Menopausal Bone Loss
The loss of bone density after menopause has long been linked to the dramatic decrease in the estrogen hormone, estradiol. But a recent series of studies in women age 40 to 55 has found that estrogen may not be the only hormone that should be considered.
“For years, the model has been that ovaries lose their ability to make a potent estrogen at menopause, and that this estrogen decline starts the bone loss,” says epidemiologist MaryFran Sowers, the John G. Searle Professor of Public Health at the University of Michigan.
However, data from the Study of Women’s Health Across the Nation (SWAN), a long-term study of over 3,000 multiethnic women, is showing that bone loss begins before the onset of menopause and before estrogen levels have really started to decline.
Sowers’s team zeroed in on follicle-stimulating hormone, FSH for short, as another culprit contributing to bone density loss. FSH is produced in the pituitary gland of the brain and serves as a messenger to the ovaries to produce sex hormones. Levels of this hormone begin to rise and become increasingly higher in the peri-menopause, well before the estrogen dip.
Sowers and her colleagues found that among the SWAN women, increased FSH levels were much more predictive of bone loss. This suggests that, in addition to signaling the ovary, FSH could signal other cells, including bone cells. Bone tissue has been shown to have receptors sensitive to this hormone, and the levels of rebuilding rate in bone tissues change in response to FSH levels.
Hormone replacement therapy with estrogen has been effective in stemming bone loss in some women, but Sowers suspects that his new insight into FSH may help explain why estrogen’s effects on bone loss vary from one individual to the next.
UM News Service
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