The long-term follow-up of patients with thionamide-treated Graves' hyperthyroidism

Since there have been few reports on the long-term prognosis of Graves' hyperthyroidism, the prognosis of 549 Graves' hyperthyroidism patients initially treated with thionamide and followed for >8 (range: 8.6-36.4) years was studied, evaluating the change in the TSH binding inhibitor immunoglobulin activity (TBII). The distribution of the time required for the first disappearance of TBII was normal after logarithmic conversion, and the mean ± 2 SD was 1.5 (0.3-8.1) years. TBII became negative once within 5 years in 78.9% of patients. However, TBII re-elevation was observed in 47.8% of this group (fluctuating type). Remission was observed in 88.9% of the non-fluctuating type (smooth remission) and 37.2% of the fluctuating type patients. TBII remained positive for >5 years in 21.1% (smoldering type) of patients, with remission observed in only 19.8% of patients. Final remission was observed in 301 (54.8%) patients; the median time to remission was 6.8 (interquartile range: 4.0-10.9) years. A longer time until normalization of TBII and higher final thyroid weight were associated with a poor prognosis. Spontaneous hypothyroidism was observed in 6.0% of patients, independent of the TBII change. Our findings suggest that remission of Graves' hyperthyroidism mostly occurred after 4-11 years treatment. While predicting the prognosis before therapy was difficult, the clinical course may suggest a better prognosis if TBII disappears within five years without TBII fluctuation or enlargement of the goiter. Patients may safely wait more than five years to undergo ablative therapy if they hope to avoid permanent hypothyroidism.