E2 ModeratePreliminaryPEM unclearCross-SectionalPeer-reviewedMachine draft
Insulin-like growth factor-I (somatomedin C) levels in chronic fatigue syndrome and fibromyalgia.
Buchwald, D, Umali, J, Stene, M · The Journal of rheumatology · 1996
Quick Summary
Researchers tested whether people with ME/CFS have lower levels of a growth hormone called IGF-I, which had previously been found to be low in fibromyalgia patients. They measured IGF-I levels in 15 people with ME/CFS, 15 with both ME/CFS and fibromyalgia, 27 with fibromyalgia alone, and 15 healthy volunteers. The study found no significant differences in IGF-I levels between any of the patient groups and healthy controls, suggesting that low IGF-I may not be a key feature of ME/CFS.
Why It Matters
This study directly addresses a proposed biological mechanism—disruption of the growth hormone-IGF-I axis—that could explain muscle pain and sleep disturbances in ME/CFS. Understanding whether this hormonal pathway is abnormal is important for identifying potential treatment targets and distinguishing between ME/CFS and fibromyalgia.
Observed Findings
- No significant differences in mean serum IGF-I concentrations between CFS, CFS-FM, FM, and healthy control groups.
- No significant differences in mean serum IGFBP-3 concentrations among the four study groups.
- Proportion of subjects with IGF-I values above or below laboratory reference ranges did not differ significantly across groups.
- Proportion of subjects with IGFBP-3 values above or below laboratory reference ranges did not differ significantly across groups.
Inferred Conclusions
- Disruption of the growth hormone-IGF-I axis is not evident in referral populations with CFS, CFS-FM, or FM, contradicting some prior findings.
- The IGF-I axis may not explain the link between muscle pain, fatigue, and sleep disturbances in this patient population.
- IGF-I abnormalities, if present in FM, may not extend to patients with CFS or concurrent CFS-FM.
Remaining Questions
- Why do these findings contradict prior reports of low IGF-I in FM patients? Are there patient subgroups or disease stages where IGF-I abnormalities are more apparent?
- Do other hormonal axes (e.g., cortisol, growth hormone secretion patterns) show abnormalities in ME/CFS?
- What alternative biological mechanisms might explain fatigue, myalgia, and sleep disturbance in ME/CFS if IGF-I is normal?
What This Study Does Not Prove
This study does not prove that the growth hormone-IGF-I axis is normal in all ME/CFS patients; it only shows no group-level difference in a single referral clinic population. It does not exclude the possibility that IGF-I abnormalities exist in other subgroups of ME/CFS patients, nor does it rule out other hormonal or metabolic disruptions. The cross-sectional design cannot establish causality or temporal relationships.
Tags
Symptom:Unrefreshing SleepPainFatigue
Biomarker:Blood Biomarker
Method Flag:Small SampleMixed Cohort
Metadata
- PMID
- 8730136
- Review status
- Machine draft
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 8 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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