Role of Selenium Supplementation in Thyroid Disease
Selenium supplementation is beneficial for patients with mild to moderate thyroid autoimmune conditions, particularly in those with Graves' orbitopathy and autoimmune thyroiditis, where it can reduce inflammatory symptoms and improve quality of life. 1, 2
Selenium and Thyroid Function
Selenium is an essential micronutrient with critical roles in thyroid function:
- The thyroid gland contains more selenium per gram of tissue than any other organ in the body 3
- Selenium is incorporated into selenoproteins that are essential for thyroid hormone metabolism and the body's antioxidant defense system 1
- Selenium is a component of deiodinases, enzymes that convert T4 to the active T3 hormone 4
- Selenium status directly affects thyroid function, and deficiency can aggravate autoimmune thyroid conditions 3
Clinical Applications in Specific Thyroid Conditions
Autoimmune Thyroiditis (Hashimoto's)
- Selenium supplementation is associated with reduced anti-thyroid peroxidase (TPO) antibody levels in patients with autoimmune thyroiditis 1
- Supplementation may improve thyroid ultrasound features and overall quality of life in these patients 1
- Patients with Hashimoto's thyroiditis have been found to have lower selenium status compared to those with non-autoimmune thyroid conditions 5
Graves' Disease and Orbitopathy
- Selenium supplementation has shown benefits in mild to moderate Graves' orbitopathy, improving quality of life and reducing eye involvement 1
- It may delay the progression of ocular disorders in Graves' disease 2
- Adjuvant selenium supplementation can enhance the restoration of biochemical euthyroidism in some patients with Graves' disease 6
Dosage and Administration
- For mild thyroid eye disease (TED), selenium supplementation has been shown to reduce inflammatory symptoms 2
- The recommended starting dose is 100 μg/day for patients with mild selenium deficiency 2
- For patients with more significant deficiency (plasma selenium <0.4 μmol/L or <32 μg/L), higher doses up to 400 μg/day may be required for 7-10 days for rapid correction 2
- The organic form of selenium appears to be the preferable formulation for supplementation 1
Monitoring and Assessment
- Plasma selenium levels should be measured to assess deficiency status, ideally along with glutathione peroxidase-3 (GPX-3) to reflect functional status 2
- C-reactive protein (CRP) and albumin should be measured simultaneously for proper interpretation of selenium status 2
- In patients with autoimmune thyroid disease, monitoring of thyroid antibodies and ultrasound features can help assess response to selenium supplementation 1
Important Considerations and Caveats
- Selenium status varies widely based on geographic location, soil composition, and dietary patterns 1
- Selenium supplementation does not appear to impact control of hyperthyroidism in populations that are not selenium deficient 2
- There is evidence of potential harm with excessive selenium intake, with upper limits before toxicity symptoms ranging from 6-12 μmol/L 2
- Selenium toxicity (selenosis) can manifest as headache, hair and nail loss, skin rash, and neurological symptoms 2
- High-dose selenium supplementation (1000-4000 μg/day) in ICU patients has not shown consistent benefits and is not recommended 2
Regional Variations in Selenium Status
- Selenium deficiency exists in many European countries, with studies showing varying levels across different regions 5
- Patients from different geographic areas may require different supplementation approaches based on baseline selenium status 5
- The effectiveness of selenium supplementation may depend on baseline selenium status, with those who are deficient potentially benefiting more 6
In conclusion, while routine selenium supplementation is not universally recommended for all thyroid patients, it shows particular promise for those with autoimmune thyroid conditions, especially mild to moderate Graves' orbitopathy and Hashimoto's thyroiditis with documented selenium deficiency.