Evidence for impaired activation of the hypothalamic-pituitary-adrenal axis in patients with chronic fatigue syndrome.
Demitrack, M A, Dale, J K, Straus, S E et al. · The Journal of clinical endocrinology and metabolism · 1991 · DOI
Quick Summary
This study examined whether ME/CFS patients have a problem with their body's stress hormone system, specifically the network that controls cortisol production. Researchers found that ME/CFS patients had lower cortisol levels than healthy people, but their bodies were responding unusually to stimulation—suggesting the problem lies in the brain's control center rather than the adrenal glands themselves.
Why It Matters
This foundational study provided early evidence that ME/CFS involves objective biological abnormalities in the HPA axis—a critical regulatory system governing stress response, energy production, and immune function. Demonstrating that the problem originates centrally (brain) rather than peripherally (adrenal glands) shifted understanding of ME/CFS pathophysiology and opened investigation into neurochemical deficiencies that might underlie fatigue and other symptoms.
Observed Findings
ME/CFS patients had significantly lower evening plasma cortisol (89.0 vs. 148.4 nmol/L, p<0.01) and 24-hour urinary free cortisol excretion (122.7 vs. 203.1 nmol/24h, p<0.0002) compared to controls.
Adrenal glands showed increased sensitivity to ACTH stimulation but reduced maximal response.
ME/CFS patients had blunted ACTH responses to CRH stimulation (128.0 vs. 225.4 pmol/L·min, p<0.04).
Cerebrospinal fluid CRH levels were similar between ME/CFS patients and controls (8.4 vs. 7.7 pmol/L, p=NS).
Inferred Conclusions
The pattern of low cortisol with elevated ACTH and intact adrenal responsiveness to direct ACTH stimulation rules out primary adrenal insufficiency.
The blunted ACTH response to CRH stimulation suggests impaired pituitary corticotroph function or reduced central CRH signaling.
ME/CFS involves a mild central adrenal insufficiency that may arise from CRH deficiency or other unidentified central stimulus deficiency.
Whether the observed glucocorticoid deficiency or CRH insufficiency is mechanistically related to ME/CFS symptomatology remains uncertain.
Remaining Questions
What This Study Does Not Prove
This study does not establish that HPA axis dysfunction causes ME/CFS symptoms or that correcting cortisol levels will resolve the condition. The normal CSF CRH levels suggest the mechanism may not be simple CRH deficiency alone, leaving the underlying etiology of the central defect undetermined. Additionally, cross-sectional design cannot establish causality or temporal relationships.
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 →
What is the specific mechanism causing reduced central drive to the pituitary-adrenal axis—is it truly CRH deficiency or impairment of other central regulators?
Does the mild glucocorticoid deficiency causally contribute to fatigue, exercise intolerance, immune dysfunction, or other ME/CFS symptoms?
What is the relationship between HPA axis abnormalities and the possible arousal-producing neuropeptide deficiencies mentioned?
Do HPA axis findings correlate with symptom severity or specific clinical phenotypes within the ME/CFS population?