Perspective: genetic and hormonal roles in bone disorders: insights of an updated bone physiology

In 1997 Professor J. Gorski suggested endocrinology needed new paradigms (Endocrine News 1997; 22:4,12). 'Connecting the dots' between diverse facts and ideas drawn from many lines of inquiry, plus accumulating evidence and increasing inadequacies of earlier ideas and terminology, led to an updated bone physiology called the 'Utah paradigm' that reveals new genetic and hormonal potential roles in bone physiology and disorders. One way to find a bone disorder's cause(s) and treatment( s) could depend on understanding the underlying physiology well enough to design effective drugs for it. In early views cell-level effects on osteoblasts and osteoclasts could explain most endocrine and genetic roles in bone disorders. The updated bone physiology supplements those views with roles of bone's tissue-level 'nephron-equivalent' mechanisms (NEMs) and their functions (NEFs), including some roles of biomechanics, whole-bone strength and muscle strength. That updated physiology reveals at least 42 nexuses above the cell level, some of them extraosseous, where genetic and/or hormonal effects might cause or help to treat varied bone problems. That multifactorial physiology also suggests that in vivo skeletal phenomena usually depend on many interlocking, laddered and nested feedback systems. Due to lack of study, how genes and hormones affect those nexuses and feedback systems still remains nearly unknown. Because studies of bone physiology in in vitro systems seldom if ever correctly predicted the in vivo effects, further live-animal research should seek the in vivo effects. This article suggests why more of that kind of research is needed, and some directions it could take.