Objective. To evaluate the activity of neuron specific enolase (NSE) in patients with primary hypothyroidism (PGT) treated with mexidol. Material and methods. Patients with PGT (n=110) were examined before and after treatment. Neuropsychological and neurological status of the patients was studied. To assess the status of the peripheral nervous system, electroneuromyography was performed and serum NSE level was determined. Results and conclusion. The NSE activity depended on gender, age of the patient, duration of endocrinopathy and presence/absence of neurological symptoms. The clear positive dynamics of the majority of the parameters studied was noted during mexidol treatment. The efficacy of antioxidant therapy in these patients was confirmed.