Central Control of Bone Mass: Brainstorming of the Skeleton

Our understanding of the biology of the skeleton, like that of virtually every other subject in biology, has been transformed by recent advances in human and mouse genetics. These advances, together with findings from the work of chicken embryologists, have radically enhanced our comprehension of the developmental biology of the vertebrate skeleton.1,2In contrast, we have learned very little, in molecular and genetic terms, about another very important part of skeletal biology, namely its physiology. Among the many questions of skeletal physiology that are largely unexplained are the following: Why and how do we stop growing? Why and how are bone and teeth the only organs to mineralize under physiological conditions? How is bone mass maintained nearly constant between the end of puberty and the arrest of gonadal functions? This review will deal with this last issue.