a diagnosis of a deficit in biopterin synthesis was made at five months of age as a result of the following : high neopterin and low biopterin levels in both blood and urine , normal dihydropteridine reductase in the liver and a sharp drop in the plasma phenylalanine level 4 h after the administration of a test dose of tetrahydrobiopterin .
C0005562
biopterin
C0068527
neopterin