What is the role of Radioiodine (I-131) therapy in treating Graves' disease?

From the Guidelines

Radioiodine therapy is a recommended treatment option for Graves' disease, particularly for patients who are not good candidates for antithyroid medical therapy or surgery, as it can provide a high cure rate with a relatively low risk of complications 1. When considering radioiodine therapy for Graves' disease, it is essential to weigh the potential benefits against the risks, including the risk of hypothyroidism and exacerbation of Graves' eye disease 1. Key considerations for radioiodine therapy in Graves' disease include:

• The patient's overall health status and ability to tolerate potential side effects
• The presence of any underlying medical conditions that may affect the treatment outcome
• The severity of the Graves' disease and the presence of any eye symptoms
• The patient's preferences and values regarding treatment options In terms of diagnostic testing, radioiodine uptake is a valuable tool for evaluating thyroid function in patients with suspected Graves' disease, as it can help confirm the diagnosis and guide treatment decisions 1. Some important points to consider when interpreting radioiodine uptake results include:
• Elevated radioiodine uptake is typically seen in patients with Graves' disease, usually above 50% at 24 hours
• The test should be performed after discontinuing medications that affect thyroid function, such as antithyroid drugs and thyroid hormones
• Patients should also avoid iodine-rich foods and supplements before testing to ensure accurate results.

From the Research

Radioiodine Treatment for Graves' Disease

• The treatment of Graves' disease with radioiodine is a common approach, with the goal of achieving euthyroidism or hypothyroidism 2, 3, 4, 5, 6.
• The optimal dose of radioiodine for treating Graves' disease is still a topic of debate, with some studies suggesting a correlation between the administered dose and the actual organ dose 2, while others found a strong association between radiation absorbed dose and treatment outcome 3.
• A systematic review and meta-analysis found that higher rates of euthyroid outcome were associated with radiation absorbed doses within the range of 120-180 Gy 3.
• Another study found that the clinical outcome of radioiodine treatment was dependent on the initial thyroid volume and the activity per gram of tissue retained at 24 hours, with higher doses resulting in higher success rates 5.
• The choice of treatment for Graves' disease depends on various factors, including the patient's preferences, size of the goiter, degree of hyperthyroidism, and presence of ophthalmopathy 6.

Factors Affecting Treatment Outcome

• The relationship between the administered dose of radioiodine and the actual organ dose is highly variable, with a mean coefficient of variation of 45% 2.
• Pretreatment variables such as free T4, free tri-iodothyronine, thyroid weight, and 24-hour urinary iodine excretion did not differ significantly among patients with different treatment outcomes 2.
• The presence of antithyroperoxidase antibodies and TSH receptor autoantibodies did not affect the treatment outcome 2.
• Higher residual levels of thyrotoxicosis at the time of radioiodine treatment were associated with worse outcomes 5.

Treatment Options

• Antithyroid drugs, radioactive iodine, and thyroid surgery are the three well-established treatment options for hyperthyroid Graves' disease 4, 6.
• Radioiodine is administered as a single oral dose, with permanent cure achieved in about 80% of cases, usually after 1 or 2 months 6.
• Surgical thyroidectomy may be total or subtotal, with complications including hypoparathyroidism and permanent paralysis of the recurrent laryngeal nerve 6.