Clinical:Case Study: Osteo... what

Original materials created in December 2002 by JoDean Nicolette, M.D.

History

CJF is a 62 y/o white woman who is a new patient. She wants to speak with you because she had a bone density test a few months ago, and was told she has “thin bones.” Her women’s magazine recommended medication to treat her “disease.” CJF is afraid of medication, and has stopped exercising because she fears she will have a fracture or a curved spine. She has no history of fracture, no other medical problems, and no history of surgery. Her health care maintenance is up to date.

Social Hx: no tobacco, rare alcohol; until two months ago she exercised by hiking and treadmill, and with weights 5x/week; she eats meat twice daily

Medications: multi vitamin daily

Family Hx: no thyroid disease, bone densities unknown, but no history of fractures

Exam: thin woman, vital signs and physica exam normal

Studies: recent bone densitometry reporting

T-scores: -1.7 at the hip, and -1.9 at the lumbar spine

Discussion

Bone mineral density (BMD)decreases with age in most women. The relationship between BMD and fracture is complex rather than linear; While it is true that women with the thickest bones have fewer fractures than women with the thinnest bones, the relationship is less clear for most women who are somewhere in the middle. Practitioners are challenged to sort out what is true risk and benefit, and what is marketing strategy, in a burgeoning “bone health” industry.

Bone mineral density is usually measured at the hip, spine, and/or total body by Dual Energy Xray Absorptiometry (DEXA). Bone mineral densities are compared to two norms, “young normal” (T-score) and “age-matched” (Z-score). Tscore compares BMD to optimal density of a 30-year old healthy adult. Z-scores are comparisons to age- and size-matched norms. Each of these scores represents the number of standard deviations the patient’s bone density is from the mean. Scores can be positive (denser than the mean) or negative (less dense than the mean). Among older adults, lower BMD is common, and possibly normal, so comparison with younger norms can be misleading. T scores are usually reported in four categories, developed by the World Health Organization (WHO):

Normal: T score = +1 to -1

Osteopenia: T score = -1 to -2.5

Osteoporosis: T score < -2.5

Severe (established) osteoporosis: T score < -2.5, w/history of osteoporotic fracture

DEXA cannot predict subsequent fracture, nor can it predict the rate (if any) of future bone loss.

While osteopenia represents a decrease in density of bone, osteoporosis represents a decrease in density along with a loss of structural integrity. Neither osteopenia, nor “baseline” bone density at menopause is well correlated with subsequent fracture. Osteoporosis can be more directly related, although imperfectly. The cause of osteoporosis is usually an alteration in the balance of osteoclast to osteoblast activity. Many factors affect this balance, both physiologic and behavioral. Physiologic factors include serum calcium levels, blood and urine pH, and hormonal levels, i.e. thyroid, parathyroid, and sex hormones. Behavioral factors include tobacco and alcohol use, calcium intake, protein intake, and exercise. According to the WHO criteria, 20% of postmenopausal women have osteoporosis. The number of fractures due to osteoporosis is poorly documented, and the resultant morbidity and mortality is difficult to quantitate. Wrist fractures are the least concerning, whereas hip fractures are the most, primarily because of the potential complications of immobility. Complications include deconditioning, pneumonia, deep venous thrombosis and pulmonary embolus, and death. One often cited study reporting 50% of women with osteoporosis suffer fractures is very misleading. The authors report the total number of fractures rather than the number of women with fractures. This means one woman with four fractures makes the incidence of fracture look quadruple to what it truly is. Also, some of these fractures were wrist, which cause much less morbidity than hip or vertebral fractures. Most women in the study had no fractures, but this is rarely reported.

Since merely having osteoporosis doesn’t mean you’ll have a fracture, the picture is clearly a complex one. Some important factors may be: genetics, muscle mass and tone around bones and joints, joint mechanics, type and frequency of falls, and use of devices such as hip protectors. Some women may benefit from use of medication, but distinction must be drawn between medications that merely increase bone density, and those that actually have been shown to prevent fracture. Bisphosphonates can increase bone density and reduce fractures of the hip and spine, but the regimen is complicated, and the adverse effects (i.e. erosive esophagitis) concerning. Estradiol and conjugated equine estrogens (CEE) have been shown to increase bone density, but only CEE has been shown to decrease fractures in healthy postmenopausal women. CEE has not been shown to reduce fractures in women with established osteoporosis. Many providers feel that the risks of chronic hormone therapy outweigh the benefits. The Selective Estrogen Receptor Modulators (SERMS) such as raloxifene, have been shown to increase bone density and prevent vertebral fractures. Calcitonin has been shown to increase bone density, but not to prevent fracture.

Plan

I discussed the difference between osteoporosis and osteopenia with CJF. She has osteopenia. I asked her to consider viewing osteoporosis as a risk factor for fracture,rather than an actual disease. We discussed other risk factors for fracture. CJF is a thin, white woman, which puts her at risk, but she has good muscle tone and mass, and excellent balance due to her rigorous exercise schedule. She does not have family history of fracture. She also does not smoke,and rarely drinks. I suggested checking TSH and PTH levels to rule out other secondary causes of bone loss. We discussed decreasing her intake of animal protein, and adding calcium supplementation (1500mg) with vitamin D (800IU). We discussed “feeling frail” as a risk of DEXA scans, and CJF gained insight into this. She reported that she may want to repeat her DEXA on a year. CJF agreed eagerly to re-start exercising both the weight-bearing and the weights. She asked for an assessment of her home for fall hazards. She wanted to do “her own research” on medications for bone density, and said she would follow up in three weeks.

References

Altkorn, D, Vokes, T. Treatment of Postmenopausal Osteoporosis.JAMA, 2001;285: 1415.

National Institutes of Health Consensus Development Conference Statement. Osteoporosis prevention, diagnosis, and therapy. March 27-29, 2000.

Tanouye, E. Merck’s osteoporosis warnings pave the way for it’s new drug. Wall Street Journal, June 28, 1995.

The Truth about Hormone Replacement Therapy. The National Women’s Health Network. Prima Publishing:Roseville,CA, 2002.