The Biorex Diagnostics Free Thyroxine (FT4) kit is intended for the quantitative determination of FT4 concentration in human serum by a Microplate Chemiluminescence immunoassay.
Thyroxine, the principal thyroid hormone, circulates in blood almost completely bound to carrier proteins. The main carrier is thyroxine-binding globulin (TBG). However, only the free (unbound) portion of thyroxine is responsible for the biological action. Further, the concentrations of the carrier proteins are altered in many clinical conditions, such as pregnancy.