Osteoporosis happens when bones lose calcium and other minerals, making them more fragile and easily broken. Whether a woman develops osteoporosis as she gets older depends on how much bone she has built up by about age 30 and how quickly she loses calcium from her bones as she gets older. While some bone loss occurs in everyone with aging, some women are more likely to get osteoporosis. Risk for osteoporosis depends on a woman's family history, her estrogen levels, her diet, the amount of exercise she gets, and whether she smokes or drinks alcohol. The loss of estrogens at menopause is considered to be responsible for a short period of quick bone loss during this life period.
Significant osteoporosis is seen in about a third of postmenopausal women in the United States.
Prevention of osteoporosis does not necessarily require hormone treatment. Successful risk reduction has also been reported using calcium and vitamin D supplements and exercise. The best prevention is adequate calcium and vitamin D intake and physical activity in childhood and adolescence. Other studies have indicated that women who used postmenopausal hormone treatment may have higher rates of ovarian cancer, gall bladder disease, and problems associated with increased blood clotting compared to women who did not use hormone treatment. Postmenopausal hormone treatment is associated with, at most, a small increase in ovarian cancer risk.