Bone Density Scan

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Bone density scan facts

  • About 40% of postmenopausal women in the U.S. have osteopenia (low bone density). An additional 7% have osteoporosis.
  • In 1995, osteoporosis-related fractures were associated with over 400,000 hospitalizations, stressing the importance of early detection and appropriate prescription therapy.
  • Bone mineral density (BMD) estimates the true mass of bone.
  • BMD analysis is recommended for women between ages 50 and 65 with risk factors for osteoporosis and for all women over the age of 65. In addition, men and women taking certain medications or having certain diseases should discuss testing with their doctor.
  • By measuring BMD, it is possible to predict fracture risk in the same manner that measuring blood pressure can help predict the risk of stroke.
  • DXA is quick, painless, and the preferred method to measure BMD.
  • Osteoporosis has many available prescription and nonprescription treatment options once the diagnosis is made.

What is osteoporosis?

Osteoporosis is a condition that is characterized by bones that are less dense than, and thus not as strong as, normal bone. Osteoporosis increases the risk of breaking a bone (fracture) with even minor trauma, such as a fall from standing height, or even from a cough or sneeze. Unfortunately, people often do not realize they have osteoporosis until either they have a fracture or have a screening test ordered by their doctor to check for osteoporosis. Osteoporosis and low bone mass affect an estimated 44 million Americans. Of those, 10 million have osteoporosis, and the remaining 34 million have a lower than normal bone mass (medically termed osteopenia) and are at higher risk of developing osteoporosis. Women are four times more likely to develop osteoporosis than men. Other risk factors include older age, family history of osteoporosis, small and thin stature, inactive lifestyle, smoking, alcohol, and use of certain medications, including steroids.

How does osteoporosis occur?

In order to understand the role of bone mineral density scanning, it is important to know a little about how osteoporosis occurs. Bone is constantly being remodeled. This is the natural, healthy state of continuous uptake of old bone (resorption) followed by the deposit of new bone. This turnover is important in keeping bones healthy and in repairing any minor damage that may occur with wear and tear. The cells that lay new bone down are called osteoblasts, and the cells responsible for resorption of old bone are called osteoclasts. Osteoporosis occurs as a result of a mismatch between osteoclast and osteoblast activity. This mismatch can be caused by many different disease states or hormonal changes. It is also commonly a result of aging, change in normal hormones as occurs after menopause, and with diets low in calcium and vitamin D. In osteoporosis, osteoclasts outperform osteoblasts so that more bone is taken up than is laid down. The result is a thinning of the bone with an accompanying loss in bone strength and a greater risk of fracture. A thinning bone results in a lower bone density or bone mass.

There are two major types of bone. Cancellous bone (also known as trabecular bone) is the inner, softer portion of the bone, and cortical bone is the outer, harder layer of bone. Cancellous bone undergoes turnover at a faster rate than cortical bone. As a result, if osteoclast and osteoblast activity become mismatched, cancellous bone is affected more rapidly than cortical bone. Certain areas in the body have a higher ratio of cancellous bone to cortical bone such as the spine (vertebrae), the wrist (distal radius), and the hips (femoral neck).

Most of a person's bone mass is achieved by early adulthood. After that time, the bone mass gradually declines throughout the rest of a person's life. There is a normal rate of decline in bone mass with age in both men and women. For women, in addition to age, the menopause transition itself causes an extra degree of bone loss. This bone loss is greatest in the first three to six years after menopause. Women can lose up to 20% of the total bone mass during this time. Since women generally have a lower bone mass to begin with in comparison with men, the ultimate result is a higher risk of fracture in postmenopausal women as compared to men of the same age. Nevertheless, it is important to remember that men may also be at risk for osteoporosis, especially if they have certain illnesses, a low testosterone level, are smokers, take certain medications, or are sedentary. The best method to prevent osteoporosis is to achieve as high a bone mass by early adulthood with a proper diet and regular exercise. Unfortunately, osteoporosis is not often considered during this time in a person's life.

Medically Reviewed by a Doctor on 9/24/2013

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Bone Density Scan - Experience Question: Please describe your experience receiving a bone density scan.
A bone density scan is recommended for menopausal women over 65 and those who have risk factors of osteoporosis.

Who Should Get a Bone Density Scan?

Bone density testing is used to assess the strength of the bones and the probability of fracture in persons at risk for osteoporosis. The test, referred to as bone densitometry or bone mineral density scan (BMD), is a simple, noninvasive procedure that takes just minutes.


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