Predictive factors for recurrence in patients with Graves’ Disease following treatment with methimazole

Graves’ disease (GD) contributes for 60–80% of all hyperthyroidism. Methimazole is the first line drug and most commonly used as antithyroid drug (ATD). However, the relapse rate following ATD therapy is 40–50%. The aimed of this study was to evaluate long-term ATD treatments and to identify prognostic factors that contribute to GD recurrence. A total of 46 GD patients who referred to the Endocrinology Clinic, Dr. Sardjito General Hospital, Yogyakarta between January 2016 and December 2018 with thyrotropin receptor antibody (TRAb) tested and treated with methimazole were included in this study. Size of goiter was measured based on WHO grading system and eye syndrome based on NOSPEC score system. Patients were classified into recurrence and remission groups based on TRAb evaluation at 12 month following treatment. Result of thyroid hormone level (FT4) and subject characteristic as predictive factors observed at 3-, 6- and 12-month post- treatment were compared and analyzed. Among 46 patient involved in this study, 23 patients demonstrated remission of hyperthyroidism based on TRAb evaluation at 12-month. The size of thyroid at onset of disease in 30 (65%) patients was grade 2 or above (p<0.05). Free FT4 levels at the end of observation (12 month) was 1.9±0.6 ng/ dL in recurrent and 1.4±0.5 ng/dL in remission group (p<0.05). TRAb levels at early of study was higher in the recurrent group (p<0.05). Logistic regression analysis demonstrated that thyroid size, FT4 level, and TRAb at diagnosis were associated with recurrencies. In conclusion, GD patients with large thyroids size, high TRAb levels, and high FT4 level at the onset of disease tended to fail to respond to ATD and were associated with recurrence incidence.