Bone density, bone turnover, and hormone levels in men over age 75

Background. Osteoporosis is a substantial problem in older men, with 25% of all hip fractures occurring in men. The mechanisms of bone loss in older men are unknown, but elevated parathyroid hormone (PTH) and diminished testosterone (T) levels are postulated as contributing factors. Methods. We measured bone mineral density (BMD), sex hormones, bone turnover markers, and calcium regulating hormones in a group of community-living men over the age of 75. Results. Thirty-five men (mean age 79; range 75-88 years) without disease or medication known to affect bone metabolism participated in the study. Whole body BMD was 1.21 ± .15 g/cm²; lumbar spine BMD (L1-L4) was 1.10 ± .15 g/cm²; femoral neck BMD was .77 ± .14 g/cm²; and trochanteric region was .71 ± .13 g/cm². The femoral neck and trochanteric region values were more than 1 SD below the mean for adult men (age 25-33 years) in 28/35 and 15/35 men, respectively. Deoxypyridinoline levels were above the normal range for premenopausal women in 23% of the men; N-telopeptide and C- telopeptide demonstrated a wide scatter, but the values remained in the normal range. T levels were found to be below normal range for adult men in 12 of 32 (38%) subjects and the PTH levels above the normal range in 8 of 35 (23%) subjects. Bone resorption markers correlated inversely with BMD of the whole body, femur, and spine (r = -.22 to -.48). There was an inverse correlation between total T and spine BMD which became insignificant after correcting for body mass index (BMI). In addition, there was no correlation between free or bioavailable testosterone and BMD. 1,25-(OH)₂D levels correlated inversely with BMD at the femur and whole body, but no association was found with PTH or 25 OH-D. Conclusions. Men over 75 years of age had a wide range of BMD but frequently had low values at femoral sites. T levels were below the normal range in 38% of men, and PTH levels were elevated in 23% of men. There was an inverse correlation between total T and spine BMD which may have been dependent on the common effect of BMI. Bone mineral density was inversely related to markers of bone resorption.