Thyroid and Selenium: Can Selenium Help Hashimoto’s Thyroiditis?

Selenium is an essential trace mineral involved in antioxidant defense and thyroid hormone metabolism. Because the thyroid contains a relatively high concentration of selenium, there is interest in whether selenium supplementation can help people with thyroid disease—particularly Hashimoto’s thyroiditis.

Why is selenium important for the thyroid?

Selenium is required for several selenoproteins involved in antioxidant protection and the metabolism of thyroid hormones. It is also involved in the function of enzymes that help convert thyroxine (T4) to the more biologically active triiodothyronine (T3).

Can selenium help in Hashimoto’s thyroiditis?

Clinical trials and meta-analyses suggest that selenium supplementation may reduce thyroid peroxidase antibody (TPOAb) levels in some people with Hashimoto’s thyroiditis. A 2024 systematic review and meta-analysis of randomized trials found reductions in TPOAb and, in some groups, TSH with selenium supplementation. However, the studies were heterogeneous and changes in thyroid antibodies do not necessarily mean that the disease has been reversed or that levothyroxine can be stopped. citeturn0search1

More recent evidence published in 2025 also reported reductions in TPOAb and some TSH measures, but the findings should still be interpreted in the context of individual patient characteristics, baseline selenium status and the limitations of the available trials. citeturn0search3

Should everyone with thyroid disease take selenium?

No. Selenium is not a routine treatment for every person with hypothyroidism, thyroid nodules or other thyroid conditions. Evidence is strongest for a possible adjunctive role in selected patients with autoimmune thyroiditis, and the clinical importance of lowering antibody levels remains uncertain. An older Cochrane review concluded that evidence was insufficient for confident routine clinical decision-making. citeturn0search0

Food sources of selenium

Selenium can be obtained from foods such as fish, seafood, eggs, meat, poultry, dairy products, cereals and some nuts. Selenium content varies substantially according to the selenium content of the soil and food source. Brazil nuts can contain particularly high amounts, so eating large quantities regularly is not a sensible way to self-dose selenium.

Can too much selenium be harmful?

Yes. More is not necessarily better. Excess selenium intake can cause toxicity, with symptoms such as gastrointestinal upset, hair or nail changes and a garlic-like breath odor among possible manifestations. Supplements should therefore be used thoughtfully rather than taken simply because a person has a thyroid problem.

What about levothyroxine?

Selenium should not be considered a replacement for levothyroxine when thyroid hormone replacement is indicated. Patients taking thyroid hormone should continue their prescribed treatment unless their endocrinologist advises a change.

Bottom line

Selenium is important for normal thyroid biology, and research suggests that supplementation may lower thyroid antibody levels in some people with Hashimoto’s thyroiditis. However, selenium is not a universal thyroid supplement and should not be used as a substitute for standard thyroid treatment. Whether supplementation is appropriate depends on the individual clinical situation, diet, possible deficiency, medications and overall treatment plan.

For more information, see our Thyroid Health Guide.

Medical note: This article is for general education and does not replace an individual medical consultation. Do not start high-dose selenium supplements without discussing them with a qualified healthcare professional.

References

• Huwiler VV, et al. Selenium Supplementation in Patients with Hashimoto Thyroiditis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Thyroid. 2024. PubMed.
• Zhang H, et al. Clinical efficacy of selenium supplementation in patients with Hashimoto thyroiditis: A systematic review and meta-analysis. Medicine. 2025. PubMed.
• van Zuuren EJ, et al. Selenium supplementation for Hashimoto’s thyroiditis: Cochrane review. PubMed.