Evaluation of TBII activity in untreated Graves' disease using solubilised thyroid membranes

The development and evaluation of a TSH radioligand receptor assay for TSH-binding-inhibiting immunoglobulins and its application to the study of patients with Graves' disease are described. Optimal conditions for the binding of 125I-TSH to solubilised thyroid membranes are defined. Polyethylene glycol precipitation was employed to prepare immunoglobulins from serum for assay and gave results comparable to ammonium sulphate precipitation. Immunoglobulins from normal serum did not interfere in the assay; preparations from patients with untreated Graves' disease gave positive results in 44 out of 56 cases. Coefficients of intra- and inter-assay variation were 7.0% and 9.8% respectively. The method is therefore not only sensitive and reproducible but is sufficiently simple and rapid for routine application.