T-3, 96 Wells

This Total T3 EIA is intended for the quantitative determination of triiodothyronine (T3) concentration in human serum. This test is useful in the diagnosis and treatment of thyroid diseases such as hyperthyroidism.

The thyroid hormones, thyroxine (T4) and 3, 5, 3’ triiodothyronine (T3) circulate in the bloodstream mostly bound to the plasma protein, thyroxine binding globulin (TBG).1 The concentration of T3 is much less than that of T4, but its metabolic potency is much greater.2,3 These as well as other hormones are produced by the thyroid gland, situated at the level of the thyroid cartilage on either side of the larynx. The thyroid gland and associated hormones are a major component of the endocrine system. They exert powerful and essential regulatory influences on growth, differentiation, cellular metabolism, and general hormonal balance of the body, as well as on the maintenance of metabolic activity and the development of the skeletal and organ systems.

T3, T4 and TSH determination are important factors in thyroid disease diagnosis. T3 determination is useful in monitoring both patients under treatment for hyperthyroidism, and patients who have discontinued anti-thyroid drug therapy. It is especially valuable in distinguishing between euthyroid and hyperthyroid subjects.4 T3 measurement has uncovered a variant of hyperthyroidism in thyrotoxic patients with elevated T3 values and normal T4 values.5 Likewise, an increase in T3 without an increase in T4 is frequently a forerunner of recurrent thyrotoxicosis in previously treated patients.

In addition to hyperthyroidism, T3 levels are elevated in women who are pregnant, and in women receiving oral contraceptives or estrogen treatment. The clinical significance of T3 is also evident in patients where euthyroidism is attributable only to normal T3, although their T4 values are subnormal.