title: Neural response to transcranial magnetic stimulation in adult hypothyroidism and effect of replacement treatment.
abstract: OBJECTIVE
  Despite clinical evidences that hypothyroidism is often associated with cognitive dysfunction, affective disorders and psychosis, the effects of thyroid hormone deficiency on the adult brain have been largely unexplored. We investigated the hypothesis that hypothyroidism might affect cortical excitability and modulates inhibitory and excitatory cortical circuits by using Transcranial Magnetic Stimulation.
  
  
  METHODS
  Cortical excitability was probed in 10 patients with overt hypothyroidism and 10 age-matched healthy controls. We tested motor thresholds and corticospinal excitability, cortical silent period and peripheral silent period, short interval intracortical inhibition, intracortical facilitation. Patients were evaluated at the time of diagnosis, as well as after 3 and 6 months replacement therapy with l-thyroxin.
  
  
  RESULTS
  At baseline, patients showed decreased cortical excitability, with increased resting and active motor threshold and decreased steepness of the motor evoked potential recruitment curves. These changes were paralleled by longer cortical silent period and decreased short interval intracortical inhibition. After 3 months replacement therapy, all the parameters but short interval intracortical inhibition were restored to normal values. Short interval intracortical inhibition returned to normal values only after 6 months of replacement therapy.
  
  
  CONCLUSIONS
  Thyroid hormones are needed to modulate cortical excitability and cortical inhibitory circuits in adults.
authors: Department of Physiology and Pharmacology, CUNY School of Medicine, New York, NY 10031, USA.
authors: Vincenzo
authors: V
authors: Rizzo
authors: Domenica
authors: D
authors: Crupi
authors: Sergio
authors: S
authors: Bagnato
authors: Angelo
authors: A
authors: Quartarone
authors: Salvatore
authors: S
authors: Benvenga
authors: Luigi
authors: L
authors: Bartolone
authors: M Felice
authors: MF
authors: Ghilardi
authors: Francesco
authors: F
authors: Trimarchi
authors: Paolo
authors: P
authors: Girlanda
authors: Fortunato
authors: F
authors: Battaglia
mesh_terms: D002540:Cerebral Cortex / Q000503:physiopathology; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy / Q000503:physiopathology* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D011999:Recruitment, Neurophysiological; D013963:Thyroid Hormones / Q000097:blood / Q000627:therapeutic use; D013972:Thyrotropin / Q000097:blood / Q000627:therapeutic use; D050781:Transcranial Magnetic Stimulation
chemical_list: D013963:Thyroid Hormones; D013972:Thyrotropin