title: Low plasma tryptophan in carcinoid patients is associated with increased urinary cortisol excretion.
abstract: BACKGROUND
  Previously we observed in patients suffering from a metastatic carcinoid tumor that irritability, aggression and lack of impulse control are associated with low levels of plasma tryptophan and presumably with low brain serotonin function. In rats we showed that a diet of low tryptophan resulted in higher stress responses and higher corticosterone production. Here we tested in carcinoid patients whether tryptophan depletion due to tumor 5-HT overproduction is associated with high cortisol production.
  
  
  METHODS
  Urinary excretion of cortisol, serotonin, 5-hydroxyindole acetic acid (the main metabolite of serotonin a marker of tumor activity), plasma levels of tryptophan and platelet content of serotonin (index of peripheral serotonin synthesis) were determined in metastatic midgut carcinoid patients. Patients (N = 25) were divided into two groups based on their plasma tryptophan levels (< or = 25 micromol/l, n = 12 and > or = 49 micromol/l, n = 13).
  
  
  RESULTS
  Carcinoid patients with low plasma tryptophan levels had significantly higher urinary excretion of free cortisol (p < 0.01), independent of tumor activity. The inter-individual differences in the low tryptophan group, however, were substantial.
  
  
  CONCLUSIONS
  In a subgroup of the patients suffering from metastatic carcinoid disease the cerebral access of plasma tryptophan is impaired, thus rendering cerebral serotonin neurotransmission suboptimal and leading to hypercortisolism. The present study provides further support to the idea that low serotonergic function is a risk for developing stress-associated psychopathology.
authors: University Center Psychiatry, University Medical Center Groningen, The Netherlands. m.a.c.tanke@med.umcg.nl
authors: Marit A C
authors: MA
authors: Tanke
authors: Ido P
authors: IP
authors: Kema
authors: Janneke
authors: J
authors: Dijck-Brouwer
authors: Bennard
authors: B
authors: Doornbos
authors: Elisabeth G E
authors: EG
authors: De Vries
authors: Jakob
authors: J
authors: Korf
mesh_terms: D001921:Brain / Q000378:metabolism; D002276:Carcinoid Tumor / Q000378:metabolism*; D005770:Gastrointestinal Neoplasms / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000652:urine*; D006897:Hydroxyindoleacetic Acid / Q000652:urine; D009362:Neoplasm Metastasis; D009363:Neoplasm Proteins / Q000378:metabolism; D012189:Retrospective Studies; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000097:blood* / Q000172:deficiency
chemical_list: D009363:Neoplasm Proteins; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D006854:Hydrocortisone