Bone mineralization in infants.

The major physiologic control of bone mineralization in infancy involves calcium and phosphorus. Ca and P metabolism in turn is affected by endogenous stores at birth and the ability to deliver and absorb exogenous sources of these minerals. Calciotropic hormones (parathyroid hormone, calcitonin and 1,25 dihydroxyvitamin D) modulate the response of major end organs - intestine, kidney and bone - to balance the need to maintain a relatively stable extracellular biochemical environment with the need for adequate mineralization of the bone. Many other factors such as glucocorticoids under pathological circumstances may disturb bone mineralization; however, the mechanisms by which they control bone mineralization in infancy under physiologic circumstances is ill understood. Clinical bone demineralization occurs primarily in infants born with extreme prematurity. In the presence of conventional vitamin D supplementation, deficiency of calcium and phosphorus appears to play a major role in its causation.