Most of the studies on effectiveness of estrogen are limited to women younger than 80. This is unfortunate because most of the hip fractures occur in women older than 80. Some studies of women over 70 have shown estrogen causes similar increases in bone density as in younger women. Anecdotal experience suggests that elderly women may develop mastalgia more easily than younger women, and that starting with a lower dose may make it easier to tolerate. Most elderly women are not willing to resume menses, and thus regimens that do not cause vaginal bleeding are more acceptable.
Studies relating to fracture incidence Bone density is a surrogate endpoint for fracture.
In order to have adequate statistical power to show prevention of fractures in normal women, a study must include 4,000 women. No studies this large have been done with estrogen. However, there have been several large epidemiological studies that address this question, and the results are summarized this figure. The relative risk of a fracture in women taking estrogen is about 0.5, suggesting that a woman who refuses to take estrogen will have twice as much chance of a fracture as one who takes estrogen. Dose and route of administration Conjugated equine estrogens have been used most commonly in the United States, and most of the large epidemiological studies have been done with this form of oral estrogen.