Vitamin D For Dummies
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Doctors diagnose osteoporosis by performing a bone densitometry test, which measures the amount of mineral per square centimeter of bone. The areas studied in a bone densitometry study are usually the lumbar spine and the upper part of the hip. The test takes about ten minutes to complete.

The bone density correlates fairly well with the tendency of a bone to fracture. Measurements at the hip and spine can predict fractures at other sites. The following diagram shows dense, healthy bones on the left; bones weakened by osteoporosis appear on the right.

Healthy bones (a) are denser than bones affected by osteoporosis (b).
Healthy bones (a) are denser than bones affected by osteoporosis (b).

Diagnosing osteoporosis

Dual-energy X-ray absorptiometry (DXA) is the most common method for studying the density of your bones. In this study, you lie on a table; then two X-ray beams — one of high energy and one of low energy — are aimed at your bones. The amount of radiation that passes through the bone is measured for each beam. This amount is determined by the thickness of the bone.

The bone density is measured by a formula using the difference between the two beams. This procedure is painless and safe; the amount of radiation is very small — about one-tenth the amount a patient receives during a routine chest X-ray.

The test is limited by differences in testing methods and technicians. Results are also affected by curvature of the spine, calcium in the abdominal aorta and blood vessels, arthritic changes in the spine, and multiple previous fractures. The test doesn’t identify the cause of low bone density.

Bone densitometry is recommended for the following groups:

  • Women age 65 or older

  • Men age 70 or older

  • Women age 60 to 64 if they’re at increased risk — mainly low in weight, but also smokers and heavy drinkers (more than five drinks a week)

  • Men between ages 50 and 70 who haven’t had sufficient testosterone

  • Anyone older than 50 who’s had a broken bone

Treating osteoporosis

When osteoporosis is in full swing, a person will need medical help in the form of drugs. Several drugs treat osteoporosis by slowing or stopping the bone loss. They don’t affect vitamin D. The current drugs of choice are the bisphosphonate class of drugs. These drugs work by binding to calcium in bone, thereby blocking the ability of osteoclasts to break down any more bone.

The most popular bisphosphonates currently are:

  • Alendronate (Fosamax), taken once a day

  • Risedronate (Actonel), taken once a week

  • Ibandronate (Boniva), taken once a month

  • Zoledronic Acid (Reclast or Aclasta), taken intravenously once yearly

Bisphosphonates aren’t completely free of side effects. Some of the more serious ones include the following:

  • Atrial fibrillation: The atria of the heart lose their regular motion and develop rapid disorganized movement.

  • Inflammation of the stomach and erosion of the esophagus: The patient needs to be able to stand or sit upright for at least 30 minutes after taking a bisphosphonate. Because all bisphosphonates are poorly absorbed, the patient must avoid food, drink, and all medications for 30 minutes. (Some bisphosphonates can be administered intravenously, and this doesn’t happen with that route of delivery.)

  • Osteonecrosis of the jaw: In osteonecrosis, one of the jaw bones is exposed through the gums, and infection and pain occurs. This condition generally occurs after a dental extraction in patients treated with the intravenous forms (ibandronate and zoledronic acid).

  • Severe pain: The pain occurs in bones, joints, or muscles.

Physicians monitor the effect of the bisphosphonates by repeating the bone densitometry study every year or two. If the bone densitometry remains stable or improves, the patient may stop the bisphosphonates after five years. Doctors continue to monitor bone density.

Lack of estrogen has been shown to be the reason women lose bone at an accelerated pace at menopause; so, naturally, estrogen replacement had previously been the mainstay of osteoporosis therapy. It is quite effective at preventing spine and hip fractures. But estrogen also has been associated with cancer, especially breast cancer, as well as heart disease, so it’s not currently recommended as a primary treatment for osteoporosis.

About This Article

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About the book author:

Alan L. Rubin, MD has been a physician in private practice for more than 30 years. He is the author of several bestselling health titles, including Diabetes For Dummies, High Blood Pressure For Dummies, and Thyroid For Dummies.

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