Osteoporosis is a condition of diminished BONE DENSITY (the extent of mineralization of the bones). Though some loss of mineralization is a normal process of aging, osteoporosis represents an accelerated loss that causes health problems. Osteoporosis weakens the BONE structure; increases the risk for FRACTURE; and may result in bone deformities, particularly of the spine. The spine and hip are most vulnerable to fracture. Osteoporosis typically affects women after MENOPAUSE, though may develop earlier in women who do not produce estrogen, and men age 75 and older. About 10 million Americans have osteoporosis, 80 percent of whom are women.
Osteoporosis appears to primarily affect women for two reasons: estrogen and body size. Researchers do not fully understand how estrogen protects bone health but they do know that when estrogen levels fall dramatically, as with menopause, bone demineralization accelerates. As well, women have inherently less body mass bone mass and MUSCLE mass—than men. Some researchers theorize that bone demineralization takes longer to affect men because their larger skeletons can withstand a greater loss of calcium before becoming thin and weak.
Early indications of accelerated bone loss include loss of more than 1⁄2 inch in height and development of kyphosis (hump in the middle of the back). However, these signs develop slowly and over considerable time, often several decades, which makes them less apparent. Health experts call osteoporosis a silent disease because there are few indications of its presence until it is well established. Often the first symptom of osteoporosis is an unexpected fracture. The wrist, spine, and hip are the most vulnerable sites for fracture. XRAY shows a characteristic porous structure to the bones, demonstrating the loss of mineral content and bone mass. Bone density tests such as DEXA scan can detect demineralization before fracture occurs.
Doctors use a scale of relative percentage of bone loss to measure the severity of osteoporosis. The scale represents bone loss as a standard deviation (SD) from the accepted norm for optimal healthy bone mass. An SD value of –2.5 or greater (2.5 SDs below the norm) is diagnostic for osteoporosis. Testing facilities report this value as a Tscore; the norm for comparison is the bone density of a young healthy person of the same gender. Another representation is the Z-score, which compares the person’s bone density to that of the norm for others of the same age and gender. Some testing facilities report bone loss as a percentage; a –2.5 SD value represents about a 35 percent loss of bone density (bone mass is 65 percent of what it should be).
Weight-bearing and RESISTANCE EXERCISE is essential to stimulate bone remodeling activity. For established osteoporosis treatment focuses on decreasing the resorption of bone to increase bone mass. Several kinds of medications can achieve this effect. Among them are calcium and vitamin D supplements, estrogen supplements, bisphosphonates, PARATHYROID HORMONE supplement, CALCITONIN supplement, and Selective estrogen receptor modulators (SERMs). Individual circumstances determine which treatment approaches are most appropriate.
The body’s ability to absorb dietary calcium diminishes with advancing age. As well, people tend to drink less milk and consume fewer dairy products, the primary sources of dietary calcium, as they get older. Most adults should take calcium supplements to get 1000 to 1200 milligrams of calcium daily combined with dietary calcium. Though calcium cannot restore bone structure that is already lost to osteoporosis, the bones need abundant calcium simply to maintain bone remodeling. Vitamin D is necessary for the body to absorb calcium.
Before the 1990s doctors routinely prescribed hormone replacement therapy (HRT) for women going through and women beyond menopause. The prevailing belief was that HRT provided protection for women against CARDIOVASCULAR DISEASE (CVD) and osteoporosis. Extensive studies demonstrated that HRT provided no protection for HEART disease and in fact increased the risk for some kinds of CVD (notably STROKE) as well as some forms of cancer.
The findings regarding osteoporosis were not as definitive as expected. Estrogen does slow the loss of bone. However, its effect is most pronounced during the first three to five years after menopause and it does not stimulate production of new bone. Though doctors sometimes prescribe estrogen replacement (in combination with PROGESTERONE supplement for women who have their uteruses) for women who are at high risk for developing osteoporosis, other medications are often more effective with fewer risks.
Bisphosphonates are medications that block the activity of osteoclasts to resorb bone and calcium. Because these drugs are relatively new, doctors do not know their long-term consequences. Bisphosphonates can stop the progression of osteoporosis as well as prevent osteoporosis from developing in men and women who have high risk. However, bone loss resumes when the person stops taking the medication.
|BISPHOSPHONATES TO TREAT OR PREVENT OSTEOPOROSIS|
Parathyroid HORMONE and calcitonin are natural hormones within the body that regulate bone remodeling. Parathyroid hormone stimulates osteoblast activity (new bone formation); calcitonin suppresses osteoclast activity. Taken as supplements, these hormones have similar actions. They are not as effective as the bisphosphonates, however.
Women who are beyond menopause can take SERMs, sometimes called designer ESTROGENS, which have many estrogen-like actions in the body. As the name suggests, however, SERMs selectively target estrogen receptors so are not entirely the same as estrogen. Some SERMs, notably raloxifene, have an estrogen-like effect on bone remodeling without estrogen-like effects elsewhere in the body. SERMs stop bone loss but do not stimulate new bone tissue.
Women over age 70 who are white or Asian and are thin have the greatest risk for osteoporosis. However, regardless of ethnicity women past menopause have increased risk for osteoporosis because of the loss of estrogen. Other risk factors for osteoporosis include long-term use of systemic CORTICOSTEROID MEDICATIONS (such as to treat AUTOIMMUNE DISORDERS or endocrine disorders), cigarette smoking, low calcium consumption, physical inactivity, excessive CAFFEINE consumption, and excessive ALCOHOL consumption.
Though fracture alone is a significant health concern, the complications of fracture can be life threatening. Fracture generates a high risk for BLOOD clots as well as for fat emboli—fragments of fatty tissue that the fracture dislodges and that make their way into the blood circulation. Blood clots and fat emboli can cause STROKE or HEART ATTACK, depending on where they lodge in the blood vessels.
Calcium and vitamin D supplementation in combination with weight-bearing or resistance exercise early in life, but particularly before demineralization becomes significant, is the most effective preventive treatment. Health experts believe nearly all osteoporosis is preventable. But as with other lifestyle-related health conditions, prevention efforts must begin in childhood and continue through life. The most effective time to supplement calcium is when the body is building bone mass—before age 20.
See also AGING, MUSCULOSKELETAL CHANGES THAT OCCUR WITH; DIET AND HEALTH; EXERCISE AND HEALTH; HIP FRACTURE IN OLDER ADULTS; OSTEOMALACIA; OSTEOPENIA; SKELETON; SMOKING AND HEALTH.
Resource: Facts On File Encyclopedia Of Health And Medicine
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