Free Triiodothyronine (fT3) ELISA
The Calbiotech, Inc. (CBI) fT3 ELISA kit is used for the quantitative measurement of free Triiodothyronine (fT3) in human serum.
Over 99% of T3 circulates in blood is bound to carrier proteins; thyroxine-binding globulin (TBG). However, only the free (unbound) portion of T3 is responsible for the biological action. Further, the concentrations of the carrier proteins are altered in many clinical conditions, such as pregnancy. In normal thyroid function as the concentrations of the carrier proteins alters, the total T3 level changes so that the freeT3 concentration remains constant. Thus, measurements of free T3 concentrations correlate more reliably with clinical status than total T3 levels. The increase in total T3 levels associated with pregnancy, oral contraceptives and estrogen therapy result in higher total T3 levels while the free T3 concentration remains basically unchanged.
The CBI fT3 is a solid phase competitive ELISA. The samples Anti-T3 Biotin and fT3 enzyme conjugate are added to the wells coated with Streptavidin. fT3 in the patient’s serum competes with a T3 enzyme conjugate for binding sites. Unbound T3 and T3 enzyme conjugate is washed off by washing buffer. Upon the addition of the substrate, the intensity of color is inversely proportional to the concentration of fT3 in the samples. A standard curve is prepared relating color intensity to the concentration of the fT3.
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