[Growth factors and cytokines in bone metabolism].

Insulin-like growth factors are present in the circulation and are also synthesized by osteoblasts so that they may function both as systemic and local regulators of bone growth. Production of insulin-like growth factors in bone are under the control of parathyroid hormone, estrogen and growth hormone. Cytokines, such as interleukin-1, interleukin-6, tumor necrosis factor, stimulate osteoclastic bone resorption, and are under inhibitory control of estrogen. Bone loss associated with age and menopause may be due in part to removal of this inhibitory influence upon cytokines production.