Evaluation of Paraoxonase (PON-1) enzyme activity in female patients diagnosed with Autoimmune Thyroidits

Objective: PON-1 is a very important antioxidant enzyme for lipid metabolism, which prevents lipid peroxidation and oxidative modifications. It is a liver enzyme and bound by HDL. PON-1 has three different physiological activities: detoxification, antioxidant and anti-bacterial activity. For this reason, it has been associated with many diseases. The PON-1 gene has two important polymorphisms. These are Q/R 192 and M/L 55. The most common polymorphism is the Q/R 192 polymorphism. Autoimmune thyroiditis is an organ-specific autoimmune disease in which the cellular and humoral immune system plays a role, which progresses with lymphocytic infiltration and marked apoptosis in the thyroid gland, resulting in thyroid cell death. It ranks first among acquired diseases that cause hypothyroidism and enlargement of the thyroid gland in children and adolescents. Autoimmune thyroiditis is also the most common cause of acquired hypothyroidism and goiter in areas without endemic iodine deficiency. H2O2 is required for thyroid hormone biosynthesis in thyrocytes. Thyroglobulin degradation is observed due to exposure of the thyroid cell culture to high concentrations of H2O2. It has been suggested that prolonged exposure of thyrocytes to H2O2 or impaired antioxidant systems contributes to the development of Autoimmune Thyroiditis by changing the antigenicity of thyroglobulin and thyroid peroxidase. In the literature, the relationship of PON-1 activity with OT has been studied in adults, but no studies have been conducted on this topic in pediatric patients. In this study, it was aimed to evaluate PON-1 activity in girls diagnosed with OT. Results: Our study consisted of a total of 99 cases, including 60 female patients with a diagnosis of autoimmune thyroiditis between the ages of 0-18 who applied to the Balıkesir University Faculty of Medicine Pediatric Endocrinology Polyclinic and 39 healthy female patients who applied to the general pediatrics outpatient clinic for control purposes between August 2022 and May 2023. The median age of the patient group was 13,68 (3,70:18,00) and the median age of the control group was 10.00 (0:17.00). Blood samples were taken from our patients while they were in the euthyroid phase. There were cases with additional diseases such as diabetes, obesity, celiac, thalassemia minor, prepubertal precox. Age, height (SDS), weight (SDS), Anti-TPO, Anti-TG, Thyroid volume (SDS), B12, Ferritin, TSH, T4, T3, Thyroglobulin, 25-OHD, Hb, HTC, MCV with PON-1 activity in the patient group variables correlation coefficients and statistical significance of the coefficients were evaluated. There is a statistically significant negative correlation between PON-1 activity and B12 (p=0.043, r=-0.262). There is a statistically significant negative correlation between PON-1 activity and weight (SDS) (p=0.010, r=-0.332). There was no statistically significant relationship between PON-1 activity and height (SDS), Anti-TPO, Anti-TG, Thyroid volume (SDS), Ferritin, TSH, T4, T3, Thyroglobulin, 25-OHD, Hb, HTC, MCV variables. PON-1 activity was compared between the patient and control groups, and no statistically significant difference was found between the patient and control groups (p=0.150). Key words: Paraoxonase, Autoimmune thyroiditis, Oxidative stress, PON-1