Fig. 2From: Diagnostic and therapeutic recommendations for the treatment of hyperphenylalaninemia in patients 0–4 years of ageIllustrative examples of neonatal BH4 loading test outcomes. BH4: Tetrahydrobiopterin; PAH: Phenylalanine hydroxylase; Phe: Phenylalanine; PTPS: 6-pyruvoyl-tetrahydropterin synthaseBack to article page