Clinical trials
Women's Health

Clinical Trials Often Exclude Women Even Though Sex Hormones Can Alter Results

“Right now, when you go to the doctor and you are given a prescription, it might not ever have been specifically tested in females,” says Deborah J. Clegg, a Professor of Biomedical Science at Cedars-Sinai Hospital in California and one of the authors of an Essay published August 9th 2016 in Cell Metabolism criticizing this approach “Almost all basic research — regardless of whether it involves rodent models, dogs, or humans — is predominately done in males. The majority of research is done with the assumption that men and women are biologically the same.”

A release from the publishers notes that clinical researchers often excludes females from their trials under the assumption that “one size fits all” — that a painkiller or antidepressant will be equally effective in subjects of either gender. Yet a growing number of scientists are arguing that hormones and other variables make a difference in how potential therapeutics behave, and both males and females must be accounted for in trials to move medical advances forward.

One reason females are excluded from studies, she says, is that across the menstrual cycle there are fluctuations in hormones such as estrogens and progesterone, in essence creating a different hormonal milieu or profile depending on the phase of cycle, which may potentially impact the research. Often overlooked in male-only studies, these sex hormones are implicated in all biological processes, including sensitivity to fatty acids, or the ability to metabolize simple sugars. These differences have implications for all clinical trials, whether they are testing the effects of a drug or a body’s ability to tolerate an organ transplant.

It is important to remember that chromosomal differences also exist between the sexes, says Clegg. There is little research examining whether drugs behave differently in the presence of an XX chromosome as opposed to an XY chromosome. Even genome-wide studies often don’t take chromosomes into account, even though sex chromosomes are an integral piece of an individual’s genomic makeup.

While researchers appreciate that there are sex differences in disease risk, less is known about how or why these sex differences occur or how they extend to the transsexual community. Clegg’s lab is currently investigating the impact of gender reassignment surgery on cardiovascular disease risk. Women are traditionally protected against cardiovascular diseases when compared to men; however, it is unclear whether a transsexual woman (a man who has transitioned to become a woman) is at a lower or higher risk for heart disease due to the presence of endogenous male chromosomes overlaid with exogenous female hormones.

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