Enzyme Immunoassay for the Quantitative Determination of Triiodothyronine (T3) in Human Serum

for in vitro diagnostic use

Product Description
The thyroid gland exerts powerful and essential regulatory influences on growth, differentiation, cellular metabolism, and general hormonal balance, as well as on the maintenance of metabolic activity and the development of the skeletal and organ system.

The hormones thyroxine (T4) and 3,5,3’ triiodothyronine (T3) circulate in the blood stream, mostly bound to the plasma protein, thyroxine binding globulin. (TBG). The concentration of T3 is much less than that of T4, but its metabolic potency is much greater. T3 determination is an important factor in the diagnosis of thyroid disease. It’s measurement has uncovered a variant of hyperthyroidism in thyrotoxic patients with elevated T3 levels and normal T4 levels. An increase in T3 without an increase in T4 is frequently a forerunner of recurrent thyrotoxicosis in previously treated patients. In other patients, euthyroidism is attributable to normal T3, although their T4 values are subnormal.

T3 determination is also useful in monitoring both patients undertreatment for hyperthyroidism and patients who have discontinued anti-thyroid drug therapy. It is especially valuable in distinguishing between euthyroid and hyperthyroid subjects.

In women, T3 levels are elevated during pregnancy, during estrogen treatment, and contraceptive hormone therapy. When T3 levels parallel TBG increases in a manner analogous to T4 levels, these changes are not a reflection of altered thyroid status.

Principle
In the T3 EIA, a second antibody (goat anti-mouse IgG) is coated on microtiter wells. A measured amount of patient serum, a certain amount of mouse monoclonal anti-T3 antibody, and a constant amount of T3 conjugated with horseradish peroxidase are added to the microtiter wells. During incubation, the mouse anti-T3 antibody is bound to the second antibody on the wells, and T3 and conjugated T3 compete for the limited binding sites on the anti-T3 antibody.
After a 60-minute incubation at room temperature, the wells are washed 5 times by water to remove unbound T3 conjugate. A solution of TMB Reagent is then added and incubated for 20 minutes, resulting in the development of blue color.
The color development is stopped with the addition of Stop Solution, and the absorbance is measured spectrophotometrically at 450nm.
The intensity of the color formed is proportional to the amount of enzyme present and is inversely related to the amount of unlabeled T3 standards assayed in the same way, the concentration of T3 in the unknown sample is then calculated.

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