title: Sex differences in plasma prolactin response to tryptophan in chronic fatigue syndrome patients with and without comorbid fibromyalgia.
abstract: BACKGROUND
  Some think chronic fatigue syndrome (CFS) and fibromyalgia (FM) are variants of the same illness process. This would imply that CFS patients with and without comorbid FM have similar biological underpinnings. To test this, we compared serotonergic-based responses, plasma prolactin (PRL), and self-reported measures of fatigue to intravenous infusion of tryptophan among patients with CFS alone, CFS + FM, and healthy controls.
  
  
  METHODS
  Men and women with CFS alone or CFS + FM and healthy subjects, none with current major depressive disorder (MDD), were given 120 mg of L-tryptophan per kg lean body mass intravenously (i.v.). Before and after tryptophan infusion, blood samples were collected, and plasma PRL, tryptophan, and kynurenine concentrations were determined.
  
  
  RESULTS
  Women with CFS alone, but not CFS + FM, showed upregulated plasma PRL responses compared with controls. There were no differences among groups of men. Plasma tryptophan and kynurenine concentrations did not differ among groups.
  
  
  CONCLUSIONS
  These results indicate that women with CFS alone have upregulated serotonergic tone that is not seen in those with comorbid FM. The lack of effect in men suggests a mechanism that might explain, in part, the increased prevalence of CFS in women. The data support the interpretation that CFS in women is a different illness from FM.
authors.affiliation: Department of Neurology & Neurosciences, UMDNJ-New Jersey Medical School, Newark, New Jersey, USA.
authors.forename: Shelley A
authors.initials: SA
authors.lastname: Weaver
authors.forename: Malvin N
authors.initials: MN
authors.lastname: Janal
authors.forename: Nadine
authors.initials: N
authors.lastname: Aktan
authors.forename: John E
authors.initials: JE
authors.lastname: Ottenweller
authors.forename: Benjamin H
authors.initials: BH
authors.lastname: Natelson
mesh_terms: D000328:Adult; D018687:Antidepressive Agents, Second-Generation / Q000008:administration & dosage*; D016022:Case-Control Studies; D015673:Fatigue Syndrome, Chronic / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011388:Prolactin / Q000097:blood*; D012727:Sex Characteristics; D014364:Tryptophan / Q000008:administration & dosage*
chemical_list: D018687:Antidepressive Agents, Second-Generation; D014364:Tryptophan; D011388:Prolactin
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