Definition
Osteoporosis, or brittle bone disease, is a disease characterized by low bone mass and architectural changes in bone tissue, leading to bone fragility and an increased risk of fractures (broken bones).

Prevalence
Osteoporosis is a major public health threat for more than 28 million Americans. While osteoporosis is often thought of as an older person's disease, it can strike at any age. In 2002 more than 10 million individuals, 8 million American women and 2 million men already had the disease and over 18 million more have low bone mass, putting them at risk of developing osteoporosis. 1 in 2 women and 1 in 8 men over the age of 50 will have an osteoporosis-related fracture in their lifetime.

Osteoporosis is responsible for more than 1.5 million fractures annually, including:

· 300,000 hip fractures.

· 700,000 vertebral fractures.

· 250,000 wrist fractures.

· 300,000 fractures at other sites.

80% of those affected by osteoporosis are women. Women can lose up to 20% of their bone mass in the 5-7 years following menopause, making them more susceptible to osteoporosis.

Osteoporosis, however, is not confined to white and asian individuals. In fact, 10% of African-American women over the age of 50 have osteoporosis and an additional 30% have low bone density. Significant risk has been reported in people of all ethnic backgrounds.

Cost
The estimated national direct expenditures (hospitals and nursing homes) for osteoporotic and associated fractures was $13.8 billion in 1995 ($38 million each day) and the cost is rising. Expenditures for the disease are expected to exceed $60 billion by the year 2030.

Symptoms
Osteoporosis is often called the "silent disease" because bone loss occurs without symptoms. People may not know that they have osteoporosis until their bones become so weak that a sudden strain, bump, or fall causes a fracture(broken bone).

Collapsed vertebrae (vertebral fractures) may initially be felt or seen in the form of severe back pain, loss of height, or spinal deformities such as kyphosis or stooped posture. 

Risk Factors
Certain people are more likely to develop osteoporosis than others. The following risk factors have been identified:

· Being female.

· Thin and/or small frame.

· Advanced age.

· A family history of osteoporosis.

· Being postmenopausal, including early or surgically induced menopause.

· Abnormal absence of menstrual periods (amenorrhea for more than 12 months).

· Anorexia nervosa or bulimia.

· A diet low in calcium.

· Use of certain medications, such as corticosteroids and anticonvulsants.

· Low testosterone levels in men.

· An inactive lifestyle.

· Cigarette smoking.

· Excessive use of alcohol.

· Being Caucasian or Asian, although African Americans and Hispanic Americans are at significant risk as well.

Detection
Specialized tests called bone density tests can measure bone density in various sites of the body. A bone density test can:

·Detect osteoporosis before a fracture occurs.

· Predict your chances of fracturing in the future.

· Determine your rate of bone loss and/or monitor the effects of treatment if the test is conducted at intervals of a year or more. 

Prevention
By about age 20, the average woman has acquired 98% of her skeletal mass. Building strong bones during childhood and adolescence can be the best defense against developing osteoporosis later.

There are four steps to prevent osteoporosis. No one step alone is enough to prevent osteoporosis, but all four may. They are:

· A balanced diet rich in calcium and vitamin D.

· Weight-bearing exercise.

· A healthy lifestyle with no smoking or excessive alcohol intake.

· Bone density testing and medication and when appropriate.

Fractures
The most typical sites of fractures related to osteoporosis are the hip, spine, wrist, and ribs, although the disease can affect any bone in the body. Although women suffer twice as many hip fractures as men, men have worse outcomes after a hip fracture.

Over 30% of men will die in the first year after a hip fracture. An average of 24% of all hip fracture patients die in the year following their fracture.

A woman's risk of hip fracture is equal to her combined risk of breast, uterine and ovarian cancer. In 1991, about 300,000 Americans age 45 and over were admitted to hospitals with hip fractures. Osteoporosis was the underlying cause of most of these injuries. One-fourth of those who were ambulatory before their hip fracture require long-term care afterward. White women 65 or older have twice the incidence of fractures as African-American women.

Medications
Although there is no cure for osteoporosis, the following medications are approved by the FDA for postmenopausal women to either prevent and/or treat osteoporosis:

· Estrogens (brand names such as Premarin®, Ogen®, Estrace®, Estraderm® and Estratab®, Prempro®, and others)

· Alendronate (brand name Fosamax®) is also approved as a treatment for men

· Calcitonin (brand name Miacalcin®)

· Raloxifene (brand name Evista®)

· Risedronate (brand name Actonel®)

· Alendronate is approved for treatment of glucocorticoid-induced osteoporosis in men and women. Risedronate is approved for prevention and treatment of glucocorticoid-induced osteoporosis in men and women.

Treatments under investigation include sodium fluoride; vitamin D metabolites; parathyroid hormone; and other bisphosphonates and SERMs.