Selenium for Thyroid Health

Research suggests that selenium plays a meaningful role in thyroid health, particularly through its involvement in thyroid hormone production and conversion, antioxidant defense via selenoproteins, and immune regulation, with multiple narrative reviews and systematic reviews consistently linking selenium deficiency to increased risk of autoimmune thyroid conditions such as Hashimoto's thyroiditis and Graves' disease. Studies indicate that selenium supplementation may reduce thyroid autoantibody levels and oxidative stress markers in people with Hashimoto's thyroiditis, and a 2025 systematic review of 14 studies found generally positive but inconsistent results across conditions, noting stronger evidence for Hashimoto's than for Graves' disease. A small randomized controlled trial found that selenium supplementation significantly reduced oxidative stress and improved hemoglobin levels in Hashimoto's patients, though changes in thyroid-specific markers like TSH and anti-TPO antibodies did not reach statistical significance, a limitation the authors attributed to the study's small size and short duration. Overall, the body of evidence is largely supportive but relies heavily on reviews and observational data, with researchers consistently calling for larger, longer-term clinical trials, better methods for assessing selenium status, and personalized approaches that account for individual genetic variation and baseline selenium levels before broader clinical recommendations can be made.