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Hard evidence for bone-building therapy.

Hard evidence for bone-building therapy

Earlier this year, a nonhormonal treatment for osteoporosis succeeded in fortifying spinal bone and reducing spinal fractures in a small group of post-menopausal women (SN: 5/26/90, p.334). Now, a much larger study strengthens the notion that brittle bones could have a solid future under this new treatment.

The experimental therapy features oral doses of etidronate, a drug that suppresses bone-eating cells called osteoclasts. Healthy bone maintenance involves a somewhat evenly matched contest between these osteoclasts and bone-forming cells called osteoblasts. With age, however, and particularly in postmenopausal women, the balance often shifts to favor osteoclasts, resulting in the porous, brittle bone that typifies osteoporosis.

A team led by endocrinologist Nelson Watts of the Emory University School of

Medicine in Atlanta studied 429 postmenopausal, osteoporotic women at seven medical centers across the United States. To prevent the crucial osteoblasts from getting lazy as their rival cells succumbed to drug treatment, Watts and colleagues simulated an osteoclast depress-and-release cycle throughout the two-year experiment. About half of the volunteers alternated between two-week periods of daily etidronate treatment and 10-week periods of osteoclast "release," in which treatment consisted only of dietary calcium supplements. The remaining patients followed the same schedule but received a placebo instead of etidronate.

Etidronate-treated women gained a significant 4 to 5 percent in spinal bone density after two years of treatment, Watts and his colleagues report in the July 12 NEW ENGLAND JOURNAL OF MEDICINE. And compared with the placebo group, these patients suffered less than half as many vertebral fractures over the course of the study. These results demonstrate the treatment's anti-fracture benefits more convincingly than the earlier, smaller study conducted by Danish and U.S. scientists, Watts says.

Today, people with advanced osteoporosis typically receive estrogen or calcitonin, the only two osteoporosis drugs currently approved by the FDA. Both of these hormonal drugs suppress osteoclasts but have serious drawbacks: Calcitonin requires injection and is very expensive, Watts says, while estrogen treatment may increase the risk of breast cancer.

Bone specialist B. Lawrence Riggs of the Mayo Clinic in Rochester, N.Y., says Watts' study is particularly encouraging because patients reported few side effects and apparently gained quality, fracture-resistant bone. Fluoride, also used experimentally to combat osteoporosis, did not fare as well in a study reported by Riggs and his colleagues in the May 22 NEW ENGLAND JOURNAL OF MEDICINE. Fluoride more often caused side effects, he notes, and did not reduce the rate of spinal fracture. "The bone formed was not of normal strength. In the peripheral skeleton, there was actually an increase in fractures," Riggs says.

Noting that the benefits of estrogen and calcitonin plateau after one or two years, Riggs says researchers need to determine how long patients can maintain the increased bone mass under intermittent etidronate therapy. Toward that end, Watts plans to follow his etidronate patients to see whether the treatment's bone-building properties will persist in the long run.
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Title Annotation:etidronate therapy for osteoporosis
Author:Stolzenburg, William
Publication:Science News
Date:Jul 14, 1990
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