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.