Background. Oxidative stress is a multifactorial process involving numerous metabolic pathways in the cell. Thyroid hormones play a significant role in reactive oxygen species production due to their ability to accelerate the basal metabolism and to change respiratory rate in mitochondria. On the other hand, thyroid hormones also differ from the cell antioxidant mechanisms in different ways, thus, creating a multivariate situation whose outcome is difficult to predict. The purpose of this study was to research the activity of oxidant and antioxidant defense in the blood and in the thyroid tissue of patients with nodular goiter against the background of autoimmune thyroiditis (AIT) and their changes due to the use of alpha-lipoic acid in preoperative preparation and in the postoperative period. Materials and methods. The activity of oxidant and antioxidant defense in the blood and in the thyroid tissue was studied in 80 patients with nodular goiter and AIT in the pre- and postoperative periods. Results. The study showed that in patients with nodular goiter and AIT, there is an activation of peroxidation and an increase in the functional ability of the antioxidant defense elements in the blood and in the thyroid tissue. Conclusions. It has been found that inclusion of alpha-lipoic acid in the integrated treatment of such patients contributes to a decrease in the activity of peroxidation, activation of antioxidant defense systems and more rapid restoration of the thyroid function.