Low concentrations of serum tyrosine in neuroleptic-free schizophrenics with an early onset.

The concentrations of serum tyrosine, phenylalanine and tryptophan have been determined in 23 male neuroleptic-free patients with schizophrenia and 28 male healthy control subjects. Tyrosine was significantly lower in neuroleptic-free patients with an early onset (starting before adulthood) than in healthy control subjects (p < 0.05), and the ratio of tyrosine to phenylalanine was significantly lower in neuroleptic-free patients with an early onset than in those with a late onset (starting at adulthood). No significant differences in these three amino acids were found between the patients with a late onset and healthy control subjects. The present findings suggest that there may be a disturbance of balance between tyrosine and phenylalanine in early-onset patients with schizophrenia.