Osteoporosis is a serious health problem in the United States. More than 10 million people have osteoporosis, and another 34 million are at risk due to low bone density (osteopenia). Each year, this disease contributes to more than 1.5 million fractures of the back, wrists and hips.

Eighty percent of people with osteoporosis are women, and it is the main cause of bone fractures in post-menopausal women and the elderly. However, men get osteoporosis as well. You could be at risk for osteoporosis for one or more reasons, such as a medical condition like rheumatoid arthritis or lupus, or from medications like corticosteroids (such as prednisone).

Bone is a changing, living tissue made up of calcium and other mineral deposits. During a lifetime, bone is broken down and built up again with strong, new bone over repeated cycles, each lasting about six months. From birth to the mid-20s, the calcium you get from food helps bone rebuild faster than it breaks down.

Your bones are the strongest they will ever be during your lifetime between ages 20 and 25, the age of highest bone-mass density or peak bone mass. At the peak, women have about 30 percent lower bone mass than men. Around age 40, bone mass begins to decline slowly. This is because bone breaks down faster than it is replaced.

During and after menopause, when estrogen levels drop, women lose bone mass faster than before. Over the first five to 10 years after menopause, women can lose up to one-third of their bone mass. Men also lose bone mass as they age, but overall, women have a lower peak bone mass and tend to lose bone mass faster than men.

Bones that have less mass are weaker and more likely to break or fracture, even with a minor fall. Because osteoporosis develops over the years, the first sign in many people is a broken bone.

Bone loss usually occurs without any symptoms long before you have a fracture. This is why osteoporosis is called a “silent disease.” Tooth loss might be a warning sign that osteoporosis has affected the jawbone. About one-third of American women lose all their teeth by their late 60s, in part due to osteoporosis.

Prevention, early detection and treatment are important because once you bones are porous enough to cause one fracture, you’re likely to have several more.