Vitamin D, calcium homeostasis, and skeleton accretion in children

Overt vitamin D deficiency early in life has classically been associated with the etiology of rickets. Recent interest has focused on vitamin D insufficiency and calcium homeostasis and bone health. A review of the literature suggests that the relationship between vitamin D status and calcium utilization has some important differences with life stage and race. In contrast to adults, serum 1,25-dihydroxyvitamin D, but not serum 25-hydroxyvitamin D, predicts calcium absorption in growing children. PTH suppression with increasing serum 25-hydroxyvitamin D varies with race in adolescents. A limitation of our understanding of vitamin D status on calcium homeostasis in children relates to the cross-sectional nature of the evidence and interventions that typically use too little vitamin D supplementation to affect status. Vitamin D status has predicted changes in BMD during growth, and higher doses have been associated with increased bone area and BMC of the hip in pubertal girls with low baseline vitamin D status. Bone accretion is related to calcium status, sexual maturity, race, and genetics. Current cross-sectional studies in children suggest that vitamin D status is less important for bone accrual than for bone health in adults. Intervention studies are needed to identify responsive groups.