INSULIN-LIKE GROWTH-FACTOR-I (SOMATOMEDIN-C) LEVELS IN CHRONIC FATIGUE SYNDROME AND FIBROMYALGIA

Objective. ,Fibromyalgia (FM) and chronic fatigue syndrome (CFS) are s imilar conditions characterized by substantial fatigue, diffuse myalgi as, sleep disturbances and a variety of other symptoms. Many patients with CFS meet strict criteria for FM. Recently, low insulin-like growt h factor-I (IGF-I) levels have been demonstrated in patients with FM, suggesting that disruption of the growth hormone-IGF-I axis might expl ain the link between the muscle pain and poor sleep. Our goal was to d etermine whether IGF-I levels are decreased in CFS, and whether such f indings are restricted to patients with concurrent FM. Methods. Radioi mmunoassays were used to determine serum concentrations of IGF-I and i ts binding protein, (IGFBP-3). Subjects were 3 patient groups seen in a referral clinic for chronic fatigue: 15 patients with CFS, 15 who me t criteria for both CFS and FM (CFS-FM), 27 with FM alone; and 15 heal thy control (HC) subjects. Results, Patients and control subjects had similar demographic and clinical characteristics. No significant diffe rences were observed among any of the 3 patient groups and control sub jects 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 or IGFBP-3. Conclusions. The se findings suggest the disruption of the growth hormone-IGF-I axis pr eviously demonstrated in FM patients is not evident in a referral popu lation of patients with CFS, CFS-FM, or FM.