TSH receptor antibody in hyperthyroid patients due to Graves' disease treated with antithyroid drugs]

As an immunologic process, TSH receptor antibody (TRab) may be synthesized by the lymphocytes within the thyroid gland. Two techniques were devised to express this TRap activity: a) thyroid stimulating immunoglobulin (TSI) expressed as thyroid c AMP synthesis and b) TSH binding inhibiting immunoglobulin (TBII) expressed as TSH displacement. In general, serum TSI and TBII activity correlated well with each other in hyperthyroid patients. Measurement of TSI and TBII is useful to assess improvement of immunologic abnormality induced by antithyroid drugs. The data so far gathered indicated that TRab disappears from the blood in about 70-80% of hyperthyroid patients in response to antithyroid drugs. However, this does not indicate that intrathyroidal TRab synthesis has ceased, since thyroglobulin is still secreted supernormally and T3 fails to suppress the thyroid in some patients. On the other hand, normalization of thyroglobulin and absence of TRab in the blood indicated complete normalization in the patients as evidenced by positive T3 suppressibility. By using a number of new drugs, further efforts must be made to completely normalize immunologic abnormality in 100% of patients. Recurrence of hyperthyroidism of Graves' disease is generally associated with re-appearance of TRab in the blood in most of the recurrent patients after discontinuation of antithyroid drugs.