The thyroid gland plays an important role in energy metabolism and the physiology of many functions within the human body. It can be particularly vulnerable to oxidative stress because reactive oxygen species (ROS) are involved in thyroid hormone production. Research indicates that certain nutrients including selenium may support balanced thyroid hormone levels and thyroid tissue function, the body’s response to oxidative stress.

The thyroid gland contains the highest amount of selenium of any organ in the human body. Selenium is an essential trace mineral that has been shown to support antioxidant status and thyroid function. It is required for the functioning of thyroid hormones at the cellular level, and it has been shown in studies to influence certain biomarkers related to thyroid and immune health.

Selenium is incorporated into the thyroid gland as selenoproteins. Certain selenoproteins have been shown to exhibit behavior to support the removal of the ROS created as a byproduct during the production of thyroid hormones. The selenoprotein-dependent phospholipid, glutathione peroxidase-4 (GPX4), has been shown to regulate apoptosis and reduce hydroperoxides in the thyroid gland.

Thioredoxin reductases (TXNRD) are another class of selenoproteins. TXNRDs are responsible for modulating oxidoreductase activity, and cytosolic TXNRDs are enzymes that exhibit antioxidant activity at the cellular level.

Selenium is also critical to the metabolism and conversion of thyroid hormones. Selenoproteins, such as iodothyronine deiodinases (DIOs), help convert thyroxine (T4) to triiodothyronine (T3), the biologically active thyroid hormone. DIOs are also responsible for the intracellular production of T3 from T4 and the production of reverse T3 (rT3). Selenium may also support a normal immune response; it has been shown to modulate the production of certain interferon-gamma-inducible cytokines, which may be associated with thyroid-related autoimmunity.

Selenomethionine is a form of selenium typically found in vegetable sources that has been shown to have the highest bioavailability and lowest potential for toxicity when compared with other selenium analogs. Some clinical studies have explored the efficacy of selenomethionine in the presence of autoimmune thyroiditis. One study investigated the efficacy of selenomethionine supplementation in 88 women with autoimmune thyroiditis for 9 months. In the treatment group, patients received 200 ug of selenomethionine daily. Serum concentrations of anti-thyroperoxidase (TPOAb) were shown to decrease by 26.6% after 3 months of treatment. A similar study reported significant reductions in TPOAb in patients receiving selenium supplementation for 6 months.

Selenium is a trace element that may have relevance to thyroid health. It has been shown in studies to support the body’s response to oxidative stress and healthy thyroid hormone balance.

By Colleen Ambrose, ND, MAT