Osteoporosis

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Osteoporosis
ICD-10	M80-M82
ICD-9	733.0
DiseasesDB	9385
MeSH	D010024

Osteoporosis Microchapters
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Associate Editor(s)-In-Chief: Cafer Zorkun, M.D., Ph.D. [2], Raviteja Guddeti, M.B.B.S. [3]

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Epidemiology

It is estimated that 1 in 3 women and 1 in 12 men over the age of 50 worldwide have osteoporosis. It is responsible for millions of fractures annually, mostly involving the lumbar vertebrae, hip, and wrist. Fragility fractures of ribs are also common in men.

Hip fractures

Hip fractures are responsible for the most serious consequences of osteoporosis. In the United States, osteoporosis causes a predisposition to hip fractures -- more than 250,000 occur annually. It is estimated that a 50-year-old white woman has a 17.5% lifetime risk of fracture of the proximal femur. The incidence of hip fractures increases each decade from the sixth through the ninth for both women and men for all populations. The highest incidence is found among those men and women ages 80 or older.

First vertebral fractures

An estimated 700,000 women have a first vertebral fracture each year. The lifetime risk of a clinically detected symptomatic vertebral fracture is about 15% in a 50-year-old white woman. However, because symptoms are often overlooked or thought to be a normal part of getting older, it is believed that only about one-third of vertebral compression fractures are actually diagnosed.

Distal radius fractures

Distal radius fractures, usually of the Colles type, are the third most common type of osteoporotic fractures. In the United States, the total annual number of Colles' fractures is about 250,000. The lifetime risk of sustaining a Colles' fracture is about 16% for white women. By the time women reach age 70, about 20% have had at least one wrist fracture.

Risk factors

Risk factors for osteoporotic fracture can be split between non-modifiable and (potentially) modifiable. In addition, there are specific diseases and disorders in which osteoporosis is a recognized complication. Medication use is theoretically modifiable, although in many cases the use of medication that increases osteoporosis risk is unavoidable.

Nonmodifiable

The most important risk factors for osteoporosis are advanced age (in both men and women) and female sex; estrogen deficiency following menopause is correlated with a rapid reduction in BMD, while in men a decrease in testosterone levels has a comparable (but less pronounced) effect. While osteoporosis occurs in people from all ethnic groups, European or Asian ancestry predisposes for osteoporosis. Those with a family history of fracture or osteoporosis are at an increased risk; the heritability of the fracture as well as low bone mineral density are relatively high, ranging from 25 to 80 percent. There are at least 30 genes associated with the development of osteoporosis. Those who have already had a fracture is at least twice as likely to have another fracture compared to someone of the same age and sex.

Potentially modifiable

• Tobacco smoking - tobacco smoking inhibits the activity of osteoblasts, and is an independent risk factor for osteoporosis.
• Low body mass index - being overweight protects against osteoporosis, either by increasing load or through the hormone leptin.
• Low calcium and vitamin D intake - calcium and/or vitamin D deficiency from malnutrition increases the risk of osteoporosis. The problem occasionally arises in calcium deficient adolescents.
• Alcoholism
• Insufficient physical activity - bone performs remodeling in response to physical stress. People who remain physically active throughout life have a lower risk of osteoporosis. The kind of physical activity that have most effects on bone are weight bearing exercises. The bony prominences and attachments in runners are different in shape and size than those in weightlifters. Physical activity has its greatest impact during adolescence, affecting peak bone mass most. In adults, physical activity helps maintain bone mass, and can increase it by 1 or 2%. Physical fitness in later life is associated more with a decreased risk of falling than with an increased bone mineral density. Conversely, people who are bedridden are at a significantly increased risk.
• Excess physical activity - excessive exercise can lead to constant damages to the bones which can cause exhaustion of the structures as described above. There are numerous examples of marathon runners who developed severe osteoporosis later in life. In females, heave exercise leads to amenorrhea (suppression of the menstrual cycle), which is associated with decreased estrogen levels.
• Heavy metals - a strong association between cadmium, lead and bone disease has been established. Low level exposure to cadmium is associated with an increased loss of bone mineral density readily in both genders, leading to pain and increased risk of fractures, especially in elderly and in females. Higher cadmium exposure results in osteomalacia (softening of the bone).
• Soft drinks - some studies indicate that soft drinks (many of which contain phosphoric acid) may increase risk of osteoporosis; others suggest soft drinks may displace calcium-containing drinks from the diet rather than directly causing osteoporosis.
• This disease can occur in young women who are athletes. It is associated with female athlete triad syndrome as one of the three components, the other two being amenorrhea and disordered eating. Female athletes tend to have lower body weight, lower fat percentage, and higher incidence of asthma than their less active peers. The low estrogen levels (stored in body fat) and/or use of corteosteroids to treat asthma can significantly weaken bone over long periods of time. Distance runners in particular are also discouraged from consuming milk products when training, which would result in lower calcium absorption than other groups.

Diseases and disorders

There are many disorders associated with osteoporosis:

• Hypogonadal states - Turner syndrome, Klinefelter syndrome, Kallmann syndrome, anorexia nervosa, hypothalamic amenorrhea, hyperprolactinemia. In females, the effect of hypogonadism is mediated by estrogen deficiency. It can appear as early menopause (<45 years) or from prolonged premenopausal amenorrhea (>1 year). A bilateral oophorectomy (surgical removal of the ovaries) or a premature ovarian failure cause deficient estrogen production. In males, testosterone deficiency is the cause.

• Other endocrine disorders - Cushing's syndrome, hyperparathyroidism, thyrotoxicosis, hypothyroidism, insulin-dependent diabetes mellitus, acromegaly, adrenal insufficiency

• Nutritional and gastrointestinal disorders - malnutrition, parenteral nutrition, malabsorption syndromes (e.g. coeliac disease, Crohn's disease), gastrectomy, severe liver disease (especially primary biliary cirrhosis) - those with an otherwise adequate calcium intake can develop osteoporosis due to the inability to absorb calcium.

• Rheumatologic disorders - rheumatoid arthritis, ankylosing spondylitis

• Hematologic disorders/malignancy - multiple myeloma, lymphoma and leukemia, mastocytosis, hemophilia, thalassemia.

• Inherited disorders of the bone - osteogenesis imperfecta, Marfan syndrome, hemochromatosis, hypophosphatasia, glycogen storage diseases, homocystinuria, Ehlers-Danlos syndrome, porphyria, Menkes' syndrome, epidermolysis bullosa, Gaucher's disease.

• Other disorders - immobilization, scoliosis

Medication

Medication - for medication potentially causing osteoporosis, the positive effects of them needs to be compared with the degenerative effects on bone.

• Steroid-induced osteoporosis (SIOP) arises due to use of glucocorticoids - analogous to Cushing's syndrome and involving mainly the axial skeleton. The synthetic glucocorticoid prescription drug prednisone is a main candidate after prolonged intake. Some professional guidelines recommend prophylaxis in patients who take the equivalent of more than 30 mg hydrocortisone (7.5 mg of prednisolone), especially when this is in excess of three months.
• Barbiturates (probably due to accelerated metabolism of vitamin D) and some other enzyme-inducing antiepileptics.
• Proton pump inhibitors - these drugs inhibit the production of stomach acid; it is thought that this interferes with calcium absorption.

Diagnosis

The diagnosis of osteoporosis is made on measuring the bone mineral density (BMD). The most popular method is dual energy X-ray absorptiometry (DXA or DEXA). In addition to the detection of abnormal BMD, the diagnosis of osteoporosis requires investigations into potentially modifiable underlying causes; this may be done with blood tests and X-rays. Depending on the likelihood of an underlying problem, investigations for cancer with metastasis to the bone, multiple myeloma, Cushing's disease and other above mentioned causes may be performed.

Dual energy X-ray absorptiometry

Dual energy X-ray absorptiometry (DXA, formerly DEXA) is considered the gold standard for the diagnosis of osteoporosis. Osteoporosis is diagnosed when the bone mineral density is less than or equal to 2.5 standard deviations below that of a young adult reference population. This is translated as a T-score. The World Health Organization has established the following diagnostic guidelines:

• T-score -1.0 or greater is "normal"
• T-score between -1.0 and -2.5 is "low bone mass" (or "osteopenia")
• T-score -2.5 or below is osteoporosis

When there has also been an osteoporotic fracture (also termed "low trauma-fracture" or "fragility fracture"), defined as one that occurs as a result of a fall from a standing height, the term "severe or established" osteoporosis is used.

Prognosis

Hip fractures per 1000 patient-years

WHO category	Age 50-64	Age > 64	Overall
Normal	5.3	9.4	6.6
Osteopenia	11.4	19.6	15.7
Osteoporosis	22.4	46.6	40.6

Although osteoporosis patients have an increased mortality rate due to the complications of fracture, most patients die with the disease rather than of it.

Hip fractures can lead to decreased mobility and an additional risk of numerous complications (such as deep venous thrombosis and/or pulmonary embolism, pneumonia). The 6-month mortality rate following hip fracture is approximately 13.5%, and a substantial proportion (almost 13%) of people who have suffered a hip fracture need total assistance to mobilize after a hip fracture.

Vertebral fractures, while having a smaller impact on mortality, can lead to severe chronic pain of neurogenic origin, which can be hard to control, as well as deformity. Though rare, multiple vertebral fractures can lead to such severe hunch back (kyphosis) that the resulting pressure on internal organs can impair one's ability to breathe.

Apart from risk of death and other complications, osteoporotic fractures are associated with a reduced health-related quality of life.

See also

• Bone healing
• Back pain
• bone mineral density
• Hip protector
• Dental X-ray
• Osteopetrosis, the opposite of osteoporosis
• Osteoimmunology

External links

• Foundation for Osteoporosis Research and Education Non-profit organization
• The International Osteoporosis Foundation
• Osteoporosis Australia
• Osteoporosis Canada
• Irish Osteoporosis Society
• Osteoporosis New Zealand Inc
• National Osteoporosis Society (UK)
• The National Osteoporosis Foundation(USA)
• The Osteoporosis Section of The Hormone Foundation

• University of Washington
• Osteopenia - A controversial diagnosis.
• Diet, Nutrition and the prevention of chronic diseases (including osteoporosis) by a Joint WHO/FAO Expert consultation (2003)

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