Serum paraoxonase 1 activity is decreased in thyroid dysfunction

Changes in serum lipid and lipoprotein concentrations occur frequently in disorders of thyroid function. LDL-cholesterol (LDL-C) oxidation susceptibility is higher in these patients than in normal population. This study aims at assessing lipids, lipoproteins, apolipoproteins and serum paraoxonase 1(PON1) activity in patients with thyroid dysfunction. Ninety-nine patients with thyroid dysfunction, (49 hypothyroid and 50 hyperthyroid) were compared with 2 separately age- and sex-matched control groups. A fasting blood sample was obtained and serum total cholesterol, triglycerides, apolipoproteins A-I and B, and PON1 activity were measured. In hyperthyroid patients, significantly lower PON1 activity (45+/-23 vs 67+/-37 IU/ml, p<0.001), triglycericles (112+/-53 vs 166+/-130 mg/dl, p<0.05), apolipoprotein A-I (137+/-26 vs 154+/-21 mg/dl, p<0.001) and apolipoprotein B (75+/-18 vs 86+/-25 mg/dl, p<0.05) were found. Hypothyroid patients had lower POW activity (46+/-21 vs 64+/-32 IU/ml, p<0.005) compared with controls, and higher total cholesterol (224+/-69 vs 185+/-41 mg/dl, p<0.001), LDL-C (133+/-59 vs 93+/-36 mg/dl, p<0.001), and apolipoprotein B (107+/-37 vs 84+/-23 mg/dl, p<0.001). The results show significant changes of lipid levels in thyroid dysfunction. In addition, a significant reduction in PON1 activity was observed in both hyper- and hypothyroid patients. Increased LDL-C oxidation in thyroid dysfunction observed in other studies, at least to some extent, can be attributed to reduced PON1 activity. (C) 2003, Editrice Kurtis.