Fibromyalgia (FM) is a painful syndrome of nonarticular origin, characterized by fatigue and widespread musculoskeletal pain, tiredness, and sleep disturbances, without any other objective findings on examination. Interestingly, some of the clinical features of FM resemble the ones described in the adult GH-deficiency syndrome. Furthermore, insulin-like growth factor (IGF)-1 levels are frequently reduced in patients with FM. To gain further insight into the mechanisms leading to dysregulation of the GH-IGF-1 axis in these patients, we assessed 24-h spontaneous GH secretion, GH responses to GHRH, and IGF-1 and IGF binding protein (BP)-3 levels before and after 4 days treatment with human (h)GH. We found that, in comparison with controls, patients with FM exhibited a marked decrease in spontaneous GH secretion as assessed by mean GH secretion (2.5 +/- 0.4 microg/L in controls vs. 1.2 +/- 0.1 microg/L in FM, P < 0.05), pulse height (4.7 +/- 0.8 microg/L in controls vs. 2.5 +/- 0.3 microg/L in FM, P < 0.05), and pulse area (4.7 +/- 1 min/mg x L in controls vs. 2.3 +/- 0.3 min/mg x L in FM, P < 0.05). In contrast, GH responses to GHRH (100 microg, i.v.) were similar in controls (mean peak, 13.5 +/- 2.5 microg/L) and in patients with FM (12.2 +/- 3 microg/L). Finally, treatment with hGH (2 IU, s.c. daily), over 4 days, led to a clear-cut increase in plasma IGF-1 and IGFBP-3 levels in patients with FM. In conclusion, our data show that patients with FM exhibited a marked decrease in spontaneous GH secretion, but normal pituitary responsiveness to exogenously administered GHRH, thus suggesting the existence of an alteration at the hypothalamic level in the neuroendocrine control of GH in these patients. Furthermore, our finding of increased IGF-1 and IGFBP-3 levels after GH treatment, over 4 days, opens up the possibility of testing the therapeutic potential of hGH in patients with FM.