What is osteoporosis?

Osteoporosis (literally “porous bones”) is a disease that thins and weakens bones to the point where they break easily, especially bones in the hip, spine (backbone), and wrist. A fall or lifting action — or even a cough — that wouldn’t injure a person with healthy bones can result in fractures in people with osteoporosis. Hip fractures in particular can cause long-term, even life-threatening, problems. Inactivity can lead to blood clots, stroke, heart attack, and pneumonia. The good news is that advances in radiology and new drug therapies have made it possible to diagnose low bone mass early on and stop — even reverse — the bone loss that leads to osteoporosis.

bone basics

To understand how osteoporosis develops, you need to know a few bone facts. Bones are made of calcium and protein. There are two types. Compact (or cortical) bone is solid and hard and found on the outer part of bones. Spongy (or trabecular) bone is filled with holes and exists on the inside of bones. Osteoporosis usually appears first in bones that are naturally spongy: spine, hip, and wrist.

Bones aren’t lifeless tissues. They are constantly undergoing remodeling, a process in which old bone is removed and new bone is added. When calcium in the blood drops too low, cells called osteoclasts dissolve tiny amounts of bone tissue. This allows the calcium to enter the bloodstream, where it’s used to regulate heart rate, muscle contractions, and blood pressure, among other body functions. By contrast, cells called osteoblasts fill in these holes with a protein, which combines with calcium and phosphate and hardens into bone. This remodeling process replaces about one-fifth of your skeleton every year.

In childhood, more bone is added than removed, so bones grow in both size and density. In adolescence, bones stop growing in size but continue to become more dense, reaching peak mass around age 30. After age 35, bone is lost faster than it is replaced — usually by 0.3 to 0.5 percent each year, which is normal. If the loss is greatly accelerated, osteoporosis results.

Osteoporosis can occur when too much old bone is removed, when too little new bone is formed, or both, though experts do not fully understand what causes these changes. Bones remain the same size, but the compact bone becomes thinner and the spongy bone more porous. The drop in estrogen at menopause appears to cause bone to dissolve at a faster rate, typically in the wrist and spine. With age, however, both men and women are slower to build new bone, which affects mostly the hip.

symptoms

In the early stages of osteoporosis, there are often no symptoms at all. That’s why osteoporosis is called the “silent disease.” People can lose bone mass over many years but not know they have a problem until a bone breaks.

As the disease progresses, small fractures may occur in the spine. When these fractures heal, the bones do not go back to their original shape, but become compressed or flattened. Standing up quickly or raising a window can cause a vertebra in the spine to collapse, so that four or five vertebrae may fit in a space previously occupied by only three.

In serious cases, this compression tilts the rib cage downward and settles it on the top of the hipbone, with the ribs pushing out the internal organs. The person will develop an outward curve of the upper spine (”kyphosis”), an inward curve of the lower spine, a protruding abdomen, and a height loss of one to eight inches or more. A woman may find clothes no longer fitting or pants getting longer. Also, because of this shift, she may feel pressure on the nerves, pulled muscles, and joint pain.

Symptoms of advanced osteoporosis include the following:

• persistent back pain
• sudden muscle spasms in back
• height loss
• curving spine
• broken bones
• rib pain
• abdominal pain
• breathing problems
• tooth loss

who gets osteoporosis?

About 25 million Americans have osteoporosis — 80 percent of them women. As many as one in two women, and one in five men, will suffer a fracture due to the disease. White and Asian women are at greater risk than African-American women, who typically have more bone mass. At greatest risk are women who have a family history of osteoporosis, who experienced an early menopause (before age 40), who smoke, or who have small body frames. After menopause, a woman’s risk increases because of the decline in estrogen production. During the first five years after menopause, for example, some women lose as much as 25 percent of their bone density.

Men have less risk of getting osteoporosis because they do not have the same kinds of hormone losses as women. Still, after age 55 or 60, men lose about one percent of their bone mass every year.

DRUGS USED TO TREAT OSTEOPOROSIS

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