Selenoproteins in human body: focus on thyroid pathophysiology

Area of Science:

• Endocrinology and Metabolism
• Nutritional Science
• Molecular Biology

Background:

• Selenium (Se) is integral to selenoproteins, including iodothyronine deiodinases, vital for thyroid hormone metabolism and antioxidant defense.
• Optimal Se intake supports Se-dependent enzyme functions, yet precise human interrelationships require further elucidation.
• Low serum Se is associated with autoimmune thyroid diseases and differentiated thyroid cancer, highlighting its significance in thyroid health.

Purpose of the Study:

• To review the complex effects of selenium on thyroid physiology and related conditions.
• To evaluate the evidence linking selenium status to autoimmune thyroid diseases, thyroid cancer, and thyroid-associated orbitopathy.
• To assess the efficacy and recommendations for selenium supplementation in various thyroid disorders.

Main Methods:

• Narrative review of studies indexed in PubMed/Medline.
• Analysis of research on thyroid physiology, selenium metabolism, and selenoprotein function.
• Synthesis of evidence regarding selenium's role in autoimmune thyroid diseases, thyroid cancer, and Graves' orbitopathy.

Main Results:

• Low selenium levels correlate with increased risk of antithyroid antibodies and autoimmune thyroid diseases.
• Selenium supplementation may decrease antithyroid antibody titers and potentially reduce levothyroxine dosage in hypothyroidism.
• Evidence for routine selenium supplementation is heterogeneous, except for mild Graves' orbitopathy, where it aids in achieving euthyroidism faster.

Conclusions:

• Selenium is crucial for thyroid function, with low levels linked to thyroid autoimmunity.
• Current evidence does not support routine selenium supplementation for all thyroid conditions.
• Further research into selenium biomarkers and personalized supplementation strategies is warranted for optimal patient selection and treatment.