Osteoporosis

Definition

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

Alternative Names

Causes

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 suffer a fracture of the hip, wrist, or vertebra (bones of the spine).

Osteoporosis occurs when the body fails to form enough new bone, or 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.

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 the age of 50, get osteoporosis more often than men.

Other causes include:

• Being confined to a bed
• Bone cancer
• Cushing syndrome
• Excess corticosteroid levels due to on-going use of medicines for asthma, certain forms of arthritis or skin diseases, and COPD.
• Hyperthyroidism
• Hyperparathyroidism

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
• Low body weight
• Smoking
• Too little calcium in the diet
• Use of certain medications, including steroids and antiseizure drugs

References

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.

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

Poole KE, Compston JE. Osteoporosis and its management.BMJ. 2006 Dec 16;333(7581):1251-6. Review.