Thyroid is one of the principal glands in the body's endocrine system. It produces T3 [triiodothyronine] and T4 [thyroxine] hormones responsible for cellular differentiation, growth, and metabolism. In hyperthyroidism and hypothyroidism, disturbance of oxidant/antioxidant balance leads to reactive oxygen species (ROS) generation. This study is to assess the effect of thyroid dysfunction on the antioxidant roles of vitamins (A, E) and Paraoxonase-1 . The study involved 55 individuals who were classified into three groups; 15 as control group, 20 as hyperthyroidism group and 20 as hypothyroidism group referred to Internal Medicine Department, 6 October University, Cairo, Egypt. Serum levels of vitamins (A, E) and Paraoxonase-1 as an antioxidants, Malondialdehyde as an index of lipid peroxidation state,T3, T4 and Thyroid stimulating hormone (TSH ) as to maintain the appropriate level of thyroid hormones in the body's cells were measured. The values of serum vitamins A, E and Paraoxonase-1 were significantly decreased in all patients with thyroid dysfunction as compared to the control group.The mean value of malondialdehyde level was significantly increased as compared to the control group. Correlation between Malondialdehyde levels with vitamin A, vitamin E and PON-1 showed a significant negative correlation in hyperthyroidism patients. It can be concluded that, the increased of the reactive oxygen species (ROS) in patients with hyperthyroidism and hypothyroidism has been accompanied with impairment of the antioxidant system .
