A Mendelian randomization study of the effect of selenium on autoimmune thyroid disease

The impact of selenium on autoimmune thyroid disease (AITD) is a subject of ongoing debate. This study aimed to analyze the causal correlations of selenium with autoimmune thyroiditis (AIT), autoimmune hyperthyroidism (AIH), and Graves' disease (GD) by Mendelian randomization (MR).

Single nucleotide polymorphisms related to selenium, AIT, AIH, and GD were sourced from the IEU Open GWAS project and FinnGen. Exposure-outcome causality was assessed using inverse variance weighted, MR-Egger, and weighted median. Horizontal pleiotropy was examined using the MR-Egger intercept, heterogeneity was evaluated with Cochran's Q test, and the robustness of the results was confirmed via leave-one-out sensitivity analysis.

The MR analysis revealed that selenium did not exhibit a causal relationship with AIT (OR 0.993, 95% CI 0.786 to 1.108, p=0.432), AIH (OR 1.066, 95% CI 0.976 to 1.164, p=0.154), or GD (OR 1.052, 95% CI 0.984 to 1.126, p=0.138). Moreover, the MR-Egger intercept and Cochran's Q test demonstrated the absence of horizontal pleiotropy or heterogeneity in these results (p>0.05). Sensitivity analysis affirmed the robustness of these results.

This MR analysis concluded that selenium was not linked to AIT, AIH, or GD risk. Therefore, indiscriminate selenium supplementation is not advisable for AITD patients without concurrent selenium deficiency.