The correlation between selenium levels and autoimmune thyroid disease: a systematic review and meta-analysis

Background: This investigation systematically evaluated the selenium levels and the effects of selenium supplementation in patients with autoimmune thyroid disease (AITD). Methods: Randomized controlled trials (RCTs) related to selenium supplementation in patients with AITD were selected from the PubMed, Medline, Web of Sciences, Embase, Cochrane Library, and Spring databases. All related literature published between January 2000 and November 2020 were included. The RCT bias risk assessment was conducted according to the Cochrane Handbook 5.0.2. The Review Manager 5.3 software was applied for meta-analysis of the included literature. Results: A total of 17 articles meeting the requirements were selected, including a total of 1,911 subjects. Meta-analysis results showed that the serum free triiodothyronine (FT3) levels in patients was greatly reduced after selenium supplementation compared to placebo treatment (MD = -0.40; 95% confidential interval (CI): -0.70-0.10; Z=2.61; P=0.009). Serum free thyroxine (FT4) levels and anti-thyroid peroxidase antibody (TPOAb) levels were also significantly reduced (MD = -0.76; 95% CI: -1.58-0.07; Z=1.79; P=0.07), and anti-thyroid peroxidase antibody (TPOAb) level was decreased observably (MD =-150.25; 95% CI: -04.06-96.43; Z=5.47; P<0.00001). The thyroid stimulating hormone (TSH) levels (MD = 0.06; 95 % CI: -0.53-0.66; Z=0.21; P=0.83) and anti-thyroglobulin antibody (TGAb) levels (MD=17.19; 95% CI: -254.86-289.25; Z=0.12; P=0.90) were not significantly different between the experimental group and the control group. Conclusions: Selenium-containing drugs were effective in treating AITD patients, and greatly reduced the levels of FT3, FT4, and TPOAb in AITD patients. These results suggested that selenium level had a great effect on AITD and selenium supplementation showed a very important effect on AITD.