Relationship of intestinal calcium absorption to 1,25-dihydroxyvitamin D [1,25(OH)2D] levels in young versus elderly women: evidence for age-related intestinal resistance to 1,25(OH)2D action - Pattanaungkul, S; Riggs, B L; Yergey, A L (J Clin Endocrinol Metab, 2000)