title: Randomised controlled trial of tyrosine supplementation on neuropsychological performance in phenylketonuria.
abstract: OBJECTIVE
  To test the efficacy of tyrosine supplementation, as an adjunct to dietary treatment, on neuropsychological test performance in individuals with phenylketonuria.
  
  
  METHODS
  A randomised controlled trial of tyrosine supplementation using a double blind crossover procedure with three four week phases.
  
  
  METHODS
  The Hospital for Sick Children, Toronto.
  
  
  METHODS
  21 individuals with phenylketonuria (ages 6 to 28 years, mean 11.3).
  
  
  METHODS
  Participants were given 100 mg/kg body weight/d of L-tyrosine or L-alanine (placebo).
  
  
  RESULTS
  At baseline, performance on several of the neuropsychological test measures was correlated with tyrosine levels. Dietary supplements of tyrosine increased plasma tyrosine concentrations; however, no change in test performance was found across the tyrosine and placebo phases of the study.
  
  
  CONCLUSIONS
  Tyrosine supplementation of this type does not appear to alter neuropsychological performance in individuals with phenylketonuria.
authors.affiliation: Department of Psychology, University of Toronto, Mississauga, Ontario, Canada. smithml@psych.utoronto.ca
authors.forename: M L
authors.initials: ML
authors.lastname: Smith
authors.forename: W B
authors.initials: WB
authors.lastname: Hanley
authors.forename: J T
authors.initials: JT
authors.lastname: Clarke
authors.forename: P
authors.initials: P
authors.lastname: Klim
authors.forename: W
authors.initials: W
authors.lastname: Schoonheyt
authors.forename: V
authors.initials: V
authors.lastname: Austin
authors.forename: D C
authors.initials: DC
authors.lastname: Lehotay
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000409:Alanine / Q000008:administration & dosage; D002648:Child; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D010649:Phenylalanine / Q000097:blood; D010661:Phenylketonurias / Q000097:blood / Q000178:diet therapy* / Q000523:psychology; D017211:Treatment Failure; D014443:Tyrosine / Q000008:administration & dosage* / Q000097:blood / Q000627:therapeutic use
chemical_list: D014443:Tyrosine; D010649:Phenylalanine; D000409:Alanine