Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 61 12 2024 08 22 722 727 EN Shahin Nosratzehi Department of Internal Medicine, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Mahin Nosratzehi Department of Internal Medicine, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran. Ebrahim Alijani Department of Immunology, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Abolfazl Payandeh Infectious Diseases and Tropical Medicine Research Center, Research Institute of Cellular and Molecular Sciences in Infectious Diseases, Zahedan University of Medical Sciences, Zahedan, Iran Tahereh Nosratzehi Department of Oral and Maxillofacial Medicine, School of Dentistry, Zahedan University of Medical Sciences, Zahedan, Iran Abdulmannan Charvaei School of Dentistry, Zahedan University of Medical Sciences, Zahedan, Iran. 2024 02 12 2024 08 05 Hashimoto's thyroiditis (HT) is one of the common causes of hypothyroidism. Although various factors are involved in its development, recently the role of oxidative stress in its pathogenesis has been known. The present study aimed to investigate the level of total antioxidant capacity (TAC), catalase (CAT), and salivary superoxide dismutase (SOD) in patients with HT compared with the control group. The present case-control design included patients aged 18-80 years suffering from HT referred to the endocrine clinic. Eligible patients were selected by the available sampling method. Complete unstimulated saliva was collected under a rest state in a comfortable room between 10:00 AM and 12:00 AM and a checklist was used to collect data. The chi-square, t-test, and Mann-Whitney U tests were used for data analysis using SPSS 22 software. The mean age of the participants was 36.55±9.37 years (range: 20-56). The two groups were the same in terms of age and gender (P>0.05). The findings indicated that the difference in the means CAT between the two groups was 22.63 which was strongly and statistically significant (P<0.001). In this study, the level of TAC and SOD in Hashimoto's thyroid patients was decreased and the level of CAT was increased. These initial findings show that oxidative stress can be associated with Hashimoto's thyroid disease or the possibility of developing this disease increase. https://acta.tums.ac.ir/index.php/acta/article/view/10968