© 2020 De Gruyter. All rights reserved.Objective: Subclinical hypothyroidism (SH) is one of the most prevalent endocrine disorders. Although recent data suggest an imbalanced oxidative status in SH, the mechanisms of increased oxidative stress are poorly figured out. The primary goal of this research was to analyze potential sources of ROS and the relationship between serum NOX-2 levels and paraoxonase-1 (PON-1) activity in SH. Serum lipid changes in SH patients which had been determined were compared to healthy control group. Materials and methods: Thirty-one patients diagnosed with SH and 30 healthy controls were included in the study. The quantitative sandwich ELISA was used for the detection of serum NOX-2 levels. Spectrophotometric method was used to determine serum PON-1 activity. Results: Higher median serum NOX-2 levels were determined in patients than in the control group (p = 0.004). Lower median serum PON-1 activity was determined in patients as to aforementioned control group (p < 0.0001). As a consequence, no statistically remarkable correlation was identified between PON-1 activity and NOX-2 levels. Triglyceride (TG) concentrations were determined as superior in patients to control group (p < 0.0001). Conclusion: Over-production of NOX-2 and decreased PON-1 activity contribute to the increased oxidative stress in SH patients. Larger prospective studies required to confirm these findings.