Based on several large studies in the last two decades, patients with hyperthyroidism have been cautioned that radioiodine ablation increases the risk of clinically significant Graves’ ophthalmopathy. Graves’ ophthalmopathy, which is also known as thyroid eye disease (TED), is marked by a wide range of signs and symptoms, including proptosis (eye bulging), eyelid retraction, eye dryness, and double vision, However, often doctors have ignored these findings and told their patients that the risk of developing eye problems was low or that the use of steroids administered before radioiodine could prevent TED from developing.
Several recent studies show that the risk of TED is not only increased after radioiodine ablation, but that remission from Graves’ disease (defined as a lowering of TSH receptor antibodies) is rare after radioiodine treatment compared to treatment with anti-thyroid drugs (ATDs). With ATDs, remission is an expected goal that is typically met. ATDs are also associated with a decreased risk of developing Graves’ ophthalmopathy because of their ability to lower thyroid antibody levels.
Study Results
In a study at Gutenberg University Medical Center, K. Ponto and his colleagues have shown that the risk of developing thyroid eye disease is 20 percent after radioiodine therapy compared to 5 percent after ATD therapy. Patients were monitored for up to two years after treatment. Of the patients who developed TED after radioiodine ablation, 80 percent developed moderate to severe conditions. However, the true incidence of TED after radioiodine is estimated to be higher because patients treated with radioiodine may develop TED as long as 30 years after the procedure. Previous studies have shown that while most people develop TED within the first two years after radioiodine treatment, the incidence also rises at about six years after the procedure.
Most studies of radioiodine, including a recent study at the University of Krakow, follow patients for two years after ablation. In the Polish study, only patients with no signs of eye disease before receiving treatment for Graves’ disease were evaluated. Patients were later examined for severe conditions of TED. Within two years of their treatment, 5 percent of patients were found to have developed severe TED. While valuable for showing the increased incidence of severe TED after ablation, more research is needed on the long-term effects, since severe TED can develop years after ablation. Previous studies have also shown that quality of life in patients with Graves' disease is most likely to be adversely affected by the development of eye symptoms.
Thyroid Antibodies, Cytokines, and Risk Factors
Both studies showed that TSH receptor antibodies,which contribute to the development of Graves’ ophthalmopathy, increase substantially within the first year after radioiodine ablation. Because the studies were limited to two years, they can’t be used to confirm several previous studies, which showed that thyroid antibody levels stay elevated for many years after radioiodine ablation. The researchers involved in the new studies concluded, however, that compared to patients using anti-thyroid drugs, the radioiodine treated patients were unlikely to achieve remission. The Polish researchers also found that even when steroids were used in an effort to suppress the immune system, levels of the pro-inflammatory cytokines IL-6 and IL-2 remained elevated after ablation. Both antibodies and cytokines contribute to the development of Graves’ ophthalmopathy and pretibial myxedema.
Controversy surrounds the administration of corticosteroids prior to radioiodine ablation. Potential side effects are generally considered too serious to recommend its use as a preventive measure. Furthermore, while corticosteroids may initially prevent a rise in TSH receptor antibodies, levels of these antibodies rise dramatically when corticosteroids are stopped. While the immediate development of TED may be prevented, corticosteroids fail to offer long-term protection.
Certain factors have been found to increase the likelihood of Graves’ ophthalmopathy. These include high levels of TSH receptor antibodies that aren’t lowered with anti-thyroid medications before treatment, smoking cigarettes (due to the direct stimulation of thyroid antigens), high T3 levels prior to treatment, and the development of untreated or poorly managed hypothyroidism. Elevated levels of the cytokines IL-2 and IL-6 were also associated with the development of clinically significant thyroid eye disease.
Sources:
Ponto K, Zang S, and G Kahaly. 2010. “The tale of radioiodine and Graves’ orbitopathy.” Thyroid, 2010, July 20(7): 785-93.
Bafdys-Waigorska A, Golkowski F, Kusnierz-Cabala, B, Buziak-Bereza, M, and A. Hubalewska-Dydejczyk. 2011. “Graves’ Ophthalmopathy in patients treated with radioiodine 131-I,” Polish Journal of Endocrinology, March 2011; 62: 214-219.
Elaine Moore - I'm a retired medical technologist and medical writer with more than 30 years experience working in hospital laboratories. Currently, I ...
Join the Conversation