آيا درمان هيپرتيروييدي در تغيير سطح سرمي ليپوپروتيين ها، آپوليپوپروتيين هاو فعاليت آنزيم پاراكسوناز سرمي موثر است ؟

Does treatment of hyperthyroidism affect serum lipids,lipoproteins and paraoxonase enzyme activity?

Thyroid hormones play an important role in the synthesis, metabolism, and catabolism of lipids. Hyperthyroid patients have increased susceptibility to oxidative stresses and thus undergo LDL oxidation. Paraoxonase is an HDL-linked enzyme which, in vitro, prevents LDL oxidation and might have an anti-atherogenic effect. The purpose of this study was to compare paraoxonase activity and lipid status before and after treatment of hyperthyroidism. 24 hyperthyroid patients and 23 control subjects were studied. In all subjects after obtaining history and anthropometric measurements, serum levels of thyroid hormones, lipids, lipoproteins, and apolipoproteins and serum paraoxonase activity were measured in a fasting blood sample. All patients were treated with methimazole and followed up for 7.3±3.9 months. Of 24 patients, 15 attained euthyroidism. There were no significant changes in weight, body mass index, and waist to hip ratio after treatment. There was significant decrease in serum levels of T4 (8.4±2.2 vs. 16.6±4.4 miug/dL, P<0.001), T3 (134±38 vs. 250±90 ngldL, P<0.05), and increase in serum TSH (1.9±2.2 vs. 0.06±0.06 miuU/mL, P<0.001). Serum paraoxonase activity significantly increased after treatment (49.0±22.8 vs. 64.6±37.8 IU/mL, P<0.001). Also, treatment caused significant increase in serum cholesterol, triglycerides, LDL-C, cholesterol to HDL and LDL to HDL ratios. HDL and apolipoproteins A-I and B levels did not change following treatment. The observed changes in serum paraoxonase activity in the present study, suggest that the enhanced oxidation observed in these patients can be, at least to some extent, caused by reduced paraoxonase activity.