Reduced serum levels of the growth hormone-dependent insulin-like growth factor binding protein and a negative bone balance at the level of individual remodeling units in idiopathic osteoporosis in men.

Idiopathic osteoporosis in younger individuals could be related to reduced bone formation rather than increased bone resorption, and disturbances in GH or insulin-like growth factor (IGF)-I production could be involved in its pathogenesis. In the present study, men with idiopathic osteoporosis were compared with healthy men, with respect to bone histomorphometry and to serum levels of IGF-I, IGF-II, IGF binding protein (IGFBP)-2 and IGFBP-3, and 24-h urinary excretion of GH. Mean wall thickness was reduced in the patients (48.3 +/- 7.2 vs. 61.7 +/- 5.4 microns, P < 0.001). Also, resorption depth was decreased, albeit to a lesser degree (54.4 +/- 3.8 vs. 60.7 +/- 5.3 microns, P < 0.01), thus creating a pronounced negative balance (-6.04 +/- 9.8 vs. 0.96 +/- 3.2 microns, P < 0.05). In the patients, serum concentrations of IGFBP-3 were reduced, compared with controls, with a 46% lower mean value; whereas levels of IGF-I, IGF-II, IGFBP-2, and GH were similar in the two groups. Thus, there was a significant negative balance caused by a pronounced decrease in wall thickness in men with idiopathic osteoporosis. The finding of low IGFBP-3 levels in these patients is interesting, in view of previous clinical and experimental findings, but its pathophysiological significance remains to be determined.