Thyroid hormones are comprised of iodine atoms. Certain physiological processes such as growth, reproductive functions and energy production, require these hormones. A selenium-dependent enzyme regulates the use of thyroid hormones by your body's cells. Selenium is necessary for normal growth and development.
Selenium
Selenium is a trace mineral that is necessary for a number of physiological functions. It is found in soil and enters the food system through plants, animals, and seafood. Your body does not produce selenium, so it is essential that you get it from dietary sources. Seafood, especially shrimp and crab, is a good dietary source of selenium. The recommended daily intake of selenium for adult females and males is 55 micrograms daily. Approximately 3 oz. of shrimp and crab have 34 and 41 micrograms of selenium, respectively.
Hypothyroidism-High Cholesterol Connection
Under-production of the thyroid hormones, triiodothyronine, or T3, and thyroxine, or T4, creates the condition known as hypothyroidism. When these hormones are low, your entire body is affected because T3 and T4 function in virtually every cell in the body. It is amazing that the small butterfly-shaped thyroid gland located at the front of your throat can cause so many physiological and psychological problems. If you have hypothyroidism, your symptoms can include cold hands, low libido, fatigue, unexplained weight gain, unclear thinking, more than normal hair loss and brittle nails. A blood test may indicate that you have elevated cholesterol levels, low circulating T4 and T3, and higher levels of thyroid stimulating hormone, or TSH.
The Selenium-Thyroid Connection
T4 is the thyroid hormone most in circulation, but the most biologically active thyroid hormone is T3. When the body needs T3, it can grab T4 from circulation and remove an iodine atom and convert it to T3. Iodine atom removal is dependent upon a selenium-based enzyme called selenium-dependent iodothyronine deiodinase, which is found your body's tissues. If you do not get enough selenium, your body can become deficient. A selenium deficiency impairs the conversion of T4 to the biologically active T3.
Selenium Deficiency
Selenium deficiency is rare in the United States. It does occur in countries where soil concentration is low. Heart disease, hypothyroidism and impaired immune system conditions can develop as a result of a selenium deficiency. These conditions are not actually caused by selenium deficiency, but they occur because of selenium's role in metabolic functions as a major component of several enzymes.
References
- "Advanced Nutrition and Human Metabolism, Fifth Edition"; Sareen Gropper et al; 2009
- "Pathophysiology-Concepts and Applications for Health Care Professionals"; Thomas Nowak and A.Gordon Handford; 2004
- Linus Pauling Institute; Selenium; April 2003
- Linus Pauling Institute; Iodine; April 2003
