Investigation of serum paraoxonase-1 activity and lipid levels in patients with hyperthyroidism

Aim: The present study was designed to investigate the relationship among the serum paraoxonase-1 (PON-1) activity, lipid levels, and thyroid hormone status in patients with hyperthyroidism. Materials and methods: The study group comprised 30 patients with primary hyperthyroidism and 18 normal healthy controls who were matched for age and sex. Serum PON-1 activity was determined by spectrophotometric methods. Results: Serum PON-1 activity was found to be lower in patients compared to controls (P 0.05). Free triiodothyronine (T3) and free thyroxine (T4) levels were significantly higher in the patient group compared to the control group (P 0.001 and P 0.001 respectively). Thyroid-stimulating hormone (TSH) and total cholesterol values were found to be lower in patients than in the controls (P 0.001 and P 0.001 respectively). Low-density lipoprotein cholesterol levels were found to be decreased in patients compared to controls (P 0.005). Triglyceride and high-density lipoprotein cholesterol levels were not significantly different between the 2 groups (P 0.05). Serum PON-1 activity was found to be negatively correlated with free T4 levels (r = −0.324, P 0.05) and positively correlated with total cholesterol (r = 0.330, P 0.05) and TSH levels (r = 0.577, P 0.001). Conclusion: Our PON-1 results show that there is decreased antioxidant defense in patients with hyperthyroidism. Therefore, we think that effective antioxidant therapy to increase PON-1 activity may be a therapeutic option in patients with hyperthyroidism.