Efficacy of Selenium Supplementation in Graves’ Orbitopathy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials with Trial Sequential Analysis

Background: Selenium (Sel) supplementation has been proposed as an antioxidant adjunct in Graves’ orbitopathy (GO), with early randomized evidence suggesting benefits in quality of life (QoL), ocular involvement, and disease progression in mild GO. However, subsequent trials across populations with different Sel status and disease severity have yielded inconsistent findings. This systematic review and meta-analysis of randomized controlled trials (RCTs) reassessed the efficacy of Sel supplementation in GO. Methods: PubMed, Scopus, and the Cochrane Library were searched from inception to 1 May 2026 for RCTs, comparing Sel supplementation with placebo or no Sel supplementation in patients with GO (PROSPERO “CRD420261395074”). Heterogeneity was assessed using I2 statistics and Cochran’s Q test. Risk ratios (RRs) were calculated using the Mantel–Haenszel method, and mean differences (MDs) using the Inverse-Variance method. Random-effects models with restricted maximum-likelihood estimation were applied. Results: Five RCTs including 303 patients were analyzed, of whom 165 (56%) received Sel. Sel supplementation was associated with a significant reduction in clinical activity score (MD −1.05; 95% CI −1.61 to −0.48; I2 = 52%; p < 0.01). No significant differences were observed in palpebral aperture (MD −0.12; 95% CI −1.22 to 0.98; I2 = 58%; p = 0.83), although this anatomical parameter should be interpreted cautiously because it may be influenced by thyroid functional status and hyperthyroidism-related Müller muscle hyperfunction. No significant differences were observed in QoL improvement (RR 1.72; 95% CI 0.43 to 6.92; I2 = 86%; p = 0.24) or visual function (MD 6.31; 95% CI −1.40 to 14.03; I2 = 45%; p = 0.11). Conclusions: Sel supplementation may improve clinical activity score in patients with Graves’ orbitopathy, but this finding should be interpreted cautiously given the small number of trials, limited sample size, and clinically relevant heterogeneity. Current evidence does not show consistent benefits for palpebral aperture, quality of life, or visual function. Larger RCTs stratified by baseline Sel status and disease severity are needed before firm conclusions can be drawn.