Endocrine Abstracts

Introduction: Thyroid hormones are the most important factors involved in the regulation of the basal metabolic state, as well as in the oxidative metabolism. Oxidative stress accompanying hyperthyroidism is caused by increased synthesis of reactive oxygen species (ROS) and changes in the antioxidant defence system.

Aim of the study: To evaluate the pro-oxidant/antioxidant status and the effect of vitamin E supplementation in damage caused by the excessive administration of thyroid hormones.

Methods: White, male Wistar rats were used in the study. Thirty male Wistar rats were divided into three groups (1-control group, 2-animals treated with L-thyroxin 10 μg/animal per day for 30 days, 3-L-thyroxin treated rats protected with vitamin E 10 mg/animal per day). Malondialdehyde (MDA), the marker of lipid peroxidation, carbonyl proteins, SH groups, glutathion (GSH) and superoxide dismutase (SOD) were determined from the serum, while MDA, carbonyl proteins, SH groups and GSH were determined from the thyroid tissue homogenates.

Results: The results showed increased levels of carbonyl proteins in serum in thyrotoxic group as compared with the control group. MDA levels did not differ significantly from the euthyroid group. SH groups, GSH and SOD decreased significantly by thyroxin treatment. Vitamin E supplementation significantly increased serum MDA levels in the thyroxin treated group as compared with the control group and with animals treated only with thyroxin. Carbonyl protein levels increased significantly in serum of the hyperthyroid supplemented rats as compared to the controls. Antioxidant capacity markers in serum of group 3 were decreased compared with group 1. MDA significantly decreased in thyroid homogenates of the group 2 as compared with group 1. Significantly high levels of the SH groups and low levels of GSH were found in thyroid homogenates of the hyperthyroid rats.

These results suggest that experimental hyperthyroidism is accompanied with increased oxidative stress and impairment of the antioxidant system.

Vitamin E supplementation in hyperthyroidism could exert beneficial effects in favour of the diminution of thyroid hormone levels.