Is selenium supplementation in autoimmune thyroid diseases justified?

This review provides an appraisal of recent evidence for or against selenium supplementation in patients with autoimmune thyroid diseases, and discusses possible effect mechanisms.

Epidemiological data suggest an increased prevalence of autoimmune thyroid diseases under conditions of low dietary selenium intake. Two systematic reviews have evaluated controlled trials among patients with autoimmune thyroiditis and report that selenium supplementation decreases circulating thyroid autoantibodies. The immunomodulatory effects of selenium might involve reducing proinflammatory cytokine release. However, clinically relevant effects of selenium supplementation, including improvement in quality of life, are more elusive. In Graves' disease, some, but not all, trials indicate that adjuvant selenium supplementation enhances the restoration of biochemical euthyroidism, and might benefit patients with mild Graves' orbitopathy.

The use of selenium supplementation as adjuvant therapy to standard thyroid medication may be widespread, but a growing body of evidence yields equivocal results. The available evidence from trials does not support routine selenium supplementation in the standard treatment of patients with autoimmune thyroiditis or Graves' disease. However, correction of moderate to severe selenium deficiency may offer benefits in preventing, as well as treating, these disorders. Molecular mechanisms have been proposed, but further studies are needed.