Posted by Larry Hoover on July 18, 2004, at 21:11:36
In reply to Re: TSH Levels and Thyroid Meds? » Larry Hoover, posted by greenwillow on July 18, 2004, at 18:59:24
> Lar,
> Please explain in more layman's terminology what you are saying about thyroid and selenium. Just curious, as I take 200 mg. selenium daily. Thanks!I'll do my best, but ask more questions if I miss the mark.
Thyroid hormone is assembled from two tyrosine molecules, and four atoms of iodine. That yields T4 (thyroid hormone, 4 iodine). T4 has few physiological effects, directly. Instead, it is really a pro-hormone (hormone precursor). An enzyme (called deiodinase) pulls off an iodine atom, and you get T3. You may be familiar with T4 (Synthroid, or levo-thyroxine) or T3 (Cytomel, thyroxine) by their drug names. T3 is active thyroid hormone.
The enzyme that converts T4 to T3 (deiodinase) requires selenium in its structure, or it cannot work. There is also another selenium-dependent enzyme that refreshes deiodinase, so it can do its job over and over again.
About 85% of the T3 that circulates in your blood is converted in the liver. Your thyroid gets first crack at selenium supplies, so it might be "unaware" that the liver is running short, and not doing the conversion very well. This is the state where selenium supplementation will have most benefit.
Selenium supplementation also positively affects autoimmune thyroiditis, by reducing anti-thyroid antibody levels. Again, selenium improves thyroid function.
However, selenium also reduces T4 synthesis somewhat. So, that kind of counterbalances some of the possible benefit, but the balance should still be to improve total availability of active thyroid hormone, T3.
Low thyroid could be a sign of iron deficiency. It could be sign of selenium deficiency. It could be a sign of iodine deficiency. It could be a sign of autoimmune thyroiditis. It could be a sign of tyrosine deficiency (most likely due to poor protein digestion, which declines with age). All these are affected by nutrient intake, so supplementation is something that can reasonably and safely be considered.
Iron status should be assessed by blood draw. Selenium status is most likely deficient, based on surveys of food intake. Very few people in the world get optimal selenium from food or water, and fewer still get too much. Iodine can be supplied by seafoods, or kelp tablets. Tyrosine is available as a pure amino.
Selenium does other very essential things in the body, so I'm none too concerned about recommending it.
Well, I'll leave it there, and take questions, if you have any.
Lar
poster:Larry Hoover
thread:366914
URL: http://www.dr-bob.org/babble/20040714/msgs/367555.html