title: Impaired vitamin D metabolism with aging in women. Possible role in pathogenesis of senile osteoporosis.
abstract: Calcium absorption decreases with aging, particularly after age 70 yr. We investigated the possibility that this was due to abnormal vitamin D metabolism by studying 10 normal premenopausal women (group A), 8 normal postmenopausal women within 20 yr of menopause (group B), 10 normal elderly women (group C), and 8 elderly women with hip fracture (group D) whose ages (mean +/- SD) were 37 +/- 4, 61 +/- 6, 78 +/- 4, and 78 +/- 4 yr, respectively. For all subjects, serum 25-hydroxyvitamin D [25(OH)D] did not decrease with age, but serum 1,25-dihydroxyvitamin D [1,25(OH)2D], the physiologically active vitamin D metabolite, was lower (P = 0.01) in the elderly (groups C and D; 20 +/- 3 pg/ml) than in the nonelderly (groups A and B; 35 +/- 4 pg/ml). The increase of serum 1,25(OH)D after a 24-h infusion of bovine parathyroid hormone fragment 1-34, a tropic agent for the enzyme 25(OH)D 1 alpha-hydroxylase, correlated inversely with age (r = -0.58; P less than 0.001) and directly with glomerular filtration rate (r = 0.64; P less than 0.001). The response was more blunted (P = 0.01) in elderly patients with hip fracture (13 +/- 3 pg/ml) than in elderly controls (25 +/- 3 pg/ml). We conclude that an impaired ability of the aging kidney to synthesize 1,25(OH)2D could contribute to the pathogenesis of senile osteoporosis.
mesh_terms: D000368:Aged; D000375:Aging; D000469:Alkaline Phosphatase / Q000097:blood; D002112:Calcifediol / Q000097:blood; D002117:Calcitriol / Q000097:blood; D002118:Calcium / Q000097:blood; D000242:Cyclic AMP / Q000652:urine; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D010024:Osteoporosis / Q000209:etiology / Q000503:physiopathology*; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000097:blood; D014807:Vitamin D / Q000378:metabolism*
chemical_list: D010281:Parathyroid Hormone; D010710:Phosphates; D014807:Vitamin D; D000242:Cyclic AMP; D000469:Alkaline Phosphatase; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium