The bones are continuously being broken down and rebuilt in a cycle that takes two to three months. From childhood into the 30s, an individual's bones absorb calcium, becoming strong and dense. As people age, however, the body start to reabsorb calcium from the bones, leading to the loss of between 0.3 and 0.5% more bone than is rebuilt.
This inequity causes the bone mass to shrink. The bones become fragile and prone to fractures even from everyday activities. These fractures often occur in the spine, hip or wrist.
About eight million women and two million men in the U.S. have osteoporosis. As many as 18 million more Americans may have low bone density.
Symptoms of Osteoporosis
Osteoporosis is a condition that has virtually no symptoms until severe bone damage has already occurred. Once the bones have been weakened by bone density loss, symptoms may include:
- Back pain
- Loss of height over time with stooped posture
- Fractures of the vertebrae, wrists, hips or other bones
Without treatment, a person with osteoporosis is likely to have fractures, most often in the spine or hips (which support the body's weight) or in the wrists from bracing against a fall. Fractures of the spine can happen even without a fall or an injury. The bones of the spine become so weak that they start to compress. These types of fractures can cause severe pain and require a long recovery period. They also cause a loss of height and stooped posture.
Hip fractures, the second most common type of fracture due to osteoporosis, usually result from a fall. Although most people do relatively well with modern surgical treatment, hip fractures can result in disability and even death from postoperative complications.
Osteoporosis Causes and Risk Factors
The strength of the bones depends on their size and density. Bone strength ultimately depends on how much calcium, phosphorus and other minerals they contain. Bone density loss can occur for a variety of reasons, including:
- Endocrine imbalances
- Not getting enough vitamin D and calcium in the diet
- Falling estrogen levels associated with menopause. Women who have reached menopause lose bone at a rate of one to three percent a year. While this slows down around the age of 60, it doesn't stop entirely. Older women may have lost between a third to a half of their bone mass, while men may lose between 20 and 35%.
- Are sedentary. Exercising regularly can help ensure that your bones stay strong throughout your life.
- Are a woman. Twice as many women have bone fractures from osteoporosis as men. This happens because women are smaller and have less bone mass to begin with and because they tend to live longer. Menopause also causes bone loss to accelerate.
- Are a man with low levels of testosterone
- Have a family history of osteoporosis
- Are older
- Are slender and small framed
- Smoke or use tobacco
- Take certain diurectics (furosemide [Lasix], bumetanide [Bumex], ethacrynic acid [Edecrin] and torsemide [Demadex]), which cause your body to excrete fluids. This can lead to a loss of calcium.
- Take corticosteroid drugs, such as prednisone, cortisone, prednisolone and dexamethasone on a long-term basis. These drugs are commonly used to treat asthma, rheumatoid arthritis and psoriasis. If you need to take a steroid medication for long periods, your doctor may monitor your bone density and recommend other drugs to help prevent bone loss.
- Take the blood-thinning drug heparin, methotrexate, some antiseizure drugs and aluminum-contain antacids
- Are Caucasian or Southeast Asian. African Americans have the lowest risk of osteoporosis; Hispanics and Native Americans appear to have an intermediate risk.
- Have short-term exposure to estrogen. Risks are higher for women who began menstruating at a later than average age and who had an earlier than average menopause. Risks are also higher for women who have had their ovaries surgically removed before age 45 without receiving hormone replacement therapy (HRT).
- Have an overactive thyroid (hyperthyroidism) or take too much thyroid hormone medication to treat an underactive thyroid (hypothyroidism)
- Have had certain medical conditions or procedures that decrease calcium absorption. These include stomach surgery, Crohn's disease, anorexia nervosa or Cushing's disease (a rare disorder in which the adrenal glands produce too much corticosteroid hormones).
- Drink too much alcohol on a regular basis, which interferes with your body's ability to absorb calcium. For men, alcoholism is one of the highest risk factors for osteoporosis.
- Are depressed. Recent studies show that women who experience depression have increased rates of bone loss.
Diagnosis of Osteoporosis
Osteoporosis can be quickly and painlessly diagnosed with a bone density test. There are two types of bone density tests:
- Dual energy X-ray absorptiometry (DEXA), which is the standard tool for diagnosis of osteoporosis
- Heel ultrasound, which is simpler and easier to use but only accurate enough for screening purposes
- Use medications that can cause osteoporosis
- Have insulin-dependent diabetes, liver disease, kidney disease or a family history of osteoporosis
- Had an early onset of menopause
- Are postmenopausal, older than age 50 and have at least one risk factor for osteoporosis
- Are postmenopausal, older than age 65 and have never had a bone density test
Hormone replacement therapy (HRT) is the best way to prevent osteoporosis in women. HRT does have side effects, including an increased risk of blood clots and gallbladder and heart diseases. Taking HRT as a combination therapy - estrogen with medroxyprogesterone acetate (such as Prempro) - for several years or more may increase your risk of breast cancer. All combination HRT regimens can cause irregular vaginal bleeding, particularly during the first year of use. More study is needed to learn if estrogen-only therapy increases your risk of breast cancer. The long-term benefits of HRT are, therefore, under intense scrutiny.
If HRT is not for you, other prescription drugs can help slow bone loss and may even increase bone density over time. They include:
- Bisphosphonates. These can reduce bone breakdown, preserve bone mass and even increase bone density in the spine and hip. The best known of these drugs is alendronate (Fosamax). Studies show it may cut the risk of hip and spine fractures in half. Etidronate (Didronel) is also sometimes given to help prevent bone loss.
- Raloxifene. This imitates estrogen's good effects on bone density, without some of the increased cancer risks. Hot flashes are a common side effect. You shouldn't use this drug if you have a history of blood clots.
- Calcitonin. Produced by the thyroid gland, calcitonin may slow bone loss and prevent spine fractures, but not hip fractures. It's given as a nasal spray, and about 12% of those who use it develop nasal irritation. It is usually given to those who are at high risk of fracture but cannot take estrogen or bisphosphonates.
- Tamoxifen, a synthetic hormone used to treat breast cancer. Although it blocks estrogen's effect on breast tissue, it has an estrogen-like effect on other cells, including bone cells. It may have serious side effects.
- Statins. Ordinarily this class of drugs is used to lower cholesterol levels, but some studies have shown that women who take statin drugs for at least a year may also lower their risk of bone fractures. Because research is ongoing, the drugs are not routinely given for osteoporosis. Side effects include potential reversible liver damage and, rarely, muscle inflammation.
Taking steps to prevent bone density loss is helpful no matter what your age or condition:
- Get enough calcium and vitamin D. Premenopausal women and postmenopausal women on HRT should have at least 1,200 milligrams (mgs) of calcium and 400 international units (IU) of vitamin D every day. Postmenopausal women not on HRT and those at risk of getting osteoporosis from taking steriods should get 1,500 mgs of calcium and 800 IU of vitamin D daily. Men under age 65 should consume 1,000 mgs of calcium every day and men over age 65, 1,500 mgs. Good sources of calcium include milk; low-fat plain yogurt; Swiss, cheddar and ricotta cheese; broccoli; canned salmon with the bones; orange juice and tofu. If you find it hard to get this much calcium from your diet, try calcium supplements.
- Exercise, which helps build strong bones and slow bone loss. It is helpful no matter when you begin, but it has the greatest benefits when you start young and do it throughout your life. Strength training lets you build the muscles and bones in your arms and upper spine. Weight-bearing exercise (walking, jogging, running, stair climbing, skipping rope, skiing and impact-producing sports) helps the bones in your legs, hips and lower spine.
- Don't smoke. Smoking speeds bone loss, perhaps by lowering how much estrogen a woman's body makes and by reducing the calcium absorbed by the intestine.
- Consider HRT. HRT is the best way to reduce a woman's risk of osteoporosis during and after menopause.
- Avoid drinking too much alcohol. Having more than two alcoholic drinks a day may cut bone formation and the body's ability to absorb calcium. There's no clear link between limited alcohol intake and osteoporosis.
- Limit caffeine.
- Maintain good posture. Keep your head held high, chin in, shoulders back, upper back flat and lower back arched to avoid stress on your spine. When you sit or drive, put a rolled towel in the small of your back. Don't lean over while reading or doing handwork. When lifting, bend at your knees, not your waist. Lift with your legs, keeping your upper back straight.
- Prevent falls. Wear low-heeled shoes with nonslip soles, and check your house for electrical cords, throw rugs and slippery surfaces that might cause you to trip or fall.
- Manage pain. Discuss pain management with your doctor. Don't ignore chronic pain. Left untreated, it can limit your mobility and cause even more pain.