Osteoporosis is a disease that thins and weakens the bones to the point that they break easily. Women and men with osteoporosis most often break bones in the hip, spine, and wrist, but osteoporosis can be the cause of bone fractures anywhere.

Osteoporosis is often called "the silent disease" because the bone loss occurs without symptoms. People may not know that they have osteoporosis until a sudden strain, bump, or fall causes a bone to break.

In the United States, 10 million people already have osteoporosis. Millions more have low bone mass, or osteopenia, placing them at increased risk for the disease. Osteoporosis can strike at any age, but it is most common among older people, especially older women. Eighty percent of the 10 million Americans with osteoporosis are women.

Women have smaller bones, and they lose bone more rapidly than men because of hormone changes that occur after menopause. Therefore, women are at higher risk for osteoporosis.

The older you are, the greater your risk of osteoporosis. Having a family history of the disease can also increase one's risk. Other factors such as diets inadequate in calcium and vitamin D, smoking, ethnicity, and inactivity can also play a role in the development of the disease.

Yes. Some commonly used medicines can result in bone loss and increase your risk of osteoporosis and fracture. These include a type of steroid called glucocorticoids, which are used to control diseases such as arthritis and asthma; some antiseizure drugs; some medicines that treat a common gynecological condition known as endometriosis; and some cancer drugs. Using too much thyroid hormone for an underactive thyroid can also be a problem.

Calcium and vitamin D are important nutrients for bone health. People over 50 should get 1,200 mg of calcium daily. People aged 51 to 70 should have 400 IU, or international units, of vitamin D daily and people over 70 should have 600 IU.

Although foods rich in calcium are believed to be the best source, most American diets do not contain enough calcium. Fortunately, calcium-fortified foods and calcium supplements can help fill the gap, ensuring that you meet your daily calcium requirement.

Milk fortified with vitamin D is a good source of vitamin D. In some cases, supplements may be necessary to meet the daily requirements.

Your body makes vitamin D in the skin when it is exposed to sunlight and some people get all the vitamin D they need this way. However, many older people, especially those who are indoors most of the time and/or live in northern areas, do not get enough vitamin D.

Also, during the winter months, many people do not get enough vitamin D. Many older people will need a dietary supplement to reach recommended levels of vitamin D.

Exercise can make bones and muscles stronger and help slow the rate of bone loss. It is also a way to stay active and mobile. Weight-bearing exercises, done three to four times a week, are best for preventing osteoporosis. Walking, jogging, playing tennis, and dancing are examples of weight-bearing exercises. Strengthening and balance exercises may help you avoid falls and reduce your chances of breaking a bone.

Proper posture and body mechanics are important when doing exercises. Activities that involve twisting your spine or bending forward from the waist, such as conventional sit-ups and toe touches, should be avoided.

Osteoporosis does not have any symptoms until a fracture occurs.

Some people may be unaware that they have already experienced one or more spine fractures. Height loss of one inch or more may be the first sign that someone has experienced spinal fractures due to osteoporosis.

People who have experienced a fracture are at high risk of having another one. A fracture over the age of 50 or several fractures before that age may be a warning sign that a person has already developed osteoporosis. Any fracture in an older person should be followed up for suspicion of osteoporosis.

The test used to diagnose osteoporosis is called a bone density test. This test is a measure of how strong -- or dense -- your bones are and can help your doctor predict your risk for having a fracture. Bone density tests are painless, safe, and require no preparation on your part.

Some bone density tests measure the strength of the hip, spine, and/or wrist, which are the bones that break most often in people with osteoporosis. Other tests measure bone in the heel or hand.

One way to measure bone density is by a DXA scan, which estimates what your risk for a fracture is. It could show that you have normal bone density. Or, it could show that you have osteopenia, or even osteoporosis.

The United States Preventive Services Task Force recommends that women aged 65 and older be screened for osteoporosis, as well as women aged 60 and older who are at increased risk for an osteoporosis-related fracture. However, the decision whether to have a bone density test is best made between a patient and his or her doctor.

Although there is no cure for osteoporosis, it can be treated. The goal of treatment is to prevent fractures. Along with making lifestyle changes, there are several medication options.

There is not one type of doctor who cares for people with osteoporosis. Endocrinologists, rheumatologists, geriatricians, and internists are just a few of the doctors who are likely to specialize in the care of people with osteoporosis. If your physician does not specialize in osteoporosis, he or she can refer you to one who does.

Several medications are approved by the Food and Drug Administration for the treatment of osteoporosis. Since all medications have side effects, it is important to talk to your doctor about which medication is right for you.

Alendronate, risedronate, ibandronate, and zoledronic acid are from a class of drugs called bisphosphonates that slow bone loss and reduce fracture risk.

Estrogen is approved for treating menopausal symptoms and osteoporosis. But because breast cancer, strokes, blood clots, and heart attacks may be increased in some women who take estrogen, women should take the lowest effective dose for the shortest period possible.

Raloxifene is approved for use in postmenopausal women. It is from a class of drugs called estrogen agonists/antagonists, commonly referred to as selective estrogen receptor modulators (SERMs). Raloxifene slows bone loss and reduces the risk of fractures in the spine.

Calcitonin is approved for the treatment of osteoporosis in women who are at least 5 years past menopause. It is a hormone produced in the thyroid gland that slows bone loss and reduces the risk of spine fractures.

Teriparatide, a form of human parathyroid hormone, is approved for use in postmenopausal women and men who are at high risk of fracture. Given daily as an injection, for up to 24 months, it increases bone density and reduces the risk of spine and other fractures.

None of these medications has been approved for children.