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Radioactive iodine therapy for hyperthyroidism does not exacerbate eye disease in patients with Graves’ disease

The background of the study. Patients with Graves’ disease may have the onset of eye disease before, at the time of, or after the onset of hyperthyroidism, and it may worsen when they are treated with radioactive iodine (I-131). This study determined the effect of I-131 therapy in patients with mild eye disease.

How the study was done. The study subjects were 72 patients with hyperthyroidism and eye disease (mild inflammation of the tissues around the eyes, double vision, and protrusion of the eyes [exophthalmos]) caused by Graves’ disease. They had eye disease for 2 to 360 months and hyperthyroidism for 0 to 132 months. Most had been taking an antithyroid drug before they were treated with I-131. One to two weeks after treatment with I-131 they were treated with thyroxine. The patients’ thyroid function was assessed and they were examined by an ophthalmologist at base line and at 2, 4, 6, and 12 months after I-131 therapy.

The results of the study. After I-131 therapy, there was a small progressive decrease in both the activity of the eye disease, diplopia, and exophthalmos (Table), and also small decreases in the width of the palpebral opening, soft-tissue swelling, and diplopia. No patient had worsening of ophthalmopathy. At all times after I-131 was given, approximately 40 percent of the patients had subclinical hyperthyroidism, and other types of thyroid dysfunction occurred as well. The dose of thyroxine was changed at each time interval to maintain normal serum thyroxine concentrations.

The conclusions of the study. Among patients with mild eye disease and hyperthyroidism caused by Graves’ disease, I-131 therapy for hyperthyroidism does not result in exacerbation of their eye disease.

The original article. Perros P, Kendall-Taylor P, Neoh C, Frewin S, Dickinson J. A prospective study of the effects of radioiodine therapy for hyperthyroidism in patients with minimally active Graves’ ophthalmopathy. J Clin Endocrinol Metab 2005;90:5321-3.