Introduction
Prediction of anti-thyroid medication efficacy in Graves' disease would be of great value. Many previous studies have not accurately defined Graves' disease nor used the same treatment protocol in all patients. Tasmania is an iodine-deficient island and the response to anti-thyroid treatment has not been reported previously.
Aim
To describe the response to anti-thyroid medication in Tasmanian patients with Graves' disease and identify any predictors of response.
Methods
We interrogated the Royal Hobart Hospital endocrine database for patients with positive TSH receptor antibodies (TRAb) from 2003-2007. Of 243 patients, 52 attended the endocrine clinic with a diagnosis of Graves' disease (TRAb >1.75 plus goitre or dysthyroid eye disease). Only patients treated with a carbimazole or propylthiouracil dose titration schedule (i.e. not including thyroxine) were included. Patient notes were reviewed to detect remission, relapse within 4 years or no resolution from medication.
Results
23 patients remitted, 18 relapsed and 11 had no resolution. Patients were younger in ‘relapse’ (37 +/- 2y) than ‘remission’ (45 +/- 3y, p=0.04). Presenting free T4 (fT4) was lower in ‘remission’ (26.82 +/- 2.83) than ‘relapse’ (38.30 +/- 3.82, p=0.02) and ‘no resolution’ (53.42 +/- 6.21, p=0.002). Presenting TRAb was higher in ‘no resolution’ (19.75 +/- 4.67) than ‘remission’ (8.67 +/- 1.70, p=0.04). There were no differences in sex, eye disease, goitre size or treatment duration. The average time to relapse was 13 +/- 2m.
Discussion
In this modest sample, 44% achieved remission, 35% relapsed within 4 years and 21% had no resolution from anti-thyroid medication. The only significant predictors of relapse were raised presenting fT4 and younger age. Raised presenting TRAb and fT4 also predict non-resolution from medication. Larger studies will clarify these predictors further. At the moment we recommend having an early discussion with patients about these potential long-term outcomes to guide future management.