Osteoporosis

Introduction

You just celebrated your seventieth birthday. It was a grand occasion, but a few days after you devoured your second piece of birthday cake, you went in for your yearly physical. At the doctor's office, you got some confusing news. You've been 5' 7" tall since high school, but now your doctor says you're 5' 6". Were you standing straight? Is the doctor's height instrument wrong? Or. . . do you have osteoporosis?

What is it?

Osteoporosis is a progressive condition that causes the loss of bone over time. The gradual weakening of bones caused by osteoporosis may eventually result in fractures (broken bones), most commonly of the hip and spine. Particularly in elderly people, broken bones are often disabling. Serious breaks can lead to other illnesses, or even death.

What causes it?

Although bone is often considered to be stable, it is actually changing continually. New bone cells are formed after old bone cells are broken down into components, such as calcium, which are taken out of the body in the blood. Osteoporosis is believed to be caused by an imbalance in two types of cells, osteoblasts and osteoclasts. Osteoblasts are responsible for making bone while osteoclasts break down bone. The process of bone break down and rebuilding is often called bone turnover, and the breakdown of bone may be known as resorption. When osteoclasts break bone down faster than osteoblasts build bone, osteoporosis occurs. The following factors can contribute to the disease:

  • Aging
  • Estrogen loss
  • Gender
  • Heredity
  • Lifestyle
  • Medications
  • Nutrition
  • Other illnesses

Who has it?

The latest estimates from the National Osteoporosis Foundation state that about 8 million American women and 2 million American men have osteoporosis. As many as 34 million more Americans may have osteopenia (lower than average bone density as compared to others of the same age and gender). Only one-third of all people with osteoporosis have been diagnosed with it and only one-seventh of those diagnosed receive treatment according to the National Osteoporosis Foundation. As the number of older individuals increases, the number of Americans who have osteoporosis or who have increased risk for getting osteoporosis is expected to increase. Osteoporosis contributed to about 2 million broken bones in 2005, according to the National Osteoporosis Foundation. In 2005, the National Osteoporosis Foundation reported that more than $19 billion are spent annually on broken bones related to osteoporosis.

In humans, the amount of bone in the body is highest between the ages of about 25 and 40. During pregnancy, the developing baby gets calcium from the mother's bones, but the mother usually regains bone density after she finishes breast-feeding. Both men and women begin to lose bone density permanently in their forties and fifties. By the age of 80, nearly 90% of women and 50% of men have osteoporosis. Because women experience more rapid bone loss in the years following menopause, they usually have an earlier risk of fractures. Approximately one-half of women over 50 years of age will experience a fracture related to osteoporosis as compared to about one-eighth of men over the age of 50 years. For a woman, the risk of a hip fracture is equal to the risk of breast, uterine, and cervical cancer combined.

What are the risk factors?

Risk factors are characteristics that may increase the chance of developing a condition. Being female greatly increases the chances of having osteoporosis. For women, other osteoporosis risk factors include:

  • Conditions (such as anorexia) or activities (such as exercising excessively) that result in the absence of menstrual cycles
  • Menopause
  • Never having had children

Men who have had their testicles removed surgically or who have lower than average levels of the male hormone, testosterone, may be at greater risk for having osteoporosis.

For both men and women, the risk of osteoporosis is also increased by:

  • Advanced age
  • Asian or white race
  • Certain chronic medical conditions (such as asthma or other lung disorders, cancer, Cushing's syndrome, diabetes, rheumatoid arthritis, parathyroid conditions, or thyroid conditions)
  • Cigarette smoking
  • Corticosteroid medications (such as dexamethasone or prednisone)
  • Excessive alcohol or caffeine consumption
  • Family history of osteoporosis
  • Low bone density
  • Low-calcium diet, especially during childhood
  • Physical inactivity
  • Previously broken bones, especially after the age of 50
  • Small body build
  • Vitamin D deficiency

Other factors that may contribute to osteoporosis are not well defined. For example, studies by the U.S. National Institute of Child and Human Development (NICHD) have shown that irregular menstrual periods in young women may signal a hormonal shortage that could lead to osteoporosis. A separate study has found that individuals with major depression may be at higher risk for developing osteoporosis. Other research suggests that abnormally elevated stress hormone levels may also contribute to bone loss. Another recent study reported that women who needed bed rest to control problem pregnancies lost more bone density than other pregnant women (averages of 4.6% as compared to 1.5%).

Click on the link below to access a checklist of risks for osteoporosis.

Risk Factor Checklist

Discuss osteoporosis prevention with your doctor. Before your next appointment, check off the following risk factors that apply to you, print out the list, and share it with your doctor. If you are potentially at risk for osteoporosis, your doctor may suggest a bone mineral density (BMD) test to help determine if you could have a fracture due to osteoporosis.

Alcohol or caffeine consumption in large amounts

Asian or white ancestry

Broken bones (especially of the hip, forearm, or spine)

Chronic medical conditions (such as asthma or other lung disorders, cancer, Cushing's syndrome, parathyroid conditions, rheumatoid arthritis, or thyroid conditions)

Early menopause (before the age of 45) naturally or from surgical removal of the ovaries

Family history of osteoporosis, broken bones, or stooped posture

Lack of exercise or sedentary lifestyle

Long-term use of some medications (such as phenytoin, prednisone or other steroids, and thyroid medications)

Never having given birth to a child

Not enough calcium in the diet

Postmenopausal or currently going through menopause

Practices or conditions that result in the absence of menstrual cycles

Small, thin body size or low body weight

Smoking cigarettes (either currently or formerly)

Surgical removal of the testicles


What is a bone density test?

Ordinary x-rays are not sensitive enough to reveal bone loss until more than 30% of the highest amount of bone is already gone. The only sure way to determine the true condition of bone is to have a bone mineral density (BMD) test. Also called bone mass measurements, BMD tests are more readily available than they were a few years ago. BMD testing is recommended for postmenopausal women with osteoporosis risk factors and for all postmenopausal women age 65 or greater (medscape). A series of BMD tests may be performed about once a year to measure the rate of bone loss, to estimate the risk of bone breaks due to osteoporosis, and to check whether or not treatments are working.

Various methods are used for the assessment of bone density - usually based on the part of the body that needs to be assessed. The tests, all painless and safe, measure bone density in the bones that break most often due to osteoporosis of the spine (back), hip and/or wrist. Among the most common BMD tests are:

  • Single-photon absorptiometry (SPA) is normally used for the forearm, heel, or lower leg.
  • Dual-energy x-ray absorptiometry (DEXA) measures BMD in the spine and hip.
  • Ultrasound may be used occasionally to assess bone density in the foot.

The measured bone density is compared to two standards, or norms, known as "age matched" and "young normal." The age-matched reading compares an individual's measured bone density to what is expected in someone of the same age, sex, and size. The young normal reading compares the measured density to the best peak bone density of a healthy young adult of the same sex as the individual being tested.

What are the symptoms?

Osteoporosis is often called a silent disease because it can progress gradually for many years without any symptoms. When symptoms do appear, the most common ones are:

  • A broken bone
  • Back pain
  • Decreased height
  • Formation of a rounded upper back (also known as dowager's hump or kyphosis)
  • Dull pain, usually in the neck or lower back

How is it treated?

Although osteoporosis has no cure, several types of medications are available to reduce the rate of bone loss, increase bone density, and reduce the number of fractures. In general, they work in two main ways: they lessen bone break down (anti-resorptive agents) or they stimulate the formation of new bone (anabolic agents). Experts recommend that these medications be taken continuously in order to gain their full benefits. Generally, bone loss resumes if the medications are stopped.

Most of the medications used to treat osteoporosis are also used to help prevent it. They include:

  • Calcium and Vitamin D
  • Hormone Replacement Therapy (Estrogens and/or Progestins)
  • Calcitonin
  • Bisphosphonates
  • Selective Estrogen Receptor Modulators (SERMs)
  • Recombinant DNA Parathyroid Hormone

While calcium, vitamin D, and exercise are important first steps for maintaining healthy bone at any age, they may not completely stop bone loss. Unless specific reasons exist not to take calcium and vitamin D, both are necessary for all individuals whether or not they take other medications for osteoporosis. According to the United States Surgeon General, calcium intake should be 1,200 mg to 1,500 mg (1.2 to 1.5 grams) per day through diet, supplements or a combination of both. Click on the "Helping Yourself" button at the top of this page to learn more about calcium-rich foods. If not enough calcium is obtained from foods, additional amounts can be taken as supplements. Calcium carbonate and calcium citrate are the preferred forms, because the body absorbs more calcium from them.

Often, calcium alone is not enough to improve bone density. Supplementing with vitamin D has been shown to help maintain bone strength and increase calcium absorption into bones. A daily intake of 400-800 IU of vitamin D for those people found to be deficient is recommended by the osteoporosis guidelines published in 2003.

Learn more about calcium and vitamin D by clicking on the link below.

Hormone replacement therapy (HRT) - HRT involves using drugs to restore estrogen and/or progesterone levels that decrease after menopause. HRT is approved for prevention and treatment of osteoporosis in women. However, long-term use of HRT may be associated with an increased risk of breast cancer, heart disease, or stroke according to the Women's Health Initiative trial. Although millions of women have used HRT, the American Heart Association (AHA) now recommends that HRT not be used for the prevention or treatment of heart disease. Alternatives to the use of HRT should be discussed with a doctor.

Calcitonin is a hormone that the human body makes in the thyroid gland. It slows the breakdown of bone. Supplemental calcitonin (Miacalcin, Fortical) comes as an injection or a nasal spray that is approved for the treatment of osteoporosis in men and women. Calcitonin supplements may be obtained from natural sources (usually salmon) or they may be made synthetically. Although generally considered to be safe, supplemental calcitonin may not be as effective as other treatments for osteoporosis. However, evidence from some studies shows that it may help to control pain associated with osteoporosis.

Bisphosphonates are a group of drugs that attach to minerals, primarily calcium, in bone. They work by decreasing the effects of osteoclasts, so less bone is broken down and bone density does not decline as rapidly. Certain bisphosphonates, such as alendronate (Fosamax), risedronate (Actonel), and ibandronate (Boniva), are approved by the FDA for the prevention and treatment of osteoporosis for both men and women. Bisphosphonates are available in tablet and injectable form and--depending on the particular medication--are administered in various dosing regimens including daily, weekly, twice monthly, monthly and every three months. Zoledronic acid (Reclast) is the newest bisphosphonate and is approved only for the treatment of osteoporosis in postmenopausal women. Zoledronic acid differs from the other available bisphosphonates because it is available as an injection given only once per year.

Raloxifene (Evista) is an oral medication that is approved for the prevention and treatment of osteoporosis in women who are past menopause and who are not taking hormone replacement therapy. Raloxifene is a member of the class of drugs called selective estrogen receptor modulators (SERMs) which attach to the sites on cells where estrogen usually attaches. This results in a decrease in bone break-down and an increase in BMD. SERMs act like estrogen in some parts of the body (such as in the bones) without causing a general estrogen effect. Some early data suggests that SERMs may decrease the risk of breast cancer as well.

Teriparatide (Forteo) is the first drug in the newest drug class for treatment of osteoporosis in men and women who are particularly likely to experience fractures. This includes individuals who have previously suffered a fracture due to osteoporosis, individuals with multiple risk factors for fractures, and those who have failed or cannot tolerate other osteoporosis treatments. Approved by the FDA in 2002, teriparatide is human parathyroid hormone (PTH) created by recombinant DNA technology. PTH is a natural human hormone that controls calcium levels in the body. Teriparatide acts like natural PTH to increase bone formation. Because the increased activity of osteoblasts builds bone up faster than osteoclast activity can break bone down, bone density may actually increase. Available only as a daily injection, teriparatide is awkward to use. It is also very expensive compared to other drugs that treat osteoporosis.

What else might help?
Bed rest or inactivity can result in rapid bone loss. According to a recent study in the Journal of Women's Health, regular exercise may actually increase bone density in the spine as well as increase muscle mass. Potentially beneficial types of exercise include aerobics, weight lifting, and resistance training. While these activities have been shown to increase bone density, no information is available on the reduction of fractures. Consult with your personal health care provider before beginning any exercise program.

To learn more about the drugs used to prevent and/or treat osteoporosis, click on the links below.

Helping Yourself

To help prevent osteoporosis:

  1. Maintain adequate intake of calcium and vitamin D. Dairy products and other foods that contain calcium should be a central part of the daily diet for all individuals. As set by the Institute of Medicine, Recommended Dietary Allowances (RDAs) are the average amounts of nutrients that meet nutritional needs for 98% of healthy individuals in a specific age and gender. The RDA of calcium for adults is 1,000 mg (one gram) to 1,200 mg (1.2 grams), depending on age. However, teenagers, women who are pregnant or breast-feeding, and postmenopausal women may need additional calcium. Dairy products (milk, cheese, and yogurt) are well-known sources of calcium. Many bakery products, cereals, flours, and orange juice products are "fortified" or "enriched" with calcium in addition to what they contain naturally. However, many of these foods are also high in calories and/or saturated fats so they should be eaten in reasonable-sized portions.
    Other Foods High in Calcium
    FoodAmount Approximate Calcium Content
    Collard greens (frozen)One cup350 mg
    Sardines canned in oil 3 ounces325 mg
    Spinach (frozen)One cup290 mg
    Blackstrap molassesOne Tablespoon170 mg
    Baked beans (canned)One cup120 to 150 mg
    Cooked navy beansOne cup125 mg

    For more detailed information about the calcium content of foods, see: http://www.nal.usda.gov/fnic/foodcomp/Data/SR17/wtrank/sr17w301.pdf

    Vitamin D intake is measured in two different ways. One microgram of vitamin D is equal to 40 International Units (IUs). For vitamin D, the RDA is 5 micrograms (200 IUs) per day. Individuals over the age of 50 years should get at least 10 micrograms (400 IUs) daily; and those over 70 are advised to increase vitamin D intake to at least 15 micrograms (600 IUs) per day. Vitamin D is formed in the body by the action of sunlight on skin. It can also be obtained from dietary supplements and from foods such as:

    • Canned salmon (3 ounces): 13.25 micrograms (530 IUs)
    • Canned tuna (3 ounces): 5 micrograms (200 IUs)
    • Low fat or skim milk (8 ounces): 2.5 micrograms (100 IUs)

    Individuals who do not get enough calcium and/or vitamin D from natural sources should discuss dietary supplementation with a doctor.

  2. Take part in regular weight-bearing exercise. Walking, jogging, and low-impact aerobics are a few examples of weight-bearing exercises that can help prevent or slow the progression of osteoporosis. However, the type of exercise is not as important as being consistent. Almost any kind of exercise done for at least 30 minutes three or more times a week will not only help to strengthen bones, it will also help to prevent cardiovascular disease.

  3. Stop smoking. Postmenopausal women who smoke cigarettes and men who have smoked for a number of years have significantly weaker bones than non-smokers in their age groups.

  4. Discuss preventive measures with a healthcare professional. Individuals who know or suspect that they are at high risk for osteoporosis should examine prevention options before the symptoms of osteoporosis are evident.

To help prevent falls that may result in fractures:

  1. Talk to your doctor or pharmacist. Older adults are more likely to fall because of common, age-related physical changes and medical conditions. Sometimes the medications that treat these conditions can cause side effects such as confusion, dizziness, or drowsiness and can affect coordination and balance. Talk to your doctor or pharmacist about whether your health conditions or medications are putting you at risk for falls.

  2. Be physically active. In addition to strengthening bones, regular exercise can strengthen muscles and improve coordination, balance, and endurance. Talk to your doctor or other healthcare professional about an exercise program that is right for you.

  3. Minimize household risks. To make your home safer, consider the following precautions:

    • Arrange furniture so that you have plenty of room to walk.
    • Remove objects from walkways and stairs that you could trip over.
    • Make sure that carpeting and rugs are secured to the floor.
    • Put non-slip strips or a rubber mat on the floor of the bathtub or shower.
    • Install grab bars in the bathtub, shower, and next to the toilet and hand rails along stairs and walkways.
    • Make sure there is enough light in all entryways, rooms, and stairways.
    • Put items you use often in easy-to-reach places.
    • Consider using a cane or walker as an assistive device.
    • Wear sensible shoes with a low heel and non-slip soles. Make sure your shoes fit well and provide plenty of support.

  4. Have your eyes checked. See your eye doctor regularly or if you think your vision has changed. Poor vision can make you less stable and increase your risk for falls.

  5. Limit alcohol. Keep your alcohol intake to a minimum. Even small amounts can affect reflexes and balance and increase your risk for falls.

What is on the horizon?

With the number of individuals who have osteoporosis expected to increase dramatically as members of the large post-World War II generation reach old age, researchers are taking several approaches to prevent and treat this condition.

First, studies are underway to develop methods of detecting osteoporosis earlier. Earlier treatment may prevent or lessen the risk of fractures as well as other results of osteoporosis (such as decreased height and rounded back).

Bone density of older adults depends on the total amount of bone acquired during growth. One study that is currently being conducted tests whether implementing a specific bone-building program during childhood will increase the development of both bone density and the amount of calcium and other minerals in bones. Although bones are strengthened for the whole body, special emphasis is placed on the spine, thigh bone at the hip, and forearm at the wrist, which are the areas most at risk for fractures due to osteoporosis. Additionally, specific types of exercises are being evaluated for their potential to enhance the formation of thicker, stronger bone at an early age.

The effects of vitamin supplementation - in particular vitamin A - are also under study. Although one recent study reinforces previous findings that men with high levels of vitamin A in their bodies are at the highest risk for fractures, other study evidence finds no association between osteoporosis and vitamin A. Vitamin K supplementation to determine if it will prevent osteoporosis in postmenopausal women is also being investigated.

A group of Swiss researchers recently studied the effects of potassium citrate on bone density. The study suggested that taking the supplement may help to partially neutralize high levels of acid that are common in modern diets and can lead to increased bone density in postmenopausal women with osteopenia. While news of the effects of potassium citrate on bone density are promising, it's too early to recommend its widespread use for prevention or treatment of osteoporosis. Future research will likely examine the effects of potassium citrate on fracture rates.

Natural foods, such as soy, contain phytoestrogens (plant-produced substances that act like estrogen in the body). In general, individuals who consume diets high in phytoestrogens - particularly phytoestrogens that belong to the subgroup of isoflavones - seem to maintain bone density. Therefore, isoflavones are of interest as potential osteoporosis prevention. Much more long-term controlled research is needed to prove a bone-saving effect for them, though.

Although lifestyle and environmental factors play important roles in delaying or preventing osteoporosis, for an estimated 50% to 90% of individuals, bone mineral density is determined primarily by heredity. Therefore, researchers are also trying to approach treatment and prevention of osteoporosis through isolation of the gene or genes responsible for osteoporosis. Currently, genetic research for osteoporosis takes two tracks. First, researchers are working to determine what specific genes may play a key role in determining and maintaining bone density. A second focus is to identify genetic differences in natural body receptors that may contribute to decreased bone density. Current research centers on estrogen receptors alpha (ERS1s) and vitamin D receptors (VDRs), but several other receptor types are also being studied.

Potential new drug therapies for osteoporosis include some medications already approved for other conditions.

Most notable are hydroxymethylglutaryl-coenzyme-A reductase (HMG Co-A) inhibitors - commonly called "statins". A class of drugs used to lower cholesterol levels, statins have recently received considerable attention for the possible treatment of osteoporosis. In some laboratory studies of animals and observational studies of humans, statins have appeared to increase bone density. Because common steps occur in both the formation of cholesterol and the activation of osteoclasts, statins may disrupt both activities by blocking certain key steps. However, these findings are very preliminary and more studies will need to be conducted before recommendations on using statins for osteoporosis can be made.

Sodium fluoride, a drug commonly used to prevent tooth decay for children, may also have benefits in building and/or maintaining bone. Results from long-term studies - primarily in postmenopausal women - have been inconclusive, however, with some studies showing that fluoride may increase bone density, and others showing little or no effects on bone.

Growth hormone (GH) deficiencies are associated with lower-than-average bone density in adults who are GH deficient or who were GH deficient as children. Supplemental GH increases the rate of bone "turnover" (the replacement of old bone cells with new ones). Soon after GH therapy is started, bone density may actually decrease as old bone is broken down faster. Over a longer time, however, the formation of new bone usually accelerates and bone density may increase.

New agents are under study among drug classes already being used to prevent or treat osteoporosis. New bisphosphonates that are in development - such as clodronate and minodronate - may need fewer doses, have different dosing schedules, and come in different dosage forms. PTH is also being developed in non-injected forms, such as transdermal patches. SERMs under study for treating osteoporosis include arzoxifene, bazedoxifene, lasofoxifene, and opsemifene. Because many SERMs seem to reduce the chance of getting breast cancer for women using them for osteoporosis, SERMs are also being studied for preventing breast cancer. They may also have cholesterol-lowering effects. Also under study is combination therapy involving treatment with an agent that builds bone (such as PTH) followed by a drug like a bisphosphonate or a SERM that lessens bone loss.

Potential new classes of drugs for preventing and/or treating osteoporosis include both agents that decrease or delay the rate of bone break down (anti-resorptive agents) and those that increase or speed up the rate of bone formation (anabolic agents). Some investigational agents may do both and some may offer additional health benefits, as well. Among some of the drug classes under various stages of investigation are:

Cathepsin K inhibitors - A type of enzyme that breaks down a body protein known as cysteine, cathepsin K is believed to activate osteoclasts. Agents that block the effects of cathepsin K may slow down bone resorption while bone formation continues at a normal rate.

Insulin-like growth factor-1 (IGF-1) - a substance produced in the liver, IGF-1 is stored in bone. Released during bone break down, it encourages the production of osteoblasts to rebuild bone cells. IGF-1 deficiencies have been associated with lower-than-expected bone density and an increased risk of osteoporosis-related fractures.

Integrin receptor inhibitors (also called disintergins) - Investigational drugs in this class (including contortrostatin, echistatin, and SC56631) block the attachment of osteoclasts to bone. Osteoclasts are prevented from beginning the process of bone break down. Integrin receptor inhibitors may also prevent or slow down the production of osteoclasts, thereby decreasing the number of osteoclasts available to break down bone. Of particular interest are integrin alphavbeta3 receptors, which may also be called vitronectin receptors.

Nitrosylated non-steroidal anti-inflammatory drugs (NO-NSAIDs) ? Certain pain-relievers known as NSAIDs (such as flurbiprofen) may be modified to release nitric oxide (NO) in the body. NO, a byproduct of body processes, has many potential effects. In particular, low levels of NO are associated with increased bone break down, but high levels of NO seem to lessen the rate of bone resorption. In theory, increasing amounts of NO in the body could help to prevent and/or treat osteoporosis.

Osteoprotegerin (OPG) - OPG is a cytokine (a protein produced within the immune system to help control immune function). Laboratory animals with low levels of OPG also tend to have faster bone turnover, poor attachment of new bone cells to old cells, and a less stable bone structure. Increasing OPG may help to normalize bone turnover.

Src inhibitors - By limiting the effectiveness of Src tyrosine kinase (STK), an enzyme that triggers osteoclast activity and inhibits osteoblasts, Src inhibitors are thought to lessen bone break down and encourage bone formation.

Strontium ranelate - An oral drug, which has been tested in laboratory studies and at least two large studies of postmenopausal women with osteoporosis, strontium ranelate appears to decrease the rate of bone break down. It also increases the rate of bone formation. Using it may actually restore lost bone density, if bone-building osteoblast activity replaces bone cells faster than osteoclasts break down bone. Strontium ranelate was recently approved for use in Europe, but is not currently approved in the United States.

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Osteoporosis Health Condition Last Updated: October 2008

Note: The above information is intended to supplement, not substitute for, the expertise and judgment of your physician, pharmacist, or other healthcare professional. It is not intended to diagnose a health condition, but it can be used as a guide to help you decide if you should seek professional treatment or to help you learn more about your condition once it has been diagnosed.

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