Selenium Supplementation for Hypothyroidism

Introduction to Selenium Supplementation

• For patients with hypothyroidism and documented selenium deficiency, the American College of Endocrinology recommends selenium supplementation at a starting dose of 100 μg/day 1

When to Consider Selenium Supplementation

• Selenium supplementation should be reserved for patients with documented selenium deficiency or those with autoimmune thyroiditis and subclinical hypothyroidism, as recommended by the Endocrine Society 1

Testing Before Supplementation

• Measure plasma selenium levels before initiating supplementation, particularly in patients with risk factors including malabsorption disorders, long-term enteral nutrition, or autoimmune thyroid disease, according to the American Thyroid Association 1
• Always measure CRP simultaneously, as inflammation significantly reduces plasma selenium levels, as noted by the European Thyroid Association 1, 2

Dosing Recommendations

• Start with 100 μg/day for patients with mild selenium deficiency or autoimmune thyroiditis, as recommended by the American College of Endocrinology 1
• For plasma selenium <0.4 μmol/L, consider up to 400 μg/day for 7-10 days for rapid correction, then reduce to maintenance dosing, according to the Endocrine Society 1, 2

Critical Pitfalls and Warnings

• Upper toxicity limits occur at plasma selenium levels of 6-12 μmol/L, and selenosis manifests as headache, hair and nail loss, skin rash, and neurological symptoms, as warned by the National Institutes of Health 1, 2
• Chronic overexposure is associated with type 2 diabetes and high-grade prostate cancer, as reported by the European Thyroid Association 2, 3

Maximum Safe Dose

• Do not exceed 400 μg/day except for short-term (7-10 days) correction of severe deficiency, as recommended by the American College of Endocrinology 1, 2

Monitoring Strategy

• Recheck plasma selenium and CRP after 3-6 months of supplementation, as suggested by the European Thyroid Association 3
• Monitor thyroid function (TSH, FT4) at 6-8 weeks if patient is on thyroid hormone replacement, according to the American Thyroid Association 4, 5

Special Populations

• For mild thyroid eye disease, selenium 100 μg/day may reduce inflammatory symptoms, as noted by the Endocrine Society 1