NA;Cytokines and growth factors are important in bone tissue as mediators of cellhyphen;tohyphen;cell and matrixhyphen;tohyphen;cell communication. Cytokines also locally mediate the effects of several hormones on bone cells. Indeed, calciotropic hormones modulate the bonehyphen;cell production rate of these factors and, conversely, can change the number of receptors for these hormones on bone cells. Most cytokines are active in bone, but the existence of a bonehyphen;specific cytokine is still questioned. Recent work has searched for estradiol modulation of osteoblastic cytokine acting on osteoclast differentiation. In mice, increased interleukinhyphen;6 production by osteoblasts is responsible for increased bone resorption occurring after ovariectomy. Interleukinhyphen;6 could also be an autocrine or paracrine factor in the pathogenesis of increased resorption occurring in giant cell tumor or in Paget's disease. During osteoporosis and agehyphen;related bone changes, modifications of the production of insulinhyphen;like growth factor I or of one of its binding proteins could be responsible for low bone formation. Interrelationships between cytokines and hormones can affect the action of parathyroid hormonehyphen;related peptide on bone cells. The field of implication of cytokines in metabolic bone disease is growing.Current Opinion in Rheumatology 1993,5colon;332hyphen;338
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