Trace Element Status and Hypothyroidism:A Systematic Review and Meta-Analysis

Introduction: The metabolism of thyroid hormones has been linked with alterations in trace element levels. However, previous reports comparing trace element levels in hypothyroid patients and healthy individuals had yielded equsivocal results. Therefore, the aim of this meta-analysis was to investigate the association between trace element (selenium (Se), zinc (Zn), iron (Fe), copper (Cu), and lead (Pb)) concentrations in hypothyroid patients and healthy subjects. Materials & Methods: Electronic databases including PubMed, Scopus, Embase, and Science Direct were searched systematically until September 2019. Twenty-five observational studies were included. Hedges’ g was used to represent effect sizes, due to trace element levels being presented in different units among studies. Results: Our results revealed that Se (Hedges’ g= −0.52; 95% CI = [−1.05, -0.002]; P = 0.049) and Zn (Hedges’ g= -0.86; 95% CI = [-1.66, -0.06]; P = 0.035) concentration significantly lower; whereas Pb level significantly higher (Hedges’ g= 0.34; 95% CI = [0.10, 0.59]; P = 0.006) in patients with hypothyroidism compared with healthy controls. There were no significant difference in the concentration of Fe, and Cu.Conclusion: We found lower Se and Zn concentration accompanied by increased Pb level in patients with hypothyroidism. Further studies, with higher quality and larger sample sizes, are required to explicate the link between trace element status and hypothyroidism.