Osteoporosis

Definition

Osteoporosis is a disease of the bones characterized by a decrease in bone mass and structural deterioration of bone tissue, leading to bone fragility and increased susceptibility to fractures of the hip, spine and wrist.

Description

Osteoporosis is a common condition, affecting as many as 20 million individuals in the United States. It has been estimated to lead to 1.3 million bone fractures a year in people over 45 years of age, which is represents 70 percent of all fractures occurring in this age group.

In osteoporosis, bone mass decreases, causing bones to be more susceptible to fracture. Bone is constantly being broken down (resorbed) by cells called osteoclasts, and rebuilt by other cells called osteoblasts. With age, more bone is resorbed than replaced.

Osteoporosis occurs when the resorption causes the bones to reach a fracture threshold (the point at which they are likely to break when subjected to a modest stress, such as falling). A fall, blow or lifting action that would not normally bruise or strain the average person can easily break one or more bones in someone with severe osteoporosis.

The body creates more bone than it loses until about the age of 30. After this, bone strength typically remains stable until menopause.

The female hormone, estrogen, helps preserve bone in women, but when estrogen secretion dwindles, usually starting at menopause, bone loss accelerates sharply for about five years. The loss continues more slowly after that, although the pace picks up somewhat after 65 or so. By their 70s, roughly half of all women have developed osteoporosis.

Injuries Associated With Osteoporosis

The spine, wrist and hip are the most common sites of osteoporosis-related fractures, although the disease is generalized, that is, it can affect any bone of the body. When the bones of the spinal column (the vertebrae) are weakened, a simple action like bending forward to make a bed or lifting a heavy roast pan out of the oven can be enough to cause a "crush fracture" or "spinal compression fracture." These vertebral crush fractures often cause back pain, decreased height, and a humped back or a "dowager's hump."

The occurrence of osteoporosis of the spine increases with age. Vertebral crush fractures are more common in women than in men, and generally occur between 55 and 75 years of age.

Wrist fractures also occur commonly among people with this disorder. For example, an otherwise healthy, vigorous women in her 50s or 60s slips on ice, falls and reaches out to catch herself, and is taken to the emergency room with a broken wrist.

Osteoporosis is often the underlying cause of the broken hips suffered by more than 200,000 Americans over age 45 each year. A fall from a standing position can fracture a hip weakened by osteoporosis. In cases of severe osteoporosis, a change of posture or weight distribution alone can actually break the hip, and the fracture then causes a fall.

People who have hip fractures due to osteoporosis are generally older than people who suffer spinal fractures. There is a more even distribution between women and men than with vertebral fractures, the rates for hip fractures being two to three times higher in women than in men.

Causes and Risk Factors

Certain people are more likely to develop osteoporosis than others.

The following risk factors have been identified:

Gender: Osteoporosis is estimated to be six to eight times more common in women than in men, partly because women have less bone mass to begin with. Furthermore, for several years after menopause, women also lose bone much more rapidly than men do, due to a fall in their bodies' production of estrogen.

Age: The risk of osteoporosis increases with increasing age in both men and women.

Menstrual Status: Women who have an early menopause, hysterectomy, irregular or non-existent menstruation due to low body weight and/or intense long term aerobic exercise are at risk.

Race: White women are at higher risk than black women, and white men are at higher risk than black men. Some experts estimate that by age 65 a quarter of all white women have had one or more fractures related to osteoporosis. Oriental women are also thought to be at greater risk for the disease, but there is not enough data to confirm this.

Inadequate Calcium Intake: Getting less than the recommended daily allowance (RDA) of calcium puts you at risk. Premenopausal women should take at least 1000 mg daily; for postmenopausal women, the RDA is 1500 mg daily. For men aged 25-65 years, the RDA is 1000 mg daily, and for men over age 65, the RDA is 1500 mg daily.

Smoking: An unknown substance in tobacco has been shown to decrease estrogen levels.

Alcohol Consumption: Alcohol is believed to have a toxic effect on bone.

Caffeine Use: Caffeine does have a mild diuretic effect, which means that it can increase the output of urine. With the increase of urine output can come an increase in urinary calcium loss as well.

Sedentary Lifestyle: Exercising fortifies the bones; not exercising puts you at risk.

Heredity: A family history of osteoporosis is a risk factor.

Long-Term Prescription Drug Use: If you use any of the following drugs consistently (six months or more) you may be at risk for osteoporosis: corticosteroids/steroids (such as cortisone, hydrocortisone, prednisone, prednisolone, and triamcinolone, to name a few), thyroid hormones (such as Thyroxine), anticonvulsants (such as Dilantin), antacids containing aluminum (such as Di-Gel, Maalox and Mylanta), loop diuretics (such as Lasix), and gonadotropin-releasing hormones.

Physique: Small body frame and underweight women are at greater risk.

Medical Disorders: Endocrine disorders, such as type I diabetes, overactive adrenal gland or thyroid gland puts you at risk for osteoporosis. Additionally, rheumatoid arthritis, inflammatory bowel disease, and estrogen deficiency caused by anorexia nervosa or bulimia, are also risk factors.

Symptoms

Osteoporosis is often called the "silent disease", because bone loss occurs without symptoms. People may not know that they have osteoporosis until their bones become so weak that a sudden strain, bump, or fall causes a bone to fracture or a vertebra to collapse.

Diagnosis

The diagnosis of osteoporosis is usually made by the doctor using a combination of complete medical history, physical examination, skeletal x-rays and bone densitometry (a bone density scan).

If the doctor finds low bone mass, he or she may want to perform additional tests to rule out the possibility of other diseases that can cause bone loss, such as a vitamin D deficiency (osteomalacia) or overactive parathyroid glands (hyperparathyroidism).

There are three types of bone density scans: dual-energy x-ray absorptiometry (DEXA), single photon absorptiometry (SPA), and quantitative computed tomography (QCT).

The most common bone density scan is the DEXA. DEXA measures bone density based on how bone absorbs two sets of photons (atomic particles with no electrical charge) generated by an x-ray tube. Measurements are obtained at the wrist, hip and lower spine. The equipment provides values for density as well as standard deviations, making it possible to estimate fracture risk. If DXEA is unavailable, the other two scans record the same outputs, but not with the accuracy of the DXEA.

Treatment

The diet should be adequate in protein, calcium (1000-1500 mg daily, as noted above), and vitamin D (400 units/day or more). Regular weight-bearing exercise is recommended, as tolerated.

The preferred treatment for osteoporosis in women is estrogen replacement therapy (ERT) to help stop bone loss, increases bone density and cut the risk of fracture roughly in half.

ERT is usually prescribed in combination with the sex hormone progesterone. Before the symptoms of osteoporosis, it can help preserve skeletal strength and maintain bone strength by slowing the rate of calcium loss from the bone. Prescribed after the diagnosis of osteoporosis, ERT can still help reduce the amount of bone loss and fracture risk.

Besides the slowing process of osteoporosis, ERT has been shown to decrease the risk of coronary heart disease, ease menopausal symptoms, decrease the chance of colon cancer, tooth loss, osteoarthritis, and possibly Alzheimer's disease. Despite these positive effects, 75 percent of all postmenopausal women decide against ERT. The disadvantages of ERT may include renewed menstrual bleeding, increased risk of breast and ovarian cancer, abnormal blood clotting and high blood pressure.

There are other options available: bisphosphonates (alendronate, tiludronate, risedronate, etidronate, and pamidronate.

In general, bisphosphonates line the surface of bone, preventing the bone-eating cells (osteoclasts) from breaking down bone.

Raloxifene can be used by postmenopausal women only, in place of estrogen for prevention of osteoporosis.

Calcitonin (Miacalcin) comes in an injectable and nasal spray form. Calcitonin is a hormone produced not only in humans, but in other animals, including salmon. The calcitonin found in salmon works in the human body at nearly 30x the potency of our own calcitonin. Calcitonin inhibits the activity of the osteoclasts and enables the bone to hold on to more calcium. Calcitonin does not build bone, but allows normal bone to form by preventing bone loss.

Prevention

The prevention of osteoporosis is a lifetime process. Most bone mass is developed before the age of 30. Thereafter, the challenge is to retain the bone mass one has. Efforts to assure the development of adequate bone mass throughout the lifespan should begin with children and adolescents through the consumption of calcium-rich diets and through frequent weight-bearing exercise. In mid-life, continued consumption of calcium and physical activity are important. If necessary, calcium supplements should be considered.

Questions to Ask Your Doctor

What are the risk factors for osteoporosis?

What diet is best for me? How much calcium and vitamin D supplementation do I need?

What types of exercise are best for my age and condition?

How can I reduce the risks of falling at home and out of the home?

Should I be taking any medications to diminish the risks of osteoporosis developing, or worsening? What are the side effects?

What is a DEXA scan?