The diurnal variation and response to dexamethasone suppression test of saliva cortisol level in autistic children.

In order to examine the function of hypothalamic-pituitary-adrenal axis (HPA-axis) in autistic children, the diurnal rhythm of saliva cortisol and the response of cortisol to the DST was investigated using saliva samples. 1) The plasma and saliva cortisol levels showed a positive correlation in normal healthy adults. Moreover, the saliva cortisol level exhibited a similar diurnal rhythm and DST response as did the plasma cortisol level. 2) The saliva cortisol level in normal children showed a similar diurnal rhythm and DST response as that in normal healthy adults. 3) Some children with infantile autism showed an abnormal diurnal rhythm or DST response for saliva cortisol. Moreover, the latter abnormality was observed more frequently in poorly-developed cases than in highly-developed cases. 4) These results suggest that the negative feedback mechanism of the HPA-axis may be disturbed in autistic children, especially the poorly-developed cases, owing to a disorder in the regulation by serotonin metabolism.