Selenium

What is Selenium?

Selenium is an essential trace element that the body needs in small amounts to maintain normal physiological function. When analyzing S-Selenium, the concentration of selenium in the blood serum is measured. Selenium functions as a necessary component of several selenium-dependent enzymes (selenoproteins) that are involved in the body's antioxidant defenses, immune regulation, thyroid metabolism and fertility.

Selenium is particularly important for the activity of the enzyme glutathione peroxidase (GPx), which protects the body's cells against oxidative damage by neutralizing hydrogen peroxide and other reactive oxygen radicals. A sufficient selenium intake is therefore crucial for cell defense, chronic disease prevention and hormonal balance.

Relationship to thyroid function

Selenium plays a central role in the metabolism of thyroid hormones. The selenium-dependent enzyme iodothyronine deiodinase is responsible for the conversion of the inactive hormone thyroxine T4 to the biologically active triiodothyronine T3. In case of selenium deficiency, this conversion can be negatively affected, which in turn can affect metabolism and energy levels. Selenium deficiency has also been linked to an increased risk of autoimmune thyroiditis (e.g. Hashimoto's disease).

When investigating thyroid disorders (such as hypothyroidism or autoimmune thyroiditis), analysis of S-Selenium can provide important information as a complement to TSH, free T3 and free T4. In some cases, selenium supplementation can be considered to support the enzymatic activity of the thyroid gland, especially in cases of documented deficiency.

Selenium metabolism in the body

Selenium is supplied to the body through food in various forms – mainly as organic selenium (selenomethionine, selenocysteine) and inorganic selenium (selenite, selenate). The best natural sources of selenium are Brazil nuts, offal, fish, shellfish, eggs, chicken, meat and dairy products. The selenium content of vegetables varies greatly depending on the soil in which they are grown. In Sweden, the selenium content in the soil is low, which means that vegetables grown here often contain lower amounts of selenium compared to imported alternatives.

Regardless of chemical form, selenium is effectively absorbed in the gastrointestinal tract and via the lungs. In the body, it binds to specific carrier proteins and is transported via the blood to tissues where it is incorporated into selenoproteins. Excess selenium within the normal range is excreted via the urine.

Symptoms of abnormal selenium levels

Abnormal levels of selenium can give rise to different symptoms depending on the direction:

• Selenium deficiency: Fatigue, muscle weakness, impaired immune function, fertility problems, hair loss, heart effects (e.g. Keshan's disease), and risk of autoimmune thyroiditis.
• Selenium excess: Nausea, metallic taste, hair and nail changes, skin rashes, and neurological problems in more severe cases.

Why analyze S-Selenium?

S-Selenium is analyzed to evaluate the body's selenium status and is used for both diagnostic and preventive purposes. The test is particularly relevant in cases of suspected deficiency, overdose via dietary supplements, and in connection with certain chronic diseases and nutritional imbalances.

• Suspected deficiency in malnutrition, intestinal disease or long-term parenteral nutrition
• Assessment of thyroid metabolism (T3/T4 conversion)
• Monitoring of supplement therapy
• Investigation of chronic inflammation, oxidative stress or infertility

Relationship to other nutrients and biomarkers

Selenium works synergistically with zinc and vitamin E in the antioxidant network. Deficiency of any of these nutritional factors can reduce the effect of selenium-dependent enzymes. Selenium also has an important interaction with iodine in the regulation of thyroid hormone and the feedback mechanism via TSH. It is therefore common to also analyze TSH, free T3, free T4 and other trace elements such as zinc when investigating selenium status.

Analysis method S-Selenium

Method: ICP-MS (inductively coupled plasma mass spectrometry)

Reference range S-Selenium

Source: Sahlgrenska University Hospital.