OBJECTIVES: Because the cortisol awakening response (CAR) has received increasing attention as a useful index of adrenocortical activity, the primary objective of this study was to investigate the presence of an awakening response for various salivary biomarkers of adrenocortical activity, including dehydroepiandrosterone-sulphate (DHEA-S), which acts as a cortisol antagonist, and α-amylase, which is a predictor of circulating catecholamine activity. Salivary biological indicators are considered to be valuable markers of hypothalamus-pituitary-adrenal (HPA) axis diurnal activity.
METHODS: In an attempt to overcome problems associated with non-adherence to the requested sampling protocol, only young, healthy males with a physiological CAR value (defined as a 50% increase in salivary cortisol within 30 min after waking) were included in the study (67 out of 102 who initially enrolled met this criterion).
RESULTS: Our results suggested that, as is already known for cortisol, DHEA-S and α-amylase have significant awakening responses. In addition, daily profile of salivary cortisol, α-amylase and DHEA-S fluctuations were analysed. Significant correlations were found between salivary cortisol, DHEA-S and α-amylase levels. The results showed that cortisol and DHEA-S concentrations were inversely correlated with α-amylase levels.
CONCLUSION: This correlation confirmed the distinctiveness of the two regulatory systems: salivary cortisol and DHEA-S concentrations reflect the activity of the HPA axis, whereas α-amylase activity is more closely related to sympathetic activity. In addition, the present study emphasizes the potential value of saliva collection (which is both easy and stress-free) in monitoring changes of adrenal function, confirming that multiple sampling (especially within 1 h after awakening) is necessary to reliably characterise biomarker activity when investigating neuroendocrine changes under various conditions.