Men have a four times greater risk than women of developing abdominal aortic aneurysms, estimated to be the cause of death in 4 percent of people over the age of 65, but the mechanism for this higher incidence has remained unknown. Researchers at the University of Kentucky now report evidence that the answer lies in male sex hormones.
They found that removing circulating androgens, including testosterone and dihydrotestosterone, from male mice lowers their risk of aneurysm to that of females, while giving females these same male sex hormones increases their risk to that of males.
Tracy Henriques, a graduate student in the laboratories of Drs. Lisa Cassis and Alan Daugherty, presented the study Monday, April 4, at the American Society for Investigative Pathology scientific sessions at Experimental Biology 2005 in San Diego.
In a well-established research method, giving hyperlipidemic mice the peptide hormone angiotensin II results in the development of abdominal aortic aneurysms. Not surprisingly, considering the gender differences in humans, male mice have a three-fold higher susceptibility to developing the angiotensin-induced aneurysms than age-matched females receiving the same drug. Recent studies in the Cassis/Daugherty laboratories revealed that removing the male sex hormones reduced the incidence of aneurysms in male mice to the same lower levels seen in the females.