Proper thyroid function is a pillar of health. The hormones it produces regulate metabolism, body temperature, digestion and a range of other biological functions. In order for this organ to be able to produce enough hormones, it needs certain micronutrients: the best known of these trace elements is iodine, but selenium also plays a significant role. The lack of selenium has a highly negative effect on thyroid function. 

How does selenium help?

Selenium is used by the body to produce certain proteins and enzymes that have various specific functions, including those needed for thyroid function. (1) The thyroid gland has a very high concentration of selenium, probably because it helps to protect its vulnerable tissue from damage.  

When adequate protection is lacking, the thyroid gland becomes a very easy target for infections, damage from increased oxidative stress and various autoimmune processes. It has been observed that individuals with autoimmune thyroid disease have much lower levels of selenium, and it has long been hypothesized that its regulation can improve the condition of patients (2). 

Research has shown selenium to be effective

In autoimmune thyroid disorders, the immune system mistakenly attacks the cells and tissues of the thyroid gland, which can lead to inflammation, tissue damage or thyroid dysfunction. Over time, the antibodies that develop cause autoimmune thyroid disorders, such as Hashimoto’s and Graves-Basedow diseases. 

Selenium, in addition to being an important antioxidant, also has anti-inflammatory effects. Selenium deficiencies are very common. Several studies have tested whether its supplementation can help with the autoimmune thyroid diseases mentioned above, but different studies have used different types of selenium and different doses, which has, unsurprisingly, produced mixed results (1,3). 

Nevertheless, it was generally observed that selenium supplementation reduced the levels of anti-thyroid antibodies (TPOab/anti-TPO) indicative of the degree of autoimmunity in several studies.  

One form of organic selenium, selenomethionine, was much more effective than inorganic selenium salt: in this 2018 review, selenomethionine significantly reduced antibody levels in 6 out of 9 studies, while selenium salt significantly reduced antibody levels in only 1 out of 4 studies (1)  

Results of a new meta-analysis

A 2021 meta-analysis and systematic review summarised the results of 17 trials testing the effects of selenium supplementation in the presence of various autoimmune thyroid diseases.  

Again, the results were similar: selenium supplementation significantly reduced the levels of anti-thyroid antibodies.(3) Thus, based on several trials, it can be concluded that selenium is a very important component for proper thyroid function and its supplementation can be quite helpful for managing autoimmune diseases.