BACKGROUND
Graves’ disease is the most common cause of hyperthyroidism in the United States. Graves’ disease is an autoimmune disease where the body makes and antibody that attacks and turns on the thyroid, making it overactive. Recently, the use of anti-thyroid drugs has been increasing, with the idea that the antibody may decrease or go away, allowing the Graves’ disease to go into remission. Towards this end, Graves’ disease has traditionally been treated with a 1-1.5 year course of anti-thyroid medications, most commonly methimazole (MMI). However, after stopping this medication, about 40-50% of the patients experience a relapse of their hyperthyroidism. If Graves’ disease relapses following a course of anti-thyroid drugs, a more definitive treatment is usually recommended, namely removal of the thyroid by surgery or destruction of the thyroid by radioactive iodine therapy. In the past few years, the approach to treatment has been changing to consider a longer course of MMI or even treatment with MMI without discontinuation. The reasons behind this approach include avoiding the adverse effects of surgery or radioactive iodine therapy, including hypothyroidism, as well as avoiding relapses of the Graves’ disease. This study was conducted to understand whether long-term therapy with low-dose MMI could protect Graves’ disease patients from relapses of hyperthyroidism.

THE FULL ARTICLE TITLE
Lertwattanarak R et al 2022 Benefits of Long-term continuation of low-dose methimazole therapy in the prevention of recurrent hyperthyroidism in Graves’ hyperthyroid patients: A randomized prospective controlled study. Int J Endocrinol 2022:1705740. PMID: 36267362.

SUMMARY OF THE STUDY
This study was conducted in Thailand. The authors studied 184 patients with Graves’ disease who had been on MMI for at least 18 months and had normal thyroid levels on low dose MMI (2.5-5 mg) for at least 6 months. Patients were divided in two groups: one group of patients were asked to stop the MMI. The patients on the other group was continued on MMI, 2.5-5 mg daily. Both groups had similar average age (about 40 years old), and about 85% were women. The patients were followed regularly for 3 years. At the end of the 3 years, the relapse rate on the group of patients that stopped the MMI was 41% versus 11% on the group that continued the medication. They also found that the risk of relapse was associated with age (patients younger than 40 years old had a higher risk of relapse). Importantly, the patients that were continued on MMI for at least 3 years, did not have any adverse effects to the medication.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study demonstrates that long-term treatment of Graves’ disease with MMI is safe and effective in preventing relapse of hyperthyroidism in the majority of the patients. This option should be offered to patients, particularly to older patients and those patients who are not interested in definitive treatments and are at higher risk for relapse if the medication were to be stopped.

— Susana Ebner MD

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