Selenium and Hypothyroidism

In the CATALYST study, researchers found that selenium supplements and placebo supplements improved the quality of life of patients with hypothyroidism to an equal extent. Accordingly, the researchers have now emphasized a need for more research into the effect of selenium supplementation on immune system function, on oxidative stress, and on low-grade inflammation in patients with thyroid diseases [Larsen 2024].

Thyroid system depicted
Depiction of the thyroid system. Attribution: Attribution: Mikael Häggström, Public domain, via Wikimedia Commons. The CATALYST study (Chronic Autoimmune Thyroiditis Quality of Life Selenium Trial) sought to establish whether selenium supplementation improves quality-of-life in patients with autoimmune thyroiditis .

The CATALYST study was a multi-center randomized, double-blinded, placebo-controlled clinical trial conducted in Denmark. The study participants were patients aged 18 or more years with serum thyroid peroxidase antibody (TPOAb) levels equal to or greater than 100 IU/mL. 82% of the study participants were women [Larsen 2024]. read more

Selenium and the Thyroid Gland

The thyroid gland is the organ in the body that contains the most selenium per gram of tissue [Wang 2023].

Illustration of thyroid gland from Wikimedia Commons
The thyroid gland makes and releases hormones that control our metabolism, i.e., regulate how we use energy. Source: https://www.nlm.nih.gov/medlineplus/.

In a 2023 review article, Wang et al summarize the reasons why adequate selenium intake and status are necessary for good thyroid health.

Humans cannot synthesize selenium: the daily intake of selenium depends on the contents of the individual’s diet.

  • The selenium content of food depends on the selenium content of the soil, which varies extensively from region to region of the world. Much of Europe has selenium-poor soil; much of the United States has soil considerably richer in selenium.
  • Selenium is a micronutrient that makes possible the body’s synthesis of some 25 identified selenoproteins containing the amino acid selenocysteine.
  • The best known selenoproteins – such as the glutathione peroxidases, the thioredoxin reductases, and the iodothyronine deiodinases – are expressed in the thyroid gland, where they contribute to thyroid hormone metabolism and to antioxidant defense.
  • A selenium deficiency will increase the risk of several kinds of thyroid diseases.

Selenium Supplementation and Thyroid Diseases

Wang et al [2023] report the following outcomes from clinical trials of selenium supplementation. They advise that we need more clinical evidence for the efficacy of selenium treatment of thyroid disorders.

  • Selenium supplementation slows the progression of Graves’ orbitopathy and improves the quality of the patients’ lives.
  • Selenium supplementation is associated with the decreased levels of anti-thyroid peroxidase antibodies and with improved thyroid ultrasound structure in patients with Hashimoto’s thyroiditis.
  • Selenium supplementation has shown variable anticancer activity in patients with thyroid cancer.

Strong Association Between Selenium and Thyroid Disease

Selenium and Graves’ disease

Wang et al [2023] reviewed the data from 11 clinical trials. Nine clinical trials showed that selenium supplementation results in faster achievement of normal thyroid function in patients with hyperthyroidism. Two clinical trials did not show the beneficial effect of selenium supplementation. The difference in outcomes may be related to differences in the form of the selenium supplementation, the dose, the duration of supplementation, and the nutritional status of the study participants. read more

Chronic Fatigue Syndrome and Impaired Selenium Transport

In a considerable number of chronic fatigue syndrome patients, researchers have observed the presence of autoantibodies to the selenium transporter Selenoprotein P. These autoantibodies disturb the normal transport of selenium to the tissues  in the body. They cause lower than normal levels of the antioxidant selenoenzyme glutathione peroxidase and lower than normal levels of deiodinase enzyme activity [Sun 2023].

Tired young woman at computer
Chronic fatigue syndrome is a complicated disorder that causes abnormal fatigue lasting six months or longer. Impaired selenium transport may be a factor underlying chronic fatigue syndrome.

Note: Autoantibodies are antibodies produced by the immune system and directed against the individual’s own proteins, in this case against selenoprotein P proteins. In an earlier study, researchers have identified autoantibodies to selenoprotein P in patients with Hashimoto’s thyroiditis, in which case the autoantibodies also impair selenium transport and selenoprotein expression [Sun 2021]. read more

Thyroid Disorders and Selenium Supplementation

Thyroid disorders.

Many clinicians treating autoimmune thyroid diseases are using selenium supplementation as one treatment modality even though, in the official guidelines, selenium supplementation is recommended only in the treatment of mild Graves orbitopathy [Winther 2020].

Thyroid gland
The thyroid gland is the butterfly-shaped organ in the front part of the neck. Thyroid hormones regulate body temperature, heart rate, and weight gain or loss. Autoimmune thyroid disorders occur when immune system cells attack thyroid gland cells. Autoimmune thyroid disorders cause overproduction of thyroid hormones (hyperthyroidism) and underproduction of thyroid hormones (hypothyroidism). Graves’ disease is the most common autoimmune hyperthyroidism. Hashimoto’s thyroiditis is the most common autoimmune hypothyroidism.

Some clinicians consider supplementation with selenium to be a pharmaceutical action that should be taken only with thyroid disorder patients with well-defined symptoms in order to alleviate the symptoms, to improve the course of the disease, or to provide a cure. Typically, in such cases, the selenium treatment is conducted for short periods, and the health benefits and side effects are evaluated and weighed [Schomburg 2020].

Other clinicians consider supplementation with selenium in a more holistic way and use selenium supplementation as a way to correct a nutritional deficiency of selenium, which is associated with thyroid disorders [Schomburg 2020]. read more

Breast Cancer Recurrence and Selenoprotein P Autoimmunity

Breast cancer prognosis is especially poor in patients with low serum selenium and serum selenoprotein P concentrations. Now, researchers have discovered natural autoantibodies with antagonistic properties to selenoprotein P uptake in breast cancer patients and  in patients with thyroid disease [Demircan 2022; Sun 2022].

Autoimmunity
Autoimmunity is the production of antibodies against the tissues or substances of one’s own body, resulting in an autoimmune disease or hypersensitivity reaction. Autoantibodies to Selenoprotein P impair the transport of the essential trace element selenium in breast cancer patients and in Hashimoto’s thyroiditis patients.

Selenium is an essential trace element that has numerous biological functions in the body, most of which are carried out by selenium-containing selenoproteins. Among the more important selenoproteins are selenoprotein P, the main transporter of selenium in the blood, and glutathione peroxidase 3 (GPX3), an important antioxidant.

The human body does not synthesize selenium. Human cells are dependent upon selenium sources in the diet. Unfortunately, the selenium content in the soil and in food varies considerably from region to region in the world. For example, the plasma selenium concentrations in people living in much of Europe are generally below, often well below, 80–90 mcg/L whereas people living in North America generally have plasma selenium levels above 120 mcg/L [Alehagen 2022]. read more

Hashimoto’s Disease Patients Benefit from Selenium Supplementation

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.

Jan Olav Aaseth
Endocrinologist Jan Aaseth, M.D., Ph. D., ERT, explains that, in Norway, the diagnosis of Hashimoto’s disease is made after a clinical examination that involves determination of the patient’s circulating levels of the thyroid hormone thyroxine (T4), thyroid stimulating hormone, and thyroperoxidase antibodies [Aaseth 2022].
The most common form of hypothyroidism is related to Hashimoto’s disease. Hashimoto’s disease is an autoimmune disorder most common among middle-aged women. Symptoms include anxiety, dry skin, fatigue and lethargy, muscle aches and muscle stiffness, negative mood, sensitivity to cold, slow thinking and poor memory.

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 read more