Osteoporosis is a common and important public health problem. Many people with osteoporosis have not achieved normal peak bone mass, while others suffer substantial bone loss during life due to various conditions.
Bone mineral density is an indirect measure of the bone calcium content that influences bone strength. Bone density can be measured by a number of techniques, the most commonly used is dual-energy X-ray absorptiometry (DEXA). In evaluating and treating patients with low bone mineral density, clinicians tend to focus on progressive loss of bone mass because most patients seek care later in life. A bone mineral density less than 2.5 SD below the young adult mean is a reasonable but arbitrary cutoff for diagnosing osteoporosis. By using this criterion, approximately 17% to 20% of white women older than the age of 50 will have osteoporosis at the hip and 5% to 8% of black women in the same age group will have osteoporosis at the hip.6 In these populations, each standard deviation below the mean is associated with an approximately twofold increase in lifetime fracture risk.7 The sites of fracture are most often the weight-bearing bones: femoral neck and spine. The radial and ulnar bones of the wrist are also at risk because they often bear much of the force of a fall.
The treatment of osteoporosis depends on its cause. For example, risk factors may be modified by minimizing the amount of glucocorticoid used to treat asthma, surgically correcting primary hyperparathyroidism, or encouraging abstinence from tobacco or decreased alcohol consumption. In a patient with vitamin D or calcium deficiency, replacement of these nutrients is relatively straightforward. Usually, ergocalciferol is replaced until the patient’s 25-hydroxyvitamin D level is in the upper limits of normal, and then the calcium is increased until the urinary excretion of calcium is normal. In France, where foods are not supplemented with vitamin D, a mere 800 IU of ergocalciferol given to nursing home patients was associated with a decrease in hip fractures of 40% during 18 months.11 Even without evidence of a deficiency of the nutrients, dietary supplementation as recommended by a recent Institute of Medicine panel is a reasonable practice.12 For persons older than 50 years with evidence of bone loss, total dietary calcium intake should be 1,200 mg. A final class of therapies is directed at excessive bone resorption.
Osteoporotic fractures are a substantial cause of morbidity in the elderly. The most common reason for osteoporosis is a genetic or dietary failure to achieve a protective maximal bone mass. Currently available therapies are directed toward preserving remaining bone. The particular therapy useful in any person depends on the person’s history and results of the laboratory evaluation