OBJECTIVE. Fibromyalgia (FM) and chronic fatigue syndrome (CFS) are similar conditions characterized by substantial fatigue, diffuse myalgias, sleep disturbances and a variety of other symptoms. Many patients with CFS meet strict criteria for FM. Recently, low insulin-like growth factor-I(IGF-I) levels have been demonstrated in patients with FM, suggesting that disruption of the growth hormone-IGF-I axis might explain the link between the muscle pain and poor sleep. Our goal was to determine whether IGF-I levels are decreased in CFS, and whether such findings are restricted to patients with concurrent FM.
METHODS. Radioimmunoassays were used to determine serum concentrations of IGF-I and its binding protein, (IGFBP-3). Subjects were 3 patients seen in a referral clinic for chronic fatigue: 15 patients with CFS, 15 who met criteria for both CFS and FM(CFS-FM), 27 with FM alone; and 15 healthy control (HC) subjects.
RESULTS. Patients and control subjects had similar demographic and clinical characteristics. No significant differences were observed among any of the3 patient groups and control subjects in the mean concentration of either IGF-I or IGFBP-3. Likewise, the proportion of subjects with values above or below the laboratory’s reference range did not differ for IGF-I orIGFBP-3.
CONCLUSIONS. These findings suggest the disruption of the growth hormone-IGF-I axis previously demonstrated in FM patients is not evident in a referral population of patients with CFS, CFS-FM, or FM.
J Rheumatol 1996 Apr;23(4):739-742.
Department of Medicine, University of Washington, Seattle, USA.