Selenium, considered a trace mineral, is required in the diet in minute amounts measured in micrograms. The average adult requires about 55 mcg of selenium per day, according to the National Institutes of Health Office of Dietary Supplements. Selenium functions as an antioxidant and also as a component of enzymes that convert thyroid hormone to its active form. While selenium deficiency is rare, inadequate levels can lead to a thyroid deficiency state known as hypothyroidism.
Hashimoto's Thyroiditis
Hashimoto's thyroiditis, an autoimmune condition that affects the thyroid gland, responds well to selenium supplementation, according to a Greek study published in the October 2010 "Thyroid" journal. In the study, participants who received selenium supplementation for three months showed a decrease in thyroid antibodies and reported a greater sense of well-being and improved mood than those who did not receive selenium. The researchers called for further studies to demonstrate improvements with selenium for other aspects of thyroid function and structure in order to determine the best candidates for selenium supplementation.
Children
Selenium supplementation may not be effective therapy for children with autoimmune thyroiditis, according to a German study published in the June 2010 "Scientific World Journal." In the study, newly-diagnosed hypothyroid patients were given 100 mcg or 200 mcg selenium per day, in addition to the thyroid medication levothyroxine, for 12 months. At the end of the study, thyroid antibody levels were comparable in all test groups, indicating that selenium supplementation was not helpful for improving thyroid function for the hypothyroid children in the study. These results are in contrast to known benefits of selenium for adults with autoimmune thyroiditis, according to the researchers.
Thyroid Weight
Selenium supplementation restored thyroid weight and function in laboratory animals in a Tunisian study, published in the June 2010 "Acta Biologica Hungarica." The hypothyroid animals exhibited significantly decreased thyroid iodine contents and plasma thyroid hormone levels. The researchers also noted increased blood supply to the thyroid, which together with decreased output of hormone, indicate the body's attempt to increase delivery of nutrients and thereby restore function to the gland. Selenium supplementation at 0.5 mg per kilogram body weight restored thyroid structure and function to near-normal levels.
Genetics
Selenium works at the genetic level to reduce levels of antibodies that attack the thyroid gland in autoimmune hypothyroid disease, according to a Chinese study on laboratory mice, published in the July 2010 "Endocrinology Journal." The study determined that the trace mineral inhibits the genes that produce the attacking antibodies. In the study, mice that received selenium supplementation had fewer of the immune cells and lower amounts of antibody to thyroid hormone than mice that did not receive selenium.
References
- National Institutes of Health Office of Dietary Supplements: Selenium
- "Acta Biologica Hungarica": Effect of selenium on hypothyroidism induced by methimazole (MMI) in lactating rats and their pups
- Pub Med: Selenium supplementation does not decrease thyroid peroxidase antibody concentration in children and adolescents with autoimmune thyroiditis
- "Endocrine Journal": Selenium upregulates CD4+CD25+ regulatory T cells in iodine-induced autoimmune thyroiditis model of NOD.H-2h4 mice
- Pub Med: A comparison of chemical composition and nutritional value of organically and conventionally grown plant derived foods
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