Radioligand receptor assay for TSH and TSH-binding-inhibiting antibodies using solubilized TSH-receptor

A radioligand receptor assay (RRA) for TSH and TSH-binding-inhibiting antibodies (TBIAb) using solubilized receptor is presented. Introducing charcoal for separation of bound and free hormone has made the assay easier to handle. The detection limit for TSH is 30 microU/ml as measured by RIA. TBIAb was found in the sera of 19 of 26 hyperthyroid patients. Only 16 sera were positive when the RRA using membrane fragments was applied.