Human Diseases and Conditions

What is osteoporosis?

Osteoporosis is a condition characterized by a decrease in the density of bone, decreasing its strength and resulting in fragile bones. Osteoporosis literally leads to abnormally porous bone that is compressible, like a sponge. This disorder of the skeleton weakens the bone and results in frequent fractures (breaks) in the bones.
Normal bone is composed of protein, collagen, and calcium all of which give bone its strength. Bones that are affected by osteoporosis can break (fracture) with relatively minor injury that normally would not cause a bone to fracture. The fracture can be either in the form of cracking (as in a hip fracture) or collapsing (as in a compression fracture of the vertebrae of the spine). The spine, hips, ribs, and wrists are common areas of bone fractures from osteoporosis although osteoporosis-related fractures can occur in almost any skeletal bone.

Sign & Symptoms

In the early stages of bone loss, you usually have no pain or other symptoms. But once bones have been weakened by osteoporosis, you may have osteoporosis signs and symptoms that include:

• Back pain, which can be severe, as a result of a fractured or collapsed vertebra
• Loss of height over time
• A stooped posture
• Fracture of the vertebra, wrist, hip or other bone

Causes
Scientists don't yet know exactly why osteoporosis occurs, but they do know that the normal bone remodeling process is disrupted.
Your bone is continuously changing — new bone is made and old bone is broken down (resorption) — a process called remodeling or bone turnover. When you're young, your body makes new bone faster than it breaks down old bone and your bone mass increases. You reach your peak bone mass around age 30. After that, bone remodeling continues, but you lose slightly more than you gain.
How likely you are to develop osteoporosis depends on how much bone mass you attained in your 20s and early 30s (peak bone mass) and how rapidly you lose it later. The higher your peak bone mass, the more bone you have "in the bank" and the less likely you are to develop osteoporosis as you age.
The strength of your bones depends on their size and density; bone density depends in part on the amount of calcium, phosphorus and other minerals bones contain. When your bones contain fewer minerals than normal, they're less strong and eventually lose their internal supporting structure.
Other factors, such as hormone levels, also affect bone density. In women, when estrogen levels drop at menopause, bone loss increases dramatically. In men, low estrogen and testosterone levels can cause a loss of bone mass.

How is osteoporosis diagnosed?

A routine X-ray can reveal osteoporosis of the bone because the bones appear much thinner and lighter than normal bones. Unfortunately, by the time X-rays can detect osteoporosis, at least 30% of the bone has already been lost. In addition, X-rays are not accurate indicators of bone density. Thus, the appearance of the bone on X-ray often is affected by variations in the degree of exposure of the X-ray film.
The National Osteoporosis Foundation, the American Medical Association, and other major medical organizations recommend a dual-energy X-ray absorptiometry scan (DXA, formerly known as DEXA) for diagnosing osteoporosis. DXA measures bone density in the hip and the spine. The test takes only five to 15 minutes to perform, exposes patients to very little radiation (less than one-tenth to one-hundredth of the amount used on a standard chest X-ray), and is quite precise.
The bone density of the patient is compared to the average peak bone density of young adults of the same sex and race. This score is called the "T score," and it expresses the bone density in terms of the number of standard deviations (SD) below peak young adult bone mass.

• Osteoporosis is defined as a bone density T score of -2.5 or below.
  
• Osteopenia (between normal and osteoporosis) is defined as bone density T score between -1 and -2.5.

It is important to note that while osteopenia is considered a lesser degree of bone loss than osteoporosis, it nevertheless can be of concern when it is associated with other risk factors (such as smoking, cortisone steroid usage, rheumatoid arthritis, family history of osteoporosis, etc.) that can increase the chances for developing vertebral, hip, and other fractures. In this setting, osteopenia may require medication as part of the treatment program.

How is osteoporosis treated and prevented?

The goal of treatment of osteoporosis is the prevention of bone fractures by reducing bone loss or, preferably, by increasing bone density and strength. Although early detection and timely treatment of osteoporosis can substantially decrease the risk of future fractures, none of the available treatments for osteoporosis are complete cures. In other words, it is difficult to completely rebuild bone that has been weakened by osteoporosis. Therefore, prevention of osteoporosis is as important as treatment. Osteoporosis treatment and prevention measures are

1. lifestyle changes, including quitting cigarette smoking, curtailing excessive alcohol intake, exercising regularly, and consuming a balanced diet with adequate calcium and vitamin D;
   
2. medications that stop bone loss and increase bone strength, such as alendronate (Fosamax), risedronate (Actonel), raloxifene (Evista), ibandronate (Boniva), calcitonin (Calcimar), and zoledronate (Reclast);
   
3. medications that increase bone formation such as teriparatide (Forteo).

Lifestyle changes

Exercise, quitting cigarettes, and curtailing alcohol
Exercise has a wide variety of beneficial health effects. However, exercise does not bring about substantial increases in bone density. The benefit of exercise for osteoporosis has mostly to do with decreasing the risk of falls, probably because balance is improved and/or muscle strength is increased. Research has not yet determined what type of exercise is best for osteoporosis or for how long it should be continued. Until research has answered these questions, most doctors recommend weight-bearing exercise, such as walking, preferably daily.
A word of caution about exercise: It is important to avoid exercises that can injure already weakened bones. In patients over 40 and those with heart disease, obesity, diabetes mellitus, and high blood pressure, exercise should be prescribed and monitored by physicians. Extreme levels of exercise (such as marathon running) may not be healthy for the bones. Marathon running in young women that leads to weight loss and loss of menstrual periods can actually promote osteoporosis.
Smoking one pack of cigarettes per day throughout adult life can itself lead to loss of 5%-10% of bone mass. Smoking cigarettes decreases estrogen levels and can lead to bone loss in women before menopause. Smoking cigarettes also can lead to earlier menopause. In postmenopausal women, smoking is linked with increased risk of osteoporosis. Data on the effect of regular consumption of alcohol and caffeine on osteoporosis is not as clear as with exercise and cigarettes. In fact, research regarding alcohol and caffeine as risk factors for osteoporosis shows widely varying results and is controversial. Certainly, their effects are not as great as other factors. Nevertheless, moderation of both alcohol and caffeine is prudent.


Last Editorial Review: 12/4/2009