Cognitive status in hypothyroid female patients: Event-related evoked potential study

Aim: Higher brain functions are adversely affected in hypothyroid patients. The central nervous system features of hypothyroidism include mental retardation, various cognitive and memory deficits that have been evaluated by different neuropsychological tests. In the present study event-related potentials (ERPs) have been used to assess the cognitive status of hypothyroid patients before and after treatment. Methods: Twenty-six newly diagnosed hypothyroid female patients with a mean age of 31.85 +/- 8.57 years and 26 female controls with a mean age of 30.92 +/- 7.24 years were the subjects of the study. The ERPs were recorded on a computerized evoked potential recorder using the 10-20 system of electrode placement and the standard auditory 'oddball' paradigm. The first recording of ERPs was done at the time of diagnosis and the second recording was done 3 months after the start of treatment in a euthyroid state. Results: Prolongation of latencies was found in the early ERP components (N100, P200 and N200) in hypothyroid patients compared to controls, while no significant group differences were found on P300. In the hypothyroid group all the ERP latencies decreased significantly after attainment of euthyroidism compared to pretreatment values. ERP amplitudes revealed no significant group differences between hypothyroid patients and controls, but significant amplitude increases were found on the waves of N200 and P300 after treatment compared with pretreatment values in the hypothyroid group. Conclusions: Hypothyroid patients showed prolongation of latencies only in the early ERP components compared to controls. In hypothyroid patients, ERP findings indicate a speeding of sensory and cognitive processing in a state of euthyroidism compared to the pretreatment condition. Copyright (C) 2008 S. Karger AG, Basel.