An automated immunoradiometric assay for human thyrotropin.

In this two-site immunoradiometric assay for thyrotropin, developed for use in the "Kemtek 3000" automated radioimmunoassay system, commercially available monoclonal antibody to thyrotropin is labeled with 125I, and the solid-phase antibody is an IgG fraction of sheep antiserum to thyrotropin, covalently coupled to reprecipitated aminocellulose. There are two incubations, totalling 3 h, the sensitivity is 0.03 milli-int. unit/L. The mean thyrotropin value for 82 healthy euthyroid subjects was 1.7 milli-int. units/L (range 0.4-3.6). For 19 overtly clinically and biochemically hyperthyroid subjects the values ranged from undetectable to 0.2 milli-int. unit/L. In this assay, euthyroid and hyperthyroid subjects can be distinguished with assay of a single basal sample. The assay appears suitable for routine use as a first-line test of thyroid function.