Send to

Choose Destination
J Pediatr. 1995 Dec;127(6):936-43.

Effect of high-dose tyrosine supplementation on brain function in adults with phenylketonuria.

Author information

Department of Pediatric Neurology, University of Heidelberg, Germany.



To characterize abnormalities of brain function in patients with phenylketonuria (PKU) who had relaxed or stopped the dietary regimen and to test whether oral high-dose tyrosine (Tyr) supplementation has a beneficial effect.


Comparison with a control group; double-blind, placebo-controlled study comprising six test times; crossover treatment groups; oral high-dose Tyr therapy (100 mg/kg body weight per day) or placebo administration for 4 weeks.


Twenty-four early-treated patients with PKU aged 20.8 (16 to 25) years; 24 control subjects.


Plasma concentrations of phenylalanine and Tyr were monitored. Neuropsychologic tasks, visual evoked potentials, and spectral analysis of electroencephalographic activity were used to evaluate brain function.


When patients with PKU were compared with control subjects, deficits in certain aspects of brain function were confirmed (i.e., a decreased ability to sustain attention, prolonged latencies of visual evoked potential peaks N1 and P2, and a reduced amount of fast-wave activity on the electroencephalogram). Baseline plasma phenylalanine and Tyr concentrations were in the typical range of adult patients with PKU. The plasma Tyr concentration increased approximately 200% during Tyr supplementation, but no beneficial effects were observed.


High-dose Tyr supplementation cannot be recommended as an "alternative" treatment for patients with PKU after relaxation or termination of strict dietary adherence.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center