Åsa Tivesten researches atherosclerosis and its correlation with sex hormones. Current findings suggest that women with low levels of testosterone may also need replacement therapy.
Dr. Tivesten was recently appointed Professor of Medicine with a specialization in endocrinology and sex hormone research. She is also a consulting endocrinologist at Sahlgrenska University Hospital and regional coordinator of hormone therapy for transsexual patients.
Her research focuses on correlations between atherosclerosis and sex hormones from every conceivable angle using both clinical and experimental methods. Medical research is often categorized as either preclinical or clinical, but Dr. Tivesten regards the approach as outdated.
“In vitro, human, animal and epidemiological studies all complement one another,” she says. “Many medical researchers employ several different methods and we shouldn’t let ourselves be pigeonholed into one category.”
She spends her days at the Wallenberg Laboratory, where a number of different research teams study the mechanisms of obesity, cardiovascular disease and related metabolic conditions. The translational setting embraces a broad range of disciplines.
“We feel at home in both preclinical and clinical research,” Dr. Tivesten says. “Academia should be integrating those two spheres in a more structured way when it comes to teaching as well as research settings.”
Much of her energy goes to learning more about testosterone, usually its effect on male metabolism. But the most recent findings by Dr. Tivesten and her team indicate that the hormone may play a more prominent role in female metabolism than previously thought. A study of mice in which testosterone could not have any effect found that females became obese, insulin-resistant and victims of atherosclerosis. The findings suggest that women with low levels of testosterone may also need replacement therapy.
An article published by the researchers in the FASEB Journal demonstrates that female mice whose androgen receptor had been deactivated were much more likely to suffer from obesity, reduced insulin sensitivity and atherosclerosis.
An arduous task
Designing a mouse model for the study was an arduous task. Because the androgen receptor is located on the X chromosome and males that lack it become infertile, special techniques were required to generate AR-knockout mice.
“The results suggest that testosterone may play a more important role in the metabolic health of women than previously thought,” Dr. Tivesten says. “Men with low testosterone levels due to a tumor of the pituitary gland or another condition receive replacement therapy. It is possible that women should as well.”
The team has also developed a mass spectrometry method to quantify androgen levels in population-based material and elsewhere with a high degree of sensitivity.
Talking about androgen deficiency in women
Both the ovaries and adrenal glands of women form testosterone. Their levels are approximately one-tenth those of men and also decline with age. The process is abrupt following an ovariectomy. Given that the pituitary gland controls testosterone production, a tumor in that area of the brain can substantially affect its levels.
“Researchers and doctors have been engaging in a lively discussion about the possible effect of androgen deficiency in women,” Dr. Tivesten says. “While the emphasis has been on general wellbeing and sexual performance, our study indicates that the risk of both atherosclerosis and diabetes may increase as well.”
She believes that long-term, comprehensive treatment studies will be needed to determine whether replacement therapy can reduce the risk of obesity and cardiovascular disease in women with testosterone deficiency.
Read The androgen receptor confers protection against diet-induced atherosclerosis, obesity, and dyslipidemia in female mice:
http://www.fasebj.org/content/early/2014/12/22/fj.14-259234.long