Serum selenium status in Graves’ disease and Hashimoto's thyroiditis in an iodine-sufficient area: A case–control study

BACKGROUND: Selenium (Se) can be found in the molecular structure of selenoproteins; including thioredoxin reductase and glutathione peroxidase and also in Type I and II deiodinases. Previous studies have shown that Se deficiency has been linked to autoimmune thyroid disease (AITD). In the present study, we investigated the serum Se levels of patients with Graves’ disease (GD), Hashimoto's thyroiditis (HT), and euthyroid individuals as a control group. MATERIALS AND METHODS: The present study was performed on patients with newly diagnosed AITD (GD and HT). The control group was matched with the case group in terms of parameters such as age and sex. Free thyroxine, free triiodothyronine, thyroid-stimulating hormone, antithyroid peroxidase, antithyroglobulin, and serum Se levels were measured in all participants. These parameters were compared between groups. RESULTS: Data from 132 patients with HT, 120 patients with GD, and 120 healthy euthyroid patients as a control group were analyzed. The Se level in patients with HT (104.36 μg/l) and GD (97.68 μg/l) was significantly lower than in the control group (122.63 μg/l) (P < 0.001). The incidence of Se deficiency in patients with HT, GD, and in the control group was 15.2%, 2.5%, and 2.5%, respectively (P < 0.001). In patients with GD, 34 patients (28.33%) had Graves’ orbitopathy. Se levels in patients with orbitopathy were significantly lower than in patients without orbitopathy. CONCLUSION: The serum Se level was significantly lower in newly diagnosed patients with GD and HT than in the control group. Overall, Se deficiency can be considered a risk factor for AITDs.