E3 PreliminaryPreliminaryPEM requiredReview-NarrativePeer-reviewedReviewed
Tetrahydrobiopterin in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Friend or Foe?
Rahman, A F M Towheedur, Benko, Anna, Bulbule, Sarojini et al. · Biomolecules · 2025 · DOI
Quick Summary
This review article examines a molecule called tetrahydrobiopterin (BH4) and its possible role in ME/CFS, particularly in patients who experience orthostatic intolerance (dizziness or fainting when standing up). The researchers found that BH4 metabolism—the way the body processes this molecule—is not working properly in ME/CFS patients with these symptoms. By understanding how BH4 goes wrong, scientists hope to explain why ME/CFS patients have problems with blood flow to the brain.
Why It Matters
Understanding what goes wrong with BH4 metabolism could help explain why some ME/CFS patients experience orthostatic intolerance and reduced blood flow to the brain—symptoms that severely limit their ability to function. If BH4 dysregulation is confirmed as a key mechanism, it could eventually lead to new treatments targeting this pathway to improve these debilitating symptoms.
Observed Findings
- BH4 metabolism is highly dysregulated in ME/CFS patients with orthostatic intolerance (ME+OI)
- ME+OI patients display severe cardiovascular abnormalities resulting in reduced effective cerebral blood flow
- OI in ME/CFS manifests as dizziness or faintness due to sudden drops in blood pressure during upright posture
- The mechanism explaining reduced cerebral blood flow in OI patients has remained unclear despite intensive investigation
Inferred Conclusions
- BH4 dysregulation may be a key molecular mechanism contributing to orthostatic intolerance in ME/CFS patients
- Targeting BH4 metabolism could potentially address the cardiovascular and cerebrovascular abnormalities observed in ME+OI patients
- Understanding BH4's role provides a potential explanatory framework for post-exertional malaise and orthostatic intolerance symptoms
Remaining Questions
- Does correcting BH4 dysregulation improve orthostatic intolerance or other ME/CFS symptoms in patients?
- What specific aspects of BH4 metabolism are dysregulated (synthesis, recycling, utilization), and why does this occur in ME/CFS?
- Are BH4 abnormalities a primary cause or a secondary consequence of ME/CFS pathology?
What This Study Does Not Prove
This review does not prove that BH4 dysregulation causes orthostatic intolerance in ME/CFS; it proposes a mechanism based on existing evidence. The study does not present new patient data or clinical trials, so it cannot demonstrate whether correcting BH4 would improve symptoms. The review is hypothesis-generating rather than hypothesis-confirming.
Tags
Method Flag:PEM_DEFINEDEXPLORATORYExploratory Only
Symptom:Post-Exertional MalaiseCognitive DysfunctionOrthostatic IntolerancePainFatigue
Biomarker:MetabolomicsBlood Biomarker
Metadata
- DOI
- 10.3390/biom15010102
- PMID
- 39858496
- Review status
- Editor reviewed
- Evidence level
- Early hypothesis, preprint, editorial, or weak support
- Last updated
- 7 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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