What is the current research on selenium supplementation in patients with Hashimoto's (autoimmune) thyroiditis?

Selenium Supplementation in Hashimoto's Thyroiditis

Selenium supplementation at a dose of 200 μg daily may reduce thyroid peroxidase antibody (TPOAb) levels and improve inflammatory symptoms in patients with mild Hashimoto's thyroiditis, particularly in those with selenium deficiency. 1

Evidence on Selenium Supplementation in Hashimoto's Thyroiditis

Efficacy on Antibody Levels

• Multiple studies demonstrate that selenium supplementation (typically 200 μg daily) can significantly reduce anti-thyroid peroxidase antibody (TPOAb) levels in patients with Hashimoto's thyroiditis 2, 3, 4
• A 2021 study showed that selenium supplementation (200 μg/day for 6 months) significantly decreased TPOAb levels in newly diagnosed Hashimoto's patients, potentially having a stabilizing effect on thyroid function 2
• Another 2021 study demonstrated significant reduction in thyroglobulin antibody (TGAb) levels after 6 months of selenium supplementation (200 μg/day), with more pronounced effects in patients with higher baseline antibody levels 5

Mechanism of Action

• Selenium appears to work through antioxidant effects, as it is an essential component of glutathione peroxidase, which protects thyroid cells from oxidative damage 1, 2
• Selenium supplementation may modulate innate immunity, which could explain its effects in autoimmune thyroid conditions 1

Patient Selection and Dosing

• Most beneficial effects are observed in:
  • Patients with mild Hashimoto's thyroiditis 1
  • Those with confirmed selenium deficiency 1, 2
  • Newly diagnosed cases 2
• The standard dose used in most studies is 200 μg daily 2, 3, 4, 5
• Supplementation duration in studies typically ranges from 3-6 months 2, 3, 5

Quality of Life Improvements

• Some studies report improvements in subjective well-being and mood with selenium supplementation 3, 4, 6
• One study showed statistically significant improvement in subjective well-being with sodium selenite 200 μg plus levothyroxine compared to placebo plus levothyroxine 3, 6

Limitations and Caveats

Evidence Quality

• The Cochrane review (2013) concluded that evidence to support or refute selenium supplementation in Hashimoto's thyroiditis is incomplete 3, 6
• Most studies have unclear to high risk of bias 3, 6
• Clinical relevance of antibody reduction remains uncertain in some studies 3

Safety Considerations

• Adverse events appear rare in studies of selenium supplementation 3
• Excessive selenium intake can lead to toxicity (selenosis), though this is uncommon at therapeutic doses 1
• A Danish RCT showed that selenium supplementation (100-300 μg/day) decreased TSH and FT4 concentrations in euthyroid subjects with marginal selenium deficiency 1

Population Considerations

• Response may vary based on baseline selenium status of the population 1
• Effects observed in selenium-deficient populations may not translate to selenium-sufficient populations 1

Clinical Approach to Selenium Supplementation

1. Assess selenium status if possible, as supplementation appears most beneficial in those with deficiency 1, 2
2. Consider baseline antibody levels - patients with higher antibody titers may show more pronounced benefits 5
3. Standard dosing: 200 μg daily of selenium (as selenomethionine or sodium selenite) 2, 3, 4
4. Monitor response after 3-6 months by measuring:
   • TPOAb and TGAb levels
   • Thyroid function tests
   • Subjective well-being/quality of life
5. Continue supplementation if positive response is observed and no adverse effects occur

Conclusion

While selenium supplementation shows promise in reducing thyroid antibody levels and improving quality of life in patients with Hashimoto's thyroiditis, particularly those with selenium deficiency, the overall evidence quality remains moderate. The most consistent benefit appears to be reduction in TPOAb levels, though the long-term clinical significance of this reduction requires further investigation.