Selenium (Se) for Thyroid
Se need for Thyroid Hormone production
Se is more concentrated in the thyroid gland than in any other human body organ
Se-dependent selenoprotein enzymes (iodothyronine deiodinases) are required to catalyze the conversion of thyoid hormone T4 to its active form T3 - Since selenium is a component of deiodinase, low selenium levels means low T3 production. T3 works inside cells to set the pace of metabolism. (Deiodinase enzymes also control the removal of an iodine molecule to convert from T3 to T2 and T2 to T1).
(Se-dependent iodothyronine deiodinase enzymes)
( E.g. Selenocysteine - Selenium combined with the amino acid cysteine)
Selenoproteins are enzymes that act in various ways to change T4 into T3 (active thyroid hormone) and reverseT3 (rT3, which inactivates T3).
Three main selenoprotein enzymes activate and inactivate thyroid hormone, are known as D1, D2, and D3.
– D1 is the primary activator of thyroid hormone for your body - working mostly in the liver and to some degree in the kidneys.
– D2 is active in the thyroid gland, brain, nerves, and heart - D2 plays the primary role in thyroid hormone activation in the brain under normal conditions, and produces thyroid hormone for the rest of the body under stressed conditions;
– D3 is mostly a brake on thyroid hormone activity - turning off active hormone.
When the body starts to run low on selenium the activation of thyroid hormone by D1 may drop by 90% and ROS activity is greatly increased - the body compensates by turning on the back up system, using the D2 enzyme to maintain active thyroid hormone.The problem with this back up system running for any great length of time is that is causes significantly increased production of ROS. Even worse, the lack of selenium has already handicapped GSH, the primary antioxidant that protects the thyroid gland and liver.Thus, selenium deficiency forces the body into a very uncomfortable metabolic coping strategy that eventually leads to slower metabolism, increased oxidative stress, and wear and tear on the thyroid gland and liver.
Se is a component of vital thyroid protective antioxidant Glutathione peroxidase (GSH) enzymes
Intracellular and secreted Se-dependent antioxidant glutathione peroxidases (GPx) protect thyroid gland from reactive oxidation species - and in particular, reduce potentially damaging H2O2 to water.
The enzyme Thyroid PerOxidase (TPO) prepares iodine for attachment to tyrosine to form thyroid hormone, a process resulting in excessive numbers of oxidants such as hydrogen peroxide and lipid peroxides. GSH enzymes are proven to protect the thyroid gland (reduce lipid hydroperoxides to their corresponding alcohols and free hydrogen peroxide to water) during thyroid hormone formation (they also help protect the inside of cells, the GI tract and the reproductive system, and are active in the fluids between cells).
By quenching/controlling these potentially harmful oxidants, selenium-dependent GSH enzymes avert thyroid stress and inflammation, which would otherwise retard thyroid hormone production.
Se is perfect antidote for increasingly present mercury exposure
Mercury is now commonly present in the atmosphere, seafood, dental amalgams, mercury-laden vaccines - but Se's affinity for mercury also strips the body of its precious selenium stores.
How much Se do we need?
The average daily intake of Se in U.S. is 60-150ug
Schroeder HA, Frost DV, Balassa JJ. 1970. Essential trace metals in man: Selenium. J Chronic Dis 23:227–243
Those with thyroid problems, a high mercury intake/ exposure, or immuno-compromised should ensure a daily intake of 200-400 mcg selenium /day from food or supplementation (E.g. organic/bioavailable seleno-methionine or selenium yeast) –experts generally agree that one should start supplementation at a 200mcg dose,increasing dose up to 400 mcg if symptoms have not not resolved over a few weeks.
– NOTE: If you increase your selenium intake you must also CONCURRENTLY supplementiodine(and vice versa) - With an iodine deficiency, any attempts to increase selenium intake will magnify any iodine deficiency causing it to become worse. The reverse is also the case.
Foods with high Selenium content
Highest levels of Se found in:brazil nuts (1 nut fresh from shell = ~100 mcg), wheat germ, seafood /shellfish, beef liver and kidney, eggs, sunflower/sesame seeds, mushrooms, garlic, onions, and kelp.