What is osteoporosis? - The NocturnalSaint

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Saturday, September 03, 2011

What is osteoporosis?

 What is osteoporosis?

Osteoporosis is a condition characterized by a decrease in the density of bone, decreasing its strength and resulting in fragile bones. Osteoporosis literally leads to abnormally porous bone that is compressible, like a sponge. This disorder of the skeleton weakens the bone and results in frequent fractures (breaks) in the bones. Osteopenia is a condition of bone that is slightly less dense than normal bone but not to the degree of bone in osteoporosis.
Normal bone is composed of protein, collagen, and calcium, all of which give bone its strength. Bones that are affected by osteoporosis can break (fracture) with relatively minor injury that normally would not cause a bone to fracture. The fracture can be either in the form of cracking (as in a hip fracture) or collapsing (as in a compression fracture of the vertebrae of the spine). The spine, hips, ribs, and wrists are common areas of bone fractures from osteoporosis although osteoporosis-related fractures can occur in almost any skeletal bone.

What are osteoporosis symptoms and signs?

Osteoporosis can be present without any symptoms for decades because osteoporosis doesn’t cause symptoms until bone fractures. Moreover, some osteoporotic fractures may escape detection for years when they do not cause symptoms. Therefore, patients may not be aware of their osteoporosis until they suffer a painful fracture. The symptom associated with osteoporotic fractures usually is pain; the location of the pain depends on the location of the fracture. The symptoms of osteoporosis in men are similar to the symptoms of osteoporosis in women.
Fractures of the spine (vertebra) can cause severe “band-like” pain that radiates from the back to the sides of the body. Over the years, repeated spinal fractures can lead to chronic lower back pain as well as loss of height and/or curving of the spine due to collapse of the vertebrae. The collapse gives individuals a hunched-back appearance of the upper back, often called a “dowager hump” because it commonly is seen in elderly women.
A fracture that occurs during the course of normal activity is called a minimal trauma, or stress fracture. For example, some patients with osteoporosis develop stress fractures of the feet while walking or stepping off a curb.
Hip fractures typically occur as a result of a fall. With osteoporosis, hip fractures can occur as a result of trivial accidents. Hip fractures also may heal slowly or poorly after surgical repair because of poor healing of the bone

What are the consequences of osteoporosis?

Osteoporotic bone fractures are responsible for considerable pain, decreased quality of life, lost workdays, and disability. Up to 30% of patients suffering a hip fracture will require long-term nursing-home care. Elderly patients can develop pneumonia and blood clots in the leg veins that can travel to the lungs (pulmonary embolism) due to prolonged bed rest after the hip fracture. Osteoporosis has even been linked with an increased risk of death. Some 20% of women with a hip fracture will die in the subsequent year as an indirect result of the fracture. In addition, once a person has experienced a spine fracture due to osteoporosis, he or she is at very high risk of suffering another such fracture in the near future (next few years). About 20% of postmenopausal women who experience a vertebral fracture will suffer a new vertebral fracture of bone in the following year.

How is osteoporosis diagnosed?

A routine X-ray can reveal osteoporosis of the bone because the bones appear much thinner and lighter than normal bones. Unfortunately, by the time X-rays can detect osteoporosis, at least 30% of the bone has already been lost. In addition, X-rays are not accurate indicators of bone density. Thus, the appearance of the bone on X-ray often is affected by variations in the degree of exposure of the X-ray film.
The National Osteoporosis Foundation, the American Medical Association, and other major medical organizations recommend a dual-energy X-ray absorptiometry scan (DXA, formerly known as DEXA) for diagnosing osteoporosis. DXA measures bone density in the hip and the spine. The test takes only five to 15 minutes to perform, exposes patients to very little radiation (less than one-tenth to one-hundredth of the amount used on a standard chest X-ray), and is quite precise.
The bone density of the patient is compared to the average peak bone density of young adults of the same sex and race. This score is called the “T score,” and it expresses the bone density in terms of the number of standard deviations (SD) below peak young adult bone mass.
    • Osteoporosis is defined as a bone density T score of -2.5 or below.
  • Osteopenia (between normal and osteoporosis) is defined as bone density T score between -1 and -2.5.
It is important to note that while osteopenia is considered a lesser degree of bone loss than osteoporosis, it nevertheless can be of concern when it is associated with other risk factors (such as smoking, cortisone steroid usage, rheumatoid arthritis, family history of osteoporosis, etc.) that can increase the chances for developing vertebral, hip, and other fractures. In this setting, osteopenia may require medication as part of the treatment program.

Medications that prevent bone loss and breakdown

Currently, the most effective medications for osteoporosis that are approved by the FDA are antiresorptive agents, which decrease the removal of calcium from bones. The bone is a living dynamic structure; it is constantly being built and removed (resorbed). This process is an essential part of maintaining the normal calcium level in the blood and serves to repair tiny cracks in the bones that occur with normal daily activity and to remodel bone based on the physical stresses placed on the bone. Osteoporosis results when the rate of bone resorption exceeds the rate of bone rebuilding. Antiresorptive medications inhibit removal of bone (resorption), thus tipping the balance in favor of bone rebuilding and increasing bone density. HRT is one example of an antiresorptive agent. Others include alendronate (Fosamax), risedronate (Actonel), raloxifene (Evista), ibandronate (Boniva), calcitonin (Calcimar), zoledronate (Reclast), and denosumab (Prolia).
Bisphosphates
Bisphosphonates decrease the risk of hip fracture, wrist fracture, and spine fracture in people with osteoporosis. Alendronate (Fosamax), risedronate (Actonel), ibandronate (Boniva), and zoledronate (Reclast) are bisphosphonates.
To reduce side effects and to enhance absorption of the medicine, all bisphosphonates taken by mouth (orally) should be taken in the morning, on an empty stomach, 30 minutes before breakfast, and with at least 8 ounces (240 ml) of water (not juice). This improves the absorption of the biphosphonate. Taking the pill sitting or standing (as well as drinking adequate amounts of liquids) minimizes the chances of the pill being lodged in the esophagus, where it can cause ulceration and scarring. Patients should also remain upright for at least 30 minutes after taking the pill to avoid reflux of the pill into the esophagus. Newer intravenous bisphosphonates, such as ibandronate (Boniva) and zoledronate (Reclast), bypass the potential esophagus and stomach problems.
Food, calcium, iron supplements, vitamins with minerals, or antacids containing calcium, magnesium, or aluminum can reduce the absorption of oral bisphosphonates, thereby resulting in loss of effectiveness. Therefore, oral bisphosphonates should be taken with plain water only in the morning before breakfast. Also, no food or drink should be taken for at least 30 minutes afterward.
Alendronate (Fosamax)
Alendronate (Fosamax) is a biphosphonate antiresorptive medication. Alendronate is approved for the prevention and treatment of postmenopausal osteoporosis as well as for osteoporosis that is caused by cortisone-related medications (glucocorticoid-induced osteoporosis). Alendronate has been shown to increase bone density and reduce fractures in the spine, hips, and arms. Fosamax is taken by mouth once a week to prevent and treat postmenopausal osteoporosis. Alendronate is the first osteoporosis medication also approved for increasing bone density in men with osteoporosis, either in a daily or a weekly dosing schedule.
Fosamax generally is well tolerated with few side effects. One side effect of alendronate is irritation of the esophagus (the food pipe connecting the mouth to the stomach). Inflammation of the esophagus (esophagitis) and ulcers of the esophagus have been reported infrequently with alendronate use.
Risedronate (Actonel)
Risedronate (Actonel) is another bisphosphonate antiresorptive medication. Like alendronate, this drug is approved for the prevention and treatment of postmenopausal osteoporosis as well as for osteoporosis that is caused by cortisone-related medications (glucocorticoid-induced osteoporosis). Risedronate is chemically different from alendronate and has less likelihood of causing esophageal irritation. Risedronate also is  more potent in preventing the resorption of bone than alendronate.
Ibandronate (Boniva)
Ibandronate (Boniva) is a bisphosphonate for prevention and treatment of postmenopausal osteoporosis. It is available in formulations for both daily and monthly oral use as well as for intravenous use every three months.
Zoledronate (Reclast)
Zoledronate (Reclast) is a unique intravenous bisphosphonate antiresorptive medication that is given once every year. This formulation seems to have very good ability to strengthen bones and prevent fractures of both spinal and non-spinal bones. The convenience of once-a-year dosing is obvious. As with all bisphosphonates, patients taking Reclast must be taking adequate calcium and vitamin D prior to and after infusion of the medication for optimal results. Generally, patients are given acetaminophen (Tylenol) the day of the infusion and for several days afterward to prevent occasional minor muscle and joint aches. The infusion lasts approximately 20-30 minutes. Reclast is used to treat and prevent osteoporosis in postmenopausal women and increases bone mass in men with osteoporosis. Reclast is also used to treat and prevent steroid-induced osteoporosis (glucocorticoid-induced osteoporosis). Reclast reduces risk of fractures after a low-trauma hip fracture. Reclast should not be used during or prior to pregnancy.
Selective estrogen receptor modulators (SERMs)
Raloxifene (Evista)
Raloxifene (Evista) belongs to a class of drugs called selective estrogen receptor modulators (SERMs). SERMs work like estrogen in some tissues but as an antiestrogen in other tissues. The SERMs were developed to reap the benefits of estrogen while avoiding the potential side effects of estrogen. Thus, raloxifene can act like estrogen on bone but as an antiestrogen on the lining of the uterus where the effects of estrogen can promote cancer.
The first SERM to reach the market was tamoxifen (Nolvadex), which blocks the stimulative effect of estrogen on breast tissue. Tamoxifen has proven valuable in women who have had cancer in one breast for preventing cancer in the second breast. Raloxifene is the second SERM to be approved by the FDA. Evista has been approved for the prevention and treatment of osteoporosis in postmenopausal women. In a three-year study involving some 600 postmenopausal women, raloxifene was found to increase bone density (and lower LDL cholesterol) while having no detrimental effect on the uterine lining (which means that it is unlikely to cause uterine cancer).
Because of its antiestrogen effects, the most common side effects with Evista are hot flashes Conversely, because of its estrogenic effects, Evista increases the risk of blood clots, including deep vein thrombosis (DVT) and pulmonary embolism (blood clots in the lung). The greatest increase in risk occurs during the first four months of use. Patients taking raloxifene should avoid prolonged periods of immobility during travel, when blood clots are more prone to occur. The risk of deep vein thrombosis with raloxifene is probably comparable to that of estrogen, about two to three times higher than the usual low rate of occurrence. Evista decreases the risk of spinal fractures in postmenopausal women with osteoporosis, but it is not known if there is a similar benefit in decreasing the risk of hip fracture. (The only agents that are definitely proven to decrease the risk of hip fracture are bisphosphonates and denosumab.)
Calcitonin (Calcimar, Miacalcin)
Calcitonin (Calcimar, Miacalcin) is a hormone that has been approved by the FDA in the U.S. for treating osteoporosis. Calcitonins come from several animal species, but salmon calcitonin is the one most widely used. Calcitonin can be administered as a shot under the skin (subcutaneously), into the muscle (intramuscularly), or inhaled nasally (intranasally). Intranasal calcitonin is the most convenient of the three methods of administration.
Calcitonin has been shown to prevent bone loss in postmenopausal women. In women with established osteoporosis, calcitonin has been shown to increase bone density and strength in the spine only.
Calcitonin is a weaker antiresorptive medication than bisphosphonates. Calcitonin is not as effective in increasing bone density and strengthening bone as estrogen and the other antiresorptive agents, particularly bisphosphonates. In addition, it is not as effective as bisphosphonates in reducing the risk of spinal fractures and has not been proven effective in reducing hip fracture risk. Therefore, calcitonin is not the first choice of treatment in women with established osteoporosis. Nevertheless, calcitonin is a helpful alternative treatment for patients who cannot tolerate other medications.
Common side effects of either injected or nasal spray calcitonin are nausea and flushing. Patients using Miacalcin Nasal Spray can develop nasal irritation, a runny nose, or nosebleeds. Injectable calcitonin can cause local skin redness at the site of injection, skin rash, and flushing.
Teriparatide (Forteo)
Teriparatide (Forteo) is a synthetic version of the human hormone, parathyroid hormone, which helps to regulate calcium metabolism. Unlike other medications for osteoporosis which reduce the resorption of bone, teriparatide promotes the growth of new bone. Forteo is self-injected into the skin. Because long-term safety is not yet established, it is only FDA-approved for 24 months of use. It reduces spinal fractures in women with known osteoporosis, but it is not known if there is a similar reduction in the risk for hip fracture.
Denosumab (Prolia)
The latest treatment approved for osteoporosis is denosumab (Prolia), an intravenous, infusible antibody that blocks a chemical messenger that plays a role in promoting bone thinning by the bone cells that are responsible for bone resorption. Prolia strengthens bone by increasing its density and reduces fractures. Prolia is administered by twice yearly injections under the skin. Denosumab is used for the treatment of postmenopausal women with osteoporosis at high risk for fracture, defined as a history of osteoporotic fracture, or multiple risk factors for fracture; or patients who have failed or are intolerant to other available osteoporosis therapy. Denosumab can cause increased risk of infections and low blood calcium levels (hypocalcemia).

Prevention of osteoporosis due to long-term corticosteroids

The long-term use of corticosteroids (such as prednisone, cortisone, and prednisolone) can lead to osteoporosis. Corticosteroids cause decreased calcium absorption from the intestines, increased loss of calcium through the kidneys in urine, and increased calcium loss from the bones. To prevent bone loss while on long-term corticosteroids, patients should
    1. have an adequate calcium (1,000 mg daily if premenopausal, 1,500 mg daily if postmenopausal) and vitamin D intake; however, calcium alone or combined with vitamin D cannot be relied upon to prevent bone loss from corticosteroids unless other prescription medications are added;
    2. discuss with their doctor the use of either alendronate, risedronate, and zoledronate, which have been approved for the prevention and treatment of corticosteroid-induced osteoporosis;
    3. discuss with their doctor about having a DXA bone density scan prior to beginning therapy and careful monitoring for osteoporosis during therapy.

Monitoring osteoporosis therapy

The controversy of bone density testing in patients already taking osteoporosis medication
The American Medical Association and other reputable medical organizations recommend that repeat bone density testing (DXA scans) not be done for monitoring osteoporosis treatment or prevention on a routine basis; it is scientifically premature to measure bone density as a way of monitoring the effects of treatment. Doctors simply do not know how to use repeated bone density measurements during therapy. Here are a few of the most important reasons:
    1. Bone density changes so slowly with treatment that the changes are smaller than the measurement error of the machine. In other words, repeat DXA scans cannot distinguish between a real increase in bone density due to treatment or a mere variation in measurement from the machine itself.
    2. The real purpose of osteoporosis treatment is to decrease future bone fractures. There is no good correlation between increases in bone density with decreases in fracture risks with treatment. For example, alendronate has been shown to decrease fracture risk by 50% but only to increase bone density by a few percent. In fact, most of the fracture reduction with raloxifene is not explained by raloxifene’s effects on bone mineral density.
    3. One density measurement taken during treatment will not help the doctor plan or modify treatment. For example, even if the DXA scan shows continued deterioration in bone density during treatment, there is not yet research data demonstrating that changing a medication, combining medications, or doubling medication doses will be safe and helpful in decreasing the future risk of fractures.
    4. Even if bone density deteriorates during treatment, it is quite likely that the patient would have lost even more bone density without treatment.
    5. Recent research has shown that women who lose bone density after the first year of HRT will gain bone density in the next two years of therapy, whereas women who gain in the first year will tend to lose density in the next two years of therapy. Therefore, bone density during treatment naturally fluctuate naturally, and these fluctuations may not correlate with the prevention of fractures due to the medication.
For all of these reasons, as surprising as it may sound to many people (and even some doctors!), rechecking bone density is not at all like checking blood pressure during treatment of high blood pressure (hypertension). Routine bone density testing during treatment is unlikely to be helpful. In the future, however, if ongoing research brings new technology or new therapies, testing decisions may change.

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