Phenylethylamine metabolism in Tourette's syndrome.

Beta-phenylethylamine, phenylalanine, and phenylacetic acid were examined in 24-hour urine samples and/or plasma samples obtained from 28 medication-free patients with Tourette's syndrome and 20 control subjects matched for age and education. Statistical analyses revealed that Tourette patients had lower plasma phenylalanine and urinary free beta-phenylethylamine compared with the controls, but did not differ on urinary total levels of phenylacetic acid. Fifty percent of the Tourette patients had a urinary beta-phenylethylamine level that was lower than the lowest control subject. In addition, urinary beta-phenylethylamine levels were inversely related to several scores from the Tourette Syndrome Global Scale. These data suggest that abnormalities in synthesis or metabolism of beta-phenylethylamine may be involved in the etiology of some patients with Tourette's syndrome.