Abstract
Selenium (Se), a microelement essential for life, is critical for homeostasis of several critical functions, such as those related to immune–endocrine function and signaling transduction pathways. In particular, Se is critical for the function of the thyroid, and it is particularly abundant in this gland. Unfortunately, Se deficiency is a very common condition worldwide. Supplementation is possible, but as Se has a narrow safety level, toxic levels are close to those normally required for a correct need. Thus, whether the obtaining of optimal selenium concentration is desirable, the risk of dangerous concentrations must be equally excluded. This review addressed the contribution by environment and food intake on Se circulating levels (e.g., geographical factors, such as soil concentration and climate, and different quantities in food, such as nuts, cereals, eggs, meat and fish) and effects related to its deficiency or excess, together with the role of selenium and selenoproteins in the thyroid pathophysiology (e.g., Hashimoto’s thyroiditis and Graves’ disease).
Highlights
Selenium (Se) is an essential micronutrient, necessary for the maintenance of different cellular functions, it is toxic like elemental Se as well as Se salts [1]
The thyroid is the organ with the highest content of selenium per tissue unit and it accumulates in the selenoproteins where it is present as SeCys [55]
Some studies suggest the correlation between Se deficiency and autoimmune thyroid diseases as well as benefits of selenium supplementation in these conditions
Summary
Selenium (Se) is an essential micronutrient, necessary for the maintenance of different cellular functions (e.g., immune–endocrine function, signaling transduction pathways), it is toxic like elemental Se as well as Se salts (even in small doses) [1]. The thyroid gland is rich in Se, which takes part in the structure of antioxidant enzymes (e.g., glutathione peroxidase—GPx—and thioredoxin reductase—TrxR—as well as the three deiodinases—D1, D2, D3) [2]. These proteins retain a key role in hormone metabolism and a powerful antioxidant activity directed against free radicals generated during the production of thyroid hormones (THs) [2]. Whether the maintenance of adequate Se levels is desirable for all individuals, the risk of high blood concentrations (e.g., through excessive supplementation or a diet with a high Se content), which could be harmful, must be avoided. The contribution of Se and selenoproteins in the thyroid physiology and their role in pathological thyroid diseases (e.g., Hashimoto’s thyroiditis and Graves’ disease) will be discussed
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