REDUCED SERUM LEVELS OF THE GROWTH HORMONE-DEPENDENT INSULIN-LIKE-GROWTH-FACTOR BINDING-PROTEIN AND A NEGATIVE BONE BALANCE AT THE LEVEL OFINDIVIDUAL REMODELING UNITS IN IDIOPATHIC OSTEOPOROSIS IN MEN

Idiopathic osteoporosis in younger individuals could be related to red uced bone formation rather than increased bone resorption, and disturb ances in GH or insulin-like growth factor (IGF)-I production could be involved in its pathogenesis. In the present study, men with idiopathi c osteoporosis were compared with healthy men, with respect to bone hi stomorphometry and to serum levels of IGF-I, IGF-II, IGF binding prote in (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 m u m, P < 0.001). Also, resorption depth was decreased, albeit to a les ser degree (54.4 +/- 3.8 us. 60.7 +/- 5.3 mu m, P < 0.01), thus creati ng a pronounced negative balance(-6.04 +/- 9.8 vs. 0.96 +/- 3.2 mu m, P < 0.05). In the patients, serum concentrations of IGPBP-3 were reduc ed, compared with controls, with a 46% lower mean value; whereas level s of IGF-I, IGF-II, IGFBP-2, and GH were similar in the two groups. Th us, there was a significant negative balance caused by a pronounced de crease in wall thickness in men with idiopathic osteoporosis. The find ing of low IGFBP-3 levels in these patients is interesting, in view of previous clinical and experimental findings, but its pathophysiologic al significance remains to be determined.