Visual, brainstem auditory and somatosensory evoked potential abnormalities in thyroid disease.

In order to investigate the neurophysiological effects of thyroid hormones, sixteen hypothyroid and twenty-seven hyperthyroid patients were studied for changes in visual, brainstem auditory and somatosensory evoked potentials. Hypothyroidism was associated with prolonged latency and reduced amplitude of visual evoked potential, prolonged latency and prolonged central conduction time of somatosensory evoked potential, and prolonged latency and interpeak latency of brainstem auditory evoked potential. Hyperthyroidism was associated with mild prolonged latency of visual evoked potential; other evoked potentials were normal. The prominent evoked potential abnormalities in hypothyroidism and mild evoked potential change in hyperthyroidism are consistent with a possibility that the central nervous system is more sensitive to a deficiency of thyroid hormone than to an excess.