Lipid Oxidation, Antioxidants and Paraoxonase Enzyme Activity in Patients with Subclinical Thyrotoxicosis

Subclinical hyperthyroidism is defined by the suppressed level of TSH and normal values of T4 and T3. The effect of this status on lipid metabolism is not well recognized this study was done to address this issue. Methods and Materials: In this case-control study, 41 patients with subclinical hyperthyroidism and 36 euthyroid subjects were recruited. Subclinical hyperthyroidism was difined as TSH<0. 3 and normal T3 and T4 values, and confirmed with the TRH test. Questionnaires for clinical data and drug history were completed for all patients and blood samples were obtained for laboratory tests. In this study the markers of lipid oxidation, antioxidants, paraoxonase enzyme activity, serum lipid levels, vit A, E and B-carotene were measured and the parameters were analysed using the appropriate statistical methods. There were no significant changes between the two groups regarding age (46±13 vs 47±13, years old), sex (30/11 vs 14/12 male/female), weight (79±14 vs 77±13 kg), body mass index and hypertension. Significantly lower serum TSH (0.16±0.1 vs 1.1±1.0, mIU/L p<0. 001) was found in the subclinically hyperthyroid group. Significantly lower level of paraoxonase enzyme activity, vit A, B caroten, oxidized LDL-C, TAC, total cholesterol, triglyceride, LDL-C and Pon/LDL ratio were found in patients with subclincal hyperthyroidsim as compared with the control group. Significant differences in lipid levels and lipid oxidation and antioxidants seen in these patients show a change in the basal methobolism of this group.