A radioimmunoassay of human TSH, employing a solid phase second antibody, and a purified globulin preparation for standardization of nonspecific protein interactions

Abstract

A modified immunoassay system for measurement of h-TSH in serum has been developed. Differences between standards and samples in nonspecific protein-protein interactions were minimized by adding a purified bovine γ-globulin preparation to the standards. For separation of bound and unbound tracer hormone a solid phase second antibody, anti-rabbit γ-globulin, coupled to cellulose, was used. In 37 healthy adults mean serum TSH was 2.0 μU/ml (SD 1.53 μU/ml), whereas in 27 hyperthyroid and 45 primary hypothyroid patients 0.9 μU/ml (SD 1.78 μU/ml) and 59.5 μU/ml (SD 33.9 μU/ml) were found respectively. The assay system showed a sensitivity of 0.5 μU/ml. The coefficient of variation within assays was 9.5% at the level of 20 μU/ml, and between assays was 2.4% at the level of 6 μU/ml. Exogenous h-TSH was completely recovered.