Osteoporosis and Bone Densitometry


What is Osteoporosis?


Osteoporosis is a disease of progressive bone loss associated with an increased risk of fractures. It literally means "porous bone." The disease often develops unnoticed over many years, with no symptoms or discomfort, until a fracture occurs. Osteoporosis often causes a loss of height and dowager's hump (a severely rounded upper back). The World Health Organization (WHO) has established the following definitions based on bone density measurement at any skeletal site in white women


Normal:T-score above -1 (BMD is within 1 SD of a �young normal� adult)


Osteopenia: T-score between -1 and -2.5 (BMD is between 1 and 2.5 SD below that of a �young normal� adult)


Osteoporosis: T-score at or below -2.5 (BMD is 2.5 SD or more below that of a �young normal� adult. Women in this group

with one or more fractures are deemed to have severe or �established� osteoporosis.)


Although these definitions are necessary to establish the prevalence of osteoporosis, they should not be used as the sole determinant of treatment decisions.










Normal vertebrae, Vertebrae with mild osteoporosis, Vertebrae with severe osteoporosis.










Left: Normal Bone Matrix                           Right: Osteoporotic Bone Matrix



Why should I be concerned?


?Osteoporosis is a major health problem, affecting 28 million Americans and contributing to an estimated 1.5 million bone fractures per year. One in two women and one in five men over age 65 will sustain bone fractures due to osteoporosis. Many of these are painful fractures of the hip, spine, wrist, arm and leg that often occur as a result of a fall. However, even simple household tasks can produce a fracture of the spine if the bones have been weakened by the disease. The most serious and debilitating osteoporotic fracture is the hip fracture. Most hip fracture patients who previously lived independently will require help from their family or home care. All hip fracture patients will require walking aids for several months, and nearly half will permanently need canes or walkers to move around their house or outdoors. Hip fractures are expensive. Health care costs from hip fractures total more than $10 billion annually - $35,000 per patient.


What causes osteoporosis?


Doctors don't know the exact medical causes of osteoporosis, but they do know many of the major factors that can lead to the disease.


Aging. Everyone loses bone with age. After age 35, the body builds less new bone to replace losses of old bone. In general, the older you are, the lower your total bone mass and the greater your risk for osteoporosis.


Heredity. A family history of fractures; a small, slender body build; fair skin; and a Caucasian or Asian background can increase the risk for osteoporosis. Heredity also may help explain why some people develop osteoporosis early in life.


Nutrition and lifestyle. Poor nutrition, including a low calcium diet, low body weight and a sedentary lifestyle have been linked to osteoporosis, as have smoking and excessive alcohol use.


Medications and other Illnesses. Osteoporosis has been linked to some medications, including steroids, and to other illnesses, including some thyroid problems.



What can I do to prevent osteoporosis or keep it from getting worse?


There is a lot you can do throughout your life to prevent osteoporosis, slow its progression and protect yourself from fractures.


Include adequate amounts of calcium and vitamin D in your diet.


Calcium. During the growing years, your body needs calcium to build strong bones and to create a supply of calcium reserves. Building bone mass when you are young is a good investment for your future. Inadequate calcium during growth can contribute to the development of osteoporosis later in life.


Whatever your age or health status, you need calcium to keep your bones healthy. Calcium continues to be an essential nutrient after growth because the body loses calcium every day. Although calcium can't prevent gradual bone loss after menopause, it continues to play an essential role in maintaining bone quality. Even if you've gone through menopause or already have osteoporosis, increasing your intake of calcium and vitamin D can decrease your risk of fracture.


How much calcium you need will vary depending on your age and other factors. The National Academy of Sciences makes the following recommendations regarding daily intake of calcium:


    Males and females 9 to 18 years: 1,300 mg per day

    Women and men 19 to 50 years: 1,000 mg per day

    Pregnant or nursing women up to age 18: 1,300 mg per day

    Pregnant or nursing women 19 to 50 years: 1,000 mg per day

    Women and men over 50: 1,200 mg per day


Dairy products, including yogurt and cheese, are excellent sources of calcium. An eight-ounce glass of milk contains about 300 mg of calcium. Other calcium-rich foods include sardines with bones and green leafy vegetables, including broccoli and collard greens.


If your diet doesn't contain enough calcium, dietary supplements can help. Talk to your doctor before taking a calcium supplement.


Vitamin D. Vitamin D helps your body absorb calcium. The recommendation for vitamin D is 200-600 iu daily. Supplemented dairy products are an excellent source of vitamin D. (A cup of milk contains 100 iu. A multivitamin contains 400 iu of vitamin D.) Vitamin supplements can be taken if your diet doesn't contain enough of this nutrient. Again, consult with your doctor before taking a vitamin supplement. Too much vitamin D can be toxic.


Exercise Regularly. Like muscles, bones need exercise to stay strong. No matter what your age, exercise can help you minimize bone loss while providing many additional health benefits. Doctors believe that a program of moderate, regular exercise (three to four times a week) is effective for the prevention and management of osteoporosis. Weight bearing exercises such as walking, jogging, hiking, climbing stairs, dancing, treadmill exercises, and weight lifting are probably best. Falls account for 50 percent of fractures, therefore, even if you have low bone density you can prevent fractures if you avoid falls. Programs that emphasize balance training, especially Tai Chi, should be emphasized. Consult your doctor before beginning any exercise program.


How Is Osteoporosis diagnosed?


The diagnosis of osteoporosis is usually made by your doctor using a combination of a complete medical history and physical examination, skeletal X-rays, bone densitometry and specialized laboratory tests. If your 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, including osteomalacia (a vitamin D deficiency) or hyperparathyroidism (overactivity of the parathyroid glands).


?Bone densitometry is a safe, painless X-ray technique that compares your bone density to the peak bone density that someone of your same sex and ethnicity should have reached at about age 20 to 25, when it is at it's highest. It is often performed in women at the time of menopause. Several types of bone densitometry are used today to detect bone loss in different areas of the body. Dual beam X-ray absorptiometry (DXA) is one of the most accurate methods, but other techniques can also identify osteoporosis, including single photon absorptiometry (SPA), quantitative computed tomography (QCT), radiographic absorptometry and ultrasound. Your doctor can determine which method would be best suited for you. Physicians utilize bone densitometry to categorize patients as normal, osteopenic, or osteoporotic following the World Health Organization (WHO) classifications. The patient�s T-score (comparison to the young adult reference) is the critical variable in diagnosis. Typically, both femurs and the spine are assessed, with the diagnosis made using the lowest T-score. Patient examination, in addition to the T-score, is key to diagnosing osteoporosis.


Fracture Risk Assessment


Bone mineral density (BMD) is the strongest tool to predict fracture risk, which increases exponentially as BMD decreases. Femur BMD is recognized as the strongest predictor of femur fracture risk, which has the highest morbidity, mortality and cost of all osteoporotic fractures. A decrease of 1 standard deviation (SD) in femur BMD corresponds to approximately a 3X increase in femur fracture risk. In comparison, a 1 SD decrease in spine BMD corresponds to a 2X increase in spine fracture risk.


Monitoring Changes


In BMD Patients may return for bone density tests every 1-3 years, depending on the expected rate of loss and their clinical situation. BMD may increase over time as a response to therapy, or it may decrease with disease progression or poor response to therapy. Precision (reproducibility) of the BMD measurements is the key factor in detecting changes in patient BMD over time.



How Is Osteoporosis treated?


Because lost bone cannot be replaced, treatment for osteoporosis focuses on the prevention of further bone loss. Treatment is often a team effort involving a family physician or internist, orthopedist, gynecologist and endocrinologist.


While exercise and nutrition therapy are often key components of a treatment plan for osteoporosis, there are other treatments as well.


Estrogen replacement therapy (ERT) is often recommended for women at high risk for osteoporosis to prevent bone loss and reduce fracture risk. A measurement of bone density when menopause begins may help you decide whether ERT is for you. Hormones also prevent heart disease, improve cognitive functioning and improve urinary function. ERT is not without some risk, including enhanced risk of breast cancer. It should be discussed with your doctor.


Anti-estrogens such as Evista increase bone mass, decrease the risk of spine fractures, and lower the risk of breast cancer. Calcitonin is another medication used to decrease bone loss. A nasal spray form of this medication increases bone mass, limits spine fractures and may offer some pain relief. Bisphosphonates, such as Actonel, Fosamax, and Boniva, markedly increase bone mass and prevent both spine and hip fractures. Daily injections of a medication called Forteo may be recommended.  Reclast is an intravenous bisphosphonate that is given once a year for the treament of osteoporosis and ostepenia.  Prolia is a subcutaneous injection administered every six months.


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