30 June 2006
Estrogenís Function Under Stress Differs Between Races
Researchers have found that estrogen levels appear to play a different role during stress in black and white women, a difference that may help explain the higher cardiovascular disease rates in blacks. Exposing the subjects to common stressful situations, the researchers found that estrogen levels dropped during stress in healthy black girls, but remained consistent in whites, explained Dr. Gregory Harshfield, of the Medical College of Georgia's Georgia Prevention Institute. Harshfield's work was presented at the Annual International Interdisciplinary Conference on Hypertension.
Estrogen, which can dilate blood vessels, is considered beneficial in stressful situations. "If you lose that protection during periods of stress in the day it may contribute to the early development of heart disease we typically see in black women," explained Harshfield. The researchers found the greatest changes in blood pressure response to stress in black girls. Blood samples taken before, during and one hour after playing a competitive video game showed their estrogen levels dropped during stress and went back up afterward.
"Conventional thinking tells us estrogen is not normally a major player in regulating blood pressure during stress," said Harshfield. "This tells us sex hormones do play a role in regulating blood pressure but, unfortunately, it's a bad one in black females."
"We are now thinking that when black girls are under stress, they are losing all the protective effects of estrogen," Harshfield explained. "In whites under stress, their estrogen levels are consistent so they are secreting vasodilators, they are blocking angiotensin and the sympathetic nervous system so the stress is not affecting them as much." He added that the prevalence of hypertension is increasing in females, particularly in black females whose prevalence is greater than black males and overall death rate from hypertension is more than twice that of white females.
Little is known about mechanisms underlying racial differences in blood pressure, according to Harshfield. His previous work has shown that, compared to their white peers, healthy black girls and boys also have reduced ability to secrete sodium following stress, which leaves their blood pressure elevated for longer periods. "Estrogen is probably another mechanism through which the blood pressure is staying elevated," he concluded.
Source: Medical College of Georgia