The Mechanisms of Bone Loss due to Estrogen Deficiency: Possible Role of Increased B-Lymphopoiesis in Bone Resorption

An estrogen deficiency, caused by either menopause or removal of the ovaries, results in a marked bone loss by increased osteoclastic bone resorption. The pathologic bone loss in this condition can be restored by estrogen replacement therapy, but the mechanism underlying this phenomenon remains unknown. There appears to be a close relationship between bone remodeling and hemopoiesis in bone marrow (Suda et al. 1992). Osteoclast progenitors are thought to be of hemopoietic origin, and they are recruited from bone marrow (Suda et al. 1992). It is also suggested that several cytokines produced by bone marrow cells affect bone remodeling (Suda et al. 1992). Recent studies indicated the possible involvement of bone-resorbing cytokines such as interleukin (IL)-1, IL-6, and tumor necrosis factor α (TNFα) in bone loss due to estrogen deficiency.