Is there hope for osteoporosis?

By LAURA BEILTHE DALLAS MORNING NEWS

DALLAS--Bones often get compared to banks. People who don't build up a healthy savings of bone density when they're young, so the analogy goes, may find themselves in debt come retirement.

Researchers are working on drugs that can offer last-minute deposits. In 2002, physicians welcomed the first new osteoporosis drug in five years, and tests of more are in the pipeline. Meanwhile, manufacturers are making existing drugs easier to take, and researchers are making discoveries in bone metabolism that may lead to more choices.

Still, challenges remain. Hormone-replacement therapy was once popular but lost favor with the discovery that it may increase the risk of heart attacks and cancer. Research published in July in the New England Journal of Medicine found mixed results for Evista, which has been a bone-strengthening alternative to hormone therapy. While use of the drug for five years reduced the risk of fractures and breast cancer by about one woman per thousand, it also increased the odds of blood clots and strokes.

Nothing offers a cure.

"We have a few good choices, but we certainly need better in several areas," says Dr. Gordon Strewler, an osteoporosis expert from Beth Israel Deaconess Medical Center in Boston.

The need is expected to increase as the population ages. Federal health authorities estimate some 10 million Americans already have bones brittle to the point of full-fledged osteoporosis, and another 34 million may be on the brink of developing the condition. Women run a greater risk than men; thin people a greater risk than heavier people.

Basically, though, osteoporosis is a disease of aging. About a third of women older than 80 will suffer a broken hip. As many as 20 percent will die from the complications.

Bones may seem solid as rocks, but they are more like rigid pipes with honeycombs inside. Their airy internal latticework constantly resculpts itself, drawing on calcium, vitamin D and exercise. Some cells remove bone from the matrix while others replace what's lost. Osteoporosis occurs when the cells on teardown duty outperform cells doing construction.

"People think of bone as kind of a dead tissue, but it's actually very alive tissue," says Dr. Dennis Black of the University of California, San Francisco.

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Bone density: The ratio of bone mass to volume, indicating bone compactness. Bone density increases rapidly through adolescence, more slowly until age 35 and then plateaus and declines. Bone density is measured most frequently in the spine, hip, wrist, forearm or heel for the detection and diagnosis of osteoporosis.

Bone mass: The amount of mineral in a bone. Although this is different from bone density, the terms often are used interchangeably.

Bone mineral density (BMD): The quantity calculated by dividing the measured bone mineral content by the measured bone area in a densitometry study. The bone mineral density carries units of gram per square centimeter and is most often compared to reference population values.

DXA: Dual X-ray absorptiometry. A type of bone-density testing that uses X-rays to measure the bone density.

Osteopenia: This term refers to a decrease in bone density that, although too low to be called normal, is not low enough to be considered osteoporotic.

Osteoporosis: A skeletal disorder characterized by compromised bone strength, creating an increased risk of fracture. Bone strength reflects the integration of two main features: bone density and bone quality.

Peak bone mass: A concept that bone mass has a maximal level given optimal conditions. Peak bone mass is believed to be controlled by genetic factors (age, sex and body size) and significantly affected by environmental factors (nutrition, exercise and general health). The concept of peak bone mass is important to the study of bone disease in this way: Those who achieve maximal (peak) bone mass may reduce the risk of serious bone loss.

--Children's Hospital Boston

Date published: 8/6/2006

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