Lee, Jin-Seok, Choi, Yujin, Joung, Jin-Yong et al. · The American journal of medicine · 2025 · DOI
This study looked at 100 people with long COVID who experience significant ongoing fatigue, similar to ME/CFS. Researchers measured fatigue levels and checked blood levels of cortisol (a stress hormone) and other immune markers. They found that people with lower cortisol levels reported worse fatigue and lower quality of life, suggesting a possible connection between this hormone and fatigue severity.
Long COVID and ME/CFS share core symptoms including fatigue and postexertional malaise, making long COVID research valuable for understanding ME/CFS pathophysiology. This study provides early biomarker insights—particularly regarding cortisol dysfunction—that may help clinicians recognize and potentially treat fatigue-dominant presentations in both conditions. These findings could inform future mechanistic studies exploring neuroendocrine abnormalities in post-viral fatigue syndromes.
This cross-sectional snapshot cannot establish whether low cortisol causes fatigue or results from it—correlation does not prove causation. The study does not assess whether these cortisol patterns are unique to long COVID or shared with other fatigue conditions, nor does it demonstrate that cortisol manipulation would improve fatigue symptoms. Single time-point measurement cannot capture dynamic changes or establish whether findings persist over time.
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
Lee, Jin-Seok, Choi, Yujin, Joung, Jin-Yong, & Son, Chang-Gue (2025). Clinical and Laboratory Characteristics of Fatigue-Dominant Long-COVID Subjects: A Cross-Sectional Study.. The American journal of medicine. https://doi.org/10.1016/j.amjmed.2024.01.025
BibTeX
@article{mecfsatlas-lee-2025-clinical-laboratory,
author = {Lee, Jin-Seok and Choi, Yujin and Joung, Jin-Yong and Son, Chang-Gue},
title = {Clinical and Laboratory Characteristics of Fatigue-Dominant Long-COVID Subjects: A Cross-Sectional Study.},
journal = {The American journal of medicine},
year = {2025},
doi = {10.1016/j.amjmed.2024.01.025},
note = {PubMed: 38331137},
url = {https://www.mecfsatlas.com/evidence/lee-2025-clinical-laboratory},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-25. https://www.mecfsatlas.com/evidence/lee-2025-clinical-laboratory
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