Endocrine Abstracts

Patients with thyroid dysfunction are more susceptible to oxidative stress, and may show enhanced LDL-C oxidation. The purpose of this study was to evaluate serum paraoxonase activity and antioxidants in patients with endogenous subclinical hyperthyroidism.

Forty-one subclinical hyperthyroid patients, 30 women and 11 men, aged 47±13 years, and 40 age and sex matched healthy controls were studied. Serum paraoxonase activity, lipid, lipoprotein, oxidized-LDL, Total antioxidant capacity (TAC), vitamin A, E and β-carotene levels were measured in fasting samples.

In subclinical hyperthyroid patients, significantly lower serum paraoxonase activity (53±26 vs 77±35 iu/ml, P<0.001), oxidized-LDL (50±12 vs 65±25 mg/dl, P<0.01), TAC (1.6±0.2 vs 1.9±0.3 μ/l, P<0.001), PON/HDL (0.96±0.65 vs 2.1±1.1, P<0.001), vitamin A, β-carotene and uric acid were found. The results show significant changes of lipid oxidation and antioxidant levels in subclinical thyrotoxicosis. In addition, the significant reduction in serum paraoxonase activity observed in these patients may predispose lipids to oxidation.