[PTH and immobilization induced osteopenia]

Decreased bone mass in the astronauts indicates that the gravity force is an important factor for bone physiology. Similarly, prolonged immobilization, such as bed-rest, induces severe osteopenia and pathological fracture. Recently the molecular mechanisms by which mechanical stress increases bone mass and immobilization induces osteopenia have been elucidated. In this manuscript, this molecular mechanism of the immobilization induced osteopenia and the promising roles of PTH in the pathogenesis and treatment of the immobilization induced osteopenia will be discussed briefly.