Serum dopamine-beta-hydroxylase activity: clinical applications in child psychiatry.

Serum dopamine-beta-hydroxylase (DBH) activity was measured in 44 children with psychiatric disorders and 44 controls in order to determine significant variables affecting its potential use as a marker for specific molecular pathology in the neuropsychiatric disorders of childhood. The assay procedure was reliable and the serum enzyme activity for individuals appears to be stable. There is a very broad distribution of serum DBH activity in the population, and it is similar in males and females. The genetic determination of serum DBH activity was clear in this study, and the enzyme activity increased with age through childhood and adolescence. Thyroid hormone had no effect on serum DBH activity in euthyroid subjects. No difference in mean serum DBH activity emerged across diagnostic groups. When the findings were considered in relation to the results of other studies, it was concluded that the wide range of serum DBH activities in normal and patient populations, as well as developmental effects on the activity of the enzyme, make comparison of DBH activity among diagnostic groups in childhood difficult. Large subject groups, and a consideration of genetic and developmental effects, will clarify possible syndrome-related differences in enzyme activity.