Low doses of 1,25-dihydroxycholecalciferol increase mature bone mass in adult normal rats.

Low doses of 1,25-DHCC cause a significant increase in trabecular and cortical bone mass of the mature rat skeleton by stimulated endosteal bone formation. The increased serum contents of calcium and inorganic phosphate give rise to a moderate nephrocalcinosis. An increased bone resorption occurs upon toxic dose levels causing profound nephrocalcinosis. Similar doses of 25-HCC do not affect the mature bone.