Selenium and the Thyroid Gland

More Good News for Clinicians

Anne Drutel; Françoise Archambeaud; Philippe Caron

Disclosures

Clin Endocrinol. 2013;78(2):155-164. 

In This Article

Abstract and Introduction

Abstract

The thyroid is the organ with the highest selenium content per gram of tissue because it expresses specific selenoproteins. Since the discovery of myxoedematous cretinism and thyroid destruction following selenium repletion in iodine- and selenium-deficient children, data on links between thyroid metabolism and selenium have multiplied. Although very minor amounts of selenium appear sufficient for adequate activity of deiodinases, thus limiting the impact of its potential deficiency on synthesis of thyroid hormones, selenium status appears to have an impact on the development of thyroid pathologies. The value of selenium supplementation in autoimmune thyroid disorders has been emphasized. Most authors attribute the effect of supplementation on the immune system to the regulation of the production of reactive oxygen species and their metabolites. In patients with Hashimoto's disease and in pregnant women with anti-TPO antibodies, selenium supplementation decreases anti-thyroid antibody levels and improves the ultrasound structure of the thyroid gland. Although clinical applications still need to be defined for Hashimoto's disease, they are very interesting for pregnant women given that supplementation significantly decreases the percentage of postpartum thyroiditis and definitive hypothyroidism. In Graves' disease, selenium supplementation results in euthyroidism being achieved more rapidly and appears to have a beneficial effect on mild inflammatory orbitopathy. A risk of diabetes has been reported following long-term selenium supplementation, but few data are available on the side effects associated with such supplementation and further studies are required.

Introduction

Selenium is an essential trace mineral that was discovered in 1817 by the Swedish chemist Berzelius. Its fundamental role was established in the 1980s when it was discovered that sodium selenite supplementation prevented or reversed the clinical signs of severe selenium deficiencies, that is, chondrodystrophy (Kashin-Beck disease) and juvenile cardiomyopathy (Keshan disease).

The thyroid is one of the organs with the highest selenium content because it expresses several specific selenoproteins of which some are implicated in thyroid hormone metabolism and others play an antioxidant defence role. The link between severe selenium deficiency and thyroid dysfunction was only established in the 90s when children with iodine and selenium deficiencies in a region of Central Africa were supplemented with selenium alone, which led to thyroid destruction and myxoedematous cretinism.[1] Since then, researchers have gained a better understanding of the links between thyroid metabolism and selenium, and it has been suggested that selenium supplementation might be useful for the treatment of autoimmune thyroid disorders.

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