单选题 Osteoporosis used to be called "the silent disease" because its victims didn" t know they had it until it was too late and they suffered a bone fracture. Today, doctors can identify osteoporosis early. Improved understanding of the disease has also led to new treatments and strategies for preventing the disease altogether. For post-menopausal women, the most common medical response to osteoporosis is hormone replacement therapy. Boosting estrogen levels strengthens the entire skeleton and reduces the risk of hip fracture. Unfortunately, it sometimes causes uterine bleeding and may increase the risk of breast cancer. To bypass such side effects, researchers have developed several alternative treatments. Synthetic estrogens called Selective Estrogen Receptor Modulators(SERMs)emulate estrogen with slight modifications. Another drug, alendronate, reduces spine, hip and wrist fractures by 50 percent. Researchers have even developed a nasal spray called calcitonin. Each of these alternatives has trade-offs, however. Patients must talk with their doctors to decide which therapy is best for them. The ideal way to address osteoporosis is by adopting a healthy lifestyle. And the best time to do this is in childhood, when most bone mass is accumulated. Because bodies continue building bone until about age thirty, some experts believe that women in their twenties can still increase their bone strength by as much as 20 percent. Calcium, which is available in low-fat dairy foods and dark green vegetables, is essential for preventing osteoporosis. So is vitamin D, which aides calcium absorption. Vitamin D comes from sunlight, but dietary supplements may be helpful in northern climates and among those who don"t get outside. The final component is regular moderate exercise because bone responds to the needs that the body puts on it. These are the simple steps that can help make "the silent disease" truly silent.