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Excessive use of alcohol depresses osteoblastic function and increases the risk of osteoporosis. Physical activity early in life contributes to higher peak bone mass and reduces the risk of falls by approximately 25%.16 Good nutrition with a balanced diet is necessary for the development of healthy bones. Calcium and vitamin D are required for the prevention and treatment of osteoporosis. There are data to support recommendations (found later in the chapter) for specific dietary calcium intakes at various stages in life.17,18 Patients at high risk also include those who pursue thinness excessively, have a history of an eating dis-order,19 restrict their intake of dairy products, don't consume enough vegetables and fruits, and have a high intake of low-calcium/high-phosphorus beverages like sodas. These beverages have a negative effect on calcium balance.

Laboratory Assessment

If the history and physical exam suggests secondary causes of osteoporosis, the physician should consider tests such as thyroid-stimulating hormone (TSH), parathyroid hormone (PTH), calcium, vitamin D, urine N-teloptide, complete blood count (CBC), chem panel, cortisol, erythrocyte sedimentation rate (ESR), or serum protein electrophore-sis, based on the differential diagnosis.20,21

Bone Densitometry Assessment

To prevent osteoporosis, the physician should attempt to establish early detection of low bone mineral density (BMD). Currently there is no accurate measure of bone strength, but BMD is the accepted method to establish a diagnosis of osteoporosis and predict future fracture risk.22,23 The World Health Organization (WHO) defines osteoporosis as a BMD 2.5 standard deviations (SDs) below the mean for young white adult women. This definition does not apply to other ethnic groups, men, or children.7,24 The U.S. Preventive Services Task Force suggests that the primary reason to screen postmenopausal women is to check for a low BMD so that early intervention may be initiated to slow the further decrease of the bone density.25 The ultimate goal is to prevent vertebral and hip fractures.

The most thoroughly studied and most widely used technique to measure BMD is the dual-energy x-ray absortiometry (DEXA) scan. This is considered to be the gold standard screening test to measure the BMD of the hip and spine. It is less expensive and involves less radiation exposure than the quantitative computed tomography (CT). Since some patients don't respond to therapy for osteoporosis, the BMD results can also be used to follow them and evaluate their response to treatment. Bone mass should be measured in postmenopausal women 1 to 2 years following the initiation of therapy.

The report of the DEXA provides a T score and a Z score. The T score is defined as the number of SDs above or below the mean BMD for sex- and race-matched young controls (not age matched). This should be distinguished from a Z score, which is defined as the number of SDs above or below the average BMD comparing the patient with the population adjusted for age, sex, and race. These results can be used to classify patients into three categories: normal, osteopenic, and osteoporotic (Table 8.1). Osteoporosis is diagnosed using the patient's T score, because the T score is a measure of current fracture risk. A T score of 1 SD below the age-predicted mean is associated with a two- to threefold increased risk of fracture. Patients with T scores more than 2 SDs below the mean have an exponential increase in their risk of fracture. Z scores have little significant value for clinical practice.

Newer measures of bone strength, such as the ultrasound, are being introduced as an alternative screening method to the DEXA scan. This measurement of bone mass is being done through peripheral bone mass assessment. In 1998, the Food and Drug Administration (FDA) approved the use of a portable ultrasound to

Table 8.1. World Health Organization (WHO) Diagnostic Criteria for Osteoporosis

Table 8.1. World Health Organization (WHO) Diagnostic Criteria for Osteoporosis

Bone Mineral Density (BMD)

Diagnosis

T score3

Normal

<1

Osteopenia

1-2.5

Osteoporosis

>2.5

Severe osteoporosis

>2.5 and history of fracture

Standard deviation (SD) below the mean in healthy young adults.

Source: WHO Study Group.7

Standard deviation (SD) below the mean in healthy young adults.

Source: WHO Study Group.7

assess bone mass through the measurement of the calcaneous. If a patient has a low T score in the ultrasound of a peripheral bone, the current recommendation is to obtain a DEXA of the hip and spine for further evaluation and treatment.11

The diagnosis and treatment of osteoporosis should be individualized based on each patient's risk factors rather than the assessment of a T score alone. Indications for bone mineral density assessment include:

Women >65 years old who are willing to start drug therapy if BMD

is found to be low Women <65 who have at least one additional risk factor for osteoporosis

Postmenopausal women with a fracture Radiographic evidence of bone loss Long-term steroid use Hyperparathyroidism

Monitoring therapeutic response if the results would affect the clinical decision.

Although there is no evidence to support this, some clinicians screen premenopausal women with BMD for the following conditions:

Prolonged oligo/amenorrhea A long-standing history of eating disorders Stress fractures

Chronic use of medications that promote bone resorption.

There is a lack of evidence to support the cost-effectiveness of universal routine bone density screenings or to support the efficacy of early preventive medications to prevent fractures. Therefore, an individualized approach is recommended25 (Table 8.2).

Bone Remodeling Assessment

Another way to assess bone strength is to measure markers of bone remodeling (turnover) in the blood or urine. There is some evidence that bone turnover rate predicts the risk of osteoporotic fractures in postmenopausal women.26 These markers include indices of bone resorption such as serum and urine levels of C- and N-telopeptide, and indices of bone formation such as osteocalcin and bone-specific alkaline phosphatase. These markers of bone turnover may be particularly

Table 8.2. Indications for Bone Mineral Density (BMD) Screening

National Osteoporosis Foundation guidelines3 Women >65 willing to start therapy if BMD low Women <65 postmenopausal with at least one additional risk factor All postmenopausal women with fractures

Women considering therapy for osteoporosis, and BMD would affect decision

Women who have received HRT for a prolonged period No formal guideline developed in premenopausal women

American Association of Clinical Endocrinologists clinical practice guidelines^

Perimenopausal women willing to start therapy if BMD low X-ray evidence of bone loss Asymptomatic hyperparathyroidism

Monitoring therapeutic response and BMD would affect decision Long-term use of glucocorticoid

BMD = bone mineral density; HRT = hormone replacement therapy. 3National Osteoporosis Foundation (NOF). Physician's guide to prevention and treatment of osteoporosis. Washington, DC: NOF, 1998, 2000

^American Association of Clinical Endocrinologists (AACE). Clinical practice guidelines for the prevention and treatment of postmenopausal osteoporosis. Endocrinol Pract 1996;2(2):157-71.

useful if obtained prior to starting treatment and then repeated in 3 to 6 months to measure the response. Despite the fact that these markers may identify changes in bone remodeling, they do not predict fracture risk.

These tests are very expensive and are not recommended for screening or as the first-line studies to follow treatment response. However, if the BMD does not increase with treatment, one might order the turnover markers for further assessment.

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