Osteoporosis is a disease in which bone mass decreases, strength of trabecular bone decreases, cortical layer becomes thinner, and bones are prone to fracture. It is determined on basis of bone mineral density (BMD) measured using dual energy x-ray absorptiometry. A BMD that is 2.5 standard deviations below normal for a 20-year-old is considered osteoporosis.Epidemiology
An estimated 10 million people have osteoporosis, and another 34 million suffer from osteoporosis, loss of bone mass that leads to osteoporosis. It causes 1.5 million fractures each year, mostly in lumbar spine, hip and wrist. Approximately 50% of women and 25% of men develop osteoporosis during their lifetime. In 2001, direct national spending (hospitals and nursing homes) on osteoporosis and related fractures was estimated at $17 billion.cause
Estrogen deficiency after menopause can lead to a rapid decline in bone density. This, combined with aging, leads to an increased risk of falls, resulting in fractures of wrist, spine, and hip. Osteoporosis can result from other hormone deficiency conditions such as testosterone deficiency. An excess of glucocorticoids or thyroxin can also lead to osteoporosis. Finally, calcium and/or vitamin D deficiency due to malnutrition increases risk of osteoporosis.Risk factors
Risk factors for osteoporotic fractures
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Hypogonadal state - Turner's syndrome, Klinefelter's syndrome, anorexia nervosa, hypothalamic amenorrhea, hyperprolactinemia.
Endocrine disorders - Cushing's syndrome, hyperparathyroidism, thyrotoxicosis, insulin-dependent diabetes mellitus, acromegaly, adrenal insufficiency Nutritional and gastrointestinal disorders - malnutrition, parenteral malnutrition, malabsorption symptoms, gastrectomy, severe liver disease, especially biliary cirrhosis, pernicious anemia. Rheumatic diseases Rheumatoid arthritis Ankylosing spondylitis Blood disorders/malignancies - multiple myeloma, lymphoma and leukemia, mastocytosis, hemophilia, thalassemia.
Genetic disorders -- osteogenesis imperfecta, Marfan's syndrome, hemochromatosis, hypophosphatemia, glycogen storage disease, homouria, Ehler-Danlos syndrome, porphyria, Menkes syndrome, epidermolysis bullosa.
Other diseases - immobility, COPD, pregnancy and lactation, scoliosis, multiple sclerosis, sarcoidosis, amyloidosis.pathogenesis
The main mechanism of osteoporosis is an imbalance between bone resorption and bone formation. Either excessive bone resorption or reduced bone formation. The bone matrix is formed by osteoblasts, and bone resorption is carried out by osteoclasts. Spongy bone is spongy bone at center of long and flat bones. Cortical bone is hard outer shell of bone. As osteoblasts and osteoclasts inhabit bone surface, cancellous bone becomes more active and more prone to bone remodeling. Long before any obvious fracture occurs, small trabecular bone spicules break off and remodel in a process known as remodeling. Under physiological stress, bones grow and change shape. The bony prominences and attachments of runners are different in shape and size from those of weightlifters. This is a collection of fractures of trabecular bones with incomplete repair, leading to manifestation of osteoporosis. Common osteoporotic fractures include wrist, hip, and spine with a relatively high trabecular to cortical bone ratio. The strength of these areas depends on trabecular bone.
Low peak bone mass plays an important role in onset and development of osteoporosis. Bone mass peaks in both men and women between ages of 25 and 35, after which it gradually decreases. Achieving higher peak bone mass through exercise and proper nutrition during adolescence is important for preventing osteoporosis.
Bone remodeling is largely influenced by dietary and hormonal factors. Calcium and vitamin D are nutrients needed for normal bone growth. Parathyroid hormone regulates bone mineral composition, and higher levels lead to calcium and bone resorption. Glucocorticoids cause increased activity of osteoclasts, which leads to bone resorption. Calcitonin, estrogen and testosterone increase activity of osteoblasts, which leads to bone growth. Loss of estrogen after menopause leads to a phase of rapid bone loss. Similarly, testosterone levels in men decrease with age and are associated with osteoporosis in men.
Physical activity causes bone remodeling. People who are physically active throughout their lives have a lower risk of developing osteoporosis. In contrast, those who were bedridden had a significantly increased risk. Exercise had biggest impact on teenagers and had biggest impact on peak bone mass. In adults, physical activity helps maintain bone mass and can increase it by 1 to 2 percent. After all, osteoporosis itself wouldn't be a serious disease if it weren't for falls that lead to fractures. Age-related sarcophagus or loss of muscle mass, loss of balance, and dementia are largely responsible for increased risk of fractures in patients with osteoporosis. Physical fitness later in life is more associated with risk of deterioration than with an increase in bone density.Natural science
Today, most cases of osteoporosis are diagnosed before symptoms appear. This is due to widespread use of DEXA scanning for osteoporosis screening. Bone density increases after treatment and risk of fractures decreases.
If left untreated, overt osteoporosis is a precursor to fractures. Some fractures, such as vertebral compression fractures or sacral insufficiency fractures, may not be obvious at first and may be interpreted by patients and physicians as very severe back pain or asymptomatic. Hip fractures and wrist fractures are more pronounced.
Hip fractures are most serious consequence of osteoporosis. Osteoporosis causes more than 250,000 hip fractures each year in United States. The estimated risk of fracture of proximal femur in a 50-year-old Caucasian woman is 17.5%. The incidence of hip fractures in all populations increased every decade from sixth to ninth. The incidence is highest in men and women aged 80 years and older.
An estimated 700,000 women suffer their first spinal fracture each year. In a 50-year-old Caucasian woman, lifetime risk of a clinically diagnosed symptomatic vertebral fracture is approximately 15%. Distal radius fractures, usually of Colles type, are third most common type of osteoporotic fracture. The total number of Colles fractures is approximately 250,000 per year. The lifetime risk of a Colles fracture in white women is about 16%. By age 70, about 20 percent of women have suffered at least one wrist fracture.Diagnostics
Dual-energy X-ray absorptiometry is considered to be able to diagnose osteoporosis when bone mineral density (BMD) is below 2.5. Blood tests and x-rays are usually done to identify possible causes of osteoporosis to rule out bone metastatic cancer, multiple myeloma, Cushing's disease, and other causes mentioned above.treatment
People with osteoporosis (such as those taking steroids) often take vitamin D and calcium supplements. Several different forms of vitamin D (D3) are used in kidney disease because kidneys cannot adequately synthesize D3 from precursors.
Bisphosphonates are prescribed for osteoporosis (or very high risk). The most commonly prescribed bisphosphonate is alendronate (fosamax?) 10 mg daily or 70 mg once a week. Recombinant parathyroid hormone (terparatide) has recently been shown to be effective in osteoporosis, either alone or in combination with alendronate.