← Back to Evidence Atlas
E3 PreliminaryPreliminaryPEM ✓Reviewed
Standard · 3 min

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?
  • Could BH4-targeted therapies be developed and tested as potential treatments for ME/CFS-related orthostatic intolerance?

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.

Topics

BiomarkersPost-Exertional Malaise

Tags

Method Flag:PEM_DEFINEDEXPLORATORY

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