Negative effects of the hormone cortisol on the inner lining of blood vessels, the endothelium, may explain how stressful events trigger heart attacks and other cardiovascular problems, according to a new study in the July 19, 2005, issue of the Journal of the American College of Cardiology.
“It is already known that acute stress impairs endothelial function. Our study suggests that cortisol may cause this,” said Michael P. Frenneaux, F.R.C.P., F.A.C.C., of the University of Birmingham, United Kingdom.
The researchers, including lead authors Andrew J. M. Broadley, M.R.C.P., and Ania Korszun, M.R.C.Psych, gave mental stress tests to 36 healthy nonsmokers. Before the stress tests, the participants were randomly assigned to receive a drug, metyrapone, which blocks the action of cortisol, or a placebo pill. The randomization was double-blinded; meaning neither the researchers nor the participants knew who was given the active drug until after the study was completed. Blood pressure patterns (baroreflex sensitivity) and a measure of how the endothelial layer of blood vessels in the arm responded to sudden changes in blood flow (flow-mediated dilation) were recorded before and after the mental stress tests.
Both measures fell in the placebo group, which indicated the stress was impairing the responsiveness of the blood vessels. This sort of impaired response is one early warning sign of cardiovascular disease. By contrast, the measurements were unchanged in the participants who had been given the cortisol-blocking drug.
“Blocking cortisol synthesis with metyrapone prevented the impairment of endothelial function which follows acute mental stress in healthy subjects,” Dr. Frenneaux said.
This study was designed only to reveal the role of cortisol in the body’s response to stressful events. Dr. Frenneaux said they are not suggesting metyrapone as a potential antistress preventive treatment. He also pointed out that this study looked only at the short-term response to stress, not the effects of chronic stress.