Part of “CHAPTER 33 – THYROID FUNCTION TESTS“

Occasional patients have autoantibodies to T₄, T₃, or both.27,31,32 Depending on the method used to separate bound from free hormone in the RIA, these patients may have spuriously high or low T₄ or T₃ values (Fig. 33-5). These antibodies are usually immunoglobulin G and can be identified by a variety of techniques, including affinity chromatography, immunoprecipitation, immunoelectrophoresis, and RIA. The presence of such antibodies should be considered when serum T₄ or T₃ measurements conflict with the clinical presentation.