[Thyrotropin-displacing antibodies in thyroid gland diseases]

Thyroid-stimulating antibodies were assayed in 798 patients with thyroid diseases and 122 controls by means of a heterologous radioreceptor assay as thyrotropin displacement activity (TDA). With an intraassay variance of 5-6% and an interassay variance of 8-13% in higher TDA values, test results were well reproducible. Thus, TDA assay is suitable for routine testing and follow-up of titers in the upper range. With only few exceptions TDA values of F greater than or equal to 11% are found exclusively in Graves' disease (sensitivity 39.2%; specificity vs other thyroid diseases 99.7%). In patients with functional autonomy in nodular goitre (Plummer's disease) TDA is consistently negative. TDA measurement is a valuable means for the detection of Graves' disease and for differential diagnosis of hyperthyroidism of undetermined pathogenesis.