Across 4 studies, 2 reported beneficial effects and 2 reported neutral effects, with effect sizes predominantly small. The strongest evidence comes from a 2025 meta-analysis of 1,610 Hashimoto thyroiditis patients showing a moderate beneficial effect at 3 months but not at 6 months, while a similar-sized 2024 meta-analysis found no significant change in thyroglobulin antibody levels. The median study duration was 182 days (6 months), but effects were inconsistent across timepoints and populations, with no clear dose or form data available.
Caveats: Evidence base is small (only 4 studies) — conclusions should be considered preliminary. Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Benefit appears time-dependent, observed at 3 months but not at 6 months in the largest meta-analysis, and the only study reporting duration lasted 6 months. Data on specific selenium forms and doses are lacking, limiting practical guidance.
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)