AGE-RELATED DECLINE OF BONE MASS AND INTESTINAL CALCIUM-ABSORPTION INNORMAL MALES

Although about 25% of all hip fractures occur in men, little is known about the pattern of their age-related bone loss and its main determin ants. The aim of this cross-sectional study was to evaluate the age-re lated changes of intestinal calcium absorption, bone mass, and bone tu rnover in normal men. In 70 normal males (age 17-91 years), we measure d spinal and forearm bone density (FBD) (by DXA), fractional intestina l calcium absorption (by oral test), serum immunoreactive parathyroid hormone (PTH), dietary calcium intake (diet records), biochemical mark ers of bone turnover (serum alkaline phosphatase (ALP), osteocalcin, u rine calcium, creatinine, and hydroxyproline), and 1,25(OH)(2)D-3 seru m levels. Vertebral bone density (VBD) showed a modest decline before age 50 and a greater decline after age 50, whereas FBD presented a sig nificant decrease with advancing age starting at age 40, suggesting a predominant age-related cortical bone loss. Intestinal calcium absorpt ion ((47)CaFA) and serum 1,25(OH)(2)D-3 also presented an age-related decline similar to FBD. Simple correlation analysis revealed that age was significantly related to (47)CaFA (r = 0.60), calcium intake (r = 0.32), VBD and FBD (r = 0.79 and 0.63, respectively), serum 1,25(OH)(2 )D-3 (r = 0.69), and serum iPTH (r = 0.72). No significant correlation was found between age and biochemical markers of bone remodeling. Par tial correlation and stepwise variable selection analyses, using (47)C aFA and bone mass as dependent variables, showed that in normal males, serum 1,25(OH)(2)D-3 and dietary calcium intake were the main contrib utors (64%) to (47)CaFA variability, whereas only age accounted for 63 % of VBD and age and dietary calcium accounted for 45% of FBD variabil ity. These results indicate that bone loss in men accelerates after ag e 50 years and that among other factors, intestinal calcium malabsorpt ion and 1,25(OH)(2)D-3 serum levels play a role.