving oral contraceptives or estrogen treatment. Total and free T3 and T4 serum levels are measured using competitive quantitative immunoassays.
Reagents for Immunoassay Development
MAb toTriiodothyronine (T3) • Cross-reactivity: T4 (<0.28%) MAb toTriiodothyronine (T3) • Cross-reactivity: Triiodothyroacetic Acid (<11%) Tetraidodothyroacetic Acid (<0.30%) MAb toThyroxine (T4) • Cross-reactivity: T3 (<1%), T2 (<1%), rT3 (<1%) MAb toThyroxine (T4) • Cross-reactivity: T3 (1.0%), rT3 (1.4%) MAb toTriiodothyronine (T3) • Reacts with both conjugate T3-BSA and free T3 • Cross-reactivity with Thyroxine is (0.1%)
E86207M
MAT01-121
MAT01-237
Suitable for use in Competitive ELISA
MKT02-007
MAT02-525
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Endocrine Disorders- Reagents for Assay Development
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