From the Guidelines
Methimazole treatment for hyperthyroidism can sometimes be associated with worsening thyroid eye disease (TED), likely due to fluctuations in thyroid hormone levels rather than a direct effect of methimazole itself. If you're experiencing worsening eye symptoms after starting methimazole, you should contact your endocrinologist immediately. The management typically involves continuing the methimazole to control hyperthyroidism while adding specific treatments for the eye disease. These may include lubricating eye drops, selenium supplementation (200 mcg twice daily), oral prednisone (starting at 40-60 mg daily with gradual tapering), or referral to an ophthalmologist for more advanced treatments like orbital radiation or surgical decompression in severe cases.
Key Considerations
- Smoking cessation is essential as smoking significantly worsens TED, as noted in studies such as 1 and 1.
- Achieving stable euthyroidism is crucial for long-term improvement of eye symptoms, so maintaining methimazole treatment while adding specific eye-directed therapies is usually the best approach rather than discontinuing the medication.
- According to 1, thyroid eye disease is an autoimmune disorder characterized by congestion and inflammation of the orbit and surrounding tissues, and typical ocular findings include soft tissue congestion with enlargement of the preseptal fat pads, eyelid retraction, exophthalmos, restrictive extraocular myopathy, and optic neuropathy.
Treatment Approach
- The goal of treatment is to control hyperthyroidism while managing TED symptoms, which may involve a multidisciplinary approach including endocrinologists and ophthalmologists.
- Treatment options may vary depending on the severity of TED and the patient's overall health status, but generally include a combination of medical and surgical interventions, as outlined in 1 and 1.
- Continuing methimazole treatment while adding specific eye-directed therapies is usually the best approach, as it allows for control of hyperthyroidism while managing TED symptoms, and is supported by the most recent evidence, including 1.
From the Research
Cause of Worsening Thyroid Eye Disease after Treatment with Methimazole (MMI)
- There is no direct evidence in the provided studies to suggest that Methimazole (MMI) causes worsening of thyroid eye disease 2, 3, 4, 5, 6.
- However, a study comparing radioiodine therapy and antithyroid medications for Graves' disease found that the development and worsening of Graves' ophthalmopathy was observed in 19% of methimazole-treated participants, with a risk ratio of 1.94 compared to radioiodine-treated participants 4.
- Another study found that radioiodine therapy for Graves' hyperthyroidism is followed by the appearance or worsening of ophthalmopathy more often than is therapy with methimazole, but worsening of ophthalmopathy after radioiodine therapy is often transient and can be prevented by the administration of prednisone 5.
- The provided studies do not investigate the cause of worsening thyroid eye disease after treatment with MMI, but rather compare the effects of different treatments on Graves' disease and thyroid eye disease 2, 3, 4, 5, 6.