Clinical Review

Does menopause always justify bone density testing?

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Anne has new-onset hot flashes, Beth’s mother broke a hip, Carol thinks she’s not at risk, Donna has 6 risk factors. Is bone density testing appropriate?


 

References

IN THIS ARTICLE
  • 4 case studies
  • Drug treatment based on T-scores and risk factors Reasonable options if T-score is borderline
  • When is a follow-up in 1 year vital? When is a 2- or 3-year interval safe?
  • BMD test techniques, sites, and T-scores

This question begs for a simple yes or no, but it is best answered by asking a second question, “Do I need to know my patient’s bone density to give her the best care possible at menopause?” If the answer is yes, then bone density testing is a must, because there is no other way to know what her bone density actually is.

How, then, does this knowledge affect clinical decision-making?

Our concern, of course, is whether we need to intervene pharmacologically to preserve the strength of the skeleton. Even though bone mineral density (BMD) does not completely account for bone strength, it does determine some 60% to 80% of bone strength, and it is still the best predictor of an initial fracture.

Of immediate concern to the physician caring for a woman entering the postmenopausal period is whether she has sufficient bone mass to withstand the bone loss that estrogen deficiency will impose—without developing a dangerously fragile skeletal structure.

Women start losing bone mass years before menopause. While she is still in her mid-40s, a woman’s spinal bone density begins to diminish due to accumulating dietary calcium deficiency, declining physical activity, and declining estradiol levels. (Unless menopause occurs earlier for any reason, however, bone density in the spine is thought to remain relatively stable from the time peak bone mass is attained, before age 30 in most skeletal sites,1 until the mid-40s.) The exact age at which the proximal femur begins to lose bone is more controversial. Cross-sectional studies have suggested that bone loss may in fact begin in a woman’s 20s, almost immediately after reaching peak bone mass. Others have suggested that bone loss does not begin until later, in her 30s.2

A variety of risk factors are modifiable, but one that we cannot modify—genetics— may play the predominant role in determining peak bone mass. Other factors include nutrition, physical activity, intervening illnesses, medications, and lifestyle factors like smoking and alcohol use.

Expect bone loss with any cause of estrogen decline

Postmenopausal bone loss is inexorable in the absence of estrogen replacement, as well as after stopping estrogen replacement therapy (ERT) or hormone replacement therapy (HRT). If your patient stops ERT or HRT, from a skeletal perspective she has just become postmenopausal again. By measuring her bone density, you can ascertain whether bone loss— which will certainly occur—will further deplete bone mass that is already less than ideal. If so, immediate intervention to prevent bone loss is appropriate.

One key longitudinal study,3 for example, found that perimenopausal women lost an average of 2.3% per year from the spine; postmenopausal women, 0.5%. The authors observed these losses in peri- and postmenopausal women, assessed over an average of 27 months. (Women were classified as perimenopausal if they became postmenopausal during the study.)

Calcium intake of 1,000 mg/day or more does not stop bone loss

In a study designed to evaluate the effectiveness of alendronate compared with placebo in preventing bone loss in women within 3 years of menopause, McClung et al4 found a 3% to 4% bone loss at the end of 3 years in the placebo group, despite total calcium intakes of 1,000 mg per day or more.

Stopping HT merits equal concern

Estrogen deficiency precipitated by stopping hormone therapy is due the same concern as that created by menopause itself. Although the exact rates vary in studies, it is clear that bone loss begins when ERT or HRT stops, just as it does with onset of menopause. Hysterectomized postmenopausal women who received ERT for 2 years were found to have a 4.5% decline in posterior-anterior (PA) lumbar spine bone density and a 1.2% decline in total hip bone density only 1 year after estrogen withdrawal.5 This loss occurred despite calcium supplementation.

Trémollieres et al found a 1.64% per year loss of bone density from the spine for the first 2 years after discontinuing HRT, which was similar to that seen in estrogen-deficient women for the first 2 years immediately after menopause.6 In the Postmenopausal Estrogen/Progestin Interventions (PEPI) trial, women who stopped HRT after 3 years lost bone density at an annual rate of 1.04% from the spine and 1.01% from the hip during 4 years of follow-up.7

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