The Association Between Serum Levels of Selenium, Copper, and Magnesium with Thyroid Cancer: a Meta-analysis

There are conflicting reports on the correlation between serum levels of selenium (Se), copper (Cu), and magnesium (Mg) with thyroid cancer. The purpose of the present study is to clarify the association between Se, Cu, and Mg levels with thyroid cancer using a meta-analysis approach. We searched articles indexed in PubMed published as of January 2015 that met our predefined criteria. Eight eligible articles involving 1291 subjects were identified. Overall, pooled analysis indicated that subjects with thyroid cancer had lower serum levels of Se and Mg, but higher levels of Cu than the healthy controls [Se: standardized mean difference (SMD)= -0.485, 95% confidence interval (95% CI)=(-0.878, -0.092), p= 0.016; Cu: SMD= 2.372, 95% CI=(0.945, 3.799), p= 0.001; Mg: SMD=-0.795, 95% CI=(-1.092, -0.498), p< 0.001]. Further subgroup analysis found lower serum levels of Se in thyroid cancer in Norway [SMD=-0.410, 95% CI=(-0.758, -0.062), p= 0.021] and Austria [SMD= -0.549, 95% CI=(-0.743, -0.355), p< 0.001], but not in Poland (SMD=-0.417, 95% CI=(-1.724, 0.891), p= 0.532]. Further subgroup analysis also found that patients with thyroid cancer had higher serum levels of Cu in China [SMD= 1.571, 95% CI=(1.121, 2.020), p< 0.001] and Turkey [SMD= 0.977, 95% CI=(0.521, 1.432), p< 0.001], but not in Poland [SMD= 3.471, 95% CI=(-0.056, 6.997], p= 0.054]. In conclusion, this meta-analysis supports a significant association between serum levels of Se, Cu, and Mg with thyroid cancer. However, the subgroup analysis found that there was significant effect modification of Se, Cu levels by ethnic, like China and Poland. Thus, this finding needs further confirmation by a trans-regional multicenter study to obtain better understanding of causal relationship between Se, Cu, and Mg with thyroid cancer of different human races or regions.