Across 4 studies, 2 reported beneficial effects (one moderate, one small) on reducing thyroglobulin antibody (TgAb) levels in patients with autoimmune thyroid disease, while 2 found neutral effects. The beneficial effect was observed at 3 months but not sustained at 6 months in one meta-analysis, and another large meta-analysis found no significant change. Overall evidence is mixed, and no predominant effect size or consistent dose range emerges.
Caveats: Evidence is mixed: two large meta-analyses (2024, 2025) reached opposite conclusions regarding selenium's effect on TgAb levels. The 2025 meta-analysis showed a moderate reduction at 3 months that was not sustained at 6 months, suggesting a transient effect. The 2024 meta-analysis found no significant effect. One systematic review on Graves' disease had a very small sample (n=15). Another study combined selenium with Myo-inositol, confounding the result. Most studies focused on Hashimoto thyroiditis patients; generalizability to other populations is unclear.
Adverse effects were comparable between the intervention and control groups (OR 0.89 [CI 0.46 to 1.75]; 16 cohorts; 1339 participants; I²=0%).
from: Selenium Supplementation in Patients with Hashimoto Thyroiditis: A Systematic Review and MThe serum TgAb levels decreased at 3 months (SMD = -0.46, 95%CI: -0.79 to -0.12, P = .007) but not at 6 months.
No significant changes were observed in TGAb
selenium supplementation was associated with significant improvements in TSH, FT4, FT3, TPOAb, TgAb, and TRAb levels
During a 6-month treatment, the use of (...) the combination of selenium, and Myo-inositol did not effectively reduce (...) TgAb (Se+Myo-inositol: SMD: -3.64, 95% CI: -9.20,1.92)