Clinical significance of thyrotrophin binding inhibitor immunoglobulins in patients with Graves' disease and various types of thyroiditis.

It is well known that thyrotrophin receptor antibodies are present in the sera of patients with autoimmune thyroid disease. There is now compelling evidence that the hyperthyroidism of Graves’ disease is due to antibodies to the thyrotrophin (TSH) receptor. The measurement of these antibodies is valuable in the diagnosis and monitoring of Graves’ disease and in predicting the outcome of treatment. In the present study, thyrotrophin binding inhibitor immunoglobulin (TBII) activites were measured by radioreceptor assay, according to the method of Shewring and Smith, in 30 patients with Graves’ disease, 13 patients with Hashimoto’s thyroiditis, 20 patients with lymphocytic thyroiditis with spontaneously resolving hyperthyroidism (LT-SRH), 5 patients with postpartum thyroiditis, and 7 patients with subacute thyroiditis. The TBII activity results a mean of 3.0±3.0% in normal controls, 44.8±8.7% in Graves’ disease, 8.69±8.06% in Hashimoto’s thyroiditis, 7.63±2.32% in LT-SRH, 3.33±1.16% in postpartum thyroiditis, and 2.67±2.33% in subacute thyroiditis respectively. These clinical and laboratory findings show that TBII also plays a role in the pathogenesis of Graves’ disease. The levels of the TBII activties in Hashimoto’s thyroiditis and LT-SRH, suggest a pathognomic role similar to that of Graves’ disease in above mentioned two disease, but that TBII activity is not significant in postpartum or subacute thyroiditis.