The thyroid, a butterfly-shaped gland found in the neck, produces hormones that affect nearly all other cells and tissues in your body, making thyroid hormone vital for maintaining normal function. To produce thyroid hormone, the gland requires iodine, a relatively rare element that forms only 0.000006 percent of the earth’s crust. Selenium, another element, stimulates the formation of specialized proteins known as selenoproteins that also help regulate thyroid function. Failing to intake the proper amounts of these elements can lead to thyroid problems.
Thyroid Hormone Production
The thyroid gland traps iodine and combines the iodine with the amino acid tyrosine to form thyroid hormones. The thyroid produces two types of thyroid hormone: thyroxine, T4; and triiodothyronine, T3. Although the thyroid produces more T4 than T3, in an approximately 80 to 20 percent ratio, T3 is the more active form, possessing about four times the strength of T4, according to Endocrineweb. Specific selenoproteins produced by combining selenium with proteins in the body stimulate the conversion of T4 to T3.
Thyroid problems may cause an over- or underproduction of thyroid hormone. Since thyroid hormone affects nearly all tissues in the body, too much or too little of the hormone causes a variety of symptoms. Failure to intake enough iodine or selenium in your diet can inhibit the production of thyroid hormones leading to a condition known as hypothyroidism. The University of Maryland Medical Center reports hypothyroidism affects approximately 2 percent of the people in the United States, with women 10 times more likely to develop the condition than men. Hypothyroidism causes fatigue, sluggishness, constipation, puffy face, sensitivity to cold, weight gain, muscle weakness and depression. Although most doctors treat hypothyroidism by prescribing synthetic thyroid hormone, if your diet is deficient in iodine or selenium, increasing your intake to the daily recommended dosage may help relieve your symptoms.
Although it is important to get enough iodine in your diet, you must be careful about taking iodine supplements as too much iodine can stimulate the production of too much thyroid hormone leading to hyperthyroidism, another thyroid complication. The Institute of Medicine recommends adults consume 150 micrograms of iodine per day. Because the thyroid traps and stores iodine, a short-term deficiency usually causes no problems. Since the production of iodized salt, the incidence of thyroid problems due to iodine deficiency in the United States is rare; however, 30 percent of the world’s population still suffers from insufficient iodine intake, according to the Linus Pauling Institute.
Your body incorporates selenium into proteins making selenoproteins. Some selenoproteins act as antioxidants, substances that protect cells from damage cause by negatively charged particles produced during chemical reactions within the body. Other selenoproteins function as enzymes, promoting reactions in your body. A selenium deficiency can decrease the amount of T3, creating symptoms of hypothyroidism. The Institute of Medicine recommends adults get 55 micrograms of selenium per day. Several foods, such as tuna, eggs and rice, serve as good sources of selenium, but Brazil nuts contain the highest concentration, providing 544 micrograms per ounce.
- National Institutes of Health Office of Dietary Supplements: Selenium; November 2009
- Linus Pauling Institute: Iodine; Victoria Drake; March 2010
- University of Maryland Medical Center: Hypothyroidism; Harvey Simon; May 2009
- Institute of Medicine Food and Nutrition Board: Dietary Reference Intake Summary; 2004
- Endocrineweb: How the Thyroid Works; October 2010