Urinary free cortisol excretion (UFC) was compared in 21
patients with chronic fatigue syndrome (CFS), in 10
melancholic depressives and in 15 healthy controls. Patients
with depression had UFC values which were significantly higher
than healthy comparison subjects, whereas UFC excretion of CFS
patients was significantly lower than the comparison group.
These findings are in keeping with currently held hypotheses
of hyperactivity and hypoactivity of the
hypothalamic-pituitary-adrenal (HPA) axis in depression and
chronic fatigue syndrome respectively. Five of the 21 CFS
patients had a co-morbid depressive illness. This sub-group
retained the profile of UFC excretion of those with CFS alone,
suggesting a different pathophysiological basis for depressive
symptoms in CFS.