Weaver, Shelley A, Janal, Malvin N, Aktan, Nadine et al. · Journal of women's health (2002) · 2010 · DOI
Researchers gave patients with ME/CFS a tryptophan infusion (a building block for serotonin, a brain chemical) to see how their bodies would respond. They found that women with ME/CFS alone had a stronger response in a hormone called prolactin compared to healthy women, but women with ME/CFS plus fibromyalgia did not show this difference. Men in all groups showed similar responses, suggesting ME/CFS may work differently in women than in men.
This study suggests that ME/CFS in women may involve different biological mechanisms than fibromyalgia, and that sex differences in ME/CFS prevalence may reflect distinct neurobiological pathways. Understanding whether ME/CFS and fibromyalgia are separate conditions has important implications for diagnosis, treatment research, and clinical management.
This study does not prove that elevated prolactin response causes ME/CFS symptoms, only that it is associated with the condition in women. The findings are correlational and based on a single tryptophan challenge test; they do not establish whether this difference is a primary cause, consequence, or marker of disease. The study also does not address whether these findings apply to men with ME/CFS or explain the mechanistic basis of the sex difference.
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
Weaver, Shelley A, Janal, Malvin N, Aktan, Nadine, Ottenweller, John E, & Natelson, Benjamin H (2010). Sex differences in plasma prolactin response to tryptophan in chronic fatigue syndrome patients with and without comorbid fibromyalgia.. Journal of women's health (2002). https://doi.org/10.1089/jwh.2009.1697
BibTeX
@article{mecfsatlas-weaver-2010-sex-differences,
author = {Weaver, Shelley A and Janal, Malvin N and Aktan, Nadine and Ottenweller, John E and Natelson, Benjamin H},
title = {Sex differences in plasma prolactin response to tryptophan in chronic fatigue syndrome patients with and without comorbid fibromyalgia.},
journal = {Journal of women's health (2002)},
year = {2010},
doi = {10.1089/jwh.2009.1697},
note = {PubMed: 20384451},
url = {https://www.mecfsatlas.com/evidence/weaver-2010-sex-differences},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/weaver-2010-sex-differences
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