Effect of estrogens on bone and other systems and hormonal substitute treatment

This article reviews recent advances in the effects of estrogen on bone and other body systems. The effect of estrogen use for the prevention of osteoporosis is no longer a matter of debate. Some issues are still discussed, however, especially with regard to the magnitude of its protection (especially for hip fracture), which would be dependent on the time at which estrogen therapy is initiated with respect to menopause as well as its total duration of use. The mechanisms of estrogen's action on bone also remains poorly understood. Controversy persists concerning the specific contribution of an indirect action through the modulation of calciotropic hormones and a direct action on bone cells in which estrogen receptors have been identified. Estrogens have been shown to reduce osteoclastogenesis by modulating the production of cytokines (interleukins, tumor necrosis factor) and transforming growth factor from bone marrow and bone cells. In addition to its effects on bone, a great number of observational studies have evaluated the relationship between estrogen use and coronary heart disease. The overall risk of coronary disease is estimated to be reduced by 50% in women who use estrogen replacement therapy. This reduction would be even greater in women with previous atherosclerosis. Moreover, recent data suggest that estrogen use could be associated with delayed onset and reduced risk for Alzheimer's disease. Overall, estrogen treatment in postmenopausal women has several proven benefits. Conversely, the potential risks of long-term estrogen therapy include a slightly increased risk of breast cancer, which would be associated with long-term use. Although the individual decision for a postmenopausal woman to start estrogen replacement therapy must take into account this risk:benefit ratio, current evidence suggests a clear advantage for estrogen's benefits over its risks.