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.

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.