Endocrine Abstracts

Introduction: Iodide administration is generally recommended in combination with anti-thyroid drugs when a rapid return to normal thyroid hormone levels is required, such as in the treatment of patients with ‘thyroid storm’. However, there are few reports concerning the combination therapy for many patients with Graves’ hyperthyroidism. In this paper, we studied the effects of potassium iodide (KI) combined with 15 mg of methimazole (MMI) to the initial treatment for hyperthyroidism, and to the changes in TRAb titers and goiter sizes during 2 years treatment.

Patients and methods: One hundred and thirty-two Japanese patients, who had moderate or severe thyrotoxicosis, were divided into two groups. The patients in group A (50 cases) were treated with 50 mg of KI and 15mg of MMI once daily, and those in group B (82 cases) were treated with 15 mg of MMI alone. There were no differences in the initial data between the two groups. The mean duration of KI administration was 11.4±6.9 weeks in group A. In both groups, the MMI doses were gradually reduced to a maintenance level after the patients became euthyroid.

Results: 1 After 4 and 8 weeks of treatment, normal FT₄ was observed in 42% and 80% of patients in group A, and in 30% and 65% of patients in group B, respectively. The mean time required to become euthyroid was 5.9±3.5 weeks in group A, and 7.3±3.7 weeks in group B. The difference was statistically significant (P=0.008). 2. The mean TRAb level before therapy was 55.0±21.7% in group A and 52.6±22.8% in group B. Those in both groups significantly decreased after 6 months of treatment. The percentage of TRAb-positive patients decreased from 100% before therapy to 56% after 1 year and to 43% after 2 years of treatment in group A, from 96% to 60% and to 45% in group B, respectively. The mean goiter size before therapy, shown by cm in diameter, was 5.5±1.1 cm in group A, and 5.3±1.1 cm in group B. After 2 years of treatment, the mean goiter size was 5.1±0.8 cm in group A, and 5.2±1.2 cm in group B, respectively. There were no differences in TRAb levels or goiter sizes between the two groups during therapy.

Conclusions: These results demonstrate the combination therapy is adequate for the treatment of patients with Graves’ hyperthyroidism, especially who have moderate or severe thyrotoxicosis, without increasing doses of MMI and risks of adverse reactions.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.