by Deborah Stewart, Accordant Medical Correspondent Osteoporosis affects over 25 million Americans and causes more than 1.5 million fractures each year. Rheumatoid arthritis patients have an increased risk for osteoporosis.

Osteoporosis is a word meaning "porous bones". Osteoporosis is a painless disease of the skeleton in which bones are slowly depleted of calcium and bone protein, resulting in the loss of bone mass. Over time the bones become increasingly thin, fragile and likely to break.

The bones are the body's repositories for calcium. About 99% of the body's calcium is held in the bones, which release the remaining 1% to circulate in the blood. Bone tissue is constantly being dissolved and replenished in order to provide the body with a supply of calcium, to repair damage caused by stress and to accomplish growth. Cells called osteoclasts break down the bone by digging little holes into it; cells called osteoblasts build it back up by filling the holes first with collagen, and then with crystals of calcium. Normally, 10-30% of the entire skeleton is remodeled over the course of a year though the coordinated processes of resorption and rebuilding.

Osteoporosis occurs when resorption and rebuilding get out of balance. The causes for imbalance are not entirely clear, but may relate to hormone levels, insufficient vitamin D, medications, and/or blood factors. When more bone is removed than is replenished, the eventual result for many people is a loss of bone density, or osteoporosis.

Studies show that rheumatoid arthritis patients have lower bone mass than other people do. RA seems to interfere with the balance of the processes involved with bone remodeling, resulting over time in the loss of bone.

The medications used to treat RA also greatly increase the risk for osteoporosis. Corticosteroids like prednisone inhibit calcium absorption in the intestines and promote calcium loss from the kidneys. Drugs that suppress the immune system, like methotrexate and cyclosporine, are also known to promote bone loss.

The risk of osteoporosis for any person depends upon the density of his or her bones. Men generally have stronger, denser bones than women and are therefore less likely to get osteoporosis. Only 20 percent of osteoporosis patients--2 million -- are men.

Men who get osteoporosis often have either a chronic problem with alcohol or a medical condition that interferes with the production of the hormone, testosterone.

Similarly, the lack of female hormones is related to the development of osteoporosis in women. In the United States, 8 million women have osteoporosis, and it is especially prevalent among women who have gone through menopause. Those who experienced early menopause or have had their ovaries surgically removed are at greater risk for osteoporosis. Women with anorexia and women who have never had a baby also have an increased risk for osteoporosis. Research has discovered that oral contraceptives do not protect women from osteoporosis, even though they contain hormones.

Yes, other factors that increase the risk of osteoporosis include:

Smoking

Advanced age

Eating disorders

A lack of calcium in the diet

Family history of osteoporosis

Asian or Caucasian ancestry

Excessive use of alcohol

Sedentary lifestyle

Lower than normal body weight

Amenorrhea (the absence of normal menstrual periods)

Long-term, excessive use of thyroid or anticonvulsant drugs

There are no symptoms of bone loss. Often patients only become aware of their osteoporosis after sustaining a fracture. People with RA or other risk factors may want to consider being tested for osteoporosis as a proactive measure. Osteoporosis is detected through bone density tests. The most accurate test is the dual-energy x-ray absorptionmetry (DEXA). This is a 2-4 minute test that measures how well bones absorb photons from x-rays. Other tests for bone density include single-energy x-ray absorptionmetry, ultrasound, or, in some cases, even dental x-rays.

Since osteoporosis is due to the primary disease of rheumatoid arthritis, controlling the RA with disease modifying drugs is the first and most important step. If the drugs selected for treatment can themselves contribute to bone loss, appropriate amounts of calcium and vitamin D will be prescribed. In addition, the best preventative measures, which involve lifestyle modifications, should be adapted. Experts recommend:

Regular exercise. Exercise must be weight bearing, meaning that it applies tension to muscle and bone and that muscles work against gravity. Examples: walking, tennis, weight lifting. The body responds to weight-bearing exercise by increasing bone density. Exercise can increase bone density by as much as 2% to 8% a year!

Sunshine. To be of benefit, calcium must be absorbed. Vitamin D must be present for calcium absorption to occur in the stomach and intestines. Vitamin D is made in the skin using the energy produced by the sun's ultraviolet rays. Many people avoid exposure to sunshine because they are concerned about skin cancer. But just 10 minutes of daily exposure is adequate to promote vitamin D production.

Healthy diet. Maintain a well-balanced diet, rich in calcium and vitamin D, and supplement it with 1,000 milligrams of daily calcium (1500 milligrams if over age 50). If exposure to sunshine is inadequate, a daily supplement of 400-800 IU of vitamin D is also advisable.

Don't smoke. Smoking increases the risk of bone fractures. Men who smoke have less bone density than male non-smokers, and their risk for fractures is five times greater. Smoking doubles a woman's risk for fractures.

Treatments for osteoporosis are aimed at stopping bone loss and building bone mass, with the ultimate goal of preventing fractures. Many of the measures that prevent osteoporosis (above) can also be used to treat it. Once osteoporosis has been diagnosed, however, a physician should evaluate any exercise program for safety. In addition to the suggestions above, treatment for osteoporosis may include:

Hormone replacement therapy (HRT) for women past menopause. HRT can help decrease bone loss and increase bone density. Studies show that the best results are obtained by replacing both female hormones, estrogen and progesterone, in a continuous low dose, along with supplemental calcium and vitamin D.

Anti-resorptive medications. These interfere with the tearing-down part of the bone remodeling process. This tips the balance toward bone building. Alendronate (Fosamax¿) and risedronate (Actonel®) are two anti-resorptive drugs.

SERM. Selective estrogen receptor modulators (SERM) provide benefits similar to hormone replacement therapy, but with no increased risks. SERM drugs inhibit bone loss and increase bone density. Raloxifene (Evista®) and Tamoxifen are SERM medications.

References

First published September 1, 1999
Last updated February 6, 2003
Copyright © 1999 Accordant Health Services, Inc. All Rights Reserved.

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