Condition
    Moderate Evidence
    Effectiveness 3/5

    Selenium for Hyperthyroidism

    Selenium improved eye symptoms and quality of life in mild Graves' orbitopathy in a European randomised trial — one of the few supplements with real thyroid evidence.

    Overview

    Selenium in hyperthyroidism is really a story about Graves disease and, more specifically, about mild Graves orbitopathy, the eye involvement that accompanies it. A landmark randomised trial in the New England Journal of Medicine found that 200 mcg per day of sodium selenite over six months improved quality of life, reduced eye involvement and slowed progression. Effects on thyroid hormone levels themselves are much less consistent. Selenium is an adjunct, not a replacement for antithyroid therapy.
    Selenium status shapes the result. The positive trial was conducted largely in a marginally selenium-deficient European population, and a 2025 randomised trial in a selenium-sufficient area did not reproduce the eye benefit. That is the practical takeaway: repletion helps people who are low, and adding selenium on top of adequate status appears to add little. Meta-analytic work supports faster biochemical improvement alongside antithyroid drugs but with heterogeneous results.

    How It Works

    The thyroid has the highest selenium concentration of any organ per gram of tissue, because selenoproteins are central to thyroid function. Iodination of thyroglobulin generates large quantities of hydrogen peroxide, and glutathione peroxidases, which are selenoenzymes, neutralise it before it damages thyrocytes. In autoimmune thyroid disease that oxidative load is elevated, so selenium availability becomes limiting.
    Selenium also underpins the iodothyronine deiodinases that convert T4 to the active T3, and thioredoxin reductase, which supports redox balance in orbital fibroblasts. In Graves orbitopathy, oxidative stress drives orbital fibroblast proliferation and glycosaminoglycan production, the process behind eye protrusion and swelling. Reducing that oxidative drive is the proposed route to the observed eye benefit.

    Dosing & Protocol

    The trial regimen is 100 mcg of sodium selenite twice daily, giving 200 mcg per day, for six months alongside standard antithyroid therapy. That six-month duration is what the evidence supports; indefinite use is not. The European upper tolerable intake for selenium is 300 mcg per day and the US limit is 400 mcg per day, so background dietary intake matters. Two Brazil nuts can supply well over 100 mcg on their own.

    Never a substitute for treatment

    Untreated hyperthyroidism risks arrhythmia, bone loss and thyroid storm. Selenium is adjunctive only and does not replace antithyroid drugs, radioiodine or surgery.

    Evidence

    Three linked studies define this pairing: the 2011 New England Journal of Medicine randomised trial of selenium in mild Graves orbitopathy, a 2018 systematic review and meta-analysis of selenium supplementation in Graves disease, and a 2025 JAMA Ophthalmology randomised trial conducted in a selenium-sufficient area that found no benefit versus control. Read together, they support selenium where status is marginal and argue against routine use where it is adequate.

    Studies linked to this pairing.

    Selenium and the Course of Mild Graves' Orbitopathy

    Score: 9/10
    2011
    rct
    n=159

    Marcocci C, Kahaly GJ, Krassas GE +2 more

    Selenium administration significantly improved quality of life, reduced ocular involvement, and slowed progression of the disease in patients with mild Graves' orbitopathy.

    View source

    Effects of Selenium Supplementation on Graves' Disease: A Systematic Review and Meta-Analysis

    Score: 6/10
    2018
    meta_analysis
    n=796

    Zheng H, Wei J, Wang L +4 more

    At 6 months, patients on selenium supplementation were more likely than controls to show improved thyroid function; however, the effect disappeared at 9 months.

    View source

    Selenium vs Control for Graves Ophthalmopathy in a Selenium-Sufficient Area: A Randomized Clinical Trial

    Score: 8/10
    2025
    rct
    n=84

    Kim HJ, Jung EH, Chung CW +2 more

    Selenium supplementation did not improve QOL or clinical parameters in patients with mild to moderate GO in selenium-sufficient regions at 6 months.

    View source

    Safety

    At 200 mcg per day for six months, selenium was well tolerated in the randomised trials with adverse event rates similar to placebo. The risk is chronic excess. Selenosis presents with garlic breath, hair and nail brittleness or loss, gastrointestinal upset, rash and, at extremes, neurological symptoms. Long-term high intake has also been associated in observational work with increased type 2 diabetes risk, which is a reason to keep courses time-limited.

    Watch the total dose

    Count Brazil nuts, multivitamins and fortified foods toward your intake. Stay below 300-400 mcg/day from all sources and keep supplementation to six months unless advised otherwise.

    Interactions & Conflicts

    Selenium does not interfere with antithyroid drugs and was given alongside them in the trials. The interactions to watch are absorption-related and cumulative. Selenium can reduce absorption of some medications when taken together, and high doses may blunt the effect of statins on HDL cholesterol in combination antioxidant regimens. The bigger practical issue is stacking multiple supplements that each contain selenium.
    Interacts withSeverityMechanismAction
    moderate
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    low
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    low
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    low
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    moderate
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    References

    Frequently Asked Questions

    Medical Disclaimer

    The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.

    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.