Radioimmunological assays for triiodothyronine(T3) or thyroxine(T4) in sera containing antibodies against the hormones.

For serum samples containing antibodies in vivo against triiodothyronine or thyroxine, the radioimmunoassays in use may give highly erroneous results. We wanted to compare the effects of two different radioimmunoassay systems on such sera, and to develop a suitable extraction procedure for use before such assays. Very different results were obtained with the use of single antibody or double antibody techniques on unextracted sera. The highest recoveries of total T3 and T4 from sera were found with two successive ethanol extractions.