Investigators from the longitudinal Study of Women's Health Across the Nation (SWAN) , have uncovered an indirect link to a woman’s risk of heart disease following menopause. The researchers say the increased incidence of heart disease may not be the result of “declines in estrogen levels per se, “ but rather the result of metabolic syndrome – increased waist circumference, elevated triglyceride levels, and lower levels of HDL (good) cholesterol – factors that drive increases in testosterone levels.
The group, led by Dr Imke Janssen (Rush University Medical Center, Chicago, IL), published their results in July 28, 2008 Archives of Internal Medicine. The SWAN study included multiple ethnic groups, including 3302 women enrolled at seven sites throughout the United States. Almost half the women were Caucasian, about a quarter were African American, 12% were Japanese, 11% were Chinese, and 5% were Hispanic, .Natural menopause, without hormone therapy, was achieved by 949 women, who were free of diabetes and metabolic syndrome at baseline. By the time of the final menstrual period, 13.7% had developed metabolic syndrome.
The researchers say that metabolic syndrome did not influence total estradiol or testosterone levels, but they did find an association with changes in "bioavailable testosterone," which is necessary to deliver estradiol and testosterone to the organs. The group writes, "For every one-standard-deviation increase in bioavailable-testosterone levels, the odds of developing metabolic syndrome increased by 10%" Bioavailable testosterone is specifically a function of sex-hormone-binding globulin (SHBG), and the researchers found that changes in SHBG were also associated with metabolic syndrome.
According to Dr. Janssen and colleagues, “these data show that the change in estrogen level is, at best, a weak and nonsignificant predictor of metabolic syndrome risk." More likely, they write, it is the “progressive testosterone dominance in sex-hormone metabolism, relative to the influence of estrogen” that increases the risk of heart disease. They were also surprised to learn that metabolic syndrome risk was greater for women in the peri-menopause period. "The increase is apparently steeper before a woman reaches menopause than after, and we were a bit surprised about that."
The researchers conclude, “The whole change of hormones with menopause is a very dynamic process, and we're just beginning to understand it. This study is part of the solution to the puzzle.” The results of the current study explain why estrogen therapy was not found to decrease a woman’s risk of heart disease in the Women's Health Initiative. Researchers now know there seems to be a link between balancing estrogen and testosterone in preventing heart disease in women.
For information on how to manage metabolic syndrome, visit the American Heart Association. Despite remaining questions, we do know that diet and exercise are key components for managing our risk of heart disease. You may also be interested in sending your Message of Support for the HEART for Women Act.
Details on cardiac outcomes from WHI reinforce lack of heart benefits of estrogen
Prudent Diet Reduces Risk of (women's) Death
Purchase: Menopause Formula From Menozac