Hormonal and anthropometric predictors of bone mass in healthy elderly men: Major effect of sex hormone binding globulin, parathyroid hormone and body weight

Osteoporosis in men is a significant health problem, and factors associated with bone mass are being investigated. Although osteoporosis is a typical feature of hypogonadism, the influence of testosterone levels and other hor monal factors on bone mass of eugonadal males is unknown. Our aim was to id entify several anthropometric and hormonal predictors that could be respons ible for the variability in bone mineral density (BMD) in healthy men. One hundred elderly men (age 68 +/- 7 years) were investigated in this cross-se ctional study. BMD was measured by dual-energy X-ray absorptiometry (DXA) a t the lumbar spine and femoral sites (femoral neck, Ward's triangle, trocha nter, intertrochanter and total femur). Anthropometric measures were obtain ed including: weight, height, body mass index (BMI), waist-hip ratio and te sticular volume. Hormonal data measures were total, free and bioavailable t estosterone. dihidrotestosterone, estradiol, sex hormone binding globulin ( SHBG), insulin-like growth factor I (IGF-I), intact parathyroid hormone (iP TH) and 1,25-dihydroxyvitamin D-3 (1,25(OH)(2)D-3). One subject was exclude d because primary hypogonadism was found. SHBG levels were increased in 53. 5% of men, and 8% showed a mild increase in iPTH levels. Twenty-eight subje cts had densitometric criteria of osteoporosis (T-score less than or equal to -2.5). All BMD sites were positively correlated with body weight (r = 0. 29-0.48, p <0.001) and BMI (r = 0.24-0.47. p <0.001). A negative correlatio n between SHBG levels and intertrochanter (IT) and total femur (TL) BMD was found (r = -0.24 and, = -0.22, p <0.05). After adjusting for age and BMI, SHBG and IGF-I levels were negatively correlated (r = -0.33, p <0.001). In multiple linear regression analysis independent predictors of bone mass wer e body weight, SHBG and iPTH levels. The best predictive model accounted fo r 24-40% of the observed variability of BMD. However, most of the BMD varia bility was explained by body weight. In conclusion in our study body weight , SHBG and iPTH levels were predictors of BMD in healthy elderly men.