OBJECTIVE: Many studies suggest mild hypocortisolism in
chronic fatigue syndrome (CFS), usually assumed to be due to
reduced suprahypothalamic drive to the
hypothalamo-pituitary-adrenal (HPA) axis. We wished to explore
further the state of the HPA axis in CFS using the 1 mug low
dose short Synacthen test.
DESIGN: Subjects received an
intravenous bolus of 1 mug Synacthen; samples for cortisol
estimation were taken at baseline and 2, 10, 20, 30, 40 and 60
minutes after injection.
PATIENTS: We tested 20 subjects
suffering from CFS according to the criteria of the Center for
Diseases Control without psychiatric comorbidity and 20
matched healthy controls. All subjects were drug free for at
least 1 month.
MEASUREMENTS: We calculated the cortisol
responses to the test as the maximum cortisol attained, the
incremental rise in cortisol over baseline (Deltavalue) and as
the integrated area under the curve.
RESULTS: There were no
significant differences in baseline cortisol or cortisol
responses between patients and controls. However, responses
generally were low, and many subjects’ peak responses were
prior to the standard 30 minute sampling time.,
These results do not lend support to the theory that patients
with chronic fatigue syndrome have a low adrenal reserve.
However, results from studies assessing the HPA axis are
proving to be inconsistent. We suggest that many other factors
may be contributing to HPA axis alterations in chronic fatigue
syndrome, including sleep disturbance, inactivity, altered
circadian rhythmicity, illness chronicity, concomitant
medication and comorbid psychiatric disturbance. These sources
of heterogeneity need to be considered in future studies, and
may explain the inconsistent findings to date.
Hudson M, Cleare AJ