Background: There is accumulating evidence of hypothalamic-pituitary-adrenal (HPA) axis disturbances in chronic fatigue syndrome (CFS). The salivary cortisol response to awakening has been described recently as a non-invasive test of the capacity of the HPA axis to respond to stress. The results of this test correlate closely with those of more invasive dynamic tests reported in the literature; furthermore, it can be undertaken in a naturalistic setting.
Aims: To assess the HPA axis using the salivary cortisol response to awakening in CFS.
Method: We measured salivary cortisol upon awakening and 10, 20, 30 and 60 min afterwards in 56 patients with CFS and 35 healthy volunteers.
Results: Patients had a lower cortisol response to awakening, measured by the area under the curve.
Conclusions: This naturalistic test of the HPA axis response to stress showed impaired HPA axis function in CFS.