title: Tryptophan depletion in chronic fatigue syndrome, a pilot cross-over study.
abstract: BACKGROUND
  Chronic fatigue syndrome (CFS) is still an enigmatic disorder. CFS can be regarded as a complex disorder with tremendous impact on lives of CFS-patients. Full recovery without treatment is rare. A somatic explanation for the fatigue is lacking. There is clinical and experimental evidence implicating enhanced serotonergic neurotransmission in CFS. Genetic studies and imaging studies support the hypothesis of upregulated serotonin system in CFS. In line with the hypothesis of an increased serotonergic state in CFS, we performed a randomised clinical trial investigated the effect of 5-HT3 receptor antagonism in CFS. No benefit was found of the 5-HT3 receptor antagonist ondansetron compared to placebo.To further investigate the involvement of serotonin in CFS we performed a placebo controlled cross over pilot study investigating the effect of Acute Tryptophan Depletion.
  
  
  RESULTS
  Five female CFS-patients who met the US Center for Disease Control and Prevention criteria for CFS were recruited. There were two test days, one week apart. Each participant received placebo and ATD. To evaluate the efficacy of the ATD procedure tryptophan and the large neutral amino acids were measured. The outcome measures were fatigue severity, concentration and mood states. ATD resulted in a significant plasma tryptophan to large neutral amino acid ratio reduction of 96%. There were no significant differences in fatigue-, depression and concentration between the placebo- and ATD condition.
  
  
  CONCLUSIONS
  These first five CFS-patients did not respond to the ATD procedure. However, a much larger sample size is needed to draw final conclusions on the hypothesis of an increased serotonergic state in the pathophysiology of CFS.
  
  
  BACKGROUND
  ISRCTN07518149.
authors.affiliation: Department of General Internal Medicine, Nijmegen Expert Centre Chronic Fatigue, Radboud University Nijmegen Medical Centre, Reinier Postlaan 4, 6525 GC Nijmegen, The Netherlands. g.the@adrz.nl.
authors.forename: Gerard K H
authors.initials: GK
authors.lastname: The
authors.forename: Robbert J
authors.initials: RJ
authors.lastname: Verkes
authors.forename: Durk
authors.initials: D
authors.lastname: Fekkes
authors.forename: Gijs
authors.initials: G
authors.lastname: Bleijenberg
authors.forename: Jos W M
authors.initials: JW
authors.lastname: van der Meer
authors.forename: Jan K
authors.initials: JK
authors.lastname: Buitelaar
mesh_terms: D000328:Adult; D000339:Affect; D018592:Cross-Over Studies; D015673:Fatigue Syndrome, Chronic / Q000097:blood / Q000175:diagnosis / Q000523:psychology / Q000628:therapy*; D005260:Female; D006801:Humans; D009426:Netherlands; D010865:Pilot Projects; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome; D014364:Tryptophan / Q000097:blood / Q000172:deficiency*; D055815:Young Adult
chemical_list: D014364:Tryptophan