Insufficient evidence to support the clinical efficacy of selenium supplementation for patients with chronic autoimmune thyroiditis.

Abstract

This study critically reappraises the documentation on the clinical efficacy of selenium supplementation in chronic autoimmune thyroiditis (AIT) with the goal of improving the normalization of the treatment of this disease. A literature search was performed in the Medline, Embase, and Cochrane Library databases. Twenty-three trials conducted in adults with AIT comparing the efficacy of selenium with or without levothyroxine (LT4) versus placebo and/or LT4 were eligible. The assessed outcomes were primarily pooled using a random- or fixed effects model based on the results of the heterogeneity test. The quality of evidence was assessed per outcome. In LT4-treated populations, patients receiving selenium demonstrated lower thyroid peroxidase antibody (TPOAb) levels at 3 months (mean difference [MD], -236.88; 95% confidence interval [CI], -353.35 to -120.41; p < 0.0001), 6 months (MD, -407.17; 95% CI, -623.60 to -190.73; p = 0.0002), and 12 months (MD, -327.03; 95% CI, -613.78 to -40.28; p = 0.0254), while thyroglobulin antibody (TgAb) levels only decreased at 12 months. In non-LT4-treated population, the selenium group demonstrated significantly lower TPOAb levels after 3 months (MD, -203.07; 95% CI, -395.44 to -10.70; p = 0.0385) and 6 months (MD, -322.27; 95% CI, -597.50 to -47.04; p = 0.0217) but not after 12 months, while TgAb levels only decreased at 3 months. There was no significant change in thyroid stimulating hormone (TSH) levels. Lower thyroid echogenicity was observed in all patients receiving selenium at 3, 6, and 12 months. However, these participants had a significantly higher risk of reported adverse effects. Current evidence does not justify the emerging use of selenium supplementation in the treatment of AIT, despite it resulting in a decrease in autoantibody levels.