Osteoporosis. By Heather Hunsaker NDFS 356

Transcription

1 Osteoporosis By Heather Hunsaker NDFS 356

2 INTRODUCTION Most Americans are not aware they have osteoporosis until after they have experienced a fracture. Without a proper diagnosis of osteoporosis, hundreds of thousands of people experience fractures every year. It is estimated that osteoporotic hip fractures utilize more hospital bed days than strokes, diabetes, or heart attacks (1). As a large sector of America s population ages, it is essential to properly diagnose and treat osteoporosis. However, even more important is to begin prevention of osteoporosis early on in life through making wise lifestyle choices. DISEASE DESCRIPTION The definition of osteoporosis is porous bone due to low bone mineral density (2). Decreases in bone mineral density make bones brittle and more vulnerable to fractures (3). Currently 10 million people in the United States experience osteoporosis, with 8 million of those people being women (4). It is essential that all men and postmenopausal women over age 65 be screened for osteoporosis. These individuals carry the greatest risk for experiencing fractures related to osteoporosis. By 2020, it is estimated that half of all Americans over age 50 will have low bone mineral density or osteoporosis (5). ETIOLOGY Loss of bone mineral density can be attributed to excess bone resorption or a peak bone mass that was never fully developed in young adulthood. Age is a major risk factor for osteoporosis. Decreases in bone mineral density become evident in older age, usually between the ages of 65 and 70 and beyond (4). This is because as age increases, the degree of bone remodeling also increases. The fine balance between bone resorption and rebuilding is thrown off, leading to a great loss of bone tissue. 1

3 Besides age, another major risk factor of osteoporosis is gender. Females are more likely to suffer from osteoporosis than men are. One in three women over the age of 50 will suffer from a fracture, while only one in five men will experience such problems (6). Females are more susceptible to osteoporosis because of menopause. During menopause, the production of estrogens slows down and eventually discontinues (4). The role of estrogen is to regulate osteoclast apoptosis. Without estrogen, osteoclasts continually break down bone without any form of regulation (7). Outside of age and gender, other risk factors include race, body mass composition, and lifestyle habits. Caucasians and Asians experience osteoporosis more often than blacks and Hispanics. Blacks and Hispanics generally have a higher bone mineral density. Another risk factor is low body weight. Low body weight is always accompanied by a lower bone mineral density. Those lacking sufficient adipose tissue are at a greater risk for developing osteoporosis. This is because the purpose of adipose tissue is to protect bone. Surprisingly, being overweight can be a protective factor against osteoporosis. However, a sedentary lifestyle can negate the protective factors of adipose tissue. Physical activity is essential for increasing bone mineral density. Exercise, especially aerobics and weight bearing exercise, will increase bone density because the stress of muscle contractions stimulates osteoblast function (4). PATHOPHYSIOLOGY AND COURSE OF THE DISEASE Bone is continuously reabsorbed by osteoclasts and rebuilt by osteoblasts. Osteoporosis is manifest when the balance of reabsorption and rebuilding is disturbed. As age increases, osteoblast function declines. Osteoclasts continually resorb bone, but osteoblasts are not actively rebuilding bone as they did in young adulthood. The mass of trabecular bone is especially reduced. Trabecular bone is found in wrists, pelvis, and vertebrae. The reduction in trabecular 2

4 bone mass will increase the likelihood of experiencing serious fractures (8). This is why hip, spine, and wrist fractures are commonly experienced by those with osteoporosis. METHODS OF MEDICAL DIAGNOSIS A series of bone mineral density tests are performed to diagnose osteoporosis. Such tests include the DXA scan, FRAX, various x-rays, and lab tests (2). The DXA scan is the most preferred method because it has a low radiation dose and moderately low cost. DXA stands for Dual Energy X-ray Absorption. Radioactive sources in DXA scans include x and gamma radiation. The x-ray beams shoot through bones and measure the thickness of bone minerals as an area density in grams per centimeter squared (9). The overall purpose of the DXA scan is to measure and analyze how thick bone is. Another diagnosis method is called FRAX. FRAX stands for Fracture Risk Assessment Tool. It is a questionnaire that measures how likely a person will develop a fracture. This questionnaire assesses fracture risk based on body mass index, prior history of fractures, medication usage, and lifestyle habits. The advantage of FRAX is that it can assess bone fracture risk with or without performing a DXA scan (10). Other common diagnosis methods include x-rays and lab tests. X-rays are rarely used to diagnose osteoporosis because they are not sensitive enough to diagnose the disease until 25 to 40 percent of bone has been lost (2). However, x-rays can be a useful tool to diagnose fractures and prevent further fractures from occurring. Lab tests are also beneficial because they determine what factors are contributing to bone loss. Common lab tests include measuring blood calcium levels or 24-hour urine calcium levels. High blood calcium levels may indicate a problem with thyroid or parathyroid function. A 25-hydroxyvitamin D test can also be used to test if the body has sufficient vitamin D stores. Another test which measures biochemical 3

5 markers (such as NTX and CTX) can estimate a person s overall rate of bone loss (11). CURRENT MEDICAL THERAPIES AND THEIR EFFECTIVENESS The main goal of medical therapy is to prevent fractures all together. However, if fractures have already occurred there are options available to aid in recovery. Various medications can be prescribed which fall into two categories antiresorptives and anabolics. The goal of antiresorptives is to slow the breakdown of bone, while the goal of anabolics is to speed up the rate of bone formation (4). Common antiresorptive options include estrogen replacement therapy, bisphosphonates, and monoclonal antibodies. The purpose of estrogen replacement therapy is to increase serum estrogen levels. Estrogen s main role is to regulate osteoclast apoptosis. Without estrogen, osteoclasts continually break down bone because there is a lack of proper regulation. There are several forms of estrogen replacement available including pills, patches, or topical sprays and treatments (7). Like estrogen replacement therapy, the goal of Bisphosphonates is to destroy osteoclasts. Bisphosphonates are composed of two phosphate molecules which mimic pyrophosphate. Pyrophosphate is a substance present on bone crystal surfaces. Bisphosphonates attach to Calcium on bones and essentially ingest osteoclasts, leading to osteoclast apoptosis. This decreases bone resorption rates and helps maintain the structural properties of bone (2). Finally, monoclonal antibodies (such as Prolia) will halt the development of osteoclasts. Prolia is a subcutaneous injection administered twice a year. Once injected, Prolia binds to and inhibits RANK, which stands for Receptor Activator of Nuclear Factor-Kappa B. Normally, RANK promotes the maturation of pre-osteoclasts into osteoclasts. Through inhibiting RANK, osteoclast development is halted (12). Intermittent PTH therapy is the only current anabolic therapy option available. This 4

6 treatment is unique because it increases osteoblast formation of new bone tissue. Although osteoporosis is irreversible, PTH therapy can help strengthen bones enough to prevent future fractures. Serum PTH is different from exogenous PTH. The role of serum PTH is to resorb bones, while the exogenous form of PTH stimulates bone formation (2, 4). Exogenous parathyroid hormone comes in two forms. One form is known as the 1-84 molecule. This molecule includes an amino acid sequence of one through eighty-four. It is the full-length version of PTH which is not FDA approved. Another form of PTH is the 1-34 molecule which is a fragmented section of PTH. It has an amino acid sequence of one through thirty-four, instead of the full length molecule of one through eighty-four. This molecule has been FDA approved solely for adults with severe osteoporosis. A common example includes Teriparatide, which is also known as Forteo (8). In one randomized controlled trial, modified PTH (1-34) molecules were administered in 25 micrograms to postmenopausal women with osteoporosis. These women were taking estrogens simultaneously with PTH therapy. After three years, vertebral bone mass increased by 13% in women taking PTH and estrogen combined therapy, compared to women who took estrogen alone. Therefore, PTH therapy coupled with estrogen replacement therapy can significantly increase bone density in the vertebrae of postmenopausal women with osteoporosis (13). APPROPRIATE NUTRITION ASSESSMENT TOOLS Appropriate nutrition assessment tools mainly rely on an evaluation of anthropometrics, genetics, and dietary intake. Evaluating body weight, height, and overall frame size will offer insight into a person s nutritional deficiencies as wells as requirements needed. Those with a low body weight are at greater risk for developing osteoporosis. Those with a BMI less than 18.5 will have weaker bones and less adipose tissue to protect their bones (4). Likewise, as 5

7 people age, they also lose height. Severe height loss can indicate a greater risk for vertebral fractures. A height loss of two and half inches since young adulthood may indicate a spinal fracture in those over the age fifty (14). Since a large degree of frame size is inherited, assessing genetics goes hand in hand with anthropometrics. Usually osteoporosis is passed down from one generation to the next. As a result, health practitioners should analyze family history to determine a patient s risk for developing osteoporosis. Along with anthropometrics and genetics, dietary intake plays a major role in nutritional assessment. Those with diets deficient in calcium and vitamin D are at greater risk for developing osteoporosis. Intake during adolescence is especially critical as this is when bones are still building peak bone mass. If peak bone mass was never reached in young adulthood due to poor diet, there is a greater risk of developing osteoporosis and debilitating fractures later on in life. Along with assessing calcium and vitamin D intake, it is also important to evaluate other lifestyle habits. Smoking and the overconsumption of alcohol can lead to the destruction of osteoblasts (4). Without proper osteoblast function, the bones will experience excess reabsorption and become increasingly porous. According to the National Osteoporosis Foundation, women who consume more than three drinks per day will have an increased risk of bone loss and fractures (8). According to the case study presented in class, an appropriate PES statement would be, Decreased bone mineral density related to decreased calcium intake as evidenced by a DXA score of -3.5 and a right hip fracture. The woman in the case study did not like consuming milk or dairy products. She regularly ate soup and salads, but her diet was deficient in calcium and vitamin D. She also had a low BMI (18.9) and was twelve pounds short of her ideal body 6

8 weight. The woman s low anthropometric measurements and incomplete dietary intake were the most likely causes of her low DXA score and hip fracture. MEDICAL NUTRITIONAL THERAPY Ensuring adequate intake of calcium and vitamin D is one of the best prevention and treatment strategies for osteoporosis. According to the Institute of Medicine, men between the ages of 51 and 70 should consume at least 1,000 mg of calcium each day. Women who are between the ages of 51 and 70 should consume 1,200 mg of calcium each day. Any adult over the age of 70 should consume 1,200 mg of calcium each day (15). A low intake of Vitamin D can also increase osteoporosis risk because the role of vitamin D is to absorb calcium (6). Those between the ages of should consume 600 IU of vitamin D. If older than age 70, they should consume 800 IU of vitamin D (15). Dairy products, fruits, and vegetables all fit into a balanced diet. These foods not only provide calcium, but several other nutrients that promote overall good health (8). If adequate calcium and vitamin D cannot be obtained through food alone, supplements may be necessary. The bioavailability of calcium in supplements is fairly comparable to the bioavailability of foods (4). Therefore, the use of supplements can promote adequate intake of micronutrients in addition to a balanced and varied diet. LONG TERM PROGNOSIS Although osteoporosis is irreversible, several measures can be taken to ensure a decent quality of life after diagnosis. Each individual has different needs, but most will benefit from a combination of medication, a balanced diet, and dietary supplements with calcium and vitamin D. Outside of medication and dietary changes, those diagnosed with osteoporosis must be prepared to prevent falls. Every year, one third of individuals over age 65 experience falls (2). Falling can lead to severe fractures, which decreases mobility and overall quality of life. Those 7

9 with visual impairment must be especially careful to avoid falls. Falls can be prevented through removing hazards in the home. For example, installing grab bars or non-skid rubber mats can create a safe environment. Wearing shoes with good support and non-slip soles can also create extra security (2, 16). These measures will not guarantee a perfect quality of life, but they will prevent being unnecessarily disabled. COCHRANE REVIEW The Cochrane review was titled Exercise for Preventing and Treating Osteoporosis in Postmenopausal Women. In this review, various exercise programs were evaluated on the basis of how much bone mineral density scores improved in postmenopausal women. It was found that the most effective exercise programs were combination programs. Combination programs included a combination of multiple types of exercise, such as walking, weight lifting, aerobics, and tai chi. In one study, the spine bone mineral density of women in combination exercise programs increased from 1.90 to These women also had a lower risk of developing fractures than women who never exercised. As a cautionary note, a few women in each exercise group experienced fractures. Therefore, doctors must prescribe exercise as a treatment using special caution and discretion based on each individual woman s health (17). ALTERNATIVE THERAPY One fascinating alternative therapy option available for those suffering with osteoporosis is called transcutaneous electric nerve stimulation. Although this therapy does not treat osteoporosis itself, it can help manage the pain associated with osteoporosis. Treatment begins with placing several electrode patches on the surfaces of the body. Wires are attached to the electrodes which create a mild current. This current causes a warm sensation that decreases the aching feeling associated with osteoporosis. The treatment can last anywhere from five to fifteen 8

10 minutes (2). CONCLUSION As a large sector of America s population ages, it is essential to properly diagnose and treat osteoporosis. However, even more important is to begin prevention of osteoporosis early on in life through making wise lifestyle choices. Several physicians refer to osteoporosis as a pediatric disease (18). This is not because osteoporosis is prevalent in children, but rather because prevention of the disease must begin in childhood. Childhood and adolescence are critical periods of time during which peak bone mass is established. Reaching optimal peak bone mass ensures a high reserve of bone (4). This decreases the likelihood of developing osteoporosis later on in life. If appropriate care is taken in childhood to build healthy bones, adverse geriatric consequences can be avoided. The best steps for prevention include consuming adequate calcium, participating in combination exercise programs, and avoiding tobacco and excess alcohol intake (19). 9

11 REFERENCES 1. Osteoporosis Canada. Osteoporosis facts and statistics. Available at Accessed March 15, National Osteoporosis Foundation. Boning Up on Osteoporosis: A Guide to Prevention and Treatment. Washington DC: National Osteoporosis Foundation; Sherwood L. Human Physiology. 6 th ed. Belmont, CA: Thomas Higher Education; Chapman-Novakofski K. Nutrition and bone health. In: Mahan LK, Escott-Stump S, ed. Krause s Food and the Nutrition Care Process. 13 th ed. St. Louis: Elsevier; 2012: National Osteoporosis Foundation. Debuking the myths. Available at Accessed March 20, International Osteoporosis Foundation. Facts and statistics. Available at: Accessed March 10, Pronsky ZM. Food and Medication Interactions. 14 th ed. Birchrunville, PA: Food- Medication Interactions; National Osteoporosis Foundation. Clinician s Guide to Prevention and Treatment of Osteoporosis. Washington DC: National Osteoporosis Foundation; Evans W. Lecture slides. Medical Physics, University Hospital of Wales. Available at: Physicists/2%20DXA%20Principles%20of%20Operation.pdf 10. Kanis JA, Johnell O, Oden A, Johansson H, McCloskey E. FRAX and the assessment of fracture probability in men and women from the UK. Osteo Int. 2008;19(4): National Osteoporosis Foundation. Making a diagnosis. Available at: Accessed March 19, Prolia (Denosumab) Injection. Helping to strengthen your bones. Available at: Accessed March 15, Lindsay R, Nieves J, Formica C, et al. Randomised controlled study of effect of parathyroid hormone on vertebral-bone mass and fracture incidence among postmenopausal women on estrogen with osteoporosis. The Lancet. 1997;350: Osteoporosis Canada. Stand tall Canada. Available at: Accessed March 21, Institute of Medicine. DRIs for calcium and vitamin D. Available at: D/DRI-Values.aspx. Accessed March 24, International Osteoporosis Foundation. Living with osteoporosis. Available at: Accessed March 24, Howe T, Shea B, Dawson LJ, et al. Exercise for preventing and treating osteoporosis in postmenopausal women. Cochrane Datatbase of Systemic Reviews. 2011;7:CD Available at: DOI: / CD pub2 18. Richards R. Lecture slides. Nutrition Through the Lifecycles, Brigham Young University, March 24, American Family Physician. Osteoporosis: part I. evaluation and assessment. Available at: Accessed March 24,