AccuDx CQ T3 / T3 (Triiodothyronine) Fast Test Kit (Immunofluorescenc Assay) is intended for in vitro quantitative determination of T3 in serum and plasma. It can be used in the monitoring of hyperthyroidism and hypothyroidism, and also used as an aid in the functional diagnosis of thyroidea. Summary: The thyroid gland exerts powerful and essential regulatory influences on growth, differentiation, cellar metabolism and general hormonal balance, as well as on the maintenance of metabolic activity and the development of the sketeal and organ system. The hormones thyroxine (T4) and triiodothy- ronine (T3) circulate in the blood stream, mostly bound to the plasma protein, throxine binding globulin (TBG). The concentration of T3 is much less than that of T4, but its metabolic potency is much greater. T3 is produced by the thyroid and secreted in response to TSH. T3 determination is an important factor in the diagnosis of thyroid disease. Its 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 thyrotoxi- cosis in previously treated patients. In other patients, euthyroidism attributable to normal T3, although their T4 values are subnormal.