Triiodothyronine (T3) is a useful marker for the diagnosis of hypothyroidism and hyperthyroidism. The level of T3 is decreased in hypothyroid patients and is increased in hyperthyroid patients, graves disease, and pregnancy. BioVision’s human Triiodothyronine (T3) kit is a solid phase competitive ELISA Kit. The samples and T3 enzyme conjugate are added to the wells coated with anti-T3 monoclonal antibody. T3 in the sample competes with a T3 enzyme (HRP) conjugate for binding sites. Unbound T3 and T3 enzyme conjugate are washed off by wash buffer. Upon the addition of the substrate, the intensity of color is inversely proportional to the concentration of T3 in the samples. A standard curve is prepared relating color intensity to the concentration of the T3.