Urinary excretion of aromatic acids in hyperphenylalaninemic states: response to a protein challenge.

A protein challenge (3g/kg) was given to 15 hyperphenylalaninemic patients for 4 days and urinary excretion of aromatic phenylalanine metabolites (e.g. phenylpyruvic acid; mandelic acid; ortho-hydroxy-phenylacetic acid) was studied by quantitative gas chromatographic analysis. Two groups of patients, different in their serum phenylalanine pattern, could be distinguished from the pattern of urinary aromatic acid excretion. In the first group, the aromatic acid excretion declined towards the end of the challenge whereas aromatic acid excretion increased throughout the challenge in the second group. The differences could be ascertained by statistical analysis.