Involvement of the Selenium Level in Plasma Glutathione Peroxidase Activity in Newly Diagnosed Patients with Graves’ Disease and Hashimoto Thyroiditis

Disturbed antioxidant enzymes activities was known to be associated to Auto-Immune Thyroid Diseases (AITD), but it is noteworthy that the selenoenzyme glutathione peroxidase (GPx) showed the lowest activity and a selenium (Se) deficiency may be the major cause.  Most studies conducted on AITD are focused on the effect of the Se supplementation on the evolution of these pathologies. The aim of this study was to evaluate the Se level in plasma of Graves’ disease (GD) and Hashimoto Thyroiditis (HT) patients and its relationship with the redox status of these AITD. For this purpose, the Se levels as well as the GPx activity were evaluated in the plasmas of 33 patients with AITD. Results were compared with those of 27 healthy controls and among the two groups of patients. Results concerning GD and HT patients revealed lower Se levels by comparison with healthy controls (p<0.01 and p<0.05 respectively). Just like the Se, the GPx activity was found to be significantly lower in GD and HT patients compared to controls (p<0.01, p<0.001 respectively). The comparison between AITD groups showed higher Se level for the HT group (p<0.05), whereas, no significant differences were noted for the GPx activity. The correlation study showed positive correlation between Se level and GPx activity in HT group (r=0.64, p<0.01); and negative correlations between Se and anti-thyroglobuline and anti-Thyroid Stimulating Hormone Receptor levels in GD group (r= -0.71, p<0.05 and r= -0.73, p<0.05 respectively). As a conclusion, our findings have shown that the Se deficiency may be involved in the redox misbalance in HT; further investigations are mandatory to elucidate the origin of the reduced GPx activity in GD patients.