Dr. Susan Love Research Foundation | Menopause & Women's Health

When you say "osteoporosis," most people know what you are talking about. But when you mention "osteopenia," it's common for someone to say, "What's that?" That's because osteopenia is a relatively new term used by doctors to describe bone density.

The term osteopenia was created shortly after the development of the dual-energy X-ray absorptiometry (DEXA) scan. A DEXA scan is used to measure bone density at the hip and spine, where fractures are most likely to occur. It is now widely used to monitor bone health.

Before the machine was put into widespread use, an international group of medical experts met to determine a consistent method for using DEXA scan readings. They decided to use a T score, a statistical term called standard deviation, which measures how far something is away from the norm; in this case, the "norm" selected was the bone density of a healthy, average woman in her mid-20s. They also decided that a –2.5 standard deviation below the norm would be used as the definition for osteoporosis.

The next question they faced was: What should we do about women who scored less than –2.5 and who did not yet have osteoporosis? They decided that it was important for these women to be aware that they had already had some bone loss. So they created a new term to classify these women, and that term was osteopenia. And they decided that the cutoff for osteopenia would be –1.

Today, any woman who scores between –1 and –2.5 on her DEXA scan is told that she has osteopenia. But what's been forgotten, says bone health expert Steve Cummings, MD, a professor of medicine and epidemiology at the University of California, San Francisco School of Medicine, is that there was no real medical basis for developing this term or choosing that number. In addition, says Cummings, when the term was developed, no one paid attention to the fact that it would result in half of all postmenopausal women being told they had this "disease"—with the implication that they should begin taking drugs to treat it.

But as Cummings points out, "Osteopenia is not a disease, does not indicate a high risk of fracture in the next five to10 years, and is really almost a variant of normal." If a woman learns she has osteopenia at age 55, he explains, it means she is just around average. "What I tell women in their 50s," he says, "is that having osteopenia means their bones are different than those of a 25-year-old, and I note that there are probably many things about them that differ from when they were 25. And I let them know that it is nothing to be alarmed about."

How should osteopenia be managed? Read more here.

Note to Women with Breast Cancer
Many women with hormone-sensitive tumors are now taking an aromatase inhibitor as part of their breast cancer treatment. These drugs—anastrozole (brand name Arimidex), letrozole (brand name Femara), and exemestane (brandenzyme that converts androgens into estrogen. Clinical trials have found that these drugs, unlike the hormone therapy tamoxifen, increase bone fracture risk.For women who have osteoporosis and are on aromatase inhibitors, bisphosphonates should help reduce fracture risk.

For women with osteopenia, though, it still makes more sense to wait until osteopenia has advanced to osteoporosis to begin taking these drugs. The exception would be a woman who is starting on an aromatase inhibitor and is already close to a –2.5 on her DEXA scan. In this case, she may want to start on a bisphosphonate while starting on the aromatase inhibitor.