[Osteoporosis and RANKL signal].

Osteoporosis is caused by imbalance between osteoclastic bone resorption and osteoblastic bone formation. From the recent results of several kinds of knockout mice, osteoclast differentiation factor (RANKL) and its soluble decoy receptor for RANKL (OPG) are essentially involved in pathogenesis of osteoporosis. Deficiency of RANKL in human has been shown to result in osteopetrosis. Furthermore, it has been reported that anti-RANKL neutralizing antibody (denosumab) will be effective new drug for osteoporosis.