Age-related changes in bone mass have been demonstrated in both men and women. A causal role in age-related bone loss has been attributed to alterations in vitamin D status, the bone mineral regulating hormones and/or renal function. it has been hypothesized that compromised vitamin D status and/or circulating levels of the active, hormonal form of the vitamin are a concomitant of aging and are responsible for part of the bone loss seen in the elderly. Studies in the Baltimore Longitudinal Study of Aging have demonstrated that there are no differences across the age span in 25-OHD or 1,25 (OH)2 D levels in normal men or women. Both men and women had an age associated increase in PTH levels that was not independently correlated with creatinine clearance. In order to determine the relationship between these parameters as well as measures of bone turnover (osteocalcin and urinary calcium) to bone mass, bone mineral density (BMD) at three sites (radius, spine and femur) was measured in normal men and women of the BLSA. Serum 25-OHD, 1,25(OH)2 D, and PTH were not related to BMD at any site in young (<48 years) men or old (>60 yrs) women. However, in old men, lower age-adjusted radius BMD was significantly associated with higher PTH and 1,25(OH)2 D and lower 25 OHD values. Young men, who had a cross-sectional decline in femoral BMD comparable to that of old men, had significant associations of high values for the markers of bone turnover with low age-adjusted BMD. These results emphasized the heterogeneity of bone loss and factors associated with it. This heterogeneity is partially dependent on age, gender, and the specific bone site involved.
