Bone and Mineral Metabolism

Background: Evidence suggests that vitamin D status in adults is positively associated with calcium absorption fraction and inversely associated with serum PTH. The objective of this study was to evaluate the relationships among vitamin D status, PTH, and calcium absorption in midpubertal boys and girls. Methods: Calcium absorption was measured by using a stable isotope method in 93 young adolescents, 12.7 1.0 years of age, receiving diets averaging approximately 900 mg/day calcium. Results: A significant positive relation to calcium absorption was found for serum 1,25-dihydroxyvitamin D (p 0.048) and PTH (p 0.007), but not for 25-OHD (p 0.77). PTH was significantly inversely related to 25-OHD and was positively related to serum 1,25-dihydroxyvitamin D and osteocalcin. PTH was marginally significantly inversely related to lumbar spinal, but not whole body, bone mineral density. Conclusions: These data suggest that in adolescents, especially in the presence of vitamin D insufficiency, PTH secretion increases to adapt to higher rates of bone formation associated with growth. This results in higher serum 1,25(OH)2D concentrations and increased calcium absorption results.