Plasma and urinary levels of biopterin, neopterin, and related pterins and plasma levels of folate in infantile autism.
Autistic children have normal tetrahydrobiopterin and folate, so these blood tests are not helpful for diagnosis or treatment choices.
01Research in Context
What this study did
Doctors measured blood and urine chemicals in autistic kids. They checked tetrahydrobiopterin, folate, neopterin, and monapterin. The goal was to see if these chemicals were low and might explain autism traits.
What they found
Tetrahydrobiopterin and folate levels were the same as in typical kids. Neopterin and monapterin were slightly lower, but the drop had no clear meaning. The authors concluded these chemicals are not useful autism markers.
How this fits with other research
Esteban-Figuerola et al. (2019) pooled many diet studies and found autistic children often miss calcium, vitamin D, and B12. Eto et al. (1992) looked at blood, not food, yet both papers agree autistic kids do not lack folate.
Gulati et al. (2026) later added homocysteine and dityrosine to the metabolic panel. They also found some differences, but like the 1992 study, levels did not track with autism severity.
Song et al. (2024) used brain scans and saw normal glutathione levels. This matches the 1992 null result: two separate labs, two separate methods, both say these metabolic pathways look typical in autistic children.
Why it matters
If parents ask about biopterin or folate supplements, you can show them this evidence: levels are already normal, so extra pills are unlikely to help. Save your time for interventions with proven benefit.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Skip ordering folate or biopterin labs and spend the session time on skill teaching instead.
02At a glance
03Original abstract
Tetrahydrobiopterin is essential for brain cells to make monoamine neurotransmitters. It has been reported that the concentrations of tetrahydrobiopterin in plasma and urine are low in certain mental disorders and that oral supplements are beneficial. A group of Japanese investigators have been conducting clinical trials of the effect of administration of tetrahydrobiopterin to autistic children and reported that it is beneficial with no significant side effects. We, therefore, initiated a study to assess plasma and urinary levels of tetrahydrobiopterin in infantile autism to see if they are reduced. Besides tetrahydrobiopterin, we also determined plasma and urinary levels of neopterin and monapterin in these individuals in order to evaluate the status of dihydroneopterin triphosphate, a key biosynthetic precursor of tetrahydrobiopterin. Sixteen autistic children and 12 healthy controls were included in this study. Results indicated that the plasma and urinary levels of tetrahydrobiopterin are not statistically different between the two groups and, therefore, no simple explanation for the beneficial effects of administration of tetrahydrobiopterin on autistic children can be offered at the present time. In contrast, plasma and urinary levels of neopterin were depressed (.01 less than p less than .05) and plasma monapterin was also significantly depressed (p less than .01) in autistic subjects compared with controls. Levels of other pterins, including folate, were not statistically different between the two groups. The basis for this depression in neopterin and monapterin is unknown. It does not seem likely that this depression could be attributed to a difference in age or T-lymphocyte/macrophage activity. However, further studies are needed to investigate these possibilities.
Journal of autism and developmental disorders, 1992 · doi:10.1007/BF01058157