Osteoporosis
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, in extreme cases, 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, with the cost of treatment estimated at $17 billion and rising, according to the National Institutes of Health (NIH). It threatens 34 million Americans, mostly older women, but older men get it too. One in 2 women and 1 in 4 men older than 50 will suffer a vertebral fracture, according to the NIH. 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. The osteoporosis seen in postmenopausal women is the most common and best-studied, but there are other causes that may be treated differently.

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 or proven preventive treatment for osteoporosis, 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. The FDA has also approved a wide variety of products to help diagnose and treat osteoporosis, including several in the last few years.

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

The skeleton is like a retirement account for minerals, but in our skeletal "account" we can deposit bone faster than we withdraw it only during our first three decades. After that, withdrawals are greater than deposits, and all we can do is try to minimize the net loss. Osteoporotic fractures are the sign of 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., a calcium expert in the FDA's Center for Food Safety and Applied Nutrition. "But even though you may be programmed for high bone mass, other factors can influence how much bone you end up with," she says. 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.

Diagnosis
Because the changes at menopause increase a woman's risk, many physicians feel it's a good time to measure a woman's bone mineral 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. The 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 an internationally accepted standard based on young Caucasian women. 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 preventive 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 in 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 FDA's Center for Devices and Radiological Health. "You always want to go back to the same machine, if you can," he says.

A newer technique for evaluating bone strength is ultrasound, and the FDA has approved several instruments for this purpose. "These machines use the same principles that are employed when using ultrasound to look at fetuses during pregnancy," says Leo Lutwak, M.D., Ph.D., of the FDA's Division of Reproductive, Abdominal, and Radiological Devices. "Although this measurement examines different properties of bone than do X-ray-based bone densitometers, the results are also useful for prediction of fracture." The devices for ultrasound measurement are cheaper and easier to use. This makes them available in more locations and allows evaluation for osteoporosis in many more subjects. "Because they don't use X-rays, they are safer and may be used for repeated examinations, even in pregnant women and children, so they provide a means for better public health practice," Lutwak says.

Another new test provides an indicator of bone breakdown. In 1995, the FDA approved 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 doesn't measure bone metabolism specifically, so it may not be used to diagnose osteoporosis.

Expanding Treatment Options
Physicians and patients now have more treatment options. 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.

An important treatment option became available to women in November 2002. Forteo (teriparatide) is the first treatment that stimulates new bone growth to increase bone mass. Forteo is a portion of human parathyroid hormone, which works in the body to regulate the metabolism of calcium and phosphate in bones. The treatment is given in daily injections and is approved for postmenopausal women who are at high risk for bone fractures.

The approval of this treatment comes with a strong caution from the FDA: In the pre-approval studies of Forteo using rats, there was an increase in the incidence of osteosarcoma, a rare but serious cancer of the bone. Because it's possible that women treated with Forteo could have increased risk for developing this cancer, doctors are advised to discuss this risk with their patients and be sure that it's the best treatment. Women who are prescribed Forteo receive an FDA-approved medication guide that explains the benefits and risks and gives other advice about how to use the treatment properly.

All other drugs approved for osteoporosis treatment act by slowing the turnover of bone, rather than stimulating new bone formation. Increases in bone mass are most pronounced in the first year or two after treatment with the drugs begins, then taper off. Any gain is helpful, even if it doesn't continue, because increases in bone mass help reduce fracture risk.

In the mid-1990s, the FDA approved the first nonhormonal treatment for osteoporosis. Alendronate, marketed as Aredia, falls within a class of drugs called bisphosphonates. In clinical trials, some bisphosphonates increased the bone mass as much as 8 percent and reduced fractures as much as 30 percent to 40 percent, depending on skeletal site.

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

Other drugs recently approved for the prevention and treatment of osteoporosis are Actonel (risedronate), a bisphosphonate similar to Aredia, and Evista (raloxifene), a drug in a class known as selective estrogen receptor modulators, or SERMs. Both drugs have been shown to reduce the risk for fracture of the spine.

Calcitonin is a hormone that plays a role in calcium and bone metabolism. When used regularly, it can slow the loss of bone. Available for many years as an injection, calcitonin treatment became much easier when FDA approved a nasal spray.

Fluoride, known for fighting dental cavities, stimulates bone building, but studies in osteoporosis patients have found that the structure of the new bone was abnormal and weaker than normal bone.

While estrogen may be a good option for some women, new guidelines developed in 2003 by the FDA advise doctors to consider alternative treatments. These changes were prompted by studies indicating that women who take estrogen or estrogen with progestin products after menopause are at higher risk for other conditions, including cardiovascular disease and breast cancer. Because of this, estrogen-containing products should only be considered for women at significant risk of osteoporosis.

Drugs Not Enough
Calcium and vitamin D supplements are an integral part of all treatments for osteoporosis. At the same time, people who take supplements should keep in mind that it is possible to consume excess amounts of these and other nutrients. Attention to diet and exercise are important not only for treatment, but also for prevention.