Biochemical evaluation of oxidative stress in propylthiouracil treated hyperthyroid patients. Effects of vitamin c supplementation

In this study the impact of vitamin C supplementation on oxidative damage a s assessed by thiobarbituric acid reactive substances and markers of antiox idant status: namely Cu/Zn superoxide dismutase, glutathione peroxidase, gl utathione reductase and glutathione were investigated in 24 hyper-thyroid p atients under propylthiouracil therapy (3x100 mg/day) for five days and in 15 healthy controls. Ascorbic acid (1000 mg/day) was given as a supplement for 1 month to both the patients and controls during the study period. Hepa rinised blood samples were taken at the beginning and the end of one month ascorbic acid supplementation. Comparison of the hyperthyroid patients with the controls revealed higher l ipid peroxidation (p<0.001), higher Cu/Zn superoxide dismutase activity (p< 0.001), higher glutathione level (<0.001) and lower glutathione reductase a ctivity (p<0.001). Vitamin C supplementation to hyperthyroid patients caused significant incre ases in glutathione concentration (p<0.001) and glutathione peroxidase acti vity (p<0.001), whereas there were significant decreases in glutathione red uctase (p<0.001) and Cu/Zn superoxide dismutase activities (p<0.01). Thioba rbituric acid reactive substances and thiobarbituric acid reactive substanc es/glutathione ratio were significantly decreased (p<0.01). Vitamin C supplementation to euthyroid controls caused significant increase s in glutathione concentration (p<0.001) and glutathione peroxidase and Cu/ Zn superoxide dismutase activities (p<0.001), whereas there was a significa nt decrease in glutathione reductase (p<0.001). The thiobarbituric acid rea ctive substances/glutathione ratio was significantly decreased (p<0.05). Our findings reveal the potentiation of antioxidant status and a relief in oxidative stress in both propylthiouracil treated hyperthyroid patients and controls in response to vitamin C supplementation.