Development and utility of a monoclonal-antibody-based, highly sensitive immunoradiometric assay of thyrotropin

Abstract

Using improved selection techniques, we isolated four monoclonal antibodies with high affinity for human thyrotropin (K(a) = 1.6 x 108 to 2.6 x 1010 L/mol). We used two of these in an immunoradiometric assay (IRMA) that also incorporates a novel phase-separation technology (Sucrosep TSH IRMA, Boots-Celltech). This assay's very low detection limit for TSH (0.03-0.08 milli-int. unit/L) and wide working range (0-250 milli-int. unit/L) allow the differential diagnosis of hypothyroid, euthyroid, and hyperthyroid patients. We compare the utility of this IRMA with that of a RIA for patients with various thyroid disorders. As determined by IRMA, a normal concentration of TSH in serum excludes hyperthyroidism or hypothyroidism, whereas an undetectable serum TSH concentration (<0.08 milli-int. unit/L) accurately predicts an abnormality in thyroid gland function.