Selenium plays an important role in optimal immune and endocrine system function. The role that selenium plays with respect to thyroid function is complex [Chmura 2022]:
The thyroid gland is the organ with the greatest amount of selenium per gram of tissue.
A 2022 review highlights the following relationships between selenium deficiency and thyroid gland dysfunction [Chmura 2022]:
Thyroid disease. Hyperthyroidism. Adjuvant treatment of thyroid disease with selenium yeast supplementation. All topics of interest. At this writing (August 2022), we await the publication of the outcomes of the GRASS clinical trial. GRASS is the acronym for the selenium supplementation for patients with Graves’ hyperthyroidism study [study protocol described by Watt 2013].
Hyperthyroidism is caused by a number of conditions, including Graves’ disease, which is a common cause. Graves’ disease is the result of immune system disorder. It can affect anyone, but it is more common in women and in individuals under the age of 40.
Hypothyroidism is the medical condition caused by an underactive thyroid gland that is not producing sufficient quantities of thyroid hormones. It is the failure of the thyroid gland to function normally.
The standard treatment for Hashimoto’s disease is twofold:
1) treatment with a synthetic hormone called levothyroxine, which works like the T4 hormone that is naturally produced by the thyroid gland
Autoimmune thyroiditis is the umbrella term for various types of thyroiditis in which the immune system mistakenly attacks the thyroid gland.
The result is often hypothyroidism, the insufficient functioning of the thyroid gland.
The two major types of hypothyroidism are Hashimoto’s disease and atrophic thyroiditis.
Thyroiditis is the medical term for inflammation of the thyroid gland.
Immune system disorder can also cause an overactive thyroid, called hyperthyroidism; Graves’ disease is the most common form.
In a 2021 review article, Filipowicz et al assert that many European endocrinologists prescribe selenium supplements to autoimmune thyroiditis patients.
For example, a 2016 survey of 815 doctors (91% endocrinologists) has shown that almost 80% of the surveyed doctors prescribe selenium supplementation to autoimmune thyroiditis patients. The rationale for the selenium supplementation is the delay of the hypothyroidism or a decrease in thyroid antibodies [Filipowicz 2021].
Sufficient selenium status is necessary for good thyroid health.
They analyzed the data from 17 journal articles based on studies of 1,911 subjects. Their meta-analysis results showed the following statistically significant associations:
However, the thyroid stimulating hormone (TSH) levels
and the anti-thyroglobulin antibody (TGAb) levels were not significantly different between the selenium treatment group and the control group.
The researchers concluded that selenium-containing drugs were effective in treating patients with autoimmune thyroid disease and greatly reduced
the levels of free triiodothyronine, free thyroxine, and anti-thyroid peroxidase antibody in these patients.
A 2017 summary of the research literature supports the idea that optimal selenium levels are needed for antioxidant protection against harmful free radicals in the thyroid gland and for the normal metabolism of thyroid hormones [Ventura 2017].
A 2018 research literature review shows that selenium supplementation can reduce anti-thyroperoxidase antibody levels and can improve thyroid ultrasound features. In addition, selenium supplementation is associated with improved symptoms and improved quality of life in patients with Graves orbitopathy [Santos 2018].
Note: Anti-thyroperoxidase antibody levels that are too high (>500 IU/ml) are associated with an increased risk of hypothyroidism in autoimmune thyroiditis, which is the most common form of thyroid disorder [Ehlers 2016].
A 2018 meta-analysis of randomized controlled trials shows that adjuvant selenium supplementation may enhance the restoration of normal thyroid function in patients with Graves’ Disease [Zheng].
Graves’ Disease is the most common cause of hyperthyroidism in adults. It is characterized by below-normal serum TSH levels and increased serum levels of free thyroxine (FT4) and/or triiodothyronine (T3). The basal metabolic status of Graves’ Disease patients is accelerated; the result is an increase in the production of harmful free radicals and reactive oxygen species [Zheng].
Intra-cellular antioxidant enzymes such as superoxide dismutase (SOD), glutathione reductase, and glutathione peroxidase (GPx) protect against the cellular damage caused by oxidative stress.
The Su.Vi.Max. study — SUpplementation en VItamines et Minéraux AntioXydants — was a big randomized, double-blind, placebo-controlled study carried out with typical French efficiency. Even though I have written the name of the study in French, there are so many English cognates that I am sure you can read the full name of the study.
The study was designed to test the health benefits of daily supplementation with a number of vitamins and minerals at nutritional dosages (roughly, one to three times the daily recommended dietary intakes) [Hercberg 1998]:
In particular, the French researchers wanted to see the effect of the daily supplementation over a long period, approximately 7.5 years, from 1994 to 2002, on the prevention of cancer and cardiovascular disease, both of which have been linked to oxidative stress and oxidative damage and might, therefore, be affected by supplementation with antioxidants.
Selenium is an essential micronutrient. We need only small quantities of it, but we do need selenium as a component of the amino acid selenocysteine. We need the selenocysteine, in turn, for the body’s synthesis of 25 identified selenoproteins that have a variety of biological functions [Bellinger].
The following outcomes are some of the health benefits associated with adequate selenium intake and status [Ventura]:
The thyroid is the small butterfly-shaped gland at the base of our necks, just above our breastbones. For such a small gland, the thyroid gland is very important. When it is healthy, it produces the hormones that regulate many bodily functions:
The most prevalent diseases of the thyroid gland are the following [Iddah]:
Selenium is a trace element. It exists only in rare quantities in the world. It is produced primarily as a by-product of the process of mining copper. It is not recyclable. It is very unevenly distributed in the soils of the earth.
Consequently, the availability of selenium in grasses and grains and, at the next stage of the food chain, in animals, varies considerably from region to region in the world. The human dietary intakes of selenium vary accordingly around the world.
Selenium a vital nutrient for humans
Selenium is a necessary micronutrient that our bodies do not produce. We get our selenium primarily from our diets. Selenium is important for good immune system function, good thyroid function, good reproductive function, and good protection of our cells’ DNA.
