Radioactive Iodine (RAI) Treatment for Graves' Orbitopathy
Radioactive iodine (RAI) treatment is the specific therapy for Graves' disease that increases the risk of worsening orbitopathy when used without corticosteroid prophylaxis. 1, 2
Mechanism and Risk Profile
RAI therapy can induce new-onset Graves' orbitopathy (GO) or exacerbate pre-existing disease through immune-mediated mechanisms triggered by thyroid tissue destruction. 3, 4
- De novo GO develops in approximately 5-10% of patients receiving RAI without steroid prophylaxis, with the majority occurring in high-risk individuals. 5
- The risk of severe GO worsening in patients with pre-existing mild orbitopathy is approximately 10% during the 12-month follow-up period after RAI. 3
- New-onset GO typically manifests 4 months post-RAI and can present acutely with restricted ocular motility, chemosis, lagophthalmos, and even vision-threatening complications. 4
Mandatory Steroid Prophylaxis Indications
Low-dose oral prednisone prophylaxis is required when RAI is selected for managing Graves' disease in patients with any of the following risk factors: 1, 2
- Pre-existing GO of any severity (even subclinical disease detected only on MRI)
- Active smoking or recent smoking history
- High serum thyrotropin receptor antibody (TRAb) levels
- Hypercholesterolemia
- History of GO even if currently inactive
Preferred Alternative Treatment Strategy
For patients with moderate-to-severe and active GO, antithyroid drugs (specifically methimazole) are the preferred treatment for managing Graves' hyperthyroidism rather than RAI. 6, 1
- This approach avoids the inflammatory trigger that RAI poses to orbital tissues. 1
- If RAI must be used despite active moderate-to-severe GO, it should only be administered with appropriate glucocorticoid coverage. 2
Clinical Pitfall to Avoid
The current risk-based approach to prophylactic glucocorticoids has significant limitations, as demonstrated by cases of severe de novo GO developing in high-risk patients who did not receive steroids because they lacked pre-existing GO. 4, 5
- All patients must be assessed for GO risk factors and counseled adequately prior to RAI in a multidisciplinary setting involving both endocrinologists and ophthalmologists. 5
- The decision to initiate steroids should err on the side of caution, particularly in smokers with high TRAb levels, even without clinically apparent GO. 5
Steroid Prophylaxis Regimen
When RAI is administered with risk factors present, low-dose oral prednisone (typically 0.3-0.5 mg/kg/day) should be initiated at the time of RAI and continued for 6-12 weeks with gradual taper. 1, 2