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Osteoporosis

By

Marcy B. Bolster

, MD, Harvard Medical School

Last full review/revision May 2020| Content last modified May 2020
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Osteoporosis is a condition in which a decrease in the density of bones weakens the bones, making breaks (fractures) likely.

  • Aging, estrogen deficiency, low vitamin D or calcium intake, and certain disorders can decrease the amounts of the components that maintain bone density and strength.

  • Osteoporosis may not cause symptoms until a bone fracture occurs.

  • Fractures can occur with little or no force and may occur after a minor fall.

  • Although fractures are often painful, some fractures of the spine do not cause pain but can still cause deformities.

  • Doctors diagnose people at risk by testing their bone density.

  • Osteoporosis can usually be prevented and treated by managing risk factors, ensuring adequate calcium and vitamin D intake, engaging in weight-bearing exercise, and taking bisphosphonates or other drugs.

Bones contain minerals, including calcium and phosphorus, which make them hard and dense. To maintain bone density (or bone mass), the body requires an adequate supply of calcium and other minerals and must produce the proper amounts of several hormones, such as parathyroid hormone, growth hormone, calcitonin, estrogen, and testosterone. An adequate supply of vitamin D is needed to absorb calcium from food and incorporate it into bones. Vitamin D is absorbed from the diet and also manufactured in the skin using sunlight.

So that bones can adjust to the changing demands placed on them, they are continuously broken down and reformed. This process is known as remodeling. In this process, small areas of bone tissue are continuously removed and new bone tissue is deposited. Remodeling affects the shape and density of the bones. In youth, the bones grow in width and length as the body grows. In later life, bones may sometimes enlarge in width but do not continue to grow longer.

Loss of Bone Density in Women

In women, bone density (or mass) progressively increases until about age 30, when bones are at their strongest. After that, bone density gradually decreases. The rate of bone loss accelerates after menopause, which occurs on average around age 51.

Loss of Bone Density in Women

Because more bone is formed than is broken down in the young adult years, bones progressively increase in density until about age 30, when they are at their strongest. After that, as breakdown exceeds formation, bones slowly decrease in density. If the body is unable to maintain an adequate amount of bone formation, bones continue to lose density and may become increasingly fragile, eventually resulting in osteoporosis.

Types of Osteoporosis

About 8 million women and 2 million men in the United States have osteoporosis. There are two main types of osteoporosis:

Primary osteoporosis occurs spontaneously. Secondary osteoporosis is caused by another disorder or by a drug.

Primary osteoporosis

More than 95% of osteoporosis in women and probably about 80% in men is primary. Most cases occur in postmenopausal women and in older men.

A major cause of osteoporosis is a lack of estrogen, particularly the rapid decrease that occurs at menopause. Most men over 50 have higher estrogen levels than postmenopausal women, but these levels also decline with aging, and low estrogen levels are associated with osteoporosis in both men and women. Estrogen deficiency increases bone breakdown and results in rapid bone loss. In men, low levels of male sex hormones also contribute to osteoporosis. Bone loss is even greater if calcium intake or vitamin D levels are low. Low vitamin D levels result in calcium deficiency, and increased activity of the parathyroid glands causes the glands to release too much parathyroid hormone (see hyperparathyroidism), which can also stimulate bone breakdown. For unknown reasons, bone production also decreases.

A number of other factors, such as certain drugs, tobacco use, heavy alcohol use, a family history of osteoporosis (for example, if a person's parents have had hip fractures), and small body stature, increase the risk of bone loss and the development of osteoporosis in women. These risk factors are also important in men.

Secondary osteoporosis

Less than 5% of osteoporosis in women and about 20% in men is secondary.

Examples of disorders that may cause secondary osteoporosis are chronic kidney disease and hormonal disorders (especially Cushing disease, hyperparathyroidism, hyperthyroidism, hypogonadism, high levels of prolactin, and diabetes mellitus). Certain types of cancer, such as multiple myeloma, can cause secondary osteoporosis, as can other chronic diseases such as rheumatoid arthritis. Examples of drugs that may cause secondary osteoporosis are progesterone, corticosteroids, thyroid hormones, certain chemotherapy drugs, and antiseizure drugs. Excessive alcohol or caffeine consumption and cigarette smoking may contribute to osteoporosis.

Risk Factors for Primary Osteoporosis

  • Family members with osteoporosis

  • A diet that is low in calcium and vitamin D

  • Sedentary lifestyle

  • White or Asian race

  • Thin build

  • Early menopause

  • Cigarette smoking

  • Excessive alcohol or caffeine consumption

Idiopathic osteoporosis

Idiopathic osteoporosis is a rare type of osteoporosis. The word idiopathic simply means that the cause is unknown. This type of osteoporosis occurs in premenopausal women, in men under age 50, and in children and adolescents who have normal hormone levels, normal vitamin D levels, and no obvious reason to have weak bones.

Symptoms

At first, osteoporosis causes no symptoms because bone density loss occurs very gradually. Some people never develop symptoms. However, when osteoporosis causes bones to break (fracture), people may have pain depending on the type of fracture. Fractures tend to heal slowly in people who have osteoporosis and may lead to deformities such as curvature of the spine.

In long bones, such as the bones of the arms and legs, the fracture usually occurs at the ends of the bones rather than in the middle. The bones of the spine (vertebrae) are particularly at risk of fracture due to osteoporosis. These fractures usually occur in the middle to lower back.

Vertebral compression fractures (fractures of spinal vertebrae) may occur in people who have any type of osteoporosis. These fractures are the most common osteoporosis-related fractures. The weakened vertebrae may collapse spontaneously or after a slight injury. Most of these vertebral compression fractures do not cause pain. However, pain can develop, usually starting suddenly, staying in a particular area of the back, and worsening when a person stands or walks. The area may be tender. Usually the pain and tenderness begin to go away gradually after 1 week. However, lingering pain may last for months or be constant. If several vertebrae break, an abnormal curvature of the spine (a dowager's hump) may develop, causing muscle strain and soreness as well as deformity.

Fragility fractures are fractures that result from a relatively minor strain or fall, such as a fall from a standing height or less, including a fall out of bed, that normally would not cause a fracture in a healthy bone. Fragility fractures commonly occur in the upper forearm bone (radius), top of the thighbone (femur), spine (vertebral compression fractures), and the bony bump (trochanter) at the upper end of the thighbone. Other bones include the upper end of the upper arm bone (humerus) and the pelvis.

Hip fracture, one of the most serious fractures, is a major cause of disability and loss of independence in older people.

Wrist fractures occur often, especially in people with postmenopausal osteoporosis.

People who have had one fracture in which osteoporosis had been a factor are at much higher risk of having more such fractures.

Fractures of the nose, ribs, collarbone, and bones in the feet are not considered osteoporosis-related fractures.

Did You Know...

  • People who have had one osteoporosis-related fracture are at much higher risk of having more of these fractures.

Diagnosis

  • Bone density testing

  • Vitamin D level

  • Tests for causes of secondary osteoporosis

A doctor may suspect osteoporosis in the following people:

  • All women age 65 or older

  • Women between menopause and age 65 who have risk factors for osteoporosis

  • All men and women who have had a previous fracture caused by little or no force, even if the fracture occurred at a young age

  • Adults age 65 or older who have unexplained back pain or loss of at least 1.2 inches (about 3 centimeters) of body height

  • People whose bones appear thin on x-rays or who have vertebral compression fractures on x-rays

  • People who are at risk of developing secondary osteoporosis

If osteoporosis is suspected and people have not had x-rays, doctors may do them to diagnose a fracture. Certain findings on x-rays suggest osteoporosis, but the diagnosis of osteoporosis is confirmed by bone density testing.

Bone density testing

Bone density testing can be used to detect or confirm suspected osteoporosis, even before a fracture occurs. A number of rapid screening techniques are available to measure bone density at the finger or the heel by dual-energy x-ray absorptiometry (DXA), which can be used to measure bone density at these sites. However, results of rapid screening tests should be confirmed with conventional DXA. Conventional DXA, the most useful test, measures bone density at the spine and hip, which are the sites at which major fractures are likely to occur. This test is painless, involves very little radiation, and can be done in about 10 to 15 minutes. It may be useful for monitoring the response to treatment as well as for making the diagnosis. DXA may also reveal osteopenia, a condition in which bone density is decreased but not as severely as in osteoporosis. People who have osteopenia also have an increased risk of fractures.

Other tests

Blood tests may be done to measure calcium, vitamin D, and hormone levels.

Tests that determine how the liver and kidneys are functioning are also done.

Further testing may be needed to rule out treatable conditions that might lead to osteoporosis. If such a condition is found, the diagnosis is called secondary osteoporosis.

Prevention

Prevention of osteoporosis is generally more successful than treatment because it is easier to prevent loss of bone density than to restore density once it has been lost. Prevention measures are recommended for anyone who has bone loss or who has risk factors for bone loss, regardless of whether they have had an osteoporosis-related fracture. Osteoporosis prevention involves

Certain measures can help prevent fractures. Many older people are at risk of falls because of poor coordination, poor vision, muscle weakness, confusion, and use of drugs that cause light-headedness when people stand or of drugs that cause confusion. Modifying the home environment for safety and working with a physical therapist to develop an exercise program can help. Strengthening exercises, including core strengthening, may help improve balance.

Treatment

  • Calcium and vitamin D

  • Weight-bearing exercise

  • Drugs

  • Treatment of fractures

Osteoporosis treatment involves ensuring adequate intake of calcium and vitamin D and engaging in weight-bearing exercises (such as walking, climbing stairs, or weight training). Drug treatment is usually recommended. When treating people who have osteoporosis, doctors also manage conditions and risk factors that can make osteoporosis worse.

Calcium and vitamin D

Consuming an adequate amount of nutrients, particularly calcium and vitamin D, is helpful, especially before maximum bone density is reached (around age 30) but also after this time. Vitamin D helps the body absorb calcium.

All men and women should consume at least 1,000 milligrams of calcium each day. Postmenopausal women, older men, children who are going through puberty, and women who are pregnant or breastfeeding may need to consume 1,200 to 1,500 milligrams each day. Foods rich in calcium include dairy products (such as milk and yogurt), certain vegetables (such as broccoli), and nuts (such as almonds).

Dietary sources of calcium are preferred to supplements (see table Amount of Calcium in Some Foods). However, if people cannot consume the recommended amounts by diet alone, they need to take supplements. Many calcium preparations are available, and some include supplemental vitamin D. The most common supplements are calcium carbonate or calcium citrate. Calcium citrate supplements should be taken by people who take a proton pump inhibitor such as omeprazole (which is used to reduce stomach acid production) or who have had gastric bypass surgery.

Table
icon

Amount of Calcium in Some Foods

Food

Serving Size

Amount of Calcium (in milligrams)

Almonds (toasted, unblanched)

1 ounce

80

Arugula (raw)

1 cup

125

Bok choy (raw, shredded)

1 cup

74

Bread (calcium fortified*)

1 slice

150 to 200

Bread (white)

1 slice

73

Bread (whole wheat)

1 slice

30

Brie cheese

1 ounce

50

Broccoli (cooked)

1 cup

180

Broccoli (raw)

½ cup

21

Buttermilk (low fat)

1 cup

284

Carnation® powder drink mix

1 packet

250

Cereal (calcium fortified*)

1 cup

100 to 1,000

Chard (cooked)

1 cup

100

Cheddar cheese

1.5 ounces

307

Collard greens

1 cup

50

Cottage cheese

1 cup

138

Cream cheese (regular)

1 tablespoon

14

Figs (dried, uncooked)

1 cup

300

Frozen yogurt (vanilla, soft serve)

½ cup

103

Gruyere cheese

1 ounce

270

Hard cheese (such as Cheddar or Jack)

1 ounce

200

Hot cocoa (calcium fortified*)

1 packet

320

Ice cream (vanilla)

½ cup

84

Kale (fresh, cooked)

1 cup

94

Kale (raw, chopped)

1 cup

100

Mackerel (canned)

3 ounces

250

Molasses (blackstrap)

1 tablespoon

135

Mozzarella cheese

1 ounce

200

Mustard greens

1 cup

40

Nonfat dry milk powder

5 tablespoons

300

Nonfat milk

1 cup

299

Oatmeal (instant)

1 package

100 to 150

Okra (cooked)

1 cup

100

Orange juice (calcium fortified*)

6 ounces

261

Parmesan cheese

1 tablespoon

70

Reduced-fat milk (2%)

1 cup

293

Salmon (canned with bones)

3 ounces

181

Sardines (canned in oil with bones)

3 ounces

325

Sesame seeds (whole-roasted)

1 ounce

280

Sour cream (reduced fat, cultured)

2 tablespoons

31

Soy milk (calcium fortified*)

1 cup

299

Swiss cheese

1 ounce

270

Tofu (firm and made with calcium sulfate)

½ cup

253

Tofu (soft and made with calcium sulfate)

½ cup

138

Turnip greens (fresh or boiled)

½ cup

99

Whole milk

1 cup

276

Yogurt (drink)

12 ounces

300

Yogurt (plain, low fat)

1 cup

415

*Calcium-fortified foods are foods with added calcium.

People should consume 800 to 1,000 international units (IUs) of supplemental vitamin D each day. People who have vitamin D deficiency may need even higher doses. Sometimes doctors check the level of vitamin D in the blood to determine how much supplemental vitamin D should be taken. The most common food source is fortified foods, mainly cereals and dairy products. Vitamin D is also present in fish liver oils and fatty fish. Supplemental vitamin D is usually given as cholecalciferol, the natural form of vitamin D, or ergocalciferol, the synthetic plant-derived form.

Weight-bearing exercise

Weight-bearing exercise, such as walking and stair-climbing, increases bone density. Exercises that do not involve weight bearing, such as swimming, do not increase bone density but do increase core strength and balance and reduce the risk of falls. Most experts recommend about 30 minutes of weight-bearing exercise daily. A physical therapist can develop a safe exercise program for people and demonstrate how to safely perform daily activities to minimize the risk of falls and spine fractures.

Curiously, in premenopausal women, high levels of exercise, such as those maintained by athletes, can actually cause a small reduction in bone density because such exercise suppresses the production of estrogen by the ovaries.

Drugs

Most of the same drugs are used for prevention and treatment.

Bisphosphonates (alendronate, risedronate, ibandronate, and zoledronic acid) are useful in preventing and treating all types of osteoporosis and are usually the first drugs used. Bisphosphonates have been shown to reduce bone turnover and thus reduce bone loss as well as reduce the risk of fractures. Alendronate and risedronate can be taken by mouth (orally). Zoledronic acid can be given by vein (intravenously). Ibandronate can be taken orally or intravenously.

An oral bisphosphonate must be swallowed on an empty stomach with a full glass of water (8 ounces) after arising for the day. No other food, drink, or drug should be consumed for the next 30 to 60 minutes because food in the stomach may decrease the absorption of the drug. Because oral bisphosphonates can irritate the lining of the esophagus, the person must not lie down for at least 30 minutes (60 minutes for ibandronate) after taking a dose. Certain people, including those who have difficulty swallowing, gastrointestinal symptoms (for example, heartburn or nausea), and certain disorders of the esophagus or stomach, should not take the bisphosphonates orally. These people can be given ibandronate or zoledronic acid intravenously. In addition, the following people should not take bisphosphonates:

  • Women who are pregnant or nursing

  • People who have low levels of calcium in the blood

  • People who have severe kidney disease

At this time, doctors do not know how long people should take bisphosphonates. Most people need to take these drugs for 3 or 6 years, and some people may need to take them for up to 10 years. How long people need to take a bisphosphonate is determined by the doctor and is based on a person's medical condition and risk factors for fracture. During and after treatment with a bisphosphonate, doctors usually do periodic tests to determine whether bone mass is decreasing. If bone mass is decreasing after stopping a bisphosphonate, treatment with a bisphosphonate or another drug may be restarted.

Osteonecrosis of the jaw is a rare condition that has occurred in some people who take bisphosphonates. In this condition, the jaw bone heals poorly, particularly in people who have had extensive dental work of the jaw bone. People who take bisphosphonates intravenously, who have had radiation therapy to the head and neck to treat cancer, or a combination are at highest risk. However, it is not truly clear whether bisphosphonates cause osteonecrosis of the jaw and, if they do, which particular drugs are most likely to cause it. There is no evidence that stopping bisphosphonates before having dental work prevents osteonecrosis. The risk of developing osteonecrosis of the jaw is exceptionally low in people taking bisphosphonates, and the likely benefits of treating osteoporosis to prevent bone fractures usually far outweigh the potential risks. When used as prescribed, bisphosphonates prevent many more fractures than cases of osteonecrosis of the jaw they might cause.

Long-term use of bisphosphonates may increase the risk of developing unusual fractures of the thighbone (femur). To reduce the risk of these fractures, doctors may have people stop taking bisphosphonates for 1 to 2 years or longer. These planned periods of time are called bisphosphonate holidays or drug holidays. How long a bisphosphonate holiday lasts is carefully considered by doctors. Doctors base the decision on certain factors such as a person's age, DXA scan results, whether they have had fractures, and how likely they are to have a fall. People who are on a bisphosphonate holiday should be routinely monitored for decreasing bone density. Because the risk of fracture does increase while people are on a drug holiday, doctors try to balance the benefits of the bisphosphonates with the possible side effects.

Overall, when used as prescribed, the benefits of bisphosphonates in preventing bone fractures far outweigh the potential risks.

Calcitonin, which inhibits the breakdown of bone, is another drug that can be used for treatment but is not prescribed frequently. Calcitonin has not been shown to reduce fracture risk, but it can help relieve pain caused by vertebral fractures. Calcitonin is usually taken by nasal spray. Its use can decrease blood levels of calcium, so these levels must be monitored.

Hormonal therapy (for example, with estrogen) helps maintain bone density in women and can be used for prevention or treatment. This therapy is most effective when started within 4 to 6 years after menopause, but starting it later can still slow bone loss and reduce the risk of fractures. However, because the risks of hormonal therapy may exceed its benefits for many women, hormonal therapy is usually not the treatment option used. Decisions about using estrogen replacement therapy after menopause are complex (see Hormone Therapy for Menopause).

Raloxifene is an estrogen-like drug that may be useful in preventing and treating bone loss, but it does not have some of estrogen's negative side effects. Raloxifene is used in people who cannot or prefer not to take bisphosphonates. Raloxifene can reduce the risk of vertebral fractures and may reduce the risk of invasive breast cancer.

Men do not benefit from estrogen but may benefit from testosterone replacement therapy if their testosterone level is low.

Denosumab is similar to the bisphosphonates in that it prevents bone loss. Denosumab is given as an injection under the skin in a doctor's office two times a year. Like bisphosphonates, denosumab very rarely causes osteonecrosis of the jaw and may increase the risk of developing unusual fractures of the thighbone. Denosumab has been studied in patients with chronic kidney disease and, with appropriate monitoring, has been found to be safe to use. People taking denosumab should not miss doses or undergo a drug holiday because delayed doses or stopping this drug may cause a loss in bone density and may increase the risk of vertebral fractures.

Romosozumab increases bone density in the hip and lumbar spine and reduces the risk of fracture in postmenopausal women. Romosozumab is given as an injection once a month for 1 year. People should not take romosozumab within 12 months after having had a heart attack or stroke.

Anabolic agents (teriparatide and abaloparatide) increase the formation of new bone, increase bone density, and decrease the likelihood of fractures. Teriparatide (a synthetic form of parathyroid hormone) and abaloparatide (a drug similar to parathyroid hormone) can be injected daily in small amounts. This therapy is used in some people who

  • Develop marked bone loss or new fractures while being treated with a bisphosphonate

  • Cannot take bisphosphonates

  • Have unusually severe osteoporosis or many fractures (particularly vertebral fractures)

  • Have osteoporosis caused by corticosteroids

Romosozumab also acts as an anabolic agent.

Treatment of pain and fractures

Back pain resulting from a vertebral compression fracture should be treated with pain relievers and sometimes moist heat and massage and/or supportive devices (such as back braces). People may be given calcitonin to decrease the pain caused by vertebral fractures. Exercises to strengthen muscles in the back may help relieve chronic back pain. After a fracture, people should usually avoid bed rest and heavy lifting. As soon as they are able, people should do weight-bearing exercises.

Fractures resulting from osteoporosis must be treated. For hip fractures, usually the joint is stabilized and often part or all of the hip is replaced surgically. Surgery may be needed for a wrist fracture, or the wrist may need to be placed in a cast. Additionally, people who have had an osteoporosis-related fracture should be treated with an osteoporosis drug and should make sure they consume adequate amounts of calcium and vitamin D.

A collapsed vertebra can be repaired by a procedure called vertebroplasty. In this procedure, which takes about an hour for each vertebra, a material called methyl methacrylate (MMA)—an acrylic bone cement—is injected into the collapsed vertebra, helping to relieve pain and reduce deformity. Kyphoplasty is a similar procedure, in which an orthopedic balloon is used to expand the vertebra back to its normal shape before the injection of the MMA. With vertebroplasty and kyphoplasty, deformity may be reduced in the MMA-injected bone, but the risk of fractures in adjacent bones in the spine or ribs does not decrease and may even increase. Other risks may include rib fractures, cement leakage, and possibly heart or lung problems. When these procedures should be done has not been clearly determined.

More Information

Drugs Mentioned In This Article

Generic Name Select Brand Names
No US brand name
ZOMETA
DRISDOL
Abaloparatide
FORTEO
DELATESTRYL
CRINONE
ACTONEL
FOSAMAX
BONIVA
EVISTA
MIACALCIN
PRILOSEC
PROLIA
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