On age-related mammalian bone loss: Insights of the Utah paradigm

an elegant design stratogem would make its loads control the strength of an organ intended to carry loads without breaking. Healthy load-bearing mammalian bones do exactly that. Physiologists begin to understand how they do it, and this article reviews some of the biological "machinery" responsible for it. Why? Because that machinery's features show what can cause age-related bone loss, how it occurs, how a long-overlooked mechanism in bone marrow would contribute to it, why loss of whole-bone strength seems more important than loss of bone 'mass', and why some absorptiometric indicators of whole-bone strength are unreliable. The machinery's features also show why strong muscles normally make strong bones, why persistently weak muscles normally make weak bones, and why loss of muscle strength usually causes a disuse-pattern osteopaenia. Those things could question long-accepted 'wisdom', but four observations concern that; (1) the questions concern what facts mean far more than the accuracy of the facts, and the basic facts now seem pretty clear; (2) this article must leave resolution of such questions and of the devils that can hide in the details, to other times, places and people; (3) the plate tectonics story showed that better facts and ideas can change accepted wisdom dramatically; (4) and poor interdisciplinary communication delayed and still delays diffusion of better facts and ideas to many skeletal science and clinical disciplines that needed and need them.