Background: Radioiodine (RAI) is a known risk factor for activation or de novo occurrence of Graves' orbitopathy (GO). Several studies demonstrated that GO can be prevented by glucocorticoids (GCs) in patients with pre-existing GO. We have previously shown that Graves' disease duration (GDd) <5 years is a risk factor for RAI-induced GO. We studied the effect of prophylaxis with either oral GCs (OGCs) or intravenous GCs (IVGCs) on GO activation in patients with GDd. Methods: In total, 99 hyperthyroid patients without GO or with pre-existing inactive GO with GDd <5 years were randomized to receive IVGCs (N = 49) or OGCs (N = 50) before RAI; 22 patients with GDd >5 did not receive steroids and were studied as controls. All patients underwent ophthalmological assessment before and 45, 90, 180 days and for a 5-year follow-up after RAI. Serum thyrotropin (TSH) receptor antibodies (TRAbs), thyroid hormones, and thyroid volume (TV) were also measured in response to RAI therapy and steroid prophylaxis. Results: No patient on prophylaxis developed GO after RAI. One woman of the control group, without steroid prophylaxis, and who had a marked elevation of her TSH, showed transient reactivation of GO, which spontaneously improved after restoring euthyroidism. On follow-up at 12 and 20 months after RAI, two patients developed overt optic neuropathy. A smaller TV was associated with a higher prevalence of RAI-induced hypothyroidism. Serum TRAbs increased significantly after RAI (p < 0.0001) but less in patients receiving steroids than in those without prophylaxis at 45 days (p < 0.01). Conclusions: The risk of RAI-induced GO can be prevented in all patients with GDd <5 years by steroids. Such treatment may not be necessary in patients with GDd >5 years. The blunting of TRAb elevation after RAI may be related to the prophylactic effect of steroids.
Keywords: Graves'; disease, Graves'; orbitopathy, radioiodine, glucocorticoids, TSH receptor antibodies.