Reduced levels of serum IGF-1 is related to the presence of osteoporotic fractures in male idiopathic osteoporosis.

Introduction: The pathophysiology of male idiopathic osteoporosis (MIO) remains unknown. The aim of this study was to evaluate the involvement of IGF-1 in MIO, and to explore the relationships between bone mineral density and serum levels of IGF-1 and sex hormones.

Methods: Inclusion criteria were osteoporosis (T-score<-2.5 SD) and/or an osteoporotic fracture. The osteoporotic patients were included after an exhaustive work-up to exclude the principal causes of secondary osteoporosis. Serum levels of IGF-1, estradiol, testosterone, SHBG, markers of bone turnover, and bone mineral density were compared between 79 MIO and 26 healthy subjects.

Results: A significant reduction in serum IGF-1 was found in MIO patients (p=0.0189). This remained significant after adjustment for body mass index (BMI). A negative correlation was found between SHBG and serum IGF-1 (r=-0.231, p=0.048). SHBG levels were higher in osteoporotic patients (p=0.001). The Free Testosterone Index (FTI, total testosterone/SHBG) (p=0.002) was also lower in MIO patients. After adjustment for FTI and BMI, a significant association was observed between IGF-1 level and the presence of an osteoporotic fracture, indicating an independent effect of IGF-1 level on fracture risk. The odds ratio (OR) for fracture for each SD decrease in IGF1 level was 1.8 [CI: 1.09-2.96] (p=0.021).

Conclusion: Our study indicates a decrease in serum IGF-1 levels in MIO. This could be either the cause or the consequence of a disturbance in sex hormone metabolism with increased SHBG serum levels.