Childhood bone mass acquisition and peak bone mass may not be important determinants of bone mass in late adulthood.

During childhood and adolescence, bone mass acquisition occurs primarily through skeletal growth. It is widely assumed that bone mass acquisition throughout childhood is an important determinant of the risk of osteoporosis in late adulthood; bone mass is thought to resemble a bank account in which deposits persist indefinitely. However, several well-controlled clinical studies suggest that increasing bone mass acquisition during childhood will have only transient effects. A likely explanation is that bone mass is governed by a homeostatic system that tends to return to a set point after any perturbation and, therefore, bone mass depends primarily on recent conditions, not those in the distant past. Indeed, in an animal model, we have shown evidence that bone mass acquisition in early life has no effect on bone mass in adulthood, in part because many areas of the juvenile skeleton are replaced in toto through skeletal growth. Therefore, it should not be assumed that alterations in childhood bone mass acquisition will affect bone mass many decades later in late adulthood. This issue remains open and the solution may depend on the type of childhood condition (for example calcium intake versus exercise) and its magnitude, timing, and duration. To date, both animal studies and clinical studies suggest that much of the effect of early bone mass acquisition does not persist.