There are two essential processes necessary for proper growth and maintenance of bone mass. These are bone resorption and bone formation. During childhood and adolescence, the bone formation exceeds bone resorption, in adults both processes are balanced, and during aging, resorption exceeds formation. Growth factors play an essential role in the coupling of bone formation to bone resorption. Bone matrix contains growth factors, produced by osteoblasts. In the process of bone resorption, the growth factors are released from the matrix and from osteoclasts. Thus, the growth factors released during bone resorption act as paracrine agents on stromal cells thereby generating more bone forming cells in proportion to the amount of bone resorbed. The amount of newly formed bone is not only determined by the amount of growth factors released from matrix during resorption, but also by the growth factors produced by both osteoblasts and osteoclasts. Some metabolic bone disorders result from the uncoupling of bone formation to bone resorption. The reduction of growth factors thus plays an important role in the pathogenesis of metabolic bone diseases.

        Key words: growth factors, bone resorption, bone formation