Changes in TSH-binding inhibitor immunoglobulins and human thyroid stimulator activities in Graves' disease after radioiodine treatment

The changes in the activities of TSH-binding inhibitor immunoglobulins (TBII) and human thyroid stimulator (HTS) were studied after I-131 treatment of Graves' disease. TBII were measured by the radioreceptor assay of TSH and HTS was measured by the increase in cyclic AMP in cultured human thyroid adenoma cells. Before the treatment TBII were positive in 10 out of 14 patients and mean activity was 79.2%, while only 1 out of 12 were positive in HTS. Three months after the treatment, TBII were positive in 11 out of 12, mean activity being 58.1% (p < 0.05). HTS was positive in 7 out of 11 (p < 0.02). Subsequently, both of these activities showed gradual decrease to the pretreatment level. Changes of TBII and HTS in 5 patients were not parallel, indicating heterogeneity in TSH-receptor related antibodies