Estrogens, bone mass, and osteoporotic fracture

In women, bone loss usually begins at the time of menopause, when the ovaries stop making estrogen. This observation led to the hypothesis that estrogen may be required for maintaining bone mass, and that estrogen deficiency may play an important role in osteoporosis (a condition of reduced bone density). Several studies have reported that bone mass is related to ovarian function. These studies found that bone mass decreased as ovarian function decreased, either due to menopause or disease. In one study, women who had their ovaries removed three years prior to the study had lower average bone mass than women of the same age who had functional ovaries. Another study reported that ovarian failure reduces calcium absorption in the intestines and increases calcium loss from the body. Ovarian function begins to decline gradually around the age of 35, and this is accompanied by a gradual decline in bone mass. Several studies have reported that estrogen supplements can prevent the loss of bone mass that occurs when the ovaries stop functioning. In one study, spinal bone mass was 29 percent greater and bone mass in the femur was 12 percent greater in women who were treated with estrogen for 10 to 15 years than in women who had not been treated. Several shorter studies, performed over a two-year period, have produced similar results. Treatment with estrogen has been reported to reduce the risk of hip and wrist fractures by 50 percent. Maintaining an adequate dietary intake of calcium and following an exercise program may enhance the effects of estrogen therapy in preventing bone loss. One study reported that the combined use of progestogen with estrogen results in a greater increase in bone mass than either agent when used alone. However, further studies are needed to verify these findings. It is not clear whether estrogen acts directly on bone cells to prevent bone loss or it stimulates the production of other factors that inhibit bone resorption. (Consumer Summary produced by Reliance Medical Information, Inc.)