RESUMO
The effect of free radicals on human beings has attracted considerable attention due to their close relation to health and disease. This study was carried out to investigate the antioxidant status in thyroid and liver due to treatment with amiodarone [AM] and the relationship between AM treatment and thyroid function in case of pre-existence of hypothyroidism. The present study comprised of two experiments, each of them extended for 2 months. The first one was designed to induce hypothyroidism and the second for treatment with AM. Serum malondialdehyde [MDA] and reduced glutathione [GSH] levels were measured as indicators of redox status. The levels of serum triiodothyronine [T3], thyroxine [T4] levels and thyroid stimulating hormone [TSH] were measured the agonist/antagonist interactions between the drug and thyroid hormones. Liver enzymes-Alanine aminotransaminase [ALT] and Aspartate aminotransaminase [AST] activities-and lipid parameters were measured in serum as well. In addition, hisopathological examinations for thyroid and liver tissues were done. The results showed that: 1] serum T3 and T4 levels were increased, while TSH levels were decreased in hypothyroid AM treated group, whereas in euthyroid AM treated group, serum T3 was decreased but serum T4 and TSH levels increased. 2] total cholesterol and LDL increased in both AM treated groups showing a state of hyperlipidemia. 3] serum MDA level was increased while serum GSH was decreased in AM treated hypothyroid group and in euthyroid AM treated one as well, inducing a state of oxidative stress. Serum MDA levels were decreased while serum GSH were increased in Hypo+. 4] ALT and AST increased in all AM treated groups. 5] hisopathological examination of thyroid and liver tissues showed some structural abnormalities due to AM treatment. Based on these results, patients with hypothyroidism should be monitored periodically their thyroid and liver functions during AM therapy due to its stimulation for the formation of reactive oxygen species, causing oxidative damage in both liver and thyroid functions and their tissues. These findings suggested that a state of hypothyroidism may exert beneficial protective and curative effects on this situation by decreasing T3, T4, ALT and AST levels, attenuating the endogenous antioxidant levels and decreasing lipid peroxidation