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A major health problem, osteoporosis or "porous bone," affects an estimated 20 million Americans. This bone loss disease is most common in the elderly and in postmenopausal women. The loss of bone mass places extra stress on the thin, fragile bone structure that remains causing bones to be susceptible to fracture. Osteoporosis is estimated to cause 1.3 million bone fractures a year in people over 45 years of age. Moreover, in 1985, the national estimated cost of osteoporotic fractures was estimated to be $7 billion a year.

Osteoporosis-related fractures can occur in any of the bones, but the main fractures occur in the vertebral spinal column, the wrist, and the hip. In the spinal column, loss of bone mass starts in women during their 50s and 60s. A simple action like bending forward can be enough to cause a "crush fracture," or spinal compression fracture.

These vertebral fractures cause loss of height and a humped back, or a "dowager's hump. Wrist fractures called a "Colles fracture" also commonly occur among women with osteoporosis. Topically, the fracture occurs when a woman falls and uses her hand to break the fall; this results in a broken wrist. Fractures of the hip are the most severe. They are associated with more death, more disability, and higher medical costs than all other osteoporotic fractures combined. Twelve to 20 percent of older people with hip fractures die within a year after the fracture. Of the survivors, only a few return to the full level of activities that they enjoyed before the hip fracture.

Risk Factors

Many risk factors for osteoporosis have been identified. They include:

Age. The chief risk factor for this disease is age; the likelihood of developing osteoporosis increases progressively as we grow older.

Being a woman. Osteoporosis is estimated to be six to eight times more common in women than in men. In early adult life women develop less bone mass than men do. Even more critical is that for years after menopause, women lose bone mass much more rapidly because of a reduction in their production of estrogen.

Early menopause. The chances of developing osteoporosis increase during early menopause or surgical menopause (after removal of the ovaries), which causes a sudden significant drop in estrogen.

Being Caucasian. White women are at higher risk than black women, and white men are at higher risk than black men. In general, blacks have 10 percent greater bone mass than whites do.

A consistently low calcium intake.

Lack of weight-bearing exercise. The significant loss of bone mass in our astronauts who spend considerable time in the weightless environment of outer space dramatically demonstrates the importance of weight-bearing exercise.

Being underweight.

A family history of osteoporosis.

Smoking cigarettes. The concentration of estrogen in the bloodstream is lowered by cigarette smoking.

Excessive use of cortisone-like drugs such as prednisone.

Symptoms

Osteoporosis is a silent disease. Usually, it develops for many years until the bones become so weak that a minor injury can cause the bones to fracture. Detection of bone loss with ordinary x-rays does not show up until a person has lost 30 percent of their bone density. Several techniques for early detection of bone loss have been developed in recent years. In one technique, photon absorptiometry, a machine measures how much the rays like x-rays penetrate the bone (measuring how dense the bones

Bone Growth and Loss

Bone continues to grow and develop throughout childhood and adolescence. During a person's twenties, bone growth increases by 15 percent. Peak bone mass, when the bones are most dense and strong, occurs at 30 to 35 years of age. After this time bone mass gradually diminishes and the bones become less dense. There is a great need to understand how bone grows and diminishes. By studying the cellular processes responsible for bone growth, researchers hope to discover new treatments for osteoporosis. There is much active and promising research in this area.

Treatment and Prevention

Scientists now know that a leading cause of osteoporosis in women is postmenopausal estrogen deficiency. They have discovered that estrogen not only slows bone loss but also prevents bone fractures if given when a woman's production of estrogen drops. It is important that the hormone be given during or shortly after menopause because estrogen given years later is of less value. Women who have gone through menopause, and especially those with an early or surgical menopause, should discuss the benefits and risks of estrogen replacement therapy with their physicians.
Another benefit of estrogen therapy is its positive effect on the cardiovascular system. Estrogen reduces cholesterol and the concentration of other lipids (fats) in the bloodstream associated with heart disease. For women on estrogen therapy, the risk of developing endometrial cancer increases from one per 1,000 women to about four per 1,000 women. Fortunately, endometrial cancer is easy to detect and is highly curable. In fact, the death rate from endometrial cancer is lower than the death rate for osteoporotic hip fracture.

One side effect women on estrogen replacement therapy may experience is periodic bleeding. This is because estrogen therapy causes the lining of the uterus to build up. Estrogen usually is prescribed for 20 days, then the hormone is stopped for the remaining 10 days. The lining of the uterus is shed during the days off estrogen.
Progestogen, another fernale hormone, given in combination with estrogen may help reduce the risk of endometrial cancer. Women in the menopausal period are encouraged to discuss estrogen or progestogen therapy with their doctors.

Treatment with aleudronats is now becoming the standard treatment for ostesporosis.

Calcium Intake

The average American consumes about 450 to 550 milligrams of calcium a day. Experts recommend that both men and women take at least 1,000 milligrams of calcium daily. This is the amount of calcium contained in three eight-ounce glasses of milk. Other sources of calcium include yogurt, cheese, salmon, canned sardines, oysters, shrimp, dried beans, and dark green vegetables such as broccoli, turnip greens, and kale.

People who do not meet their daily requirements of calcium through their diet are encouraged to take a daily supplement of calcium such as calcium carbonate, calcium lactate, calcium gluconate, or calcium citrate. Older men and women should increase their calcium intake up to 1,200 to 1,500 milligrams a day, or about four to five glasses of milk, because calcium absorption from the digestive tract is reduced in the elderly.

Exercise

Research has shown clearly that inactivity leads to bone loss. Studies revealed that astronauts in space lost a great deal of bone from lack of exercise against gravity. A program of moderate weight-bearing exercise three to four hours a week, such as brisk walking, running, tennis, or aerobic dance, is recommended. Swimming is not as valuable because it is not a weight-bearing exercise.

Experimental Treatments

Several promising treatments for osteoporosis are being investigated. Calcitonin, a new drug approved by the Food and Drug Administration in 1984, slows the breakdown of bone. Calcitonin, produced naturally in the body, is a hormone produced by the thyroid gland. The synthetic form is given by daily injection and is expensive. Recently, a less expensive nasal spray of calcitonin has been developed.

Scientists also are studying fluoride combined with calcium for osteoporosis. Still experimental, flouride is promising in that it has been shown to increase bone mass. Some people experience side effects including nausea, vomiting, diarrhea, and pain in their lower extremities. Fluoride compounds currently are available for treatment- in Germany and France. However, more research is needed before this treatment can be proven to be both safe and effective.

Until recently, there were no clues as to how the hormone, estrogen, prevented osteoporosis. Now investigators have reported the discovery of estrogen receptors on bone. New methods might be harnessed to treat osteoporosis. Through continued research, there is hope for future treatments of osteoporosis.