Osteoporosis, osteopenia, bone density
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What is Osteoporosis?

researched and written by the ProjectAWARE group, 2001

Derived from Latin, osteoporosis literally means porous bone, which involves both the mineral (inorganic) and the non-mineral (organic matrix) components of bone.

Osteoporosis is a progressive bone disease in which bone tissue is normally mineralized, but the amount of bone is decreased and the structural integrity of trabecular bone is impaired, becoming more brittle. Cortical bone becomes more porous and thinner. While thinner bone itself is not necessarily more prone to breakage, bone that is both thinner and brittle is more prone to fracture.6, 34

Bone strength reflects the integration of two main features: bone density and bone quality. Bone density is expressed as grams of mineral per area or volume, and in any given individual is determined by peak bone mass and amount of bone loss. Bone quality refers to architecture, turnover, damage accumulation (e.g., microfractures) and mineralization. Osteoporosis is a significant risk factor for fracture, and a distinction between risk factors that affect bone metabolism and risk factors for fracture must be made.33

Although the entire skeleton may be involved in postmenopausal osteoporosis, bone loss is usually greatest in the spine, hips and ribs, and the posture is changed with progression of the disease.23 Small, fine-boned women have more reason for concern than women with larger frames and heavier bones. Race and ethnicity also appear to play a role. Women of Asian or European extraction are more likely to develop osteoporosis, while women of African descent are less likely to be affected.3

Osteoporosis can be further characterized as either primary or secondary. Primary osteoporosis can occur in both genders at all ages but often follows menopause in women and occurs later in life in men. In contrast, secondary osteoporosis is a result of medications, other conditions, or diseases. Examples include glucocorticoid-induced osteoporosis, hypogonadism, hyperthyroidism, and celiac disease.33

Remodeling of bone takes place throughout adult life, with osteoclasts resorbing old bone and osteoblasts creating new bone. These cells continuously renew the skeleton while maintaining its strength and density. Normally, in the adult skeleton, 3 percent of cortical bone and 25 percent of trabecular bone is remodeled each year.18

As hormone levels decline, the clasts move further ahead and the blasts fall further behind, resulting in increased bone loss and decreased bone replacement.47 Postmenopausal bone loss is associated with an increase in both the number and activity of osteoclasts in trabecular bone.18

It is known that estrone stimulates the development of the osteoblasts (as well as myoblasts, which form muscle tissue). DHEA also plays a role; in bone, DHEA is aromatized to estrone. Testosterone, easily aromatized to estradiol, no doubt also plays a role; in fact one study found free testosterone to be the best biomarker of postmenopausal spinal bone integrity.14

Estrogen produced in the body has an important role in maintaining the structure and calcification of bone. With the drop in estrogen at menopause, this crucial support is withdrawn, and the ability to absorb and assimilate dietary calcium is often reduced at this time as well.19

Osteoporosis involves more than balanced hormones. It is a complex condition involving lifestyle, nutritional and environmental factors as well.47 Studies have concluded that prevention is the most important step, and that women of all ages should be encouraged to take 1,000 to 1,500 mg of supplemental calcium daily, participate in regular weight-bearing exercise, avoid medications known to compromise bone density, institute hormone replacement therapy at menopause unless contraindicated and avoid tobacco and excessive alcohol intake.41

The World Health Organization formed a committee in 1994 to define osteoporosis. That committee created four diagnostic categories: Normal, Osteopenia, Osteoporosis, and Established osteoporosis.6

Osteoporosis afflicts 75 million persons in the United States, Europe and Japan, and results in more than 1.3 million fractures annually in the United States. Because osteoporosis is usually asymptomatic until a fracture occurs, family physicians must identify the appropriate timing and methods for screening those at risk.41

Next:  When does Osteoporosis start?  


For More Information:

Osteoporosis Resource Center: Collections of Medscape's key clinical content, always kept current. You can also find a comprehensive FAQ at this site. (Registration is required, but it's free.) Link added Jan 1, 2004





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The Whole Story

Jump to any aspect, or read all the parts of this segment.
What is osteoporosis?
When does it start?
Risk Factors for Osteoporosis & Fracture
Diagnostic Tests
Improving & Maintaining Bone Health
Foods, Herbs & Supplements at a Glance






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Updated 05/16/2010