Selenium deficiency
📖 About
- 🧪 Selenium deficiency is rare globally, even in regions with relatively low dietary intake.
- Selenium is an essential trace element, incorporated into selenoproteins (e.g. glutathione peroxidase) that protect against oxidative stress.
- Deficiency manifests only in areas with exceptionally low intake or in special clinical settings (e.g. long-term TPN).
🌍 Aetiology – Selenium Intake Around the World
- New Zealand & 🇫🇮 Finland: 30–50 mcg/day (low intake).
- USA / 🇨🇦 Canada: 100–250 mcg/day (adequate intake).
- Some areas of China: 10–15 mcg/day (very low intake, deficiency diseases described).
🩺 Clinical Features
- Keshan disease: Reversible dilated cardiomyopathy affecting children and young women; prevented (not cured) by sodium selenite 50 mcg/day PO.
- Siberian Russia & 🇨🇳 China: Kashin-Beck disease – chronic osteoarthropathy in children, linked to selenium deficiency and other cofactors (e.g. mycotoxins).
- 💉 Long-term TPN without supplementation: muscle pain, tenderness, proximal weakness, which improves with selenium replacement.
- 🧑⚕️ Possible role in impaired immunity and thyroid hormone metabolism (selenium required for deiodinases).
🔍 Investigations
- Plasma selenium levels or glutathione peroxidase activity in RBCs can be measured.
- ⚠️ These are not standard routine tests and often only done in research or specialist centres.
💊 Management
- Selenium replacement (oral or IV, depending on context).
- Typical supplementation: 50–200 mcg/day.
- ⚠️ Avoid excessive intake: high doses may cause selenosis (symptoms include brittle hair/nails, garlic breath odour, neurological issues).
- Prevention: ensure supplementation in long-term TPN and in endemic low-intake regions.
📚 References
🧾 Clinical Case – Selenium Deficiency
A 45-year-old man on long-term parenteral nutrition without adequate trace element supplementation
presents with fatigue, proximal muscle weakness, and brittle hair/nails.
Examination reveals mild cardiomegaly and nail discoloration.
Blood tests show low plasma selenium and raised creatine kinase.
Diagnosis: Selenium deficiency, known to cause cardiomyopathy, muscle dysfunction, and immune impairment.
He improved after selenium supplementation was added to his nutritional regimen.
