Premenopausal Osteoporosis Poses Special Clinical Challenges

A woman being examined for bone density.
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ATLANTA—Osteoporosis in premenopausal women is uncommon compared with its frequency in post-menopausal women, but when it is suspected, it poses some difficult questions for clinicians: How should it be diagnosed in this understudied population? If found, should it be treated—and how?

Elizabeth Shane, MD, professor of medicine at Columbia University and attending physician at New York-Presbyterian/Columbia University Medical Center, who gave the Oscar S. Gluck, MD, Memorial Lecture at the 2019 ACR/ARP Annual Meeting, said that although the data for osteoporosis in premenopausal women are limited, important points can help guide its assessment and management.

Limits of Bone Density Scores

She cautioned against an overreliance on bone density scores in premenopausal women in their diagnosis.

In women younger than 50 a low bone mineral density (BMD) score could be due to a low peak bone mass or just due to a small stature, Dr. Shane said, and is not necessarily a sign of a problem requiring medical intervention. “It may be that this person just comes from a family with low bone density.”

And a low BMD in women younger than 50 doesn’t carry the same risk of fracture; young women have more muscle mass than older women and fewer falls, for example.

Dr. Shane

What’s more, BMD score cut-off points for a diagnosis of normal bone mass, low bone mass and osteoporosis in post-
menopausal women were “never intended and shouldn’t be used” for diagnosis of premenopausal women, Dr. Shane said.

The International Society for Clinical Densitometry (ISCD) recommends that Z scores, which compare a patient’s bone density to that of a person of the same age and gender, be used in the assessment of premenopausal women instead of T scores, which compare a patient’s bone density to an average 30-year-old adult.

The ISCD recommendations for diagnosis of osteoporosis in premenopausal women are a BMD Z score of -2.0 or less plus a secondary cause of osteoporosis, or a history of vertebral or non-vertebral low-trauma fractures at a major site, whether or not the BMD is low.

Secondary Causes

The goal of an evaluation in this population is to identify secondary causes of osteo­porosis, particularly causes that are treatable.

“In my opinion, anybody who has a low T or Z score deserves an evaluation to make sure that there’s nothing going on that could be rectified, and perhaps improve their bone density by a targeted inter­vention,” Dr. Shane said. “If I see one hip fracture, that’s it for me.”

Common causes of osteoporosis in premenopausal woman include excessive gluco­corticoid use, premenopausal estrogen deficiency, gastrointestinal disease and effects of other medications, such as anti-epileptic drugs. But many cases are idiopathic, she said.

Tetracycline-labeled transiliac bone biopsy, primarily a research tool, may be indicated in patients who have unexplained low-trauma fractures and can help guide therapy in some cases, Dr. Shane said.

In a cross-sectional study, 64 women with idiopathic premenopausal osteoporosis—some with a fracture history and some with a low BMD—underwent central skeletal quantitative computed tomography (QCT) along with 40 healthy controls. Those with low BMD had a worse volumetric BMD and bone strength compared with controls than those with a fracture history.¹

Diagnosis is just the first tricky hurdle, Dr. Shane said. “The dilemma is whether you should treat at all, and then [the next step] if you decide that you must treat—for whatever reason you choose—is to decide how to treat,” she said.