By Diane M. Yoakam, R.N., M.S.N., HealthAtoZ contributing writer
Take the osteoporosis challenge and learn more about this debilitating disease.
What is osteoporosis?
Osteoporosis is a disease marked by a loss of bone mass and a consequential reduction in bone strength. In the U.S, 10 million people are thought to already have the disease and almost 34 million more may have low bone mass. Of the 10 million, 8 million are women and 2 million are men.
How is bone formed in the body?
An ongoing process of bone turnover and growth continues throughout a person's life. There are two types of cells involved in this process. These are called osteoblasts (bone-forming cells) and osteoclasts (bone-destroying cells). In the first step of bone formation, the osteoblasts make a protein called collagen, and the collagen is twisted around to form a matrix that fills in cavities left by the osteoclasts. The collagen matrix is then hardened by calcification. The process of bone remodeling is carefully regulated. Hormones produced by the parathyroid and thyroid glands tell the osteoclasts to break down bone when calcium is needed in the blood. When calcium phosphate in food is absorbed, it affects the levels of calcium in the blood. Vitamin D helps your body absorb calcium so that it can be used in bone building.
Bone formation exceeds bone loss throughout childhood, adolescence and early adulthood. During these developmental stages, bones continue to grow until they reach their peak mass or density. Between ages 32 and 35, the tables are turned, and bone loss exceeds bone formation. As we age, the bone loss may reach such a level that it is considered to be a disease (osteoporosis). Although a net loss of bone is inevitable, preventative measures involving preparation and discipline can be introduced to help minimize the loss.
What are risk factors for developing osteoporosis?
Osteoporosis has many risk factors
Menopause. When women enter menopause, they stop producing estrogen, and the rate of bone loss increases. In the seven to 10 years following menopause, the rate of bone loss increases from about 1 percent a year to 3 percent per year. Men continue to lose bone mass at a steady rate of about 1 percent a year. Because women have smaller skeletons than men, they have less bone mass from the outset, contributing further to the higher incidence of osteoporosis in women than in men. Women who have had their ovaries surgically removed before menopause are also at risk of developing osteoporosis.
Low levels of physical activity. Weight-bearing exercise thickens your bones by increasing blood flow to them. The increase in blood flow is accompanied by increased access to nutrients used in the bone-building process. Low levels of physical activity, on the other hand, lead to weaker bones and an increased chance of developing osteoporosis.
Smoking and alcohol consumption. Research has shown smoking cigarettes lowers estrogen levels and consequently speeds up the rate of bone loss. Alcohol reduces bone formation by interfering with osteoblast cell activity.
Diet. When dietary calcium intake is inadequate, the body is deprived of the raw materials it needs to maintain bone mass and strength. Low levels of calcium intake prevents young people from reaching their peak bone mass. The failure of older adults to get enough calcium in their diets means they will be less likely to ward off bone loss later on.
Medical history and medications. Medical conditions such as thyroid disease, kidney problems, malabsorption syndromes and liver conditions can cause osteoporosis. In addition, certain medications, particularly steroid drugs used to treat certain conditions can have a detrimental effect on bones, especially when taken for a long time.
Family history. If someone in your immediate family has osteoporosis, then the chances are greater that you have inherited a tendency to develop this disease.
Low body weight. People who have a low percentage of body fat (less than 15 percent) may be more likely to develop osteoporosis than people with higher percentages. The lower your body fat, the less weight you bear on your bones, and the less dense they become to support your weight.
Will I have any symptoms if I develop osteoporosis?
Most women don't know they have the disease until they have a fracture, often involving the wrist or hip, after a minor fall. Other women may find themselves getting shorter as they age or developing a hunched back (dowager's hump).
How can I be tested to determine if I have osteoporosis?
Bone density tests are a practical way to accurately measure bone density and diagnose osteoporosis. They can alert your doctor to the early stages of osteoporosis before a fracture occurs. Bone density testing is safe and painless, but it does involve a very small dose of radiation.
During the exam, bone density measurements of your spine, hip, wrist, heel or femur (thigh bone) may be taken. The test measures the bone mineral density of each area. These measurements are then compared to a reference group based on your age, weight, sex and ethnic background. The doctor makes a diagnosis of your bone status and determines your risk of developing fractures.
What are the best ways to minimize bone loss?
Exercise. Experts agree weight-bearing exercise is essential in minimizing bone loss and maintaining the highest possible density in your skeleton. Typical weight-bearing exercises include walking, jogging, bicycling, stair climbing or dancing. Also, experts suggest you do some type of weight-training. Weight training can strengthen all major muscle groups: arms, shoulders, chest, back, abdomen, hips and legs. Weight training involves the use of dumbbells or other objects, such as bands and tubes that provide resistance. Talk with a physician and a trainer before starting any exercise regimen.
Calcium. Women need to ingest 1,000 milligrams to 1,200 milligrams of calcium each day. Nevertheless, studies show the average person ingests only 450 mg to 550 mg a day. If the daily intake of dietary calcium is too low, the body uses calcium stored in the bones. Although it is generally known that dairy products are good sources of calcium, many people do not know of other food sources, including canned sardines and salmon, canned or fresh oysters, broccoli, collard greens, turnips, soybeans, tofu and almonds. Calcium supplements may be recommended if dietary intake of calcium continues to be inadequate.
Medications. Prescription medications can help slow bone loss and even help rebuild bone.
What medications are available?
Teriparatide (Forteo®), a synthetic form of a natural human hormone called parathyroid hormone, is the first osteoporosis medication to increase the rate of bone formation in the bone remodeling cycle. The drug forms new bone, increases bone mineral density and bone strength. Teriparatide can be taken by men or postmenopausal women with osteoporosis. The drug can be used by people who have had an osteoporosis-related fracture or who cannot use other osteoporosis treatments. Side effects include nausea, leg cramps and dizziness.
Medications that help slow the resorptive phase of the bone-remodeling cycle are:
Bisphosphonates. Bisphosphonates, such as alendronate (Fosamax) and risedronate (Actonel), prevent and treat postmenopausal women by reducing bone loss, increasing bone density and reducing the risk of fractures. Side effects are not common but may include abdominal pain, nausea, heartburn or irritation of the esophagus, the tube leading to your stomach. The FDA warns that people taking these drugs may have severe muscle and bone pain occurring within days, months, or years after starting the medication. Tell your doctor about pain or other side effects.
Calcitonin. This is a naturally occurring hormone. Miacalcin® and Calcimar® are two synthetic forms of calcitonin that help slows bone loss, increase spinal bone density and may relieve pain from bone fractures. Calcitonin reduces the risk of spinal fractures but may not decrease the risk of other fractures. Calcitonin can be taken as an injection or nasal spray. The injectable form may cause an allergic reaction and side effects including flushing of the face and hands, urinating more often, nausea, and a skin rash. Side effects for the nasal version are not common but may include nasal irritation, back pain, bloody nose and headaches.
Selective estrogen receptor modulators (SERMs). Raloxifene (Evista®) prevents and treats postmenopausal osteoporosis. SERMs have the helpful effects of estrogen therapy without the potential disadvantages. Raloxifene increases bone mass and reduces the risk of spine fractures. Side effects are not common but may include hot flashes and deep vein thrombosis (a blood clot starting in the legs).
Men
Your doctor may prescribe Alendronate or residronate, shown to be helpful for men with osteoporosis. Another drug called Teriparatide may also be prescribed for men who are at increased risk for fractures.
This article was reviewed and updated June 2007.
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