Selenium, Serum/Plasma
Other names: Selenium, Blood
Selenium is an essential trace element that plays a crucial role in various biological functions, including antioxidant defense, thyroid hormone metabolism, and immune response. The Selenium, Serum/Plasma test measures the concentration of selenium in the blood to evaluate an individual's selenium status.
Function in the Body:
- Selenium is a key component of selenoproteins, which are involved in antioxidant activity, protecting cells from oxidative damage caused by free radicals.
- It plays a role in the synthesis of thyroid hormones and contributes to immune system function.
Sources of Selenium:
- Selenium is obtained through the diet, primarily from foods such as Brazil nuts, seafood, meat, eggs, and certain grains. The selenium content in foods depends on the selenium levels in the soil where they are grown.
Clinical Importance:
- Deficiency: Selenium deficiency can lead to compromised immune function, thyroid dysfunction (e.g., hypothyroidism), and increased oxidative stress. It is also associated with specific conditions such as Keshan disease (a heart disorder) and Kashin-Beck disease (an osteoarthropathy).
- Excess Selenium: On the other hand, high selenium levels can cause selenosis, a condition characterized by symptoms such as gastrointestinal disturbances, hair loss, nail brittleness, and neurological damage in extreme cases.
Selenium Measurement:
- The Selenium, Serum/Plasma test measures the concentration of selenium in micrograms per liter (µg/L) to assess nutritional status or detect selenium toxicity. This test can be used for individuals suspected of selenium deficiency, those on long-term parenteral nutrition, or those exposed to high environmental selenium levels.
Normal Ranges:
- The reference range for selenium in serum or plasma typically falls between 70 to 150 µg/L, but this can vary slightly depending on the laboratory and the population studied.
Conditions Requiring Selenium Monitoring:
- Thyroid Disorders: Selenium is involved in converting thyroid hormones (T4 to T3), and inadequate levels may contribute to thyroid dysfunction.
- Cardiovascular Health: Selenium's antioxidant properties protect against oxidative damage, potentially reducing the risk of cardiovascular disease.
- Cancer: Some studies suggest that adequate selenium levels may reduce the risk of certain cancers due to its role in DNA repair and immune modulation, though this remains a topic of ongoing research.
Procedure for Testing:
- The test requires a blood sample, either from serum (the clear liquid part of the blood) or plasma (the liquid part of the blood when anticoagulants are added). The test is typically performed through standard venipuncture.
What does it mean if your Selenium, Serum/Plasma result is too high?
Elevated Selenium Levels in Serum/Plasma: Clinical Guide
Selenium toxicity (selenosis) occurs when serum levels exceed 150 μg/L. This condition typically results from excessive supplementation, occupational exposure, or dietary sources. While selenium is essential for health, elevated levels can cause progressive symptoms ranging from mild gastrointestinal issues to severe neurological complications. Treatment focuses on exposure elimination and supportive care.
Normal Ranges and Diagnostic Thresholds
- Recommended Daily Intake (RDI): 55 mcg/day for adults
- Normal Serum Range: 70-150 μg/L
- Toxicity Threshold: >300 μg/L
- Severe Toxicity: >1000 μg/L
Sources of Selenium Exposure
Dietary Sources
- Brazil nuts (highest natural source: 544 mcg/nut)
- Organ meats
- Seafood
- Fortified foods
Occupational Exposure
High-risk industries include:
- Mining and metal processing
- Electronics manufacturing (solar cells, semiconductors)
- Agricultural work in selenium-rich soil regions
- Glass and ceramic production
- Research laboratories
Supplementation
- Multi-vitamin supplements (typically 55-200 mcg)
- Standalone selenium supplements
- Specialty supplements for thyroid conditions
Diagnosis and Testing
Primary Tests
- Serum/Plasma Selenium Panel
- Acute exposure marker
- Results available within 24-48 hours
- Most reliable diagnostic indicator
- Supporting Tests
- Urine selenium (elevated for 2-3 weeks post-exposure)
- Hair analysis (shows long-term exposure)
- Nail analysis (indicates exposure over previous 6-12 months)
Additional Assessments
- Liver function tests (AST, ALT, bilirubin)
- Kidney function (creatinine, BUN)
- Complete blood count
- Thyroid function tests
Clinical Manifestations
Mild Toxicity (Serum levels 200-500 μg/L)
Onset: Usually within 1-2 weeks of exposure
- Metallic taste in mouth
- Garlic-like breath odor
- Mild nausea
- Fatigue
- Irritability
Moderate Toxicity (Serum levels 500-1000 μg/L)
Onset: Days to weeks after exposure
- Persistent gastrointestinal symptoms
- Vomiting
- Diarrhea
- Hair thinning or loss
- Brittle nails with white spots
- Skin rashes
- Joint pain
- Muscle tenderness
- Tremors
- Memory difficulties
Severe Toxicity (Serum levels >1000 μg/L)
Requires immediate medical attention
- Respiratory distress
- Myocardial infarction
- Renal failure
- Severe neurological symptoms
- Paralysis
- Status epilepticus
- Coma
Treatment Protocol
Immediate Interventions
- Discontinue all selenium sources
- Assess airway, breathing, circulation
- Start IV fluid therapy if indicated
- Monitor vital signs and mental status
Ongoing Management
- Fluid and electrolyte maintenance
- Nutritional support with low-selenium diet
- Regular monitoring of selenium levels
- Symptom-specific treatment
- Antiemetics for nausea
- Pain management
- Skin care for dermatological symptoms
Severe Cases
- Chelation therapy consideration
- Intensive care monitoring
- Mechanical ventilation if needed
- Dialysis for kidney failure
Recovery and Monitoring
Expected Timeline
- Mild cases: 2-3 weeks
- Moderate cases: 1-3 months
- Severe cases: 6+ months with potential permanent effects
Follow-up Schedule
- Weekly selenium levels until normalized
- Monthly liver and kidney function tests
- Quarterly neurological assessments if indicated
- Annual monitoring after recovery
Prevention Strategies
General Population
- Limit Brazil nut consumption to 1-2 nuts daily
- Read supplement labels carefully
- Avoid multiple supplements containing selenium
- Be aware of local soil selenium content
Occupational Safety
- Use appropriate PPE in high-risk industries
- Regular workplace monitoring
- Annual health screenings
- Employee education programs
Special Considerations
High-Risk Groups
- Patients with thyroid conditions
- Individuals in selenium-rich geographical areas
- Pregnant women
- People with kidney disease
When to Seek Emergency Care
Immediate medical attention required for:
- Severe breathing difficulties
- Chest pain
- Neurological symptoms
- Mental status changes
- Severe abdominal pain
References and Resources
1. MacFarquhar JK, Broussard DL, Melstrom P, et al. Acute selenium toxicity associated with a dietary supplement. Arch Intern Med. 2010;170(3):256-261.[7]
2. Rayman MP. Selenium and human health. Lancet. 2012;379(9822):1256-1268.
3. Vinceti M, Filippini T, Rothman KJ. Selenium exposure and the risk of type 2 diabetes: a systematic review and meta-analysis. Eur J Epidemiol. 2018;33(9):789-810.
4. National Institutes of Health. Selenium: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/
5. World Health Organization. Selenium in Drinking-water: Background document for development of WHO Guidelines for Drinking-water Quality. https://www.who.int/water_sanitation_health/dwq/chemicals/selenium.pdf
Citations:
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC9302111/
[2] http://www.annclinlabsci.org/content/36/4/409.long
[3] https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=1015&toxid=215
[4] https://www.efsa.europa.eu/en/efsajournal/pub/7704
[5] https://vetster.com/en/conditions/horse/selenium-poisoning
[6] https://pubmed.ncbi.nlm.nih.gov/34931411/
[7] https://pmc.ncbi.nlm.nih.gov/articles/PMC3225252/
[8] https://www.science.org/doi/10.1126/science.231.4734.111.a
[9] https://publications.goettingen-research-online.de/bitstream/2/19920/1/10.1177_0960327109360046.pdf
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What does it mean if your Selenium, Serum/Plasma result is too low?
Selenium deficiency often develops due to prolonged reliance on total parenteral nutrition (TPN)—which bypasses normal dietary intake—or from highly restricted diets lacking selenium-rich foods. Insufficient selenium negatively affects numerous physiological systems throughout the body, leading to various health issues. Specifically, it can disrupt:
- Endocrine and reproductive systems, potentially causing hormonal imbalances and impaired fertility.
- Hepatic (liver) function, increasing vulnerability to oxidative stress and liver damage.
- Cardiovascular health, elevating the risk of heart problems, including cardiomyopathy.
- Immune function, weakening the body’s defense against infections.
- Gastrointestinal tract, impairing digestion, absorption, and overall gut health.
- Musculoskeletal system, contributing to muscle weakness, fatigue, and joint discomfort.
Ensuring adequate selenium intake through balanced diets or supplementation is essential for maintaining these critical physiological functions.
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