Selenium is an essential mineral that plays an important antioxidant role in the body. It is present in tissues like the liver at around 10 mg total. Sources of selenium include meats, seafood, grains and organs like liver and kidney. Selenium is absorbed in the duodenum and transported bound to proteins in the bloodstream. It is mainly excreted through urine and has a recommended daily intake of 50-200 μg. Selenium is an important component of the antioxidant enzyme glutathione peroxidase, which helps convert harmful oxygen free radicals into less toxic forms. It also aids in thyroid hormone conversion and protects against heavy metal toxicity. Selenium deficiency can result in conditions like cardiomyopathy, muscular dystrophy and Keshan disease.

1. Selenium Metabolism
Gandham. Rajeev

2. Selenium
• Selenium was found to prevent liver cell
necrosis & muscular dystrophy.
• Total body content of selenium around 10 mg
and it is present mainly in liver.
• Sources:
• Richest sources are meat, sea foods, liver,
kidney and grains.
• RDA
• 50 to 200 µg/day.

3. Absorption and excretion
• Selenium is absorbed mainly from the
duodenum.
• Selenium after absorption is transported
bound to plasma proteins particularly β-
lipoproteins in humans.
• Main route of excretion of selenium appears
to be through urine.

4. Functions
• Selenium, as selenocysteine is an essential
component of the enzyme glutathione
peroxidase.
• Glutathione peroxidase functions as an
antioxidant enzyme.
• It suppresses the oxidative stress by
converting oxygen free radicals into less
toxic forms or non-toxic forms.

5. Relationship of glutathione peroxidase,
selenium & vitamin E
GSH peroxidase contains selenocysteine

6. • The presence of selenium in the diet reduces
the requirement of vitamin E, since vitamin E
also acts as an antioxidant.
• Selenium may exert anticancer effects
because of its antioxidant role.
• Selenium containing enzyme 5’deiodinase
converts thyroxine (T4) to triiodo-thyronine
(T3) in thyroid gland.

7. • In selenium deficiency, conversion of T4 to T3 is
impaired resulting in hypothyroidism.
• Selenium binds with certain heavy metals &
protects body from their toxic effects.
• Selenocysteine is considered as 21st standard
amino acid since it is coded by UGA, which is a
termination codon.
• Selenium is incorporated to proteins as
selenocysteine during protein synthesis.

8. Deficiency
• Causes:
• Low soil content of selenium & malnutrition.
• Clinical features:
• Chronic selenium deficiency is associated with
cirrhosis of liver, cardiomyopathy leading to
congestive cardiac failure, muscular
dystrophy, loss of appetite, nausea,
abnormal electrocardiograms.

10. Keshan Disease
• Muscular dystrophy
• Loss of appetite,
• Nausea.

11. Selenium toxicity
• Selenium toxicity is rare.
• Selenosis is the toxicity due to excessive
consumption of selenium.
• Clinical features are hair loss, dermatitis and
irritability.
• Liver & neuromuscular disorders that are
usually fatal.

13. Thank You