What Is the Connection between the Thyroid and Selenium?

Researchers seeking to understand the role that trace minerals play in the function of the body have uncovered an important connection between the thyroid and selenium. The mineral has been found to help the thyroid produce sufficient levels of the thyroid hormone. In fact, patients with selenium deficiency are at risk for developing a poorly functioning thyroid gland. Although selenium is thought to bolster the function of the thyroid gland, patients should avoid taking too much of this mineral to prevent the toxicities associated with having high blood levels of it.

In order to explain the connection between the thyroid and selenium, it helps to understand the basics of thyroid function. One of the body's endocrine organs, the thyroid's main purpose is to produce thyroid hormone, which helps regulate the body's metabolism. The thyroid gland synthesizes the thyroid hormone through a number of different chemical reactions. This synthesis is helped by iodo-thyronine deiodinase 2, an enzyme — a type of protein that facilitates chemical reactions. Selenium helps with the function of this enzyme.

The connection between the thyroid and selenium can be further strengthened by examining the symptoms caused by selenium deficiency. In addition to causing problems with the muscle of the heart and the actions of the immune system, selenium deficiency can cause hypothyroidism, a state in which an insufficient amount of thyroid hormone is produced by the thyroid. Although selenium deficiency is rare in the US, it is occasionally seen in certain regions of the world, such as in parts of China, where the soil contains little selenium.

A number of researchers have investigated whether patients who have hypothyroidism that is not due to selenium deficiency should take supplemental selenium. For example, they have tested the benefits of giving selenium to patients with Hashimoto's thyroiditis, which is an autoimmune condition in which the body attacks its own thyroid gland, making it hard for it to produce sufficient quantities of its hormones. Although selenium supplements are not regularly prescribed to hypothyroid patients by physicians, it is possible that with more research this could become a standard recommendation.

One way to bolster the function of the thyroid by ensuring the body has enough selenium is by eating foods rich in this trace mineral. Examples of selenium-rich foods include tuna, brazil nuts, beef, and turkey. A number of grains can be high in selenium, but the amount they contain often depends on the selenium content of the soil they grew in. Over-the-counter selenium supplements are available at pharmacies, health food stores, and on the Internet.

Unfortunately, the positive connection between the thyroid and selenium does not mean that taking very high amounts of selenium is beneficial for promoting health. In fact, experts recommend that a person's maximum daily intake of selenium not exceed 400 micrograms per day. With excess intake people can develop problems such as hair loss, vomiting, nausea, fatigue, dry skin, and nerve damage.