seen for analysing serumthyroxin, which compensates for the change in the content of thyroxinbindande globulin

摘要

The method is a dual competitive protein binding assay in which serum thyroxine competes with radioactively labeled thyroxine for binding cites on patient and reagent thyroxine binding globulin (TBG). Preferably, a polyurethane sponge which may contain an ion exchange resin is used to separate the free from the protein bound thyroxine. The assay is based on the capacity of a dilute acid to release thyroxine from its protein bound form in patient serum samples. Upon pH adjustment, the partially renatured serum proteins compete with added exogenous thyroxine binding globulin for the liberated serum thyroxine and added radioactively labeled thyroxine. The value obtained by the assay is indicative of the patient's true thyrometabolic state. As an example, the euthyroid patient with an elevated thyroxine binding globulin level resulting from pregnancy or estrogen therapy will have a value in the euthyroid range rather than an elevated value.