What Causes Osteoporosis?
There is no single cause of osteoporosis.
Our bodies constantly build new bone and remove older bone. In childhood, more bone is built than removed, and so the bones grow in size. After age 30 or 40, however, the cells that build new bone do not keep up with those that remove bone. The total amount of bone then decreases, and osteoporosis may develop as a result.
The average rate of bone loss in men, and in women who have not yet reached menopause, is small. But after menopause, bone loss in women accelerates to an average of one to two percent a year.
This is because after menopause, the level of the female hormone estrogen in a woman's body sharply decreases. Estrogen protects the skeleton by helping the body's bone-forming cells to keep working. After menopause, when the level decreases, some of this protection is lost.
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How-To Information:
Activity stimulates new bone formation, but immobility (for example, after a bone fracture) can result in bone loss. This is called osteopenia, which means "bone deficiency."
People immobilized by bedrest and astronauts on weightless space flights have loss of bone density. Weight-bearing exercise is vitally important to help keep osteoporosis from developing.
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