No evidence for reduced spontaneous or growth-hormone-stimulated serum levels of insulin-like growth factor (IGF)-I, IGF-II or IGF binding protein 3 in women with spinal osteoporosis

Abstract

To test the hypothesis that a dysfunctional growth hormone (GH)-insulin-like growth factor (IGF) axis may play a role in the pathogenesis of osteoporosis, we compared the levels of IGF-I, IGF-II and IGF binding protein 3 (IGFBP-3) in 15 women with spinal osteoporosis (i.e. at least one non-traumatic vertebral fracture) and 15 normal age-matched women. Furthermore, the response to 3 days' treatment with recombinant human GH (r-hGH) (0.2 IU kg-1.day-1) was determined. The basal levels of IGF-I, IGF-II and IGFBP-3 were similar in patients and controls (mean +/- SEM): IGF-I, 16.5 +/- 1.3 versus 16.0 +/- 1.3 nmol/l (NS); IGF-II, 79.9 +/- 3.6 versus 72.5 +/- 4.1 nmol/l (NS); and IGFBP-3, 125.7 +/- 6.5 versus 130.3 +/- 7.8 nmol/l (NS). Stimulation with r-hGH elicited increased levels of IGF-I, IGF-II and IGFBP-3 within both groups (p < 0.001). The maximal values expressed as a percentage of baseline were: IGF-I, 341 +/- 26% versus 369 +/- 22%, IGF-II, 125 +/- 4% versus 119 +/- 5%, IGFBP-3, 141 +/- 5% versus 147 +/- 7% in osteoporotic patients and controls, respectively. No significant differences were observed between patients and controls in either their maximal response or in the area under the response curves. Our results do not support the hypothesis of a dysfunctional GH-IGF axis in women with spinal osteoporosis.