While making a presentation at the American Heart Association's annual Scientific Sessions in New Orleans on November 11, the researchers said that their new findings might help understand why men are twice as likely to develop heart disease as women.
The researchers said that older women, who produced a relatively high amount of oestrogen, were more likely to develop coronary artery calcium (CAC), a component of the fatty plaque that builds up in blood vessels and hardens arteries.
Older men with relatively high amounts of testosterone, according to the team, were also more likely to develop CAC.
However, once CAC is present, higher testosterone appears to help prevent CAC from progressing too quickly in men's arteries.
"We know many things that increase the risk of cardiovascular disease, such as high cholesterol and diabetes," says Dr. Erin D. Michos, assistant professor of medicine at the Johns Hopkins University School of Medicine and its Heart and Vascular Institute.
"But 10 percent to 20 percent of people who get heart disease don't have these risk factors, so we need to understand other factors that might be involved. Our results suggest that someday, in addition to testing your cholesterol and blood sugar levels to assess your heart disease risk, your doctor may want to measure your sex hormone levels as well," the researcher added.
For their research, the researchers used data from 2,700 male and 1,646 postmenopausal female participants in the ongoing Multi-Ethnic Study of Atherosclerosis (MESA) study, which has been tracking patients of four different races since 2000 to determine factors that influence risk of developing cardiovascular disease.
The Hopkins team revealed that the participants in their study were those who had not received hormone replacement therapy.
At the beginning of the study, participants answered detailed questionnaires about their demographics and medical history, and they received a basic health assessment measuring their height, weight and blood pressure.
The subjects also received a CT scan measuring their baseline level of CAC, and had their blood drawn to measure blood concentrations of various sex hormones, including estradiol, the dominant type of oestrogen in women, and testosterone, the dominant sex hormone in men.
While about 50 per cent of the subjects had a second CT scan 18 months later, the other half had their second scan 37 months after the initial scan.
The researchers compared the two scans, and found that in women who had no baseline CAC, the researchers found that women with higher amounts of oestrogen were 30 percent more likely to develop CAC by their second scan than women with lower levels of oestrogen. The risk was most pronounced in women older than 65 years of age.
Levels of oestrogen did not seem to significantly affect whether CAC increased in women who already had CAC at baseline.
In men who had no CAC at baseline, the researchers found that the subjects with higher testosterone levels were 48 percent more likely to develop CAC than those with the lowest testosterone levels, with the risk greatest among men older than 55 years of age.
In men who already had CAC at baseline, higher testosterone levels appeared to have a protective effect, reducing the chances that CAC measurements would increase at follow-up.
Michos said that the role of sex hormones in cardiovascular disease was complex, with often diverse and contradictory effects.
Though their study focused on early atherosclerosis in the coronary arteries, the researchers said that sex hormones might also affect heart disease risk through other mechanisms, including influencing inflammation, blood clotting, and whether blood vessels are constricted or relaxed.
Michos and her colleagues are currently planning to study how sex hormone levels might affect the risk of specific cardiovascular incidents, such as heart attacks and strokes, in men and women.