What is the role of menopause in the development of osteoporosis?

Updated: Jun 06, 2018
  • Author: PonJola Coney, MD; Chief Editor: Richard Scott Lucidi, MD, FACOG  more...
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Answer

Answer

Although osteoporosis is one of the most pervasive conditions in older women, it often is not taken seriously enough by menopausal women. With proper intervention, osteopenia is a largely preventable sequela of menopause. Osteoporosis is defined as a bone mineral density (BMD) equal to or greater than 2.5 standard deviations (SDs) below the peak bone mass, or T score. Osteopenia is defined as a BMD that is 1.0-2.49 SDs below the T score. [23]

In a 2001 meta-analysis of data from 22 trials involving a total of 8800 women, Grady and Cummings found a 27% reduction in risk of nonvertebral fractures in older women who received hormone therapy. [24] For hip and wrist fractures, the risk reduction was 40%, increasing to 55% in women younger than 60 years. The data from the Women’s Health Initiative (WHI) also demonstrated decreased bone fractures in women on hormone therapy.

After the findings of the WHI were released, millions of women in the United States discontinued hormone therapy. Karim et al evaluated the impact of this cessation and found that women who discontinued hormone therapy were at higher risk for hip fracture and lower BMD than women who continued hormone therapy; they also found that the protective effect of hormone therapy against hip fracture disappeared within 2 years of cessation. [25]

The onset of menopause leads to rapid loss of BMD because bone resorption, uncoupled from bone formation, is accelerated while formation continues at the premenopausal rate. Trabecular bone is affected more than cortical bone; thus, bone loss is more commonly observed at vertebral, coaxial, and radial sites. The normal bone loss associated with senescence is different from the accelerated loss observed after menopause. Bone loss in just the few years after onset of menopause may be as high as 20% of lifetime bone loss. [24]

The overall effect of menopausal bone loss is reduction of bone strength, leading to an increased risk of fracture. The younger the woman is when ovarian function ceases, the more severe bone loss is likely to be. Similarly, the lower the woman’s bone mass is when she enters menopause, the more severe the osteoporosis will be.

The severity of osteoporosis is also related to race, being worse in whites than in Asians and least severe in women with dark complexions. Other risk factors are smoking and slender build. Osteoclasts have been shown to have estrogen receptors, and these are hypothesized to be the mechanism by which estrogen replacement protects against osteoporosis.


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