When was your last bone density scan?

Examples of diseases that may cause secondary osteoporosis are chronic kidney failure and hormonal disorders (especially Cushing's disease, hyperparathyroidism, hyperthyroidism, hypogonadism, and diabetes mellitus).


THE MERCK MANUAL MEDICAL LIBRARY: The Merck Manual of Medical Information--Home Edition

Bone, Joint, and Muscle Disorders

Osteoporosis
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Osteoporosis is a condition in which a progressive decrease in the density of bones weakens the bones, making fractures likely.

Bones contain minerals, such as calcium and phosphorus, which make them hard and dense. To maintain bone density, 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 also needed to absorb calcium from food and incorporate it into bones. Vitamin D is absorbed from the diet and also manufactured in the skin by sunlight (see Vitamins: Vitamin D).

So that bones can adjust to the changing demands placed on them, they are continuously broken down and reformed, or remodeled (see Biology of the Musculoskeletal System: Bones). In this process, small areas of bone tissue are removed and new bone tissue is deposited. This process is continuous and moves through healthy bone. 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.

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 outstrips 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 become increasingly fragile, eventually resulting in osteoporosis.

Types

About 8 million women and 2 million men in the United States have osteoporosis. There are two main types of osteoporosis: primary osteoporosis, which occurs spontaneously, and secondary osteoporosis, which is caused by another disease and occurs in fewer than 5% of people who have osteoporosis. Examples of diseases that may cause secondary osteoporosis are chronic kidney failure and hormonal disorders (especially Cushing's disease, hyperparathyroidism, hyperthyroidism, hypogonadism, and diabetes mellitus). Examples of drugs that may cause secondary osteoporosis are corticosteroids, barbiturates, and anticonvulsants. Excessive alcohol consumption and cigarette smoking may worsen preexisting osteoporosis but are unlikely to cause it on their own.

Primary osteoporosis has three subtypes: postmenopausal osteoporosis, senile osteoporosis, and idiopathic osteoporosis. Most older women who have osteoporosis have a combination of postmenopausal and senile osteoporosis.

Postmenopausal Osteoporosis: Postmenopausal osteoporosis (type I osteoporosis) is caused by a lack of estrogen, the main female hormone, which helps to regulate the incorporation of calcium into bone in women. (Type I osteoporosis also occurs in men who are castrated or in men with low testosterone levels, as may occur in older men; however, it is 6 times more common in women.) Usually, postmenopausal osteoporosis develops in women after menopause, between the ages of 51 and 75, but it can begin earlier or later. Although bone loss is gradual in women leading up to menopause, it accelerates at menopause. Indeed, women can lose up to 20% of their bone mass in the 5 to 7 years after menopause. Not all women are at equal risk of developing postmenopausal osteoporosis. For example, low body weight increases the risk of postmenopausal osteoporosis, probably for two reasons:

* Thin women have smaller bones than do heavier women, even at about age 30 when their bones are at their strongest.
* Thin women usually have lower body fat than do heavier women; estrogen levels are lower in thin women because fat tissue activates certain forms of estrogen.

Women most at risk for osteoporosis are white, fair-skinned, and thin and/or with a light frame. Black and Hispanic women are less prone to osteoporosis than are white and Asian women. The main reason appears to be that, because black and Hispanic women have stronger bones in young adulthood, they can tolerate the bone loss that occurs with age and menopause better than other women can. Other risk factors include advanced age, menopause that occurred early or was surgically induced, abnormal absence of menstrual periods (amenorrhea), and anorexia nervosa.

Senile Osteoporosis: Senile osteoporosis (type II osteoporosis) probably results from an age-related calcium deficiency or a vitamin D deficiency and an imbalance between the rate of bone breakdown and new bone formation. Senile means only that the condition occurs in older people. It usually affects people older than 70 and is twice as common in women as in men. Women often have both senile and postmenopausal osteoporosis.

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 children and young adults who have normal hormone levels, normal vitamin levels, and no obvious reason to have weak bones.

Risk Factors for Osteoporosis in Women

* Family members with osteoporosis
* Insufficient calcium in the diet
* Sedentary lifestyle
* White or Asian race
* Thin build
* Use of certain drugs, such as corticosteroids and excessive amounts of thyroid hormones
* Early menopause
* Cigarette smoking
* Excessive alcohol consumption

Symptoms

At first, osteoporosis produces no symptoms because bone density loss occurs very gradually. Some people never develop symptoms.

Eventually, however, bone density may decrease enough for bones to collapse or fracture, producing severe sudden pain or gradually developing aching bone pain and deformities. 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. In the bones of the spinal column (vertebrae), the fracture usually occurs in the middle to lower back; this type of bone is particularly at risk for fracture due to osteoporosis.

Vertebral crush fractures (fractures of spinal vertebrae) may occur in people who have any type of osteoporosis; these fractures are called osteoporotic fractures. The weakened vertebrae may collapse spontaneously or after a slight injury. Chronic back pain may occur because of these fractures. Usually, pain starts suddenly, stays in a particular area of the back, and worsens when a person stands or walks. The area may be tender. Usually the pain and tenderness go away gradually after a few weeks or months. 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.
Photographs

Compression Fracture

Bones in other parts of the body may fracture, often because of a minor strain or fall. One of the most serious fractures is a hip fracture, a major cause of disability and loss of independence in older people (see Fractures: Hip). Wrist fractures, called Colles' fractures (see Fractures: Arm), occur commonly, especially in people with postmenopausal osteoporosis. In addition, fractures tend to heal slowly in people who have osteoporosis.

Diagnosis

A doctor may suspect osteoporosis in anyone, especially an older woman, who breaks a bone with little or no force. Bone mineral 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 density at the wrist or the heel; however, the most useful test is the dual-energy x-ray absorptiometry (DEXA), which measures bone density at the sites at which major fractures are likely to occur: the spine and hip. This test is painless and can be performed in about 5 to 15 minutes. It is useful for people at high risk of developing osteoporosis and for those in whom the diagnosis is uncertain. It is also useful for monitoring the response to treatment.

Blood tests may be performed to measure calcium and phosphorus. Further testing may be needed to rule out treatable conditions that might lead to osteoporosis. If such a condition is found, the diagnosis is secondary osteoporosis.

Prevention

Prevention is generally more successful than treatment—it is easier to prevent loss of bone density than to restore density once it has been lost. Prevention involves maintaining or increasing bone density by consuming adequate amounts of calcium and vitamin D, engaging in weight-bearing exercise, and, for some people, taking certain drugs.

Consuming an adequate amount of calcium and vitamin D is effective, especially before maximum bone density is reached (around age 30) but also after this time. About 1500 milligrams of calcium and 400 to 800 units of vitamin D daily are recommended. Drinking two 8-ounce glasses of vitamin D-fortified milk, eating a balanced diet, and taking a vitamin D supplement are important, but many women may also need to take a calcium supplement. Many calcium preparations are available; some include supplemental vitamin D.

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. Exercise is also important to improve balance, which can help to prevent a fracture that may occur from falling. Curiously, in premenopausal women, high degrees of exercise, such as occurs in athletes, can actually cause a small reduction in bone density because such exercise suppresses the production of estrogen by the ovaries.

Drugs called bisphosphonates, such as alendronate or risedronate, may be used alone as preventive therapy or, in women, combined with estrogen replacement therapy.

Estrogen replacement therapy helps maintain bone density in women. 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. Decisions about using estrogen replacement therapy after menopause are complex (see Menopause: Hormone Therapy), because the treatment may have side effects and risks, including an increased risk of uterine cancer and a slightly increased risk of breast cancer. Taking progesterone with the estrogen reduces the risk of uterine cancer but not of breast cancer.

Raloxifene is an estrogen-like drug that may be less effective than estrogen in preventing bone loss, but it does not have estrogen's typical side effects on the breast and uterus. Raloxifene is used in people who cannot or prefer not to take estrogen.

Treatment

Treatment is aimed at increasing bone density. The first step is to consume or take an adequate daily amount of calcium and vitamin D.

The bisphosphonates (alendronate and risedronate) are useful in preventing and treating all types of osteoporosis. These bisphosphonates have been shown to increase bone mass in the spine and hips and reduce the incidence of fractures. A bisphosphonate must be swallowed with a full glass of water (6 to 8 ounces) on arising for the day, and no other food, drink, or drug should be consumed for the next 30 minutes. Because bisphosphonates can irritate the lining of the esophagus, the person must not lie down after taking a dose for at least 30 minutes, and then must not lie down until after something has been eaten.

Certain people, including those who have difficulty in swallowing, cannot take the bisphosphonates by mouth. In these people, another bisphosphonate, pamidronate, can be given intravenously. In addition, the following people should not take bisphosphonates: people who have certain disorders of the esophagus or stomach, women who are pregnant or nursing, people who have low levels of calcium in the blood, and people who have severe kidney disease.

Calcium and vitamin D supplements are usually recommended for women and men, especially if tests show that their body is not absorbing adequate amounts of calcium. Men do not benefit from estrogen but may benefit from testosterone replacement therapy if their testosterone level is low. Men may also benefit from taking a bisphosphonate.

Calcitonin, which inhibits the breakdown of bone, is also used for treatment, particularly for people who have painful fractures of the vertebrae. Calcitonin can be taken by injection or nasal spray. Its use can decrease blood levels of calcium; these levels must be monitored.

Parathyroid hormone injected daily in small amounts can increase the formation of new bone, increase bone density, and decrease the likelihood of fractures. Although this medication is promising, it is not yet available.

Fluoride supplements can increase bone density. However, because the resulting bone may be abnormal and fragile, fluoride supplements are not generally recommended. New forms of fluoride, which may not have side effects on bone quality, are being tested.

Fractures resulting from osteoporosis must be treated. For hip fractures, usually part or all of the hip is replaced surgically (see Fractures: Hip). Surgery may be needed for a wrist fracture, or the wrist may need to be placed in a cast. Supportive back braces are used temporarily for people with painful vertebral crush fractures.

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 polymethylmethacrylate (PMMA)—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, prior to the injection of the acrylic bone cement.

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