Change of circulating thyroid autoantibody titers in Graves' hyperthyroidism after antithyroid drugs therapy

Parallel measurements of circulating thyroglobulin (Tg), microsomal [TPO(mic)] and TSH-receptor antibodies [TSH-R(rr)] were performed in 30 cases of Graves' hyperthyroid patients who received antithyroid drug (ATD) therapy for 2.8 +/- 1.7 years (range: 0.5-5.0 years). Before ATD therapy, positive Tg, TPO(mic) and TSH-R(rr) antibodies were found in 33.3%, 83.3% and 86.7% of our patients with Graves' disease, respectively. The titers of Tg and TPO(mic) antibodies remained unchanged in most patients after ATD treatment. However, the TSH-R(rr) antibody titers decreased in 46.7%, elevated in 26.7% and unchanged in 26.7% after ATD therapy. Six cases got long-term remission. Measurements of Tg and TPO antibodies have no value in forecasting the outcome of the disease. The change of circulating TSH-R(rr) antibody from positive to negative is more predictive of remission after ATD therapy than the decrease of thyrotropin-binding inhibiting immunoglobulin index only. However, the former change indicating a persistent remission is not certain.