Why Do Bones Break Down? And The Results Of Bone Break Down!

Although bones may seem like hard and lifeless structures, bones are living tissues that are like muscle. Bones respond to exercise and a healthy diet by becoming stronger. Bones make up our skeletons and provide structure and support for our bodies. However, bones are more than that; they also act like a storehouse for minerals that our bodies need, such as calcium. During a person's lifetime, the body constantly breaks down old bone (through a process called resorption) and builds up new bone. Any time old bone is broken down faster than new bone is made, net bone loss occurs. Bone loss can lead to low bone density (osteopenia), weakness of the bone, and eventually osteoporosis.

Osteoporosis (or porous bone) is a disease in which bones become weak and fragile. Porous bones are more likely to break. Osteoporosis is a serious disease that affects millions of people worldwide. Without prevention or treatment, osteoporosis can progress without pain or symptoms until a bone breaks (fracture). Fractures commonly occur in the hip, spine, and wrist. Osteoporosis is the underlying cause of more than 1.5 million fractures annually (300,000 hip fractures, approximately 700,000 vertebral fractures, 250,000 wrist fractures, and more than 300,000 fractures in other areas). The estimated national cost (hospitals and nursing homes) for osteoporosis and related injuries is $14 billion each year in the United States.

Bone loss occurs when more bone is resorbed than is formed by the body. Many factors determine how much old bone is resorbed and how much new bone is made. Some factors people have control over (such as diet), but some factors are out of their control (such as age).

Most new bone is added during childhood and teenage years. As a result, bones become larger, heavier, and stronger (denser). Bone formation continues until the peak bone mass (maximum solidness and strength) is reached. Peak bone mass (or bone density) is reached around age 30. After age 30, bone resorption slowly begins to exceed new bone formation. This leads to bone loss. Bone loss in women occurs fastest in the first few years after menopause, but bone loss continues into old age. Factors that can contribute to bone loss include having a diet low in calcium, not exercising, smoking, and taking certain medications such as corticosteroids. Corticosteroids are medications prescribed for a wide range of diseases, including arthritis, asthma, inflammatory bowel disease, lupus, and other diseases. Corticosteroids may cause osteoporosis when used chronically.

The only reliable way to detect bone loss is to have a bone mineral density (BMD) test. People with strong risk factors for osteoporosis should have a BMD test.

Recommendations in the United States are that all women 65 years and older should have a BMD test. Postmenopausal women younger than 65 years who have one or more risk factors (in addition to being postmenopausal and female) should have a BMD test. Tests that are used to measure BMD include dual energy x-ray absorptiometry (DXA), quantitative computed tomography (QCT), and quantitative ultrasound (QUS). See Bone Mineral Density Tests for more information.

For more information contact:

National Institutes of Health

Osteoporosis and Related Bone Diseases-

National Resource Center2

AMS CirBethesda, MD 20892-3676

(800) 624-BONE (624-2663)

OsteoInfo@osteo.org

Author: Bruce A Baethge, MD, Rheumatology Fellowship Director, Associate Professor, Department of Internal Medicine, Division of Rheumatology, University of Texas at Galveston