E0 ConsensusModerate confidencePEM not requiredReview-NarrativePeer-reviewedReviewed
Standard · 3 min
The neuroendocrinology of chronic fatigue syndrome.
Cleare, Anthony J · Endocrine reviews · 2003 · DOI
Quick Summary
This review examined how hormones—particularly the stress hormone cortisol and others made by the brain and glands—may be altered in ME/CFS patients. The researchers found that some patients have lower cortisol levels than expected, and their bodies may respond differently to stress, but these changes vary significantly from person to person. The review suggests that many factors like inactivity, poor sleep, and ongoing stress likely contribute to these hormone changes rather than a single cause.
Why It Matters
Understanding hormonal abnormalities in ME/CFS is crucial because the HPA axis regulates stress response, energy production, and immune function—all impaired in this disease. This review identifies that hormone changes may contribute to symptom persistence and highlights the need for more rigorous prospective studies to establish whether correcting these abnormalities could improve patient outcomes.
Observed Findings
Some ME/CFS patients show reduced cortisol output compared to controls
Patients demonstrate heightened negative feedback of the HPA axis and enhanced glucocorticoid receptor function
Impaired ACTH and cortisol responses to various physiological and psychological challenges
Evidence suggesting altered dehydroepiandrosterone sulfate (DHEA-S) function in some patients
Abnormalities in serotonin function detected in several studies
Inferred Conclusions
HPA axis disturbance in ME/CFS is heterogeneous and multifactorial in origin rather than representing a single, uniform dysfunction
Multiple confounding factors including inactivity, sleep disturbance, psychiatric comorbidity, and ongoing stress likely contribute to observed endocrine changes
Neuroendocrine abnormalities in some patients may be linked to symptom production or persistence, though the functional significance remains unclear
Remaining Questions
Are the observed hormonal changes in ME/CFS primary pathogenic features or secondary consequences of the disease and its lifestyle factors?
Do hormonal abnormalities predict disease severity, prognosis, or recovery trajectory?
What This Study Does Not Prove
This review does not prove that HPA axis dysfunction is the primary cause of ME/CFS or that it occurs uniformly in all patients. The presence of hormonal changes does not establish whether they are causing symptoms or are secondary consequences of the disease and its associated factors like inactivity and sleep disruption. The heterogeneity of findings means no single hormonal pattern defines ME/CFS.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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