SERUM IGF-1 IS LOW AND CORRELATED WITH OSTEOBLASTIC SURFACE IN IDIOPATHIC OSTEOPOROSIS

We have previously reported that bone formation is impaired on histomo rphometric analysis of bone in patients with idiopathic osteoporosis. In the present study, 30 patients with idiopathic osteoporosis (18 men and 12 women mean age 44 +/- 12 years) and spinal and/or appendicular fractures were studied. Compared with control values, bone biopsy ana lysis demonstrated reduced bone volume (13.0 +/- 4.4 vs. 23.2 +/- 4.4, p < 0.0001), osteoid volume (0.13 +/- 0.13 vs. 0.32 +/- 0.19, p = 0.0 01), osteoid surface (5.9 +/- 4.3 vs. 12.1 a 4.6, p = 0.0004), and dim inished double-labeled mineralizing surface (MS/BS 2.0 +/- 2.1 vs. 5.1 +/- 2.7%, p = 0.0001) in the patients. Since insulin-like growth fact or 1 (IGF-1) is one of the major determinants of bone growth and remod eling, we measured the circulating level of this growth factor in thes e patients. The mean serum IGF-1 concentration was lower in patients a s compared with 33 healthy age-matched controls (193 +/- 59 SD ng/ml v s. 232 +/- 79). A significant difference was noted between the two gro ups only in subjects younger than 36 years. In patients with idiopathi c osteoporosis, regression analysis of serum IGF-1 against the various histological parameters measured from the bone biopsy disclosed signi ficant correlation's between serum IGF-1 and osteoblastic surface (r = 0.429, p = 0.032), mineralizing bone surface with a double label (r = 0.480, p = 0.015), and the bone formation rate (r = 0.457, p = 0.021) . These findings suggest that in young eugonadal individuals with idio pathic osteoporosis, reduced IGF-1 concentrations may have an etiologi cal role in the development of this disease.