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Osteoporosis is the thinning of bone tissue and loss of bone density over time.

Thin bones

Osteoporosis is the most common type of bone disease. An estimated 10 million Americans have osteoporosis, as well as another 18 million who have low bone mass, or osteopenia, which may eventually lead to osteoporosis if not treated.

Researchers estimate that about 1 out of 5 American women over the age of 50 have osteoporosis. About half of all women over the age of 50 will have a fracture of the hip, wrist, or vertebra (bones of the spine).

Osteoporosis occurs when the body fails to form enough new bone, when too much old bone is reabsorbed by the body, or both.

Calcium and phosphate are two minerals that are essential for normal bone formation. Throughout youth, your body uses these minerals to produce bones. If you do not get enough calcium, or if your body does not absorb enough calcium from the diet, bone production and bone tissues may suffer.

As you age, calcium and phosphate may be reabsorbed back into the body from the bones, which makes the bone tissue weaker. This can result in brittle, fragile bones that are more prone to fractures, even without injury.

Usually, the loss occurs gradually over years. Many times, a person will have a fracture before becoming aware that the disease is present. By the time this occurs, the disease is in its advanced stages and damage is severe.

Watch this video about: Osteoporosis

The leading causes of osteoporosis are a drop in estrogen in women at the time of menopause and a drop in testosterone in men. Women, especially those over age 50, get osteoporosis more often than men.

Other causes include:

• Being confined to a bed
• Cushing syndrome
• Excess corticosteroid levels due to ongoing use of medicines for asthma, certain forms of arthritis or skin diseases, and COPD.
• Hyperthyroidism
• Hyperparathyroidism
• Rheumatoid arthritis and other inflammatory conditions

White women, especially those with a family history of osteoporosis, have a greater-than-average risk of developing osteoporosis. Other risk factors include:

• Absence of menstrual periods (amenorrhea)
• Drinking large amount of alcohol
• Early menopause
• Eating disorders
• Family history of osteoporosis
• Low body weight
• Smoking
• Too little calcium in the diet
• Use of certain medications, including steroids and antiseizure drugs

There are no symptoms in the early stages of the disease.

Symptoms occurring late in the disease include:

• Bone pain or tenderness
• Fractures with little or no trauma
• Loss of height over time
• Low back pain due to fractures of the spinal bones
• Neck pain due to fractures of the spinal bones
• Stooped posture

Bone mineral density testing (specifically a densitometry or DEXA scan) measures how much bone you have. This test has become the gold standard for osteoporosis evaluation. For specific information on such testing, see bone density test.

A spine CT can show loss of bone mineral density. Quantitative computed tomography (QCT) can evaluate bone density. However, it is not as available and is more expensive than a DEXA scan.

In severe cases, a spine or hip x-ray may show fracture or collapse of the spinal bones. However, simple x-rays of bones are not very accurate in predicting whether someone is likely to have osteoporosis.

You may need other blood and urine tests if your osteoporosis is thought to be due to a medical condition, rather than simply the usual bone loss seen with older age.

Some persons with osteoporosis become severely disabled as a result of weakened bones. Hip fractures leave about half of patients unable to walk independently. This is one of the major reasons people are admitted to nursing homes.

Although osteoporosis is debilitating, it does not affect life expectancy.

• Compression fractures of the spine
• Disability caused by severely weakened bones
• Hip and wrist fractures
• Loss of ability to walk due to hip fractures

Call your health care provider if you have symptoms of osteoporosis or if you wish to be screened for the condition.

Calcium is essential for building and maintaining healthy bone. Vitamin D is also needed because it helps your body absorb calcium. Following a healthy, well-balanced diet can help you get these and other important nutrients throughout life.

Other tips for prevention:

• Avoid drinking excess alcohol
• Don't smoke
• Get regular exercise

A number of medications are approved for the prevention of osteoporosis.

Cranney A, Papaioannou A, Zytaruk N, et al. Clinical Guidelines Committee of Osteoporosis Canada. Parathyroid hormone for the treatment of osteoporosis: a systematic review. CMAJ. 2006 Jul 4;175(1):52-9.

Gass M, Dawson-Hughes B. Preventing osteoporosis-related fractures: an overview. Am J Med. 2006 Apr;119(4 Suppl 1):S3-S11. Review.

Estrogen and progestogen use in postmenopausal women: July 2008 position statement of The North American Menopause Society. Menopause. July/August 2008;15(4)584-602.

Management of osteoporosis in postmenopausal women: 2006 position statement of The North American Menopause Society. Menopause. 2006 May-Jun;13(3):340-67.

National Osteoporosis Foundation. Clinician's Guide to Prevention and Treatment of Osteoporosis. Feb. 2008. Accessed July 23, 2008. Available online at http://www.nof.org/professionals/Clinicians_Guide.htm