Alterações bioquímicas e estresse oxidativo associados ao hipotireoidismo

Abstract

Overt hypothyroidism is characterized by decreased of thyroid hormones synthesis, with elevation of thyroid-stimulating hormone (TSH). It s a common disorder in population with highest prevalence in women and with aging. Frequently is associated with lipid metabolism alterations, represented by lipid parameters elevation and consequently with atherosclerosis development. The association between hypercholesterolemia and oxidative stress already well established, however oxidative stress presence in hypothyroidism is controversy. The oxidative stress is characterized by an increase in oxygen reactive species (ROS) generation or antioxidant system deficiency. In the present study were determined biochemical and oxidative stress biomarkers in overt hypothyroidism patients. The biochemical markers, total cholesterol (TC), LDL-cholesterol(C-LDL), cholesterol HDL (C-HDL) and trycerides (TG) were measured in serum samples in these patients. Lipid peroxidation was measured by thiobarbituric acid reactive substances (TBARS) levels. Antioxidant system evaluation was performed by superoxide dismutase (SOD) and catalase (CAT) actvities and non-enzymatic antioxidants levels were evaluated by reduced glutathione (GSH) and vitamin E (VIT E) levels.The results demonstrated an increase in biochemical markers (TC, C-LDL and TG) in hypothyroid group, when compared to control group. In relation to lipid peroxidation, was observed an increased in TBARS levels in patients with hypothyroidism when compared to control group. The same was observed for antioxidants defenses SOD and CAT. Nonenzymatic antioxidants, such vitamin E, were higher in hypothyroid group in relation to controls, while GSH levels remained unchanged with hypothyroidism. These results suggest the association between overt hypothyroidism and hypercholesterolemia and oxidative stress. The high levels of cholesterol presented by hypothyroidism patients, has a stronger influence under oxygen reactive species (ROS) generation and in consequence under the oxidative stress. The increase in SOD and CAT activities, suggest antioxidant system induction as a mechanism to combat the ROS generation and high lipid peroxidation. In conclusion, overt hypothyroidism has association with hypercholesterolemia and oxidative stress biomarkers increase.