The thyroid gland housed in the front of your neck below the voice box creates, stores and releases hormones necessary for cellular health and normal daily functions. The thyroid gland is signaled by the pituitary gland, located deep inside your brain, to start producing the hormones T3, or triiodothyronine, and T4, or thyroxine. Normal levels of T3 and T4 regulate your metabolism and aid in various functions of lifetime growth and development. Selenium is one of many nutritional essentials helping to keep your thyroid balanced to prevent gland disorders and thyroid cancer.
Thyroid Gland Disorders
A thyroid gland that produces too much or too little hormone results in disorders like hyperthyroidism, hypothyroidism and goiter. Hyperthyroidism occurs when your body creates too much thyroid hormone, whereas hypothyroidism occurs when too little hormone is produced. Goiter is present in either condition and is characterized by an enlarged thyroid gland that may or may not contain smaller lumps, referred to as nodules. Essentially, thyroid gland disorders develop as a result of heredity, aging, autoimmune disorders, or an interaction from medications. However, dietary deficiencies from iodine and selenium can also contribute to an imbalance in your thyroid gland.
Iodine and Selenium
The mineral iodine, which enters your body through food sources, is crucial in proper thyroid functioning. Low iodine levels can result in hypothyroidism. Selenium is a complementary mineral important for facilitating iodine storage. Low selenium can increase the likelihood of iodine deficiency, resulting in limited thyroid hormone production. According to the Linus Pauling Institute, selenium enzymes and iodine work together to convert the inactive hormone T4 into active T3 to circulate properly in your bloodstream and signal different cellular functions.
Selenium and Thyroid Cancer
Standard daily intake of selenium helps to maintain normal development and production of thyroid hormones. However, selenium may also prove effective in reducing thyroid cancer cell growth, notes the American Thyroid Association. Four types of thyroid cancer can occur, including papillary, follicular, medullary and anaplastic. Papillary and follicular thyroid cancer spreads slowly and has the best prognosis for remission. Medullary thyroid cancer impacts both lobes of the thyroid and is characterized by multiple tumors. Prognosis for medullary type is fair to poor. Anaplastic thyroid cancer is a rare and aggressive type with poor prognosis. Preliminary research on follicular, papillary and anaplastic thyroid cancer reported by the ATA found that selenium inhibits the growth of cancer cells depending on dosing. Clinical trials are underway to determine the long-term effectiveness of selenium for preventing thyroid cancer development.
Selenium Intake and Sources
The recommended dietary allowance for selenium in adults over 19 years old is 55 micrograms per day, notes the Office of Dietary Supplements. Selenium is not commonly associated with causing toxicity when taken in high doses, but the upper limit is set at 400 micrograms per day. Sources of selenium include tuna, which contains 63 micrograms in a 3 oz. serving; turkey with 32 micrograms per 3.5 oz. serving; and one whole egg with 14 micrograms. Whole wheat bread offers 10 micrograms per slice, and 1 cup of fortified oatmeal provides 12 micrograms. Selenium supplements are not necessary if you eat a well-balanced diet. However, your physician may recommend supplementation through use of a multivitamin containing selenium if you have an iodine deficiency.
References
- Office of Dietary Supplements: Selenium
- The Complementary Medicine Practice: Hypothyroid Nutrition
- Linus Pauling Institute: Selenium
- American Thyroid Association: Dietary Supplement May Be Future Treatment for Thyroid Cancer
- "Endocrinology: An Integrated Approach"; The Thyroid Gland; S. Bussey and S. Whitehead; 2001
- Columbia University Medical Center: Thyroid Cancer
