Selenium - Serum

Introduction

As a Nurse Practitioner with an autonomous practice in Florida, I have witnessed firsthand the importance of understanding biomarkers in promoting and maintaining health. One such essential biomarker is Selenium, a trace mineral that plays a significant role in numerous bodily functions. This article delves deep into the background, clinical implications, and factors affecting serum selenium levels, providing you with a comprehensive understanding of its importance.

Background on Selenium

Selenium is a crucial nutrient involved in various physiological processes. It is integrated into special proteins called selenoproteins, which are vital for antioxidant activity, thyroid hormone metabolism, inflammation control, and the regulation of the immune and reproductive systems. Perhaps one of the most renowned selenoproteins is glutathione peroxidase, a family of antioxidant enzymes that protect cell membranes and lipids from oxidative damage.

Sources of Selenium

Dietary selenium primarily comes from plant foods, the selenium content of which depends on the soil in which they are grown. The soil in regions such as the midwestern states of Nebraska and North and South Dakota in the USA is rich in selenium. In contrast, the southeast coastal areas have selenium-poor soil, leading to dietary insufficiencies. Meat and seafood also contribute to dietary selenium, but supplementation may be necessary in cases of deficiency.

Selenium and Health

Selenium’s role in protecting LDL cholesterol from oxidation is particularly significant, as oxidative damage is a major contributor to atherosclerosis and other chronic diseases like cardiovascular disease, renal disease, and cancer. Cardiac tissue is especially sensitive to selenium availability, and a deficiency can lead to cardiac dysfunction.

Clinical Implications of Selenium Levels

Selenium levels in the blood correlate with glutathione peroxidase activity and reflect tissue stores of selenium. The measurement of selenium can be categorized as serum/plasma, whole blood, or red blood cell, with approximately 75% of selenium in whole blood found in the plasma/serum component.

Ranges for Serum Selenium

• Standard Range: 63.00 – 160.00 µg/L (0.80 – 2.03 µmol/L)
  
• Optimal Range: 70.00 – 121.00 µg/L (0.89 – 1.54 µmol/L)

   

When to Test for Selenium Levels

Testing selenium levels is typically indicated to determine deficiencies or excesses in the body, particularly in individuals with dietary insufficiencies or those exposed to industrial sources of selenium.

Low Selenium: Deficiency and Health Outcomes

Low levels of selenium in the blood signify selenium deficiency, which may arise from several factors:

• Dietary Insufficiency: Particularly prevalent in areas with selenium-deficient soil.
  
• Parenteral Nutrition: Absence of selenium in nutrition for longer than one week can lead to deficiency.
  
• Genetic Factors and Malnutrition: These can also contribute to low selenium levels.

   

Health Implications of Selenium Deficiency

1. Atherosclerosis: Selenium deficiency impairs antioxidant systems that protect lipids such as LDL cholesterol from oxidation, leading to atherogenesis.
   
2. Cardiac Dysfunction: A lack of selenium contributes to cardiomyopathy, congestive heart failure, and atherosclerotic disease.
   
3. Cell Membrane Damage and Hemolytic Anemia: With reduced levels of protective antioxidant enzymes, cell membranes, including those of red blood cells, suffer oxidative damage.
   
4. Chronic Diseases: Low selenium exacerbates oxidative damage, implicating it in chronic conditions such as renal disease, cardiovascular disease, cancer, and dementia.

    

High Selenium: Toxicity and Health Risks

Elevated serum selenium levels may indicate toxicity, often resulting from excessive supplementation or industrial exposure.

Health Implications of Selenium Toxicity

1. Blood Glucose Dysregulation: Excess selenium can disrupt blood sugar regulation if serum levels exceed optimal ranges.
   
2. Thyroid Dysfunction: Overabundance of selenium can interfere with thyroid hormone balance, reducing T3 production.

    

Symptoms of Selenium Toxicity

Symptoms of toxicity include nervous system abnormalities, fatigue, red swollen skin (especially on hands and feet), joint pain, dry brittle hair and nails, nail discoloration, hair loss, diarrhea, nausea, and a garlic-like odor on the breath.

Other Factors Affecting Selenium Levels

Interfering Factors

Various factors can interfere with selenium levels, including dietary habits, geographic location, and underlying health conditions.

Drug Associations

Certain medications can influence selenium levels, either leading to increased or decreased serum concentrations. It is crucial for healthcare providers to consider these associations when evaluating selenium status in patients.

Conclusion

Selenium is an essential nutrient that plays a pivotal role in maintaining health through its involvement in antioxidant defense, thyroid function, and immune regulation. Understanding the ranges and clinical implications of serum selenium levels helps in identifying and managing both deficiencies and toxicities effectively.

As a functional medicine practitioner, a comprehensive evaluation in Florida facilitates identification of cellular-level and molecular imbalances driving cardiometabolic dysfunction. By integrating evidence-based therapies with regenerative medicine medical care services—where antioxidant support and thyroid health are often impacted—we offer patients a regenerative, preventive framework to rebuild resilience and optimize wellness. Call (904) 799-2531 or schedule online to request your personalized metabolic and thyroid health assessment.

Further Reading

• Lubiński et al. (2018) studied serum selenium levels in patients with laryngeal cancer and found that higher selenium levels (>70 μg/L) were associated with significantly improved survival outcomes, suggesting potential therapeutic benefits of selenium supplementation in advanced cancer.
  https://pubmed.ncbi.nlm.nih.gov/29284049/

• Wozniak et al. (2024) evaluated serum selenium concentration as a diagnostic marker in colorectal cancer patients, showing correlations between selenium deficiency and disease status, and developed regression models for selenium levels based on clinical variables.
  https://pmc.ncbi.nlm.nih.gov/articles/PMC10962284/

• Zhang et al. (2025) investigated the association of serum selenium levels with diabetic retinopathy, revealing a U-shaped relationship where moderate selenium levels reduced disease risk, highlighting the importance of balanced selenium status in clinical outcomes.
  https://www.frontiersin.org/articles/10.3389/fmed.2025.1546214/full

• Rayman (2020) reviewed recent clinical studies on selenium supplementation, emphasizing its antioxidant roles, potential in cancer radiotherapy support, and benefits in restoring serum selenium levels to improve patient outcomes.
  https://pubmed.ncbi.nlm.nih.gov/32998101/