Randomised controlled trial of tyrosine supplementation on neuropsychological performance in phenylketonuria.
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.
Smith
M L
ML
Department of Psychology, University of Toronto, Mississauga, Ontario, Canada. smithml@psych.utoronto.ca
Hanley
W B
WB
Clarke
J T
JT
Klim
P
P
Schoonheyt
W
W
Austin
V
V
Lehotay
D C
DC
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
D014443:Tyrosine; D010649:Phenylalanine; D000409:Alanine