The Thyroid and the Selenium

Abstract
Selenium, which is toxic in high concentrations, is essential for the body. This trace element known for its antioxidant function is the cofactor of many enzymes.  Selenium plays a role in many metabolic processes involving the enzymes glutathion peroxidases, deiodinases, thioredoxin reductases, and selenoprotein P that protect the organism from oxidative damages in humans. Selenium as a trace element plays role both structurally and as cofactor in the regulation of inflammatory processes, immune and endocrine functions.  It has been shown that selenium may be a protector against some cancer types, increases male fertility, reduces cardiovascular mortality, and represses formation of inflammatory mediators in asthma.  In first research studies, selenium drew attention with its anti-carcinogenic effects.  Afterwards, its effects on thyroid hormone were started to be investigated in 1990s. As the studies on selenium increase, among the questions that frequently arise is whether to give selenium supplementation to healthy persons and patients with known thyroid pathology, especially to pregnant women, beside the iodine supplementation that has been used for a long time in the world and Turkey.  In order to be able to give better answers to these questions, we tried to analyze the articles including selenium treatment related to thyroid disorders in the literature.