Research synthesisHigh evidenceMixed effect size5 studies · 4 beneficial · 1 neutral · 0 harmful
Across 5 studies, 4 reported beneficial effects of selenium supplementation on reducing thyroid peroxidase antibody (TPOAb) levels, with effect sizes ranging from small to large. Two large meta-analyses (2024 and 2025) demonstrated statistically significant moderate-to-large reductions (SMD -0.46 to -0.96). Effects were typically observed in clinical populations with Hashimoto thyroiditis or Graves-Basedow disease, over durations of 3–6 months (median study duration 182 days).
- Studied populations: patients with Hashimoto thyroiditis (HT); patients with Graves-Basedow disease (GBD) or GBD orbitopathy
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). One systematic review reported a neutral effect when selenium was combined with Myo-inositol in euthyroid HT patients, suggesting possible subgroup differences. Most studies did not specify the form of selenium used, limiting dose-form conclusions. Effect sizes varied substantially across studies (small to large) without a clear modal magnitude.
Generated May 18, 2026