and Medicine for Seniors
Higher heart disease risk for men
due to high testosterone, low estrogen
Sex hormones testosterone nor
estrogen caused changes in "bad," cholesterol, blood pressure, or body
weight in this study
March 8, 2015 - Why men have more
heart disease than premenopausal women has been a puzzle, but a new
study shows that the sex hormones testosterone and estrogen alter
cardiovascular risk factors in a way that raises a man's risk of heart
Results of the study were presented
Saturday at the Endocrine Society's 97th annual meeting in San Diego.
Men have higher testosterone and
lower estrogen levels than premenopausal women. Therefore, doctors have
suspected that testosterone may promote cardiovascular disease or that
estrogen may protect against it, or both, according to Elaine Yu, MD,
MSc, the study's lead investigator and an assistant professor at Harvard
Medical School, Boston.
Their study, conducted in 400
healthy men ages 20 to 50, found that higher levels of testosterone led
to lower levels of HDL cholesterol, or "good" cholesterol, but 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
"These observations may help
explain why men have a higher risk of cardiovascular disease," Yu said.
Yu and her research team were able
to determine whether estrogen or testosterone regulated various
cardiovascular risk factors by comparing two groups of men whose hormone
levels were temporarily changed with combinations of medications.
At the start of the study, all men
received the drug goserelin (Zoladex, AstraZeneca) to suppress their own
production of testosterone and estrogen. Then the 198 men in the first
group received daily treatment for four months with either a placebo
(dummy) gel or one of four doses of testosterone gel (AndroGel, AbbVie),
ranging from low to high (1.25 to 10 grams). This treatment set the
men's testosterone levels from very low (as in before puberty) to
high-normal, Yu said.
The other group, made up of 202
men, received the same treatment as in group 1 but also received
anastrozole (Arimidex, AstraZeneca) to block conversion of testosterone
to estrogen. Men naturally convert some testosterone to estrogen.
Blocking this process resulted in very low levels of estrogen in the
second group, according to Yu.
Study participants had their weight
measured and had fasting blood tests for markers of heart disease and
diabetes. At the start and end of the study, they had a thigh scan with
quantitative computed tomography (CT) to measure muscle fat.
The researchers 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 said.
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.
Grants from the National Institutes
of Health and AbbVie supported this study. The drugmakers provided the
medications used in this study at no cost.
Founded in 1916, the Endocrine
Society is the world's oldest, largest and most active organization
devoted to research on hormones and the clinical practice of
endocrinology. To learn more about the Society and the field of