Association of serum paraoxonase activity with insulin sensitivity and oxidative stress in hyperthyroid and TSH-suppressed nodular goitre patients

Summary objective Low serum paraoxonase (PON) activity is thought to be a risk factor for the development of atherosclerosis. The present study was designed to evaluate PON1 activity and its relationship with preatherosclerotic markers such as lipid peroxidation and insulin resistance in hyperthyroid patients before and after propylthiouracil (PTU) treatment and in subjects with iatrogenic subclinical hyperthyroidism. patients and design Twenty patients with hyperthyroidism, 20 patients with euthyroid multinodular goiter (MNG) and 20 age‐ and sex‐matched healthy controls were enrolled in the study. Insulin sensitivity index, PON activity and lipid peroxidation were measured at baseline and 2 months after achieving euthyroidism or subclinical hyperthyroidism. Levothyroxine was given as a part of TSH suppression therapy in multinodular goitre patients. measurements Insulin sensitivity was determined by an oral glucose tolerance test (OGTT) based on the insulin sensitivity index (ISI) formula, serum paraoxonase activity was determined with a spectrophotometric method. Lipid peroxidation was measured by the formation of thiobarbituric acid reactive substances (TBARs). results ISI was significantly lower in the hyperthyroid group than baseline levels in MNG patients and controls (P