The subject of vitamin-D investigation from the medical point of view had until recently been considered all but closed, since the vitamin's uses in the prevention of rickets and osteomalacia, as well as in the treatment of hypoparathyroidism, renal osteodystrophy, familial hypophosphatemia, and other forms of refractory rickets, appeared clear and well defined. Much, however, remained to be learned at the basic or molecular level. It was the major advances in this area that have all but overturned this complacency in the medical world.
Chronologically, perhaps the first revolutionary concept was that vitamin D in some way exerts its action by interacting with nuclei of intestine and bone to induce transcription of a specific deoxyribonucleic acid which codes for a protein which in turn functions in intestinal calcium transport or in the mobilization of bone. This involvement with the genetic machinery opens the possibility that some forms of familial vitamin-D