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October 2000
Vol. 3, No. 8, p. 96.

Diseases and disorders
By Mark S. Lesney

An epidemic of osteoporosis?

photo of elderly lady in rehab

As with many other diseases of aging, osteoporosis continues to be considered simply a natural byproduct of women getting old. It is not. It is a clinical condition of the skeletal system that most commonly affects postmenopausal women. It is caused by improper calcium metabolism, primarily the shift in balance from bone building to bone resorption. The disease is eminently preventable through diet, vitamin and mineral supplements, and appropriate exercise regimens begun early in life (excluding certain conditions in which it is an ancillary symptom); later in life, in some cases, the disease can be prevented by estrogen replacement therapy. For those people who are already victims, current treatments remain palliative, not curative. But there is some hope on the horizon for hormonal therapies that stimulate bone creation rather than merely inhibit its loss (see box, “Promising parathyroids?”).

Generations at risk
Although an estimated 28 million Americans are currently at risk for osteoporosis, predictions for the future are much gloomier. Some scientists estimate that half of all women and 20% of men older than 50 will suffer an osteoporosis-related frature in their lifetime. Changed and changing nutritional patterns in American women over the past half century, including the propensity for weight-loss diets, have created an epidemic waiting to happen. Leon Speroff, of the Oregon Health Science Center in Portland, reported at the 1999 American College of Obstetricians and Gynecologists meeting that the estimated number of hip fractures will increase sixfold between 1999 and 2050. Women today have lower bone density than women did 200 years ago:
Promising parathyroids?
The First World Congress on Osteoporosis was held in Chicago in June. Some of the most promising future therapies were diagram of parathyroid glandspresented. In particular, researchers at Helen Hayes Hospital in West Haversham, NY, showed that parathyroid hormone (PTH), in conjunction with estrogen replacement therapy, increased the activity of osteoblasts, the cells that form bones. This is significant because existing medications only decrease the activity of osteoclasts, the cells that break down bones, relying on an improved balance of breakdown versus synthesis for their effect. In contrast, PTH promotes new synthesis. Women in combined PTH-estrogen therapy showed a 12.8% increase in spinal bone mass and a 4.4% increase in total hip mass. Another study presented at the World Congress showed that PTH could increase bone size as well as density.
The change is attributed to smoking, a sedentary lifestyle, fewer pregnancies, and reduced calcium intake. Sufficient dietary calcium is required to create healthy bone mass early in life to offset potential losses. Supplements are often required to maintain the daily 1200–1500 mg recommended for teenagers and the elderly and the daily 1000 mg recommended for children and adults. Fewer than 5% of Americans are estimated to meet these targets. Properly gauging actual calcium intake can be confusing because different foods and supplements vary widely in calcium bioavailability. Vitamin D is also critical to achieve optimal calcium absorption. Surprisingly, despite NIH recommendations and the fact that any drug therapy for osteoporosis also requires sufficient calcium and Vitamin D to be fully effective, nearly 30% of women taking the top three prescription osteoporosis medications do not use supplements.

Spinal shrinkage—the “dowager’s hump” of public perception—is not the real problem in osteoporosis. Fractures caused by low bone density are. According to Stephen Katz, the director of the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the major fracture sites associated with osteoporosis are the hip, spine, and wrist. Hip fractures pose the greatest threat (10–20% mortality within six months). In severe cases, the act of bending down to pick up a newspaper is sufficient to cause a spinal fracture.

Sources: National Osteoporosis Foundation (www.nof.org); National Institute of Arthritis and Musculoskeletal and Skin Diseases (www.nih.gov/niams)

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