Science Update

Recent Randomized Controlled Trial Explores Role of Selenium and Vitamin D in Thyroid Health

Graves disease is an autoimmune thyroid condition and is the most prevalent form of hyperthyroidism. Decreases in vitamin D and selenium levels circulating in the body have been associated with the incidence of Graves disease.  

The thyroid gland plays an important role in energy metabolism and the physiology of many of the body’s systems. The thyroid gland can be particularly vulnerable to oxidative damage. Certain nutraceuticals have been shown to support thyroid function and immune health. The thyroid gland contains the highest amount of selenium of any organ in the human body. Selenium is an essential trace element that has been shown to support healthy thyroid hormone metabolism. It may also support antioxidant status and a normal immune response. Clinical studies also indicate that supplementation with selenium may support healthy levels of antibodies associated with autoimmune thyroiditis. Vitamin D may support immune health. Low vitamin D levels have been associated with an increased risk of autoimmune thyroid conditions.  

A randomized controlled trial recently published in Frontiers in Endocrinology by Gallo and colleagues assessed the efficacy of supplementation with selenium and vitamin D on parameters related to thyroid function in adults newly diagnosed with Graves disease. Individuals between the ages of 18 and 70 (who were otherwise in good health) were assessed for vitamin D and selenium status. Those included in the study had values <120 mcg/L for selenium and <30 ng/mL for 25(OH)D (circulating calcidiol or vitamin D2). Individuals in the treatment arm received 100 mcg of selenium daily and 7,000 IU of cholecalciferol (vitamin D3) weekly for 6 months. Both the treatment and control groups had received prescription therapy for Graves disease.  

The authors reported significantly greater reductions in the levels of serum free thyroxine (fT4), a thyroid hormone, in the treatment group as compared to the control group both in short- and long-term assessments (45 days and 270 days, respectively). Improvements in quality of life were also observed in the treatment group as compared to the control. Study strengths, as reported by the authors, include pre-screening of selenium and vitamin D levels; limitations include a relatively small sample size.  

Overall study conclusions were that supplementation with selenium and vitamin D may support thyroid function in individuals with Graves disease and lower status of selenium and vitamin D. More research is necessary before further conclusions can be made. However, research suggests that vitamin D and selenium may support thyroid health and a healthy immune response. 

By Colleen Ambrose, ND, MAT