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

Abstract

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.