Osteoporosis

Causes

Osteoporosis has many causes, including including genetic conditions, hormone and nutritional abnormalities, and other medical diseases. Women are more likely to have osteoporosis than men, but still there are many men with osteoporosis. People with African ancestry have lower risk of osteoporosis than others.

About 80% of the bone density is determined by heredity, and 20% by lifestyle (such as diet, exercise, smoking, and various medications.) This list shows some of the more common factors that influence the bone density in Caucasian women older than 65 years. The bars to the right show benefit and the ones to the left show harm. This list is from the Study of Osteoporotic Fractures (Bauer).
 

Factors that increase the risk of falls or accidents also are important. These include muscle weakness, poor balance, poor eyesight, or unsafe objects in the home that people trip over. A fall to the side is six times more likely to result in a hip fracture than a fall in another direction. Thin persons are more likely to get fractures when they fall, and wearing hip protection padding can reduce the number of hip fractures.

Histology

Normal	Osteoporosis

Bone biopsies show trabeculae that are not well connected, and also may be thinner (The mineralized bone stains green). There is more marrow space, and the cortex is thin. Osteoporosis can result from increased bone resorption or decreased bone formation (or both), as described in the page about bone remodeling . The most common form of osteoporosis is caused by estrogen deficiency, which primarily increases bone resorption. The following animations show normal bone remodeling and, in comparison, bone remodeling for 30 months after menopause. Notice how "holes" develop in the bone due to more active osteoclasts. Also, thinning can lead to tiny breaks.

Normal

After menopause

Click to see animations. You can line them up side-by-side and watch them again by selecting 'refresh' from the edit menu.

Treatment

The methods for preventing or treating osteoporosis are listed in this figure of the "Basic CDE's". Some of these should be started during childhood and adolescence! Prescription medications can be added for patients who have more serious disease. The following drugs have been approved by the FDA. In clinical trials, those taking the medication had fewer fractures than those taking a placebo. Physicians and scientists are developing and studying even more drugs. There are many more choices than there were a decade ago, but there are also still many unanswered questions about the best ways to prevent osteoporotic fractures.

estrogen raloxifene alendronate risedronate ibandronate calcitonin teriparatide

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