[Case studies of the effect of tyrosine administration in children with phenylketonuria on cognitive processes]

Eight patients with phenylketonuria and low protein nutrition were treated in a double blind crossover study for the time of 3 month with 150 mg tyrosine per kg body weight and day and placebo thereafter or vice versa. The concentration of phenylalanine in serum was not influenced by the administration of tyrosine whereas tyrosine in serum markedly increased. Psychological tests were 7 times repeated in monthly intervals. From the study it is to suggest that there is an improvement of the test results caused by an effect of training due to the repeated tests and an additional improvement caused by tyrosine.