Selenium deficiency
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.
