Background: This study aimed to compare the effectiveness and safety of long-term methimazole (MMI) and radioiodine (RAI) in the treatment of toxic multinodular goiter (TMNG). Methods: In this randomized, parallel-group trial, 130 consecutive and untreated patients with TMNG, aged <60 years, were enrolled and randomized to either long-term MMI or RAI treatment. Both groups of patients were followed for 60-100 months, with median durations of 72 and 84 months in the MMI and RAI groups, respectively. Results: In the MMI and RAI groups, 12 and 11 patients, respectively, were excluded because of side effects, choosing other modes of treatment and not returning for follow-up; 53 and 54 patients, respectively, completed the study for 60-100 months. In the MMI group, two patients (3.8%) experienced subclinical hypothyroidism, and 51 (96.2%) remained euthyroid until the end of study. The dosage of MMI to maintain euthyroidism was 6.3 ± 2.0, 4.5 ± 0.9, and 4.1 ± 1.0 mg daily during the first, third, and fifth years of continuous MMI treatment. One patient had elevated liver enzymes, and three developed skin reactions during the first three months, but no adverse effects from MMI occurred from 4 to 100 months of therapy. In the RAI group, 22 (41%) became hypothyroid, 12 (22%) had persistence or recurrence of hyperthyroidism, and 20 (37%) became euthyroid after 16.7 ± 2.7 mCi 131I. Conclusion: Long-term, low-dose MMI treatment for 60-100 months is a safe and effective method for treatment of TMNG, and is not inferior to RAI treatment.
Keywords: longterm; methimazole; radioiodine; toxic multinodular goiter.