Endocrine Abstracts

Selenium is an essential element for humans. Important dietary sources of selenium include meat, seafood, and grains. Selenium is incorporated into a range of selenoenzymes with antioxidant properties. Being crucial for the activity of the deiodinase enzymes, selenium is especially important for the synthesis and metabolism of thyroid hormones. Selenium in relation to thyroid diseases has been widely explored. Epidemiological studies have shown that a low selenium status is associated with an increased risk of autoimmune thyroid diseases. This linkage may be causal as selenium supplementation seems to reduce the titer of thyroid autoantibodies in patients with autoimmune thyroiditis, probably by reducing proinflammatory cytokines. However, it is unsettled whether selenium supplementation affects the clinical course of autoimmune thyroiditis or improves quality of life in patients with this disease. In patients with mild Graves’ orbitopathy, selenium supplementation reduces the orbital inflammation, while it remains to be shown that it also leads to faster remission of the hyperthyroidism. Two ongoing randomized clinical trials, one in Graves’ disease and one in autoimmune thyroiditis, will help clarify the role of selenium supplementation in these disorders. Although current evidence does not support routine selenium supplementation as adjuvant treatment in patients with autoimmune thyroiditis or Graves’ disease, such an approach is widely used by clinicians. While selenium deficiency should be corrected, a too high intake of selenium may result in adverse health effects. Therefore, the inclusion of selenium in the therapeutic armamentarium should be based on data from large and well-designed clinical trials.