Fig. 4From: Urinary metabolomics of young Italian autistic children supports abnormal tryptophan and purine metabolismQuantification of tryptophan metabolites: a kynurenine pathway; b serotonin/melatonin pathway; c–d bacterial degradation products. Peak areas for each metabolite were normalized by urinary specific gravity. Nominal P values: *P < 0.05, **P < 0.0.1, ***P < 0.001Back to article page