New York, March 9 (IANS): A new study shows that the sex hormones testosterone and estrogen alter cardiovascular factors in a way that raises a man's risk of heart disease.

Men have higher testosterone and lower estrogen levels than pre-menopausal women.

"Therefore, doctors have suspected that testosterone may promote cardiovascular disease or that estrogen may protect against it, or both," said Elaine Yu, lead investigator and assistant professor at Harvard Medical School, Boston.

The study, conducted in 400 healthy men aged 20 to 50, found that higher levels of testosterone led to lower levels of HDL cholesterol or "good" cholesterol while estrogen appeared to have no effect on HDL cholesterol.

In contrast, the investigators reported that low levels of estrogen led to higher fasting blood glucose (sugar) levels, worsening insulin resistance and more fat in muscle, markers for developing diabetes which is itself a risk factor for heart disease.

"These observations may help explain why men have a higher risk of cardiovascular disease," Yu noted.

The researchers also found that neither testosterone nor estrogen regulated changes in LDL or "bad" cholesterol, blood pressure and body weight.

"It appears that these common risk factors for cardiovascular disease are not regulated by sex hormones," Yu added.

In summary, higher testosterone levels and lower estrogen levels in men worsen cardiovascular risk factors that may help to explain gender differences in heart disease.

The results were presented at the Endocrine Society's 97th annual meeting in San Diego, California, last week.