Abstract
Bony remodeling is inextricably linked with the processes of calcium homeostasis. The coupling of the two is so intimate that they can be studied adequately only together and at a level of complexity of the whole organism. An induced alteration in one of them produces a compensatory response in the other. An alteration of one of the steps in bone remodeling starts a cascade of events which includes a shift in the balance between internal and external calcium effector organs, a change in the secretion of parathyroid hormone, calcitonin, and so forth, and ultimately a change in the frequency of activation of new packets of bone remodeling. Together, these systems constitute the substratum which is deranged in metabolic bone disease and the apparatus whereby physiologic and pharmacologic agents act on bone. The response time of the remodeling system is so slow, lasting months, and most studies of agents which affect the system have been of such short duration, that much of the present knowledge of the response of the intact system is little more than misinterpretation of data, based as it is on observed transients rather than on ultimate effects.