Lower dose prednisone prevents radioiodine-associated exacerbation of initially mild or absent graves' orbitopathy: a retrospective cohort study.

Context: Radioiodine (RAI) therapy may cause progression of mild or absent Graves' orbitopathy (GO), preventable by oral prednisone. Optimal doses of prednisone are undefined.
Objective: The aim of this study was to compare the effectiveness of reported doses [starting dose, >0.3 mg/kg body weight (bw)], and lower (<0.3 mg/kg bw)] doses of prednisone.
Design and Setting: We conducted a retrospective matched cohort study at a University Center.
Patients: Of 111 RAI-treated Graves' patients with mild or no GO, 35 received no steroid prophylaxis (absence of GO and/or risk factors for RAI-associated GO progression); 28 received low-dose prednisone (starting dose, 0.16-0.27 mg/kg bw; mean +/- sd, 0.22 +/- 0.03 mg/kg bw; group 1); and 48 received higher doses (group 2). Among the latter, 28 (starting dose, 0.32-0.56 mg/kg bw; mean +/- sd, 0.36 +/- 0.05 mg/kg bw) were matched with group 1 according to several relevant variables. Prednisone was started 1 d after RAI and withdrawn after 6 wk.
Main Outcome Measures: We assessed ocular changes (1, 3, and 6 months after RAI) and side effects of prednisone.
Results: Two of 35 patients not receiving steroid prophylaxis (6%) developed mild-to-moderate GO (clinical activity score, 2/7 and 3/7) after RAI. No patients in group 1 or group 2 had GO progression. Side effects were very mild and inconstant, although more frequent in group 2. Both groups showed an increase in bw, an increase that was significantly higher in group 2.
Conclusion: Lower doses of oral prednisone (about 0.2 mg/kg bw) are as effective as previously reported doses (0.3-0.5 mg/kg bw). A shorter treatment period (6 wk) is probably sufficient. The increase in bw is less using lower doses of prednisone.