Osteoporosis: Current Evaluation and Treatment

Osteoporosis is a chronic bone disease that affects 25 million Americans, 80% of whom are women, usually after the onset of menopause. It is characterized by low bone mass and deterioration of bone at the microscopic level resulting in increased fragility and high risk of fractures.

Osteoporosis accounts for more than a million fractures a year in the US, including 500,000 fractures of vertebrae in the spine and 300,000 hip fractures. Hip fractures cause an excess mortality of up to 20% at the one-year mark, with as much as half of patients requiring admission to a nursing home. In 1995, direct medical costs related to osteoporosis were about $13.8 billion. As the population ages, osteoporosis will become even more common and medical costs are expected to triple by 2020. Sometime in their life, half of the world's population of white women will have a fracture related to osteoporosis.

Writing in the journal Comprehensive Therapy (Vol. 26 No. 3), Medical College of Wisconsin faculty outline the current standards of osteoporosis evaluation and treatment. Joan L. Milott, MD, Assistant Professor of Internal Medicine, was the lead author with assistance from Sandra S. Green, MD, Assistant Professor of Internal Medicine, and Marilyn M. Schapira, MD, MPH, Associate Professor of Internal Medicine.

Bone is a living tissue that remodels itself throughout life. However, peak bone mass is reached at about age 30 and begins to decline thereafter. Menopause increases the rate of bone mass loss. Cigarette smoking, body weight of less than 127 pounds, alcohol abuse, low sun exposure, family history, and a history of fractures as an adult are other risk factors for osteoporosis. Postmenopausal osteoporosis is more common in white and Asian women than in women of other races.

Measuring bone mineral density may be done in several ways. Single-energy X-ray absorptiometry measures of bone density in the radius in the forearm or the heel bone may help to predict hip fractures. Dual-energy X-ray absorptiometry (DEXA) can measure the same areas as well as the hip and spine for bone mineral density. DEXA is more expensive, but most institutions consider it the preferred diagnostic method. Ultrasound of the heel and shin may also be used, or computerized tomography (CT scan).

To accurately diagnose osteoporosis a physician must be able to exclude other causes of low bone mass. A complete medical history and physical exam, including a gynecological exam, is recommended. The National Osteoporosis Foundation suggests that all postmenopausal women under age 65 with one additional risk factor should be tested for osteoporosis. All women over age 65, postmenopausal women with fractures, and women on prolonged hormone replacement therapy (HRT) should also be tested. In many cases, Medicare will cover bone mass measurements. Follow-up measurements spaced less than two years apart are of dubious value.

Fundamental to all prevention and treatment efforts is adequate intake of calcium and vitamin D. In postmenopausal women, calcium supplementation alone can reduce the rate of loss or even increase bone mass. Women with osteoporosis, who are older or have low calcium intake show the most benefit from calcium supplementation. The National Institutes of Health Consensus Conference recommends 1000mg of calcium a day for women 65 years and younger on estrogen HRT, and 1500mg a day for women younger than 65 and not on estrogen HRT and for women older than 65 years of age. The most commonly used form of calcium supplementation is calcium carbonate, such as OsCal 500 or TUMS.

Vitamin D deficiency is common in the elderly, often from a poor diet, low exposure to sunlight or aging skin's inability to synthesize vitamin D3. Vitamin D, 400 IU per day, should be added in these cases.

Estrogen replacement therapy, raloxifene, alendronate and calcitonin are all FDA-approved pharmacological treatments to prevent and/or treat osteoporosis. Estrogen hormone-replacement therapy, the mainstay of both prevention and treatment of the disease, stimulates bone formation and prevents bone loss. Estrogen HRT, such as conjugated equine estrogen (Premarin), estradiol (sold under several brand names) or estropipate (Ogen, Ortho-Est), has been shown to reduce the risk of fractures in various groups of women. For women who have retained their uterus, estrogen must be supplemented with progestin therapy to prevent potential changes in uterine tissue. Estrogen HRT may also alleviate menopausal symptoms and prevent heart disease. However, it may also increase the risk of breast cancer.

Raloxifene is an alternative to estrogen HRT for prevention of osteoporosis. Raloxifene (Evista) has demonstrated a beneficial effect on bone mineral density and is well tolerated. It should not be used by women who are pregnant or have a history of blood clots. It may cause menopausal symptoms such as hot flashes. Raloxifene has been found to cause an increase in BMD of the total body and hip similar to estrogen HRT, but has less of an effect on BMD of the lumbar spine (lower back). Raloxifene has also been shown to lower LDL cholesterol and is being studied as a way to prevent breast cancer.

Alendronate is another alternative to both prevent and treat osteoporosis. Studies have shown that it increases bone mineral density at all skeletal sites and decreases the rate of fractures. Alendronate (Fosamax) must be taken on an empty stomach and may cause gastrointestinal discomfort. It should not be taken by patients with a history of swallowing difficulties or abnormal narrowing of the esophagus.

Calcitonin is FDA-approved for treatment, but not prevention, of osteoporosis, although trials have shown it prevents loss of spinal BMD. Salmon calcitonin (Calcimar, Miacalcin) is also available as a nasal spray (Miacalcin). Calcitonin use decreases the rate of vertebral fractures in women with osteoporosis. It also may provide pain relief in some patients with fractures.

Phyto-estrogens comprise an alternative therapy being studied for its effect on bone mineral density. The precursors of these substances are found in soybean products, seeds, berries and whole-grain cereal foods. Intestinal bacteria then convert them to hormone-like compounds.

A patient's medical history, including risk of cardiac disease, breast cancer and osteoporosis, will largely determine which pharmacological treatment is most appropriate.

Drs. Milott and Green practice in the Froedtert & Medical College Primary Care Center, and Dr. Schapira practices at the Zablocki VA Medical Center. Froedtert Hospital and the VA Medical Center are major affiliates of the Medical College of Wisconsin.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.