Melatonin and Dopamine as Biomarkers to Optimize Treatment in Phenylketonuria: Effects of Tryptophan and Tyrosine Supplementation

Melatonin levels were not increased with the higher dose of Trp supplementation, but dopamine levels were increased with the higher dose of Tyr supplementation. Serotonin synthesis appears to be suppressed by high phenylalanine levels at the Trp hydroxylase level.