ASSOCIATION BETWEEN INTESTINAL VITAMIN-D-RECEPTOR, CALCIUM-ABSORPTION, AND SERUM 1,25-DIHYDROXYVITAMIN-D IN NORMAL YOUNG AND ELDERLY WOMEN

The exact mechanism for the decrease in intestinal calcium absorption with age is not get understood, A decrease with age in serum 1,25-dihy droxyvitamin D (1,25(OH)(2)D) or a decrease in the intestinal vitamin D receptor (VDR) protein concentration are possible causes, The object ive of this study was to examine the effect of age on these factors, F ifty-nine young women age 25-35 years were compared with 41 elderly wo men age 65-83 years who underwent measurements of VDR, calcium absorpt ion using a 20 mg and 100 mg calcium carrier, and calciotropic hormone s, Calcium absorption by both tests was lower in the elderly women com pared with the young women (p < 0.05), Serum 1,25(OH)(2)D and duodenal VDR protein concentration were not significantly different between th e two age groups, Serum 1,25(OH)(2)D correlated with the 20 mg calcium absorption test in both young (r = 0.35, p < 0.007) and elderly women (r = 0.58, p < 0.0001) and with the 100 mg calcium absorption in the elderly (r = 0.32; p < 0.05), VDR did not correlate with calcium absor ption in young women or elderly women, nor did VDR correlate with seru m 1,25(OH)(2)D and serum 25-hydroxyvitamin D. In summary, the decrease in calcium absorption cannot be explained by a decrease in intestinal VDR The correlation between serum 1,25(OH)(2)D and both calcium absor ption tests only accounts for 12-30% of the variance in the age-relate d change in the calcium absorption tests, Other factors, not yet under stood, are responsible for the decline in calcium absorption with age.