Definition
The word osteoporosis literally means "porous bones." It occurs when bones lose an excessive amount of their protein and mineral content, particularly calcium. Over time, bone mass, and therefore bone strength, is decreased. As a result, bones become fragile and break easily. Even a sneeze or a sudden movement may be enough to break a bone in someone with severe osteoporosis.
Description
Osteoporosis is a serious public health problem. Some 28 million people in the United States are affected by this potentially debilitating disease, which is responsible for 1.5 million fractures (broken bones) annually. These fractures, which are often the first sign of the disease, can affect any bone, but the most common locations are the hip, spine, and wrist. Breaks in the hip and spine are of special concern because they almost always require hospitalization and major surgery, and may lead to other serious consequences, including permanent disability and even death.
To understand osteoporosis, it is helpful to understand the basics of bone formation. Bone is living tissue that is constantly being renewed in a two-stage process (resorption and formation) that occurs throughout life. In the resorption stage, old bone is broken down and removed by cells called osteoclasts. In the formation stage, cells called osteoblasts build new bone to replace the old. During childhood and early adulthood, more bone is produced than removed, reaching its maximum mass and strength by the mid-30s. After that, bone is lost at a faster pace than it is formed, so the amount of bone in the skeleton begins to slowly decline. Most cases of osteoporosis occur as an acceleration of this normal aging process—a form referred to as primary osteoporosis. The condition can also be caused by other disease processes or prolonged use of certain medications that result in bone loss—a form called secondary osteoporosis.
Osteoporosis occurs most often in older people and in women after menopause. It affects nearly half of all men and women over the age of 75. Women, however, are five times more likely than men to develop the disease. They have smaller, thinner bones than men to begin with, and they lose bone mass more rapidly after menopause (usually around age 50), when they stop producing a bone-protecting hormone called estrogen. In the five to seven years following menopause, women can lose about 20% of their bone mass. By age 65 or 70, though, men and women lose bone mass at the same rate. As an increasing number of men reach an older age, they are becoming more aware that osteoporosis is an important health issue for them as well.
Causes and symptoms
A number of factors increase the risk of developing osteoporosis. They include:
* Age. Osteoporosis is more likely as people grow older and their bones lose tissue.
* Gender. Women are more likely to have osteoporosis because they are smaller and so start out with less bone. They also lose bone tissue more rapidly as they age. While women commonly lose 30–50% of their bone mass over their lifetimes, men lose only 20–33% of theirs.
* Race. Caucasian and Asian women are at higher risk for the disease than women of African or Hispanic ethnicities.
* Figure type. Women with small bones and those who are thin are more liable to have osteoporosis.
* Early menopause. Women who stop menstruating early because of heredity, surgery or a lot of physical exercise may lose large amounts of bone tissue early in life. Conditions such as anorexia and bulimia may also lead to early menopause and osteoporosis.
* Lifestyle. People who smoke or drink too much, or do not get enough exercise have an increased chance of getting osteoporosis.
* Diet. Those who do not get enough calcium or protein may be more likely to have osteoporosis. People who constantly diet are more prone to the disease. It has been shown that adolescent girls (but not boys) have insufficient calcium intake levels in the diet. This calcium deficiency occurs during a period of rapid bone growth, stunting the peak bone mass ultimately achieved; thus, these individuals are at greater risk of developing osteoporosis.
* Genetics. People with a family history of osteoporosis are more likely to contract the disease.
* Chronic use of medication. Certain types of medication, such as steroids, interfere with the body's ability to absorb calcium or accelerate calcium depletion, damaging bone density.
Osteoporosis is often called the "silent" disease, because bone loss occurs without symptoms. People often do not know they have the disease until a bone breaks, frequently in a minor fall that would not normally cause a fracture. A common occurrence is compression fractures of the spine. These can happen even after a seemingly normal activity, such as bending or twisting to pick up a light object. The fractures can cause severe back pain, but sometimes they go unnoticed—either way, the vertebrae collapse down on themselves, and the person actually loses height. The hunchback appearance of many elderly women, sometimes called "dowager's hump" or "widow's hump," is due to this effect of osteoporosis on the vertebrae.
Diagnosis
Certain types of doctors may have more training and experience than others in diagnosing and treating people with osteoporosis. These include geriatricians, who specialize in treating the aged; endocrinologists, who specialize in treating diseases of the body's endocrine system (glands and hormones); and orthopedic surgeons, who treat fractures, such as those caused by osteoporosis.
Before making a diagnosis of osteoporosis, the doctor usually takes a complete medical history, conducts a physical exam, and orders x-rays, as well as blood and urine tests, to rule out other diseases that cause loss of bone mass. The doctor may also recommend a bone density test. This is the only way to determine if osteoporosis is present. It can also show how far the disease has progressed.
Several diagnostic tools are available to measure the density of a bone. The most accurate and advanced of the densitometers uses a technique called DEXA (dual energy x-ray absorptiometry). With the DEXA scan, a double x-ray beam takes pictures of the spine, hip, or entire body. It takes about 20 minutes to do, is painless, and exposes the patient to only a small amount of radiation—about one-fiftieth that of a chest x ray. The ordinary x ray is one, though it is the least accurate for early detection of osteoporosis, because it does not reveal bone loss until the disease is advanced and most of the damage has already been done. Other tools that are more likely to catch osteoporosis at an early stage are computed tomography scans (CT scans) and machines called densitometers, which are designed specifically to measure bone density. The CT scan, which takes a large number of x rays of the same spot from different angles, is an accurate test, but uses higher levels of radiation than other methods.
People should talk to their doctors about their risk factors for osteoporosis and if, and when, they should get the test. A woman should have bone density measured at menopause, and periodically afterward, depending on the condition of their bones. Men should be tested around age 65. Men and women with additional risk factors, such as those who take certain medications, may need to be tested earlier.
Treatment
There are a number of good treatments for primary osteoporosis, most of them medications. In addition, calcium (0.5 to 2 g/day) and vitamin D (400 to 800 IU/day) supplementation can reduce the rate of bone loss in women who are more than five years postmenopausal. Fracture reduction efficacy of calcium and vitamin D supplementation, administered independently, has been demonstrated in women older than 75 years of age.
For people with secondary osteoporosis, treatment may focus on curing the underlying disease.
Drugs
For most women who have gone through menopause, the best treatment for osteoporosis is hormone replacement therapy (HRT). Many women participate in HRT when they undergo menopause, to alleviate symptoms such as hot flashes, but hormones have other important roles as well. They protect women against heart disease, the number one killer of women in the United States, and they help to relieve and prevent osteoporosis. HRT increases a woman's supply of estrogen, which helps build new bone, while preventing further bone loss.
Some women, however, do not want to take or are not candidates for hormones, because some studies show they are linked to an increased risk of breast cancer or uterine cancer. Other studies reveal that risk is due to increasing age. (Breast cancer tends to occur more often as women age.) Whether or not a woman takes hormones is a decision she should make carefully with her doctor. Women should talk to their doctors about personal risks for osteoporosis, as well as their risks for heart disease and breast cancer.
Novel delivery systems of HRT have been developed. For example, Vivelle is a estradiol transdermal system that is used for prevention of osteoporosis. It uses a "patch" to continously deliver the hormone estradiol through the skin.
Studies have shown women who started taking HRT within five years of menopause show significantly reduced rates of hip fractures than women who began HRT more than five years postmenopausal. However, even while taking HRT, 10 to 20% of women continue to lose bone density and therefore may require additional intervention.
For people who cannot or will not take estrogen, other agents can be good choices. These include:
* bisphosphonates
* calcitonin
* selective estrogen receptor modulators
* sodium fluoride
* androgens
Although there are a number of bisphosphonates used for the treatment of various forms of osteoporosis and resorptive bone diseases, alendronate (sold under the brand name Fosamax), etidronate (sold under the brand name Didronel), and risedronate (sold under the brand name Actonel) are some of the agents most commonly used for therapeutic treatment of postmenopausal osteoporosis. Biphosphonates act by decreasing bone resorption or breakdown. For example, alendronate attaches itself to bone that has been targeted by bone-eating osteoclasts. It protects the bone from these cells. Osteoclasts help the body break down old bone tissue.
Alendronate has shown to be an effective agent in preventing bone loss and building bone in recently post-menopausal women and is especially useful in women who have contraindications for HRT. It has been licensed for the treatment and prevention of vertebral and nonvertebral postmenopausal osteoporosis. Alendronate has proven safe in very large, multi-year studies, but not much is known about the effects of its long-term use. Side effects are generally minimal with abdominal pain, nausea, dyspepsia, constipation and diarrhea occurring in 3% to 7% of patients treated with alendronate. It can be taken daily, and now a new formulation has been developed that can be taken weekly.
Etidronate has been shown to reduce the rate of new vertebral and nonvertebral fractures. It appears to be well tolerated in clinical studies.
Calcitonin is a hormone that has been used as an injection for many years. It is also marketed as a nasal spray. It also slows down bone-eating osteoclasts. Side effects are minimal, but calcitonin builds bone by only 1.5% a year, which may not be enough for some women to recover the bone they lose.
Selective estrogen receptor modulators (SERMs) such as raloxifene, droloxifene, idoxifene, and tamoxifen are used as alternatives to hormone replacement therapy (HRT) which commonly use estrogen. SERMs have been shown to protect against postmenopausal bone loss without the estrogenic side effects. Raloxifene was the first SERM to be approved in the osteoporosis market for prevention and treatment of osteoporosis. Raloxifene binds to estrogen receptors and mimics estrogen's action on bone by preventing bone loss, and improving cholesterol metabolism, therefore acting as an agonist. It also acts as an estrogen antagonist in the uterus and the breasts, by not imitating the action of estrogen. These drugs may thus improve blood lipid profiles and protect against breast cancer. There is an enhanced risk of venous thromboembolic events during raloxifene therapy, especially during the first four months of therapy. It also has a propensity to induce hot flashes, and leg pain.
Sodium fluoride has been used as an anabolic agent to stimulate bone formation. However, a high incidence of side effects, mainly gastrointestinal symptoms and lower extremity pain syndrome have occurred in clinical trials.
Androgens have been used for reducing bone loss. Androgens are classified as anabolic steroids, which include nandrolone, stanozolol and testosterone, are used as antiresorptive agents. Androgens are important for postmenopausal women as they serve as a substrate for the peripheral production of estrogens.
The treatments currently available are antiresorptive, which limits the ability to increase bone mass. Other bone-building agents are under investigation including parathyroid hormone which has been clinically evaluated but is still awaiting FDA approval as of March 2001. The biphosphonates have demonstrated the most dramatic reduction in fracture rates and may be the best choice for women with severe osteoporosis. Estrogen's effect may be similar, but has not been established in large randomized trials. Raloxifene may be particularly useful in women who wish to benefit from a breast cancer risk reduction. Calcitonin may be the least potent but may be useful in women who cannot tolerate other therapies.
Surgery
Unfortunately, treatment for osteoporosis is usually tied to fractures that result from advanced stages of the disease. For complicated fractures, such as broken hips, hospitalization and a surgical procedure are required. In hip replacement surgery, the broken hip is removed and replaced with a new hip made of plastic, or metal and plastic. Though the surgery itself is usually successful, complications of the hip fracture can be serious. Those individuals have a 5%–20% greater risk of dying within the first year following that injury than do others in their age group. A large percentage of those who survive are unable to return to their previous level of activity, and many end up moving from self-care to a supervised living situation or nursing home. Getting early treatment and taking steps to reduce bone loss are vital.
Alternative treatment
Alternative treatments for osteoporosis focus on maintaining or building strong bones. A healthy diet low in fats and animal products and containing whole grains, fresh fruits and vegetables, and calcium-rich foods (such as dairy products, dark-green leafy vegetables, sardines, salmon, and almonds), along with nutritional supplements (such as calcium, magnesium, and vitamin D), and weight-bearing exercises are important components of both conventional prevention and treatment strategies and alternative approaches to the disease. In addition, alternative practitioners recommend a variety of botanical medicines or herbal supplements. Herbal supplements designed to help slow bone loss emphasize the use of calcium-containing plants, such as horsetail (Equisetum arvense), oat straw (Avena sativa), alfalfa (Medicago sativa), licorice (Glycyrrhiza galbra), marshmallow (Althaea officinalis), and yellow dock (Rumex crispus). Homeopathic remedies focus on treatments believed to help the body absorb calcium. These remedies are likely to include such substances as Calcarea carbonica (calcium carbonate) or silica. In traditional Chinese medicine,
KEY TERMS
Alendronate—A nonhormonal drug used to treat osteoporosis in postmenopausal women.
Anticonvulsants—Drugs used to control seizures, such as in epilepsy.
Biphosphonates—Compounds (like alendronate) that slow bone loss and increase bone density.
Calcitonin—A hormonal drug used to treat post-menopausal osteoporosis.
Estrogen—A female hormone that also keeps bones strong. After menopause, a woman may take hormonal drugs with estrogen to prevent bone loss.
Glucocorticoids—Any of a group of hormones (like cortisone) that influence many body functions and are widely used in medicine, such as for treatment of rheumatoid arthritis inflammation.
Hormone replacement therapy (HRT)—Also called estrogen replacement therapy, this controversial treatment is used to relieve the discomforts of menopause. Estrogen and another female hormone, progesterone, are usually taken together to replace the estrogen no longer made by the body. It has the added effect of stopping bone loss that occurs at menopause.
Menopause—The ending of a woman's menstrual cycle, when production of bone-protecting estrogen decreases.
Osteoblasts—Cells in the body that build new bone tissue.
Osteoclasts—Cells that break down and remove old bone tissue.
Selective estrogen receptor modulator—A hormonal preparation that offers the beneficial effects of hormone replacement therapy without the increased risk of breast and uterine cancer associated with HRT.
practitioners recommend herbs thought to slow or prevent bone loss, including dong quai (Angelica sinensis) and Asian ginseng (Panax ginseng). Natural hormone therapy, using plant estrogens (from soybeans) or progesterone (from wild yams), may be recommended for women who cannot or choose not to take synthetic hormones.
It should be noted, however, that very few clinical trials are conducted on alternate therapies and therefore efficacy cannot be established.
Prognosis
There is no cure for osteoporosis, but it can be controlled. Most people who have osteoporosis fare well once they get treatment. The medicines available now build bone, protect against bone loss, and halt the progress of this disease.
Health care team roles
Doctors, nurses, physical therapists, radiation technologists, and dietitians all play roles in the process of controlling osteoporosis. Because osteoporosis is treatable but not curable, the main responsibility for controlling the progress of the disease rests with the patient. All of these team members play an important role in identifying risk of osteoporosis before it strikes and in convincing the patient to take appropriate steps (including lifestyle modification) to minimize the dangers of fracturing major bones.
Prevention
Building strong bones, especially before the age of 35, and maintaining a healthy lifestyle are the best ways of preventing osteoporosis. To build as much bone mass as early as possible in life, and to help slow the rate of bone loss later in life:
Get calcium in foods
Experts recommend 1,500 milligrams (mg) of calcium per day for adolescents, pregnant or breast-feeding women, older adults (over 65), and postmenopausal women not using hormone replacement therapy. All others should get 1,000 mg per day. Foods are the best source for this important mineral. Milk, cheese, and yogurt have the highest amounts. Other foods that are high in calcium are green leafy vegetables, tofu, shell-fish, Brazil nuts, sardines, and almonds.
Take calcium supplements
Many people, especially those who do not like or cannot eat dairy foods, do not get enough calcium in their diets and may need to take a calcium supplement. Supplements vary in the amount of calcium they contain. Those with calcium carbonate have the most amount of useful calcium. Supplements should be taken with meals and accompanied by six to eight glasses of water a day. Calcium supplements and antacids interfere with absorption of alendronate and should be taken at least one half hour later.
Get vitamin D
Vitamin D helps the body absorb calcium. People can get vitamin D from sunshine with a quick (15–20 minutes) walk each day or from foods such as liver, fish oil, and vitamin-D fortified milk. During the winter months it may be necessary to take supplements (400–800 IU/day).
Avoid smoking and alcohol
Smoking reduces bone mass, as does heavy drinking. To reduce risk, do not smoke and limit alcoholic drinks to no more than two per day. An alcoholic drink is1.5 oz (44 mL) of hard liquor, 12 oz (355 mL) of beer, or 5 oz (148 mL) of wine.
Exercise
Exercising regularly builds and strengthens bones. Weight-bearing exercises—where bones and muscles work against gravity—are best. These include aerobics, dancing, jogging, stair climbing, tennis, walking, and lifting weights. People who have osteoporosis may want to attempt gentle exercise, such as walking, rather than jogging or fast-paced aerobics, which increase the chance of falling. Try to exercise three to four times per week for 20–30 minutes each time. As physical activity improves muscle strength and coordination it may also aid in reducing the risk of fall-related fractures.
Those at risk should avoid medications known to compromise bone density, such as glucocorticoids, thyroid hormones and chronic heparin therapy.
Resources
BOOKS
Adams, John S. and Barbara P. Lukertet. Osteoporosis: Genetics, Prevention and Treatment. Boston: Kluwer Academic, 1999.
Kessler, George J., et al. The Bone Density Diet: 6 Weeks to a Strong Body and Mind. New York: Ballantine Books, 2000.
Krane, Stephen M., and Michael F. Holick. "Metabolic Bone Disease: Osteoporosis." In Harrison's Principles of Internal Medicine. 14th ed. Ed. by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998.
Lane, Nancy E., ed. The Osteoporosis Book. New York: Oxford University Press, 1998.
McIlwain, Harris, et al. Osteoporosis Cure: Reverse the Crippling Effects With New Treatment. New York: Avon Books, 1998.
Notelovits, Morris, et al. Stand Tall! Every Woman's Guide to Preventing and Treating Osteoporosis. 2nd ed. Gainesville, FL: Triad Publishing Co., 1998.
PERIODICALS
Feder, G., et al. "Guidelines for the Prevention of Falls in People over 65." British Medical Journal 321 (2000): 1007-1011.
McClung, Michael R., et al. "Effect of Risedronate on the Risk of Hip Fracture in Elderly Women." The New England Journal of Medicine 344, no. 5 (2001): 333-40.
ORGANIZATIONS
Arthritis Foundation, 1330 W. Peachtree St., PO Box 7669, Atlanta, GA 30357-0669. (800) 283-7800.
National Center for Complementary and Alternative Medicine (NCCAM), 31 Center Dr., Room #5B-58, Bethesda, MD 20892-2182. (800) NIH-NCAM. Fax: (301) 495-4957.
National Osteoporosis Foundation, 1150 17th Street, Suite 500 NW, Washington, DC 20036-4603. (800) 223-9994.
Osteoporosis and Related Bone Diseases-National Resource Center. 1150 17th St., NW, Ste. 500, Washington, DC 20036-4603. (800) 624-BONE.
