E0 ConsensusModerate confidencePEM unclearReview-NarrativePeer-reviewedMachine draft
The underlying sex differences in neuroendocrine adaptations relevant to Myalgic Encephalomyelitis Chronic Fatigue Syndrome.
Thomas, Natalie, Gurvich, Caroline, Huang, Katherine et al. · Frontiers in neuroendocrinology · 2022 · DOI
Quick Summary
This review examines why ME/CFS affects women much more often than men and how sex hormones may play a role. The authors found that female hormonal changes—such as those during menstrual cycles, pregnancy, and menopause—are linked to ME/CFS onset and symptoms. They suggest that differences in how men's and women's bodies handle stress hormones like cortisol and estrogen may help explain why women develop ME/CFS more frequently and sometimes experience different symptoms.
Why It Matters
Understanding sex differences in ME/CFS is crucial because women represent approximately 75% of diagnosed patients, yet sex and hormonal biology remain understudied in ME/CFS research. This review provides a framework for recognizing how hormonal transitions may trigger or worsen ME/CFS, potentially leading to better diagnostic criteria, sex-specific treatment strategies, and improved clinical outcomes for the majority of ME/CFS patients.
Observed Findings
- ME/CFS shows a 3:1 female-to-male prevalence ratio with documented sex differences in clinical phenotype and aetiological triggers
- Reproductive endocrine events (menstrual cycle fluctuations, pregnancy, postpartum, perimenopause) are temporally associated with ME/CFS onset and symptom modulation in women
- Sex differences exist in multiple neuroendocrine systems relevant to ME/CFS: gonadal steroid hormones, adrenal stress response (cortisol), and renal aldosterone regulation
- Estrogen, progesterone, aldosterone, and cortisol levels show established sex-based differences that may contribute to disease vulnerability and symptom diversity
Inferred Conclusions
- Sex chromosomes and sex steroid hormone biology play significant roles in ME/CFS vulnerability, onset timing, and symptom expression
- Reproductive and endocrine transitions represent critical periods of increased ME/CFS risk in women, suggesting hormonal fluctuation as a modifiable risk factor
- The broad physiological effects of steroid hormones across multiple body systems may explain the heterogeneous clinical presentation observed in ME/CFS patients
- Future ME/CFS research and clinical practice must integrate sex, age, and steroid hormone biology into study design and patient management strategies
Remaining Questions
- What are the precise mechanisms by which estrogen, progesterone, and other sex steroids influence ME/CFS pathophysiology at the cellular and systems level?
What This Study Does Not Prove
This narrative review does not prove causation between hormonal changes and ME/CFS—it identifies associations and suggests biological mechanisms that require experimental validation. The review does not establish which hormonal factors are primary drivers of disease versus secondary consequences of illness, nor does it demonstrate that hormone-targeted treatments will be effective. Individual patient experiences may vary considerably from population-level patterns described.
Tags
Symptom:Post-Exertional MalaiseCognitive DysfunctionUnrefreshing SleepFatigue
Biomarker:Blood Biomarker
Method Flag:Sex-Stratified
Metadata
- DOI
- 10.1016/j.yfrne.2022.100995
- PMID
- 35421511
- Review status
- Machine draft
- Evidence level
- Established evidence from major reviews, guidelines, or evidence maps
- Last updated
- 10 April 2026
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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