ACUTE HYPOTHYROIDISM LEADS TO REVERSIBLE ALTERATIONS IN CENTRAL-NERVOUS-SYSTEM AS REVEALED BY SOMATOSENSORY-EVOKED POTENTIALS

Although functional alterations in the central nervous system (CNS) an d peripheral nerves are well documented in overt hypothyroidism, littl e is known about alterations of CNS in acute hypothyroidism. Sixteen p atients with differentiated thyroid carcinoma were studied when prepar ed for radioiodine scanning after stopping levothyroxine (L-T-4) thera py for 6 weeks to determine whether acute hypothyroidism leads to alte ration in somatosensory evoked potentials (SSEPs). Repeat SSEPs were p erformed on the same patients at 6 months following L-T, therapy when patients were euthyroid. Neurophysiological findings were compared wit h a group of 20 normal controls with no history of thyroid disease. Pe ripheral and central conduction in the median and tibial nerve stimula ted SSEPs studied. A significant prolongation of central conduction ri me in SSEPs was found in patients with acute hypothyroidism when compa red to those in control subjects. Abnormal latencies were not correlat ed with thyroid hormone levels. These neurophysiologic abnormalities w ere completely restored to normal at 6 months after L-T-4 therapy. We conclude that acute hypothyroidism leads to reversible alterations in CNS as determined by SSEP recordings. Our results also suggest that SS EPs could be useful tests to monitor functional alteration of the CNS in acute hypothyroidism.