Sørland, Kari, Sandvik, Miriam Kristine, Rekeland, Ingrid Gurvin et al. · Frontiers in medicine · 2021 · DOI
This study found that blood vessels in people with ME/CFS don't work as well as they do in healthy people. The researchers measured how blood vessels widen and respond to changes in blood flow, and found these responses were reduced in ME/CFS patients. Interestingly, when patients received a strong immune-suppressing drug called cyclophosphamide, improvements in symptoms didn't match up with improvements in blood vessel function.
Endothelial dysfunction—impaired regulation of blood flow—could explain key ME/CFS symptoms like orthostatic intolerance and post-exertional malaise. This study provides objective biological evidence of a vascular defect in ME/CFS, supporting the hypothesis that blood vessel dysfunction is a core feature of the disease rather than a secondary effect.
This study does not prove that endothelial dysfunction causes ME/CFS symptoms, only that the two co-exist. The lack of correlation between endothelial function changes and clinical response to cyclophosphamide suggests endothelial dysfunction may not be the primary target of this drug's therapeutic effect, or that other mechanisms drive symptom improvement. The study cannot determine whether restoring endothelial function would improve symptoms.
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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Sørland, Kari, Sandvik, Miriam Kristine, Rekeland, Ingrid Gurvin, Ribu, Lis, Småstuen, Milada Cvancarova, Mella, Olav, et al. (2021). Reduced Endothelial Function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome-Results From Open-Label Cyclophosphamide Intervention Study.. Frontiers in medicine. https://doi.org/10.3389/fmed.2021.642710
BibTeX
@article{mecfsatlas-srland-2021-reduced-endothelial,
author = {Sørland, Kari and Sandvik, Miriam Kristine and Rekeland, Ingrid Gurvin and Ribu, Lis and Småstuen, Milada Cvancarova and Mella, Olav and Fluge, Øystein},
title = {Reduced Endothelial Function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome-Results From Open-Label Cyclophosphamide Intervention Study.},
journal = {Frontiers in medicine},
year = {2021},
doi = {10.3389/fmed.2021.642710},
note = {PubMed: 33829023},
url = {https://www.mecfsatlas.com/evidence/srland-2021-reduced-endothelial},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/srland-2021-reduced-endothelial
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