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Boning Up on Osteoporosis

Boning Up on Osteoporosis

by Carolyn J. Strange

Consider an insidious condition that drains away bone--the hardest, most durable substance in the body. It happens slowly, over years, so that often neither doctor nor patient is aware of weakening bones until one snaps unexpectedly. Unfortunately, this isn't science fiction. It's why osteoporosis is called the silent thief.

And it steals more than bone. It's the primary cause of hip fracture, which can lead to permanent disability, loss of independence, and sometimes even death. Collapsing spinal vertebrae can produce stooped posture and a "dowager's hump." Lives collapse too. The chronic pain and anxiety that accompany a frail frame make people curtail meaningful activities because the simplest things can cause broken bones: Stepping off a curb. A sneeze. Bending to pick up something. A hug. "Don't touch Mom, she might break" is the sad joke in many families.

Osteoporosis leads to 1.5 million fractures, or breaks, per year, mostly in the hip, spine and wrist, and costs $10 billion annually, according to the National Osteoporosis Foundation. It threatens 25 million Americans, mostly older women, but older men get it too. One in three women past 50 will suffer a vertebral fracture, according to the foundation. These numbers are predicted to rise as the population ages.

Osteoporosis, which means "porous bones," is a condition of excessive skeletal fragility resulting in bones that break easily. A combination of genetic, dietary, hormonal, age-related, and lifestyle factors all contribute to this condition.

Changing attitudes and improving technology are brightening the outlook for people with osteoporosis. Nowadays, many women live 30 years or more--perhaps a quarter to a third of their lives--after menopause. Improving the quality of those years has become an important health-care goal. Although some bone loss is expected as people age, osteoporosis is no longer viewed as an inevitable consequence of aging. Diagnosis and treatment need no longer wait until bones break.

There is no cure for osteoporosis, and it can't be prevented outright, but the onset can be delayed, and the severity diminished. Most important, early intervention can prevent devastating fractures. The Food and Drug Administration has revised labeling on foods and supplements to provide valuable information about the level of nutrients that help build and maintain strong bones. FDA has also approved a wide variety of products to help diagnose and treat osteoporosis, including several in the last few years.

Bone Life

Bone consists of a matrix of fibers of the tough protein collagen, hardened with calcium, phosphorus and other minerals. Two types of architecture give bones strength. Surrounding every bone is a tough, dense rind of cortical bone. Inside is spongy-looking trabecular bone. Its interconnecting structure provides much of the strength of healthy bone, but is especially vulnerable to osteoporosis.

"We tend to think of the skeleton as an inert erector set that holds us up and doesn't do much else. That's not true," says Karl. L. Insogna, M.D., director of the Bone Center at Yale School of Medicine, New Haven, Conn. Every bit as dynamic as other tissues, bone responds to the pull of muscles and gravity, repairs itself, and constantly renews itself.

Besides protecting internal organs and allowing us to move about, bone is also involved in the body's handling of minerals. Of the 2 to 4 pounds of calcium in the body, nearly 99 percent is in the teeth and skeleton. The remainder plays a critical role in blood clotting, nerve transmission, muscle contraction (including heartbeat), and other functions. The body keeps the blood level of calcium within a narrow range. When needed, bones release calcium.

A complex interplay of many hormones balances the activity of the two types of cells--osteoclasts and osteoblasts--responsible for the continuous turnover process called remodeling. Osteoclasts break down bone, and osteoblasts build it. In youth, bone building prevails. Bone mass peaks by about age 30, then bone breakdown outpaces formation, and density declines.

The skeleton is like a retirement account, but in our skeletal "account" we can deposit bone only during our first three decades. After that, all we can do is try to postpone and minimize the steady withdrawals. Osteoporosis is the bankruptcy that occurs when too little bone is formed during youth, or too much is lost later, or both.

"You've got to get as much bone as you can and not lose it," Insogna says. "The most important risk factor for osteoporosis is a low bone mass."

"The upper limit of bone mass that you can acquire is genetically determined," says Mona S. Calvo, Ph.D., in FDA's Office of Special Nutritionals. "But even though you may be programmed for high bone mass, other factors can influence how much bone you end up with," she says. (See"Reducing Your Risk.") For instance, men tend to build greater bone mass, which is partly why more women face osteoporosis.

But there's another reason. With the decline of the female hormone estrogen at menopause, usually around age 50, bone breakdown markedly increases. For several years, women lose bone two to four times faster than they did before menopause. The rate usually slows down again, but some women may continue to lose bone rapidly. By age 65, some women have lost half their skeletal mass. Because the changes at menopause increase a woman's risk, many physicians feel it's a good time to measure a woman's bone density, especially if she has other risk factors for osteoporosis.

"The best way to gauge a woman's risk for osteoporotic fracture is to measure her bone mass," says Insogna.

Routine x-rays can't detect osteoporosis until it's quite advanced, but other radiological methods can. FDA has approved several kinds of devices that use various methods to estimate bone density. Most require far less radiation than a chest x-ray. Doctors consider a patient's medical history and risk factors in deciding who should have a bone density test. The method used is often determined by the equipment available locally. Readings are compared to a standard for the patient's age, sex and body size. Different parts of the skeleton may be measured, and low density at any site is worrisome.

Bone density tests are useful for confirming a diagnosis of osteoporosis if a person has already had a suspicious fracture, or for detecting low bone density so that preventative steps can be taken.

"There's a profound relationship between bone mass and risk of fracture," says Robert Recker, M.D., director of the Osteoporosis Research Center at Creighton University, Omaha, Neb.

Readings repeated at intervals of a year or more can determine the rate of bone loss and help monitor treatment effectiveness. However, estimates are not necessarily comparable between machine types because they use different measurement methods, cautions Joseph Arnaudo, in the Center for Devices and Radiological Health. "You always want to go back to the same machine, if you can," he says.

Another new test provides an indicator of bone breakdown. FDA approved in 1995 a simple, noninvasive biochemical test that detects in a urine sample a specific component of bone breakdown, called NTx. Clinical labs can get results in about 2 hours. The NTx test, marketed as Osteomark, can help physicians monitor treatment and identify fast losers of bone for more aggressive treatment, but the test may not be used to diagnose osteoporosis.

Expanding Treatment Options

Physicians and patients now have more treatment options than ever. Under FDA guidelines, drugs to treat osteoporosis must be shown to preserve or increase bone mass and maintain bone quality in order to reduce the risk of fractures. "We want to be sure that the bone is normal or stronger than it was," says Gloria Troendle, M.D., deputy director of the division of metabolism and endocrine drug products in FDA's Center for Drug Evaluation and Research.

Before 1995, the only choices were the hormones estrogen and calcitonin. While enthusiasm for new weapons against osteoporosis is warranted, one of the old ones is still the top choice.

"Estrogen remains the first thing that women should consider," says Insogna, because the hormone not only helps prevent osteoporosis, but also protects against heart disease.

"If you think about what's missing at menopause, it's the hormones," says Paula Stern, Ph.D., a pharmacologist at Northwestern University Medical School, Chicago, Ill.

Estrogen replacement therapy is the best prevention for the drop in bone mass at menopause, and there are more ways to take it than ever. But it's not for everyone. Because estrogen increases the risk of certain cancers and other diseases, taking it may not be appropriate, or it may be given in combination with another female hormone, progesterone, which can also cause undesirable side effects. A woman and her doctor need to carefully weigh the risks and benefits. According to the National Osteoporosis Foundation, a woman's risk of developing a hip fracture is equal to her combined risk of developing breast, uterine and ovarian cancer.

Women who can't or don't want to take hormones--some 30 to 50 percent--have other treatment avenues. For example, calcitonin treatment became much easier when FDA approved a nasal spray in the summar of 1996. Calcitonin, one of the hormones responsible for regulating the level of calcium in the blood, inhibits osteoclasts, the bone dissolvers. The drug, marketed as Miacalcin, is a potent, synthetic version of the hormone, and has been shown to slow and reverse bone loss. The stomach quickly destroys the drug, so before the spray was available, calcitonin had to be injected every day or two.

Later in 1996, FDA approved the first nonhormonal treatment for osteoporosis. Alendronate, marketed as Fosamax, falls within a class of drugs called bisphosphonates, which hinder bone breakdown remodeling sites by inhibiting osteoclast activity. In clinical trials lasting three years, alendronate increased the bone mass as much as 8 percent and reduced fractures as much as 30 to 40 percent, depending on skeletal site. Lengthier studies are ongoing.

To avoid damage to the esophagus, Fosamax should be taken according to instructions. These instructions include taking the drug in the morning upon awaking and at least a half hour before eating. The drug should be taken with 6 to 8 ounces of water, and the person should remain upright for a half hour after taking it. Fosamax should not be taken by people who cannot stand or sit upright or who have disorders that prevent esophageal emptying into the stomach.

"All the drugs approved so far are things that just stop bone turnover. They're not really stimulating more bone production," says Troendle.

Bone mass increases because even though osteoclasts can't start new remodeling sites, osteoblasts continue filling in existing cavities. Increases in bone mass are most pronounced in the first year or two after treatment begins, then taper off. Any gain is helpful, even if it doesn't continue, because increases in bone mass help reduce fracture risk. But experts would like to encourage even greater gains.

Fluoride, known for fighting dental cavities, stimulates bone building, but early studies in osteoporosis patients found that the structure of the new bone was abnormal and weaker than normal bone. Gastrointestinal side effects were also a problem. Investigators are working to find a formulation and dosage regimen that will result in building normal bone.

Drugs Not Enough

Calcium and vitamin D supplements are an integral part of all treatments for osteoporosis. Everyone should make sure they get enough of these two nutrients, but especially women and others at risk for osteoporosis. Attention to diet and exercise are important not only for treatment, but also for prevention.

"If you go to the doctor and get a prescription, and that's all you do, you're probably not going to be helped very much," Recker says.

Calcium intake is critical, and those who need it the most--younger women and girls--don't get enough. (See"Calcium (Ac)Counts.") But calcium alone can't build bone. Without vitamin D, calcium isn't sufficiently absorbed. Most people get enough vitamin D because skin produces it in sunlight. But people confined indoors who have a poor diet--which includes many older Americans--or who live in northern latitudes in winter may be deficient.

A lifelong habit of weightbearing exercise, such as walking or biking, also helps build and maintain strong bone. The greatest benefit for older people is that physical fitness reduces the risk of fracture, because better balance, muscle strength, and agility make falls less likely. Exercise also provides many other life-enhancing psychological and cardiovascular benefits. Increased activity can aid nutrition, too, because it boosts appetite, which is often reduced in older people. The biggest reason older people don't get enough calcium, Recker says, is that they simply don't eat much.

"The truth is, you don't have to do very much to get most of the benefits of exercise," Recker says. He suggests 30 minutes of brisk walking five days a week. Add a little weightlifting, and that's even better. It's always smart to ask your doctor before starting a new exercise program, especially if you already have osteoporosis or other health problems.

Brighter Horizons

"A number of new things seem to be in the offing, eventually to come to us, and we're looking forward to getting some additional treatments for osteoporosis," says Troendle.

Uses of existing drugs may be broadened. Early drug trials are often conducted with patients who have severe disease, often after a fracture has occurred or bone loss is quite serious. Some studies under way are testing to see if certain drugs are effective in less severe cases, if they can be started sooner, or used in combination.

The search for bone-building drugs continues. Some naturally occurring bone-specific growth factors have been identified and their use as drugs is being investigated. "The way I visualize the ideal future is that we'll be able to give Drug X that builds up bone to where it's stronger and the risk of fracture is no longer present, then Drug Y maintains it by preventing breakdown," says Stern.

In the realm of devices, researchers are exploring the use of ultrasound to assess bone health. Such tests would eliminate radiation exposure and probably cost less. The study of risk factors also continues. "We consider that to be the research that has the greatest public health significance," says Sherry Sherman, Ph.D., of the National Institute on Aging. The institute has begun the Study of Women's Health Across the Nation, a large-scale national examination of the health of women in their 40s and 50s. Researchers expect to learn a great deal about the factors affecting women's health during these transitional years and beyond. Studies of genetics, biochemical markers, and life habits are already turning up new insights.

Osteoporosis has been described as an adolescent disease with a geriatric onset, highlighting the importance of beginning to take steps--in exercise and diet--early in life to reduce its disabling impact in later years.

Carolyn J. Strange is a science and medical writer living in Northern California.

Reducing Your Risk

A host of factors can affect your chances of developing osteoporosis. The good news is that you control some of them. Even though you can't change your genes, you can still lower your risk with attention to certain lifestyle changes. The younger you start, and the longer you keep it up, the better. Here's what you can do for yourself:

  • Be sure you get enough calcium and vitamin D.
  • Engage in regular physical activity, such as walking.
  • Don't smoke.
  • If you drink alcohol, do so in moderation.

A sedentary lifestyle, smoking, excessive drinking, and low calcium intake all increase risk. Although coffee has been suspected as a risk factor, studies so far are inconclusive.

Other factors are beyond your control. Being aware of them can provide extra motivation to help yourself in the ways you are able, and aids you and your doctor in health-care decisions. These risk factors are:

  • being female: Women have a five times greater risk than men.
  • thin, small-boned frame
  • broken bones or stooped posture in older family members, especially women, which suggest a family history of osteoporosis
  • early estrogen deficiency in women who experience menopause before age 45, either naturally or resulting from surgical removal of the ovaries
  • estrogen deficiency due to abnormal absence of menstruation (as may accompany eating disorders)
  • ethnic heritage: White and Asian women are at highest risk; African-American and Hispanic women are at lower, but significant, risk.
  • advanced age
  • prolonged use of some medications, such as excessive thyroid hormone; some antiseizure medications; and glucocorticoids (certain anti-inflammatory medications, such as prednisone, used to treat conditions such as asthma, arthritis and some cancers).

Risk factors may not tell the whole story. You may have none of these factors and still have osteoporosis. Or you may have many of them and not develop the condition. It's best to discuss your specific situation with your doctor.

Calcium (Ac)Counts

Your skeletal calcium bank has to last through old age. Frequent deposits to this retirement account should begin in youth and be maintained throughout life to help minimize withdrawals. Most women get much less calcium than they need--as little as half.

Nutritionists recommend meeting your calcium needs with foods naturally rich in calcium. Adequate calcium intake in childhood and young adulthood is critical to achieving peak adult bone mass, yet many adolescent girls replace milk with nutrient-poor beverages like soda pop. "Bone health requires a lot of nutrients and you're likely to get most of them in dairy products," says Connie Weaver, Ph.D., who heads the department of food and nutrition at Purdue University, Indiana. "They're a huge package rather than just a single nutrient." With so many low-fat and nonfat dairy products available, it's easy to make dairy foods part of a healthy diet. People who have trouble digesting milk can look for products treated to reduce lactose. A serving of milk or yogurt contains about 350 milligrams (mg) of calcium. Fortified products have even more.

"People who don't consume dairy foods can meet their calcium needs with foods that are fortified with calcium, such as orange juice, or with calcium supplements," says Mona S. Calvo, Ph.D., in FDA's Office of Special Nutritionals. Other good sources of calcium are broccoli and dark-green leafy vegetables like kale, tofu (if made with calcium), canned fish (eaten with bones), and fortified bread and cereal products.

Nutrition labels can help you identify calcium-rich foods. But keep in mind that the label value is a guideline based on a FDA's Daily Value for calcium, which is 1,000 mg, and your calcium needs may be greater, Calvo says.

What about too much calcium? As much as 2,000 mg per day seems to be safe for most people, but those at risk for kidney stones should discuss calcium with their doctors. Calcium is critical, but even a high intake won't fully protect you against bone loss caused by estrogen deficiency, physical inactivity, alcohol abuse, smoking, or medical disorders and treatments.

--C.J.S.

To Learn More

For more information, contact:

  • National Osteoporosis Foundation, 1150 17th St., N.W., Suite 500, Washington, DC 20036; (202) 223-2226; World Wide Web:http://www.nof.org/. For locations of your nearest bone density testing sites, call (800) 464-6700.
  • Osteoporosis and Related Bone Diseases National Resource Center (ORBD-NRC); (800) 624-BONE; TDD: (202) 223-0344.
  • Older Women's League (OWL), 666 11th St., N.W., Suite 700, Washington, DC 20001; (202) 783-6686.
  • North American Menopause Society, c/o University Hospitals of Cleveland, Department of Obstetrics and Gynecology, 11100 Euclid Ave., Suite 7024, Cleveland, OH 44106; (216) 844-8748; World Wide Web:http://www.menopause.org/.

This article originally appeared in the September 1996 FDA Consumer.
The version below is from a reprint of the original article and contains revisions made in August 1997.