The combined dexamethasone/corticotropin-releasing hormone stimulation test is more closely associated with features of diurnal activity of the hypothalamo-pituitary-adrenocortical system than the dexamethasone suppression test

Background: The dexamethasone suppression test (DST) is a widely used endocrine test in psychiatry, but was reported to not allow reliable inferences with regard to the basal activity of the hypothalamo-pituitary- adrenocortical (HPA) system. We compared the association of the standard DST and the combined dexamethasone/corticotropin-releasing hormone (DEX/CRH) challenge with parameters of diurnal cortisol profiles. Methods: We performed a DEX/CRH challenge and 24-hour cortisol profiles in 25 depressed patients (mean age: 47.4 ± 16.0 years) and 33 age-matched healthy controls (mean age: 51.4 ± 19.3 years). Results: A path analysis showed cortisol area under the curve (AUC) after CRH (= DEX/CRH status) to be dependent upon minimal 24- hour cortisol and evening frequency of pulsatile cortisol release. In contrast, post-dexamethasone cortisol (= DST status) was related to 24-hour mean cortisol. Simple linear regressions supported an association of cortisol AUC with several parameters of the diurnal cortisol profiles, which was not true for the standard DST. Conclusions: We conclude that the combined DEX/CRH challenge test is more closely associated with the activity of the HPA system than the standard DST in healthy and depressed subjects.