Radioimmunoassay for Human Testosterone-Estradiol Binding Globulin*

Abstract

We isolated testosterone-estradiol-binding globulin (TeBG) from human pregnancy plasma and used the isolated protein to obtain a rabbit antiserum to it. Using immunochemical techniques, the antiserum was demonstrated to be both monospecific and to have the ability to remove TeBG-binding activity from human serum. This antiserum was used to develop a RIA for human TeBG. The sensitivity is such that TeBG can be determined in as little as 0.005 microliter serum or plasma, although we routinely use 0.5-1.0 microliter. The correlation between the RIA and an established binding assay, using 63 different specimens, was 0.995.