Selenium is an essential element, classified in a group of
proteins called the selenoproteins, which are synthesized
through the involvement of sulfur-containing amino
acids and selenium. Selenium, officially recognized as an
essential trace element in 1990, has been indicated to
be beneficial as a an immune enhancer, as a synergist to
vitamin E, as a protectant against harmful exposure to
heavy metals, in particular mercury, and as a co-factor
for glutathione peroxidase, which acts as a coenzyme
in a number of oxidation-reduction reactions. It is also
particularly important in males, as a regulator of male
hormones and as a supporter of prostate function.
Selenium and vitamin E both play important roles in the
detoxification of peroxides and free radicals.
An additional action of selenium is its integral part of
the enzyme type 1 iodothyronine deiodinase, which
catalyzes the deiodination of the iodothyronines. This
action is notably the deiodination of thyroxine (T4) to
triiodothyronine (T3), which is the most active of thyroid
hormones. Selenium is also an essential element in the
selenoproteins, a group of proteins whose reactions
involve sulfur-containing amino acids and selenium.
These are in turn joined via selenophosphate to form
selenocysteine. The most widely studied selenoprotein is
glutathione peroxidase, which catalyzes the reduction of
various organic peroxides as well as hydrogen peroxide.
The supplementation of selenium has also been studied
in the critically ill population. It has been noted that in
critical illness, selenium levels decline. Supplemental
selenium has been shown to significantly improve patient
outcomes. This has been postulated to be due to the anti-
oxidant effects of selenium, since the inflammatory response
to critical illness leads to massive production of free
radicals.
