Selenium, Iodine and Iron–Essential Trace Elements for Thyroid Hormone Synthesis and Metabolism

Abstract

The adequate availability and metabolism of three essential trace elements, iodine, selenium and iron, provide the basic requirements for the function and action of the thyroid hormone system in humans, vertebrate animals and their evolutionary precursors. Selenocysteine-containing proteins convey both cellular protection along with H2O2-dependent biosynthesis and the deiodinase-mediated (in-)activation of thyroid hormones, which is critical for their receptor-mediated mechanism of cellular action. Disbalances between the thyroidal content of these elements challenge the negative feedback regulation of the hypothalamus–pituitary–thyroid periphery axis, causing or facilitating common diseases related to disturbed thyroid hormone status such as autoimmune thyroid disease and metabolic disorders. Iodide is accumulated by the sodium-iodide-symporter NIS, and oxidized and incorporated into thyroglobulin by the hemoprotein thyroperoxidase, which requires local H2O2 as cofactor. The latter is generated by the dual oxidase system organized as ‘thyroxisome’ at the surface of the apical membrane facing the colloidal lumen of the thyroid follicles. Various selenoproteins expressed in thyrocytes defend the follicular structure and function against life-long exposure to H2O2 and reactive oxygen species derived therefrom. The pituitary hormone thyrotropin (TSH) stimulates all processes required for thyroid hormone synthesis and secretion and regulates thyrocyte growth, differentiation and function. Worldwide deficiencies of nutritional iodine, selenium and iron supply and the resulting endemic diseases are preventable with educational, societal and political measures.

The association between serum copper concentration and prevalence of diabetes among US adults with hypertension (NHANES 2011–2016)

“…At the meantime, more and more studies are focusing on the role of trace elements in the development of diabetes. Although trace elements are found at extremely low levels in the body, they are involved in the composition of molecular structures such as hormones, nucleic acids and catalytic enzymes 31 . Trace elements are closely related to the biological functions of molecules, and the abnormal levels can affect the metabolism and functions of tissues and cells 32,33 .…”

“…Although trace elements are found at extremely low levels in the body, they are involved in the composition of molecular structures such as hormones, nucleic acids and catalytic enzymes. 31 Trace elements are closely related to the biological functions of molecules, and the abnormal levels can affect the metabolism and functions of tissues and cells. 32,33 For example, in a meta-analysis of 22 cohort studies, Zhao et al identified an inverse association between magnesium intake and diabetes.…”

Effects of selenium and iodine on Kashin-Beck disease: an updated review

“…Compared with simple Se deficiency, concurrent Se and iodine deficiency further diminishes the activity of glutathione peroxidase, increasing the vulnerability of target cells, such as chondrocytes, to oxidative stress and leading to chondrocyte apoptosis ( 114 ). Moreover, Se supplementation may expedite iodine metabolism in instances of insufficient iodine intake ( 113 ). This leads to the deiodination of circulating thyroid hormones, accelerating iodine loss in the kidney and faeces and exacerbating iodine deficiency ( 113 ).…”

“…Moreover, Se supplementation may expedite iodine metabolism in instances of insufficient iodine intake ( 113 ). This leads to the deiodination of circulating thyroid hormones, accelerating iodine loss in the kidney and faeces and exacerbating iodine deficiency ( 113 ). The administration of Se supplements, whether preventive or interventional, should be preceded by ensuring adequate iodine levels to prevent iodine loss.…”

Nutrition and thyroid disease

“…The trace element selenium (Se) is an essential micronutrient that is incorporated in the form of the amino acid selenocysteine (Syc) in selenoproteome, consisting of 25 proteins (selenoproteins) most of which are in the thyroid, the latter being iodothyronine deiodinase (DIO1), glutathione peroxidases (GPXs), thioredoxin reductases (TXRNDs), and selenoprotein P (SELENOP) [9]. SELENOP, which plays an important role in Se storage, transport, and supply, is found abundantly in the thyroid, and represents a reliable biomarker for Se status in humans [10].…”