Lack of association of anabolic hormone status and muscle strength with regional and whole body bone mineral density in healthy men aged 60-79 years

Abstract

This study investigated the capacity of muscle strength and anabolic hormone status to predict regional and whole body bone mineral density (BMD) in older men. Fifty-two healthy men aged 60-79 years served as subjects. BMD of the lumbar spine, proximal femur, upper and lower limbs, and whole body was assessed by dual X-ray absorptiometry. Dynamic muscle strength for several upper and lower body muscle groups was determined by the one-repetition maximum and isometric grip strength by dynamometry. Anabolic hormone status was assessed by the ratio of testosterone (T) to sex hormone binding globulin (SHBG), given as the free androgen index (FAI), and the ratio of insulin-like growth factor I (IGF-I) to IGF binding protein-3 (IGFBP-3). Age was associated with declines in dynamic strength and the log FAI. In stepwise regression analysis, only body mass was an independent predictor of whole body and upper limb BMD (R2 = 0.13), and hip adductor strength predicted the Ward's triangle (R2 = 0.14). For lumbar spine BMD, triceps extensor strength was significantly correlated (r = 0.36, p < 0.01), while no strength or hormonal variable was associated with the femoral neck, trochanter, or lower limb. The lack of association between muscle strength and BMD was generally unaltered after controlling for hormone status and body mass. There was no difference in BMD when analyzed by tertiles of log FAI or IGF-I/IGFBP-3 or by tertiles of muscle strength. These results suggest that in healthy community-dwelling men in the seventh and eighth decade, muscle strength and hormonal status are not significant contributors to regional or whole body BMD.