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Osteoporosis:
Etiology, Treatment, and Prevention
By: Amy Ebling


Osteoporosis is a major health threat for more than twenty-eight million Americans (2). Of the twenty-eight million affected, eighty percent are women (2). The majority of the people with this disabling disease are over the age of forty-five (5). Every year, osteoporosis leads to 1.3 million fractures, primarily in the hip, spine, and wrist (15). Death can also result from this debilitating disease as fractures can end in death. Twenty-four percent of the hip fractures due to osteoporosis that occur every year in those over the age of fifty can cause death in the year following the fracture (2). This is largely due to the immobility that results when a bone is broken, and thus a loss of functional independence. Osteoporosis is also an extremely costly disease, with the estimated costs being about 13.8 billion every year (5). Therefore, osteoporosis clearly creates obvious costs in terms of human suffering, loss of life, reduced functional independence, and health care costs.

Osteoporosis, meaning "porous bone", is the most common metabolic disease among adults (4). The disease is "characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased susceptibility of fractures of the wrist, hip, and spine." (10). The amount of calcium present in the bones slowly decreases to the point where the bones become so brittle they break. The fractures that occur due to the disease can cause complications such as prolonged hospitalization and decreased independence (5). This condition and its resultant fractures have become a major cause of disability and death among both men and women. The fact that the actual cause of the disease is unknown makes diagnosing and treating the disease even more difficult (4).

One of the aspects of the disease that is not a mystery is that the disease seems to interfere with the normal processes that occur in bones. The bones of the skeleton, which are made of a tough matrix of the protein collagen and hardened by minerals like calcium and phosphorous, respond to the pull of muscles and gravity that occur with normal movement (15). Even this normal movement causes slight damage that needs to be repaired, so that bone is constantly being broken down and reformed (15, 11). The processes involved in bone remodeling are regulated by the body's hormones and involve the action of two types of bone cells. The first type of cells, called osteoclasts are responsible for hollowing out holes in the bones, releasing small amounts of calcium into the blood (11). The second type of cells, the osteoblasts, rebuild the skeleton and fill in the holes made by the osteoclasts with collagen and calcium (11). This cycle is necessary for growth and repair of minor damages that occur from everyday stress on the bone.

Bones form in childhood and grow in both size and density. By the time a person reaches the age of seventeen, ninety percent of their bone mass has already been built (3). At the age of eighteen, the bones stop their growth in size, but still increase in density, until the twenties when peak bone mass is reached (3). After the age of thirty, bone tissue starts to diminish gradually because the processes of bone remodeling fall out of sync (2). At this time, bone formation is outpaced by bone breakdown and bone density begins to decline (15). The skeleton becomes increasingly devoid of substance and can no longer withstand normal stress, leaving it so fragile that even coughing can cause serious damage. This is the start of osteoporosis.

Called the "silent disease," early osteoporosis has no visible symptoms (2). A person with beginning deterioration of bone may only have complaints of mild to severe back pain and may notice a loss in height (2). In fact, one can have osteoporosis for years before experiencing a broken bone (3). Since the disease happens slowly over the years, neither the patient nor the physician may be aware of the weakening of the bones until a break unexpectedly occurs (15). For example, early compression fractures of the spine may go undetected, but after a large percentage of calcium is lost, the vertebra of the spine start to collapse, causing a stooped posture (11). This stooped posture can lead to disfigurement, such a dowager's hump, in the back and other complications, such as abdominal problems and difficulty breathing Once disfigurement of the body, such as the dowager's hump, appears, the disease has progressed and usually becomes increasingly apparent in fractures of other sites, like the hip or forearm (11). The fractures cause pain, since the fibrous covering around bones is sensitive to pain, and may press on nerve roots, further intensifying pain (4). The chronic pain and anxiety of a weakening frame cause people to stop participation in meaningful activities because the bones have become so brittle that a simple activity, like sneezing or stepping off a curb, can result in a fracture (15).

Osteoporosis can be classified into two types; primary and secondary. Primary osteoporosis occurs in postmenopausal women between the ages of fifty and seventy-five years of age and is the most common type. Secondary osteoporosis is related to changes that happen with the normal aging process that can leave the bones weaker and more prone to breakage (2). However, it can also be caused by underlying conditions, such as endocrine hormone conditions, that interfere with the process of bone formation (2). Secondary osteoporosis can occur in both men and women above the age of seventy, although it is also more commonly found in women. The significant difference between the two classifications of osteoporosis is that primary osteoporosis shows the relation of the disease to estrogen loss.

Given that osteoporosis affects more women than men, it should come as no surprise that a prime risk factor in developing the disease is that of being of the female gender. A further increase in risk occurs after menopause. At menopause, the female hormone estrogen declines. Estrogen plays an important role in preserving bone strength by preventing the release of calcium into the bloodstream (11). Therefore, years after menopause, women lose bone mass two to four times greater than they did before menopause because there is not enough calcium retention in the bones (15). The rate of bone loss will vary between individuals, and may actually slow down, but for most women the rate remains rapid (15). Even though osteoporosis can be associated with menopause that occurs as a part of the normal aging process, women who have gone through menopause prematurely or have had surgeries, such as hysterectomies or removal of the ovaries, should consider themselves at risk of developing osteoporosis because these conditions also result in a decline in estrogen production (11). On the whole, any factor resulting in estrogen deficiency will increase the rate of bone loss (5).

While osteoporosis seems to be prejudiced to the female gender, males should not consider themselves totally free of risk of developing osteoporosis. Osteoporosis seems to develop less in men than women because the cycle of bone breakdown outpacing bone formation begins later in the aging process for men and progresses slower (5). Men also do not undergo a life process, such as that of menopause, that decrease the production of hormones, leaving them susceptible to bone weakness (5). None the less, men are at increased risk for developing osteoporosis if they have a medical condition that reduces their hormone levels of testosterone, as some prostrate cancer treatments do (8).

Gender should not be the only thing evaluated when determining who is at risk of developing osteoporosis. Genetics also seems to play a role. A family history of osteoporosis will predispose a person to the risk of osteoporosis. Recently, a gene has been discovered that seems to influence bone density (1). The gene holds a receptor for Vitamin D, which affects the way the body turns calcium into bone (1). While future research needs to be conducted, recognition of this gene may alert patients to potential dangers, so early preventive measures can be implicated.

Ethnicity can also be a determining factor in who may develop osteoporosis. For an unknown reason, osteoporosis seems to be more prevalent in individuals of Asian and Caucasian descent. When compared, bones seem to develop identically in children of white descent and children of black descent (1). However, at puberty white children lay down an average 11% increase in bone mass, while black children lay down an average 34% increase in bone mass (1). Since the cause of this difference is not clearly understood, it has been decided that the reason must lie in the unique programming of genes that exist between the ethnicities (1).

Body composition is to be considered when determining risk factors of osteoporosis. Individuals with low body weight and muscle mass appear to be more likely to develop osteoporosis (11). This may be another reason why men do not have as high a risk in developing the disease, since males have a higher bone density and muscle mass than that of women (5). Eating disorders resulting in low body weight, like anorexia, may increase the risk further because malnutrition will affect the minerals available to the bones for absorption. Anorexia can also alter menstrual periods, thereby altering hormone production (5). That is not to say obesity, or higher body weight, is a preventive measure because high body weight has other health considerations that can be just as dangerous and life threatening as osteoporosis. Rather, a normal body weight should be maintained and a healthy diet followed.

An individual's lifestyle choices may have an impact on their chances of falling victim to osteoporosis. Excessive consumption of alcohol can inhibit osteoblast activity, affecting the rate at which bone is built (3). Smoking is also a hazard for several reasons. Smoking will increase the rate of bone loss, and also places the patient at risk of developing other life threatening complications, such as cancer (1, 3). A sedentary lifestyle may also be to blame, since bones are not given the opportunity to respond to stress, therefore the normal processes that need to occur to maintain healthy bone fail to take place. However, on the opposite side of the spectrum, women who run excessively, such as those who participate in many marathons, may be at increased risk of developing osteoporosis because the physical affects of such activity interrupts menstrual cycles, or in extreme cases, brings the menstrual cycle to a halt (1).

Medications for other conditions unrelated to osteoporosis may impact the normal bone process and lead to osteoporosis. Steroids increase bone breakdown, while thyroid supplements interfere with the hormonal control regulating the bone turnover cycle (2,5). Antacids, especially those containing aluminum, interfere with calcium function (5). Anti-seizure medications have also been suspected in causing problems that result in osteoporosis (11). It should be noted however that concern of developing osteoporosis lies in prolonged use of these medications (i.e. several years of using a steroid).

Age also appears to have an impact on who will develop osteoporosis. With advancing age bones become weaker and less dense (11). This is due to the unequal cycle of bone breakdown and formation that happens as part of the normal aging cycle. As can be expected, bones that are more fragile are more likely to be injured.

A person can present with many of the above mentioned risk factors and never develop osteoporosis. However, if an individual appears to be at risk of developing osteoporosis, diagnostic tests may be ordered to assess the individual's current bone mass and monitor changes that may occur. A problem presents though because osteoporosis, unlike other diseases, will not be detected by routine x-rays (15). Changes in bone density will not show up on an x-ray until bone mass has reached a 30% loss (2). Therefore, more sophisticated techniques are required to evaluate bone density.

A bone mineral density test, which measures bone density at various sites, is the most reliable way to assess bone strength and predict future problems (3, 10). Density of bone is measured by detecting how bone absorbs photons that are generated by very low levels of x-rays (11). Readings are compared to a standard for the patient's age, sex, and body size (15). According to the World Health Organiziation, patient's have normal bone density if their bone mineral density is not more than one standard deviation below the average standard (6). If the patient's bone mineral density falls between 1 and 2.5 standard deviations below the average standard, the person is considered to have osteopenia, which can often be a precursor to the development of osteoporosis (6). Osteoporosis is diagnosed if the person's bone mineral density is more than 2.5 standard deviations below the average standard (6).

While the procedures associated with a bone mineral density test are painless and simple, they may not be widely available (11). Also, different machines use different measurement methods, so estimates acquired from different machine types may not be comparable (15). Therefore, a patient should return to the same machine the original measurements were obtained from to preserve consistency.

Once a diagnosis of osteoporosis has been reached, the focus becomes treating the breakdown of bone and preserving what bone mass the person has. While there is no cure for osteoporosis, drug interventions are helpful in preventing fractures. The current medications used to treat osteoporosis aim at reversing the bone remodeling cycle by stimulating bone formation and inhibiting bone breakdown (5). It should be noted that the greatest increase in bone density occurs in the first year and after two years may begin to taper off (15). Nonetheless, any gain is helpful, even if it does not continue. Another important consideration is that drug therapy is individualized based on the patient's symptoms and tolerance to the drug. Therefore, the use of certain drugs may not be appropriate in all cases.

The most common drug used to treat osteoporosis in postmenopausal women is hormone replacement therapy. Hormone replacement therapy increases bone density, reduces fractures, and improves balance which decreases the fractures that result from falls (11). Estrogen replacement therapy seems to provide the best prevention of fractures after menopause, since estrogen prevents bone breakdown and the release of calcium into the blood (11, 15). This particular therapy is indicated in women who have gone through menopause, either as part of the normal aging process or prematurely (5). As with any drug, side effects may result from taking estrogen. Adverse side-effects of long-term daily estrogen administration include an increased risk of developing breast cancer, vaginal bleeding, the formation of blood clots, and elevated blood pressure (5). Estrogen may also be given in combination with another hormone, like progesterone, which may result in additional side-effects, such as headaches, bloating, anxiety, and mood swings (5).

Another group of drugs used for therapy are called selective estrogen receptor modulators. This group works as weak estrogen and is beneficial to people who are unable to use conventional forms of estrogen replacement therapy (5). This class of drugs also has side effects, although they are more mild and consist of hot flashes and leg cramps (5). Evista is a drug of this class and has been approved by the FDA for preventing spinal fractures (11). Evista helps prevent osteoporosis by building bone and also stops the thinning of bone (3).

Biphosphonates is yet another class of drugs used to treat osteoporosis. The drug Fosamax is an example of a name brand drug from this category currently being marketed in the treatment of osteoporosis (3). This is the most potent medication being used to treat osteoporosis and helps increase bone mass and reduce fracture risk (3). Fosamax is a non-hormonal treatment that hinders bone breakdown by inhibiting osteoclast activity (15). A common side-effect resulting from the use of a drug from the biphosphonate class is gastrointestinal problems (11). Irritation of the esophagus, abdominal pain, nausea, and heartburn are among the complaints that accompany this medication (5). There are special precautions accompanying the use of these drugs and they must be adhered to to prevent side effects (15).

Calcitonin may be an alternative treatment for those who can not tolerate estrogen or for those in which estrogen is contra-indicated (5). Calcitonin does not build bone, instead it slows bone loss and relieves some of the pain associated with fractures (5). Calcitonin inhibits the activity of specialized bone cells called osteoclasts so that bone can hold on to more calcium and keep bone from becoming more brittle (5). Miacalcin, a potent synthetic version of this hormone, is given in the form of a nasal spray (15). Common side effects that may result from using this nasal spray include a runny nose, irritation, nose bleeds, and headaches (5).

Fluoride may also used to treat osteoporosis. It stimulates the production of new osteoblasts, leading to an increase in bone mineral density (5). However, the new bone may have abnormal texture or be less mineralized and fragile, which may be a harmful side-effect causing more injury (5). Gastrointestinal side effects are also a concern with the use of this drug (15). Other common side effects include lower extremity pain and stress fractures (5).

As of current information, the FDA guidelines state drugs used to treat osteoporosis must be shown to preserve or increase bone mass and maintain bone quality in order to reduce the risk of fractures (15). There is currently no FDA approved Abone builder" available (3). Treatment for men has been poorly researched and remains largely unsupported by experimental evidence (5). Evidence does suggest that some drugs, such as Fosamax and Miacalcin, may work the same in men as in women (5). Testosterone replacement therapy may prove to be an option for men with low levels of osteoporosis, but must be further researched (5). As of now, none of the osteoporosis medications have been approved by the US FDA for men (5).

Since no cure for the treatment of osteoporosis is available, prevention of the disease becomes of the utmost importance. The two major determinants in developing osteoporosis seem to be peak bone mass and the rate of bone loss (5). These two determinants are influenced by a number of genetic and environmental factors (5). The upper limit of bone mass that can be acquired is genetically predetermined, however, the preservation of that upper limit can be achieved through various means, such as exercise, increased calcium intake, and making and committing to lifestyle changes.

Exercise is important for good bone health. Physical activity determines the strength, shape and mass of bone because bone strength increases in response to increasing activity (7). Exercise improves bone health, increases muscle strength, coordination, balance, and leads to better overall health (5). The benefits gained from exercise can also decrease the risk of falls, thereby decreasing the risk of fractures. .

The best exercise for the bones of the body is weight-bearing exercise, or any activity that allows stress to be placed on the bones, such as walking or weight lifting (3). Weight-bearing exercise applies tension to muscles and bone encouraging the body so it can compensate for added stress by increasing bone density (11). One does not have to do much to benefit from exercise, only about thirty minutes of walking five days a week (15). In particular, exercise targeted to strengthen the back and improve posture may prove beneficial when the later stages of osteoporosis approach and may help prevent disfigurement by encouraging good postural habits.

Exercise is certainly very important, but the wrong type of exercise can do more harm than good (9). For example, compression fractures of the spine in patients with osteoporosis occur with forward bending movement (like picking something up from the floor) (9). Therefore, patients should avoid exercise that compresses the spine, such as crunches, proving that exercise untailored to the patient's stage of osteoporosis can be dangerous. Individuals should not go to a gym and enlist the services of a personal trainer because not all trainers have an adequate knowledge base regarding osteoporosis and may suggest exercise that causes more harm to the patient, such as fractures (9). It is important to talk to the doctor before starting a new exercise program, especially if osteoporosis has already been diagnosed (15). It is recommended that patients be referred to a physical therapist who has specialized training in developing exercise programs so that a customized and safe program can be developed for a individual patient (9).

Calcium is also needed for good bone health (3). The skeleton holds about ninety-nine percent of the body's calcium (11). The remaining one percent is left free to circulate in the blood and is essential for other body functions, like muscle contraction, blood clotting, and nerve transmission (11). When the body does not get enough calcium, it takes calcium from the bones, weakening them (3). If the body excretes more calcium than it retains the result is a reduction in bone mass (2).

Keeping in mind the important role of calcium in the body and the effects of not receiving enough calcium, it is disturbing that most people do not get enough calcium (3). Only about fifteen percent of girls and thirty-five percent of boys ages twelve to nineteen get the calcium they need (3). Adequate calcium intake in childhood and young adulthood is critical to achieving the upper limit of bone mass available based on individual genetic programming. However, many children are substituting drinks with no nutritional value, like soda, in place of calcium rich beverages, such as milk, and do not receive the amount of calcium necessary for the development of healthy bones (3). Teenagers obsessed with weight and calories may cut milk out of their diets because they believe it to be fattening (3). Yet the problem is not isolated to those in the bone developing stage (children). Adults need calcium to maintain bone mass. As the aging process continues, men and women absorb less calcium from their diets, but do not replace it by increasing their calcium intake (3). This leads to less calcium in the body, and therefore less calcium available to preserve the strength of bone.

While studies agree that most people need more calcium, there is disagreement about how much is enough. The National Academy of Sciences suggests one thousand milli-grams per day (7). However, active women who eat healthfully do not need to count every milli-gram (7). Nutritionists recommend meeting calcium needs with foods naturally rich in calcium (15). Milk and milk products, especially those fortified with vitamin D, are still the best sources of calcium (3). Dark green, leafy vegetables contain calcium, but not as much as dairy products (3). However, they are still necessary for a well-balanced diet. If one can not consume dairy products, many products, like orange juice, are now fortified with calcium (15). If the focus is on eating a varied diet that includes a wide assortment of plant foods, while limiting the intake of junk food, the necessary amount of calcium needed will be met (7).

If adding more calcium by consuming a well-balanced diet does not help, calcium supplements may offer a solution. Most available brands are inexpensive and have no side-effects (3) Calcium and vitamin D supplements are an integral part of all treatments for osteoporosis (15). Increasing calcium before menopause allows women to enter menopause with a greater bone density (5). One thing that is important to note is that calcium supplements come in a variety of different compounds, each with different levels of absorbency (11). The calcium from these supplements must be absorbed by the body to gain the effects of the calcium, so certain compounds may work better in certain individuals. A simple test to determine absorbency is to place a calcium tablet in a glass of white vinegar at full strength (11). Check to be sure the tablet breaks up within thirty minutes (11). If it does, the tablet has adequate absorbency (11). However, an individual should still realize that just because a certain brand of a calcium supplement has good absorbency in a glass of vinegar does not necessarily guarantee good absorbtion by the body. A doctor can suggest which type of calcium supplement may be appropriate based on the individual's medical needs. Getting too much calcium should be of no concern since the body sheds the excess naturally (7).

Calcium alone is not enough to protect bones (7). Bone health depends not only on how much calcium you eat but on how much you retain in your bones, which is affected by other nutrients in your diet, such as Vitamin D (7). Vitamin D plays an important role in calcium absorption and in normal mineralization on new bone (5). Most people get enough vitamin D because the skin produces it in sunlight, but people confined indoors may not get enough (15). Fifteen minutes a day with the face and arms exposed to the sun will prompt the body to make vitamin D (7). Lowfat dairy products are also readily available sources of Vitamin D (7).

Preventive measures against osteoporosis should begin early in life and teens in particular need to be taught the importance of exercise and diet (5). The younger one starts lifestyle changes, and the longer one keeps them up, the better for that person later in life (15). Exercising regularly and eating a balanced diet throughout the teenage years and early adulthood is crucial (7). Lifestyle changes, such as getting enough calcium and vitamin D, not smoking, and drinking alcohol only in moderation are important to decrease the chance of developing osteoporosis later in life (15). Prevention is always preferable to treatment since no therapy fully restores lost bone mass (5).

Physical therapy has therefore become an important discipline in both preventing and treating osteoporosis. Physical therapy goals for patients who are at risk of developing osteoporosis need to focus on maintaining bone mass through exercise, like weight training, and patient education on proper diet and lifestyle. Physical therapy goals for patients with established osteoporosis include the same aspects of those patients only at risk of developing osteoporosis, while also incorporating coordination training to reduce the liklihood of falls and methods of pain reduction (4). Physical therapists should concentrate on restoring everyday functional activities, to allow patients with osteoporosis to maintain their independence (4). All positions involving flexion should be avoided, such as crunches, because these positions can cause further fracture to the spine (4). Prevention of falls, especially in the elderly, is especially important because of the high incidence of fracture that accompanies a fall (5).

Currently, the only measures that can be taken to fight osteoporosis are to prevent it from beginning, or managing the bone breakdown process so that further deterioration slowed. The search for bone building drugs continues and some naturally occurring bone specific growth factors have been identified and their use as drugs is being investigated (15). Studies are under way to test to see if certain drugs are effective in less severe cases, if they can be started sooner, or used in combination (15). Laboratory tests, such as blood and urine samples, are being evaluated to determine if they can effectively diagnose osteoporosis. Some advances have been made, but no test that offers a firm diagnosis can be developed (15). Researchers are also beginning to look at environmental influences associated with industrial countries, like the United States that may contribute to the development of osteoporosis (2). Since menopause is universal to all women, resulting estrogen deficiency is presumably similar for all women (2). So the differences in the occurrence of osteoporosis among women of different countries can not be explained purely on the basis of estrogen deficiency (2).

Osteoporosis still remains a large threat to the elderly, primarily women. The disease continues to grow in prevalence, yet there still is no cure. Unless prevented or actively treated, osteoporosis will continue to limit both quantity and quality of life for many people and significantly add to health care dollars (13).

References

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  2. Goodman, CC., Snyder, TE. (2000). Differential Diagnosis in Physical Therapy. Philadelphia, PA. F.A. Davis Company. p. 27.
  3. Heins, K. You Can't Wish Away Osteoporosis. Better Homes and Gardens Nov. 2000, pp. 272-272D.
  4. Hertling, D., Kessler, R. (1996). Management of Common Musculoskeletal Disorders. Philadelphia, PA. Lippincott. pp. 637-638.
  5. Iqbal, MM. Osteoporosis: Epidemiology, Diagnosis, and Treatment. Southern Medical Journal Jan 2000, Vol. 93 Issue 5, pp. 2-19.
  6. Kauffman, Timothy L. Geriatric Rehabilitation Manual. Churchill Livingstone, Philadelphia, PA. 1999. p. 83.
  7. Mandelbaum-Schmid, J. A Bone to Pick. Walking Magazine Jul/Aug 2000, Vol. 15 Issue 5, pp. 34-36.
  8. McIlwain, Harris; Bruce, Debra; Silverfield, Joel; Burnette, Michael. Osteoporosis: Prevention, Management, Treatment. John Wiley& Sons, Inc. New York, NY. 1988.
  9. Meeks, S. Sit-ups, Other Exercises May Injure Older Patients with Osteopotosis. Geriatrics Sep 2000, Vol, 55 Issue 9, pp. 30-31.
  10. National Osteoporosis Foundation. Http://www.nof.org/.
  11. Osteoporosis. Http://content.health.msn.com/contetn/dmk/dmk_article_40065.
  12. Pauls, J., Reed, K. (1996). Quick Reference to Physical Therapy. Gaithersburg, MD. Aspen Publishers Inc. pp. 654-658.
  13. Ribeiro, V., Blakeley, J., Laryea, M. Women's Knowledge and Practices Regarding the Prevention and Treatment of Osteoporosis. Health Care for Women International Jun 2000, Vol. 21 Issue 4, p. 347.
  14. Rosen, C. (1996). Osteoporosis Diagnostic and Therapeutic Principles. Totowa, NJ. Humana Press.
  15. Strange, CJ. Boning Up on Osteoporosis. FDA Consumer 1999, pp. 1-7.

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