IMPORTANCE Graves ophthalmopathy significantly diminishes patients' quality of life due to its immune-mediated inflammatory effects on the orbital tissues. Selenium, with its antioxidative properties, has shown potential for improving Graves ophthalmopathy progression and quality of life (QOL); however, its effectiveness in selenium-sufficient regions is not well established.

OBJECTIVE To determine whether selenium supplementation improves QOL in patients with mild to moderate Graves ophthalmopathy in selenium-sufficient regions.

DESIGN, SETTING, AND PARTICIPANTS The Efficacy of Selenium Supplementation for Mild-to-Moderate Graves' Ophthalmopathy in a Selenium-Sufficient Area (SeGOSS) trial was a randomized, open-label multicenter study. Eighty-four patients with mild to moderate Graves' ophthalmopathy were enrolled; 70 completed the study. Participants were selected based on Graves ophthalmopathy diagnosis and sufficient selenium levels. Data were analyzed from October 2023 to March 2024.

INTERVENTIONS Participants received selenium supplementation combined with vitamin B complex for 6 months.

MAIN OUTCOMES AND MEASURES The primary outcome was improvements in Graves ophthalmopathy QOL (GO-QOL) scores at 6 months. Secondary outcomes included changes in GO-QOL scores at 3 months, the proportion of patients showing improvement based on GO-QOL scores, clinical activity score, and ophthalmic examinations at 3 months and 6 months, and changes in thyroid autoantibodies at 3 months and 6 months.

RESULTS There was no improvement in changes in the total GO-QOL scores between the selenium group (31 female patients [83.8%] and 7 male patients [16.2%]; mean [SD] age, 40.8 [11.7] years) and control group (24 female patients [72.7%] and 9 male patients [27.3%]; mean [SD] age, 42.9 [14.2] years) for the primary outcome at 6 months (mean [SD], 12.2 [22.5] vs mean [SD], 11.2 [20.2]; difference, 0.9; 95% CI, -9.3 to 11.3; P = .85). However, at 3 months, a higher proportion of patients in the selenium group showed improved GO-QOL scores compared with the control group (78.4 vs 48.5%; difference, 0.30; 95% CI, 0.08-0.51; P = .01). The selenium group also had higher rates of improvement in proptosis reduction (49.5 vs 15.1%; difference, 0.31; 95% CI, 0.11-0.51; P = .01) at 3 months, though these effects were not sustained at 6 months.

CONCLUSIONS AND RELEVANCE These results suggest that selenium supplementation did not improve QOL or clinical parameters in patients with mild to moderate GO in selenium-sufficient regions at 6 months. Some potential QOL benefits noted at 3 months supports consideration of further investigation of selenium for patients seeking treatment for Graves ophthalmopathy .

TRIAL REGISTRATION Clinical Research Information Service Identifier KCT0004040.