BACKGROUND
Graves’ disease is a common cause of hyperthyroidism. It is caused by an antibody that attacks and turns on the thyroid, making it overactive. Treatment options include anti-thyroid medications, radioactive iodine therapy and surgical removal. Although the popularity of using long term antithyroid medications to treat hyperthyroidism has increased in recent years, some patients prefer or require more permanent solutions such as radioactive iodine therapy or surgery to remove the gland. Surgery removes the thyroid gland and patients require long term thyroid hormone replacement. Radioactive iodine therapy usually destroys the gland and causes hypothyroidism that also requires thyroid hormone replacement in most cases. Sometimes radioactive iodine therapy fails to treat the hyperthyroidism and patients can require either repeat radioactive iodine therapy treatments or alternative treatments including antithyroid medications or surgery to control the overactive thyroid. This study sought to examine the factors that predict radioactive iodine therapy failure in patients with Graves’ disease.

THE FULL ARTICLE TITLE
Shalaby M et al Predictive factors of radioiodine therapy failure in Graves’ Disease: A meta-analysis. Am. J. Surgery. 223 287-296. 2021. PMID: 33865565.

SUMMARY OF THE STUDY
This study included results from 18 studies with a total of 4822 study participants (approximately 75% were women). The studies were analyzed if they included adult patients treated for Graves’ disease with one dose of radioactive iodine therapy and followed for a minimum of 6 months post treatment. The authors defined radioactive iodine therapy failure as persistent hyperthyroidism on thyroid laboratory testing or use of antithyroid medications 6-12 months after radioactive iodine therapy.

Results indicated overall radioactive iodine therapy failure rate to be 20.2% in this study. Males were more likely to demonstrate radioactive iodine therapy failure. Indicators of potentially more severe Graves’ disease such as higher free T4 levels, larger thyroid glands, and higher pretreatment 24 hr iodine uptake were also associated with radioactive iodine therapy failure. Additionally, prior use of antithyroid medications and longer time between the diagnosis of Graves’ disease and radioactive iodine therapy were also associated with higher failure rates. There were no significant differences noted based on dose of radioactive iodine therapy administered or patient age. This analysis identified certain patient factors that may impact radioactive iodine therapy success rates and should be discussed with the patient when treatment options for Graves’ disease are being presented to assist in decision making.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
There are several options for treating Graves’ disease including radioactive iodine therapy, antithyroid medications and surgery. Many patients choose radioactive iodine therapy for treatment for a variety of reasons. This study identified potential risk factors for radioactive iodine therapy failure that should be discussed with patients so they can make informed decisions with their clinicians about which treatment option may be best for them.

— Whitney W. Woodmansee MD

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