Cognitive Functions in Hyperthyroid Patients: P300 and Working Memory

Background: Thyroid hormones are quite important for the normal physiological functions and the cognitive functions of brain. Objectives: In the present study, event related potentials (ERPs) have been used to assess the cognitive status of hyperthyroid patients before treatment. Methods: The study was conducted on 26 hyperthyroid patients and 26 healthy volunteers, Plasma levels of fT3, fT4, and TSH were measured pre- and post-treatment in hyperthyroid and control groups. ERPs were recorded with MP150 system using the 10-20 system of electrode placement and the standard auditory “oddball” paradigm, n- back working memory tasks. Result: Prolongation of latencies of P300 was seen in hyperthyroid patients compared to controls (p=0.001). P300 amplitudes were also higher in hyperthyroid patients (p=0.001). In the euthyroidized patients P300 amplitudes diminished for stimuli 1 and 3 at WM1 and WM2 tasks compared hyperthyroid patients (p<0.001). Conclusion: The prolonged P300 latency in hyperthyroid patients that indicated the delayed cognitive information processing and the increased P300 amplitude that was related to the increased activity of cognitive information and attention after the start of treatment in a euthyroid state. This study showed us that the treatment of hyperthyroidism may improve cognitive performance.