Normal pterin values in urine and serum in neonates and its age-related change throughout life

Tetrahydrobiopterin (BH4) deficiency has been described as a form of hyperphenylalaninaemia in which severe neurological symptoms develop despite early treatment with low phenylalanine diet. In recent years it has become apparent that biopterin deficiency may be caused by a defect either of dihydropteridine reductase (DHPR, EC 1.6.99.10) or dihydrobiopterin synthetase (DHBS) (Niederwieser et al., 1979). Since it was proposed that treatment with precursors of the neurotransmitters involved could prevent neurological deterioration if started within the first months after birth (Curtius et al., 1979), screening of all neonates with hyperphenylalaninaemia for biopterin disorders, and a non-invasive reliable method for the diagnosis of two types of BH4 deficiency are needed urgently. Assessment of pterin derivatives in biological fluids, mostly in urine, by high performance liquid chromatography (HPLC) is proposed as a reliable diagnostic method and Crithidia fasciculata bioassay is also a very sensitive method of measuring biopterin activity. Thus normal values of pterin derivatives during the neonatal period are needed. Nevertheless, few reports on a small number of neonates have so far been found (Niederwieser et al., 1980). In this study we describe normal values of pterin derivatives in urine and biopterin activity in serum, and their age-related change in early neonates, young infants, children and adults.