Tehran University of Medical Sciences Acta Biochimica Iranica 0001-5261 3 4 2025 12 21 215 220 Arshia Abbaszadeh Department of Biology, Ur.C., Islamic Azad University, Urmia, Iran Mohammad Reza Asgharzadeh Department of Biology, Ur.C., Islamic Azad University, Urmia, Iran Zafar Gholinejad Department of Medical Laboratory Sciences, Ur.C., Islamic Azad University, Urmia, Iran. 2025 09 14 2026 02 05 Objective: Oxidative stress plays a key role in the pathogenesis of rheumatoid arthritis (RA). Glutathione peroxidase (GPx) is a peroxidase enzyme that defends mammalian cells against oxidative stress.  The Pro198Leu polymorphism of the GPx-1 gene, has been reported to influence its activity. This study aimed to investigate the association of this polymorphism with RA risk in an Iranian population. Methods: In this case-control study, 45 RA patients and 45 healthy controls were enrolled. Genomic DNA was extracted from blood samples, and genotyping for the Pro198Leu polymorphism was performed using the PCR-RFLP technique. Statistical analysis was conducted using SPSS software, employing chi-square tests and ANOVA. Results: The mean age of all participants was 55.69 years. Genotype distribution was as follows: CC (50.0%), CT (44.4%), and TT (5.6%). Chi-square analysis revealed no significant difference in genotype frequencies between patients and controls (p = 0.779). Furthermore, no significant association was found between genotypes and age or gender. All groups were in Hardy-Weinberg equilibrium. Conclusion: The findings indicate that the GPx-1 Pro198Leu polymorphism is not significantly associated with the risk of developing RA in the studied population. https://abi.tums.ac.ir/index.php/abi/article/view/159 https://abi.tums.ac.ir/index.php/abi/article/download/159/123