Methimazole protection against oxidative stress induced by hyperthyroidism in Graves disease

To examine the dynamics of oxidative stress in patients with hyperthyroidism before and during the treatment with methimazole using the measurement of conjugated dienes, malondialdehyde, and Schiff bases in blood serum.

In eight female patients with diagnosed Graves disease and 8 healthy control subjects (7 females and one male) several parameters of oxidative stress (the level of conjugated dienes [CD], malondialdehyde [MDA] and Schiff bases [SB]) were estimated before and during the treatment with methimazole (Metizol -POLFA) as well as by hormonal and immunological tests. In addition, serum levels of TSH, free thyroxine (FT4), free triiodothyronine (FT3), antibodies against thyroperoxidase (anti-TPO) and thyroglobulin (anti-Tg) and low density lipoprotein-cholesterol fraction (LDL-Ch) were estimated.

We observed increased concentrations of free thyroxine (FT4) and free triiodothyronine (FT3), as well as of antithyroperoxidase (anti-TPO) and antithyroglobulin (anti-Tg) antibodies. At the same time, TSH level was significantly suppressed. The concentrations of thyroid hormones and of TSH normalised after the methimazole treatment. The examined parameters, i.e., CD, MDA, and SB, were evaluated as proportions of each of them to the level of low density lipoproteins-cholesterol fraction (LDL-Ch). This fraction of cholesterol contains many polyunsaturated fatty acids, being a substrate for the peroxidation of lipids. Additionally, the CD/MDA ratio was calculated.

The increase of the CD/LDL ratio in Graves hyperthyroidism and its normalisation in the course of the treatment with methimazole suggests that the drug can be protective against the oxidative stress induced by overproduction of thyroid hormones. The ratio of CD/MDA decreased in all the patients, as compared to the control group, showing a high speed of lipid peroxidation.