Serum T3 Level and Duration of Minimum Maintenance Dose Therapy Predict Relapse n Methimazole-Treated Graves Disease

Long-term outcomes of anti-thyroid drug treatment in childhood-onset Graves' disease

OBJECTIVE

Outcomes of childhood-onset Graves' disease (GD) and suggested duration of anti-thyroid drug (ATD) therapy have been controversial. This study aimed to determine long-term outcomes following ATD therapy, including remission and relapse rates.

DESIGN, PATIENTS AND MEASUREMENTS

A retrospective study of 265 paediatric patients with GD who were initially treated with ATD was conducted. Long-term outcomes were analysed.

RESULTS

Median (IQR) age at diagnosis was 11.5 (9.4, 13.7) years. Duration of ATD treatment was 4.3 (2.3, 6.7) years and time since diagnosis to the enrolment was 7.1 (3.8, 10.9) years. There were 77, 93 and 95 patients who underwent definitive treatment, had ATD discontinuation, and were still being treated with ATD, respectively. The remission rate was 21% (56 out of 265 patients) and relapse rate was 40% (37 out of 93 patients). Cumulative incidence of first remission increased with the duration of ATD treatment with maximum remission rate at 5.3 years following ATD therapy. Among patients who experienced relapse, approximately 50% had disease relapse which occurred within 1 year after ATD discontinuation. Patients with goitre size of less than 3.5 cm, thyroid-stimulating hormone receptor antibody of less than 10 IU/L, no ophthalmopathy at diagnosis and methimazole dose requirement of less than 0.25 mg/kg/day at 1 year after treatment were more likely to achieve remission.

CONCLUSIONS

Remission rate of childhood-onset GD was relatively low following ATD treatment. Longer-term ATD therapy was associated with increased remission rate. Approximately 50% of patients with relapse had disease relapse within 1 year following ATD discontinuation.

Serum T3 Level and Duration of Minimum Maintenance Dose Therapy Predict Relapse n Methimazole-Treated Graves Disease

Background

Methimazole (MMI) has been advocated as a preferred option for most Graves disease (GD) patients. However, long-term remission after a course of MMI treatment is achieved in only 20% to 40% of patients, depending on the duration of follow-up.

Objective

To evaluate clinical factors for predicting relapse of GD in Thai patients after MMI treatment.

Methods

A retrospective analysis was performed of newly diagnosed patients with GD who achieved remission of hyperthyroid GD after at least 12 months of MMI treatment. Long-term outcomes were assessed and predictive factors of early and late relapse were evaluated.

Results

A total of 443 patients with newly diagnosed GD who were treated with MMI for at least 12 months from 1985 to 2019, and were able to discontinue medication, were studied. The mean age at diagnosis was 37.0 ± 11.4 years and 81.7% were female. Of the 320 patients (72.2%) who achieved initial remission after MMI treatment for 23 months, 106 patients (33.1%) experienced late relapse during the mean follow-up duration of 9.7 years after MMI withdrawal. The remission rates decreased from 36.4% at the first year after stopping MMI to only 20.7% at 10 years. High initial serum triiodothyronine (T3) level and duration of minimum maintenance dose therapy (MMDT) of <6 months were associated with late disease relapse after remission.

Conclusion

The long-term remission rate of Graves hyperthyroidism was achieved in one-fifth of MMI-treated Thai patients. Predictive markers for late relapse included high initial serum T3 level and a duration of MMDT of <6 months.