Women are women and men are men – for the most part. Ovaries and testes can be removed, and hormones blocked or supplemented but it doesn’t change the genetic makeup of our cells. Well not yet at least. So, people born with an XY chromosome have different potentials and responses to disease and treatments than those without an XY chromosome, and it’s not all about sex hormones or environmental conditions.
The differences can be easily explained by looking at the different heights of XX and XY . Most XY males and XX females in the population stand between approximately 1.5 and 1.8 meters tall, but the extremes of short and tall are exclusively females and males, respectively, and the mean heights are different. This difference in height has no direct relationship to male hormones such as testosterone, or female hormones such as estrogen but rather relates to male versus female chromosomes.
So, it is no surprise that research is continuing to validate the chromosomal sex differences between men and women – irrespective of cis or trans status. Data from the Hiroshima, Nagasaki, Chernobyl and Fukushima nuclear disasters clearly shows that tumors occurred more frequently in XY male survivors. Similarly, the rates of secondary cancers in XY males whose initial diagnosis and treatment were at less than 60 years of age are consistently greater than those in XX females.
It is not all one way though with non-hormonal cancers. Girls suffer more from cancers of the adrenal gland than boys.
If cancers have different rates in XX and XY persons, it follows that treatments for non-sex hormone related cancers will work differently. For example, the X chromosome has an effect on suppressing cancer genes and two Xs provide a backup safety of this effect if one gene goes haywire. Similarly, the Y chromosome provides greater benefit for some of the treatments for melanoma and lung cancer.
We already know that excretion of toxins and excess drugs occurs differently in XX and XY. XX women metabolise toxins in the liver for excretion in the digestive tract, whereas XY men remove toxins through the kidney. This partially explains the higher rates of liver disease in XX women and kidney disease in XY men.
Clearly your cis is always important. Neither changes in external appearance nor hormonal balance will change the way our individual cells work. It’s an evolving picture for transitioning individuals who will have to be alert to the possibilities of a complex range of susceptibility to disease and treatments. For example, cervical cancer smears and mammograms will still be important for trans females as will prostate checks for trans males.
For those cis identified, checking with clinicians about X and Y differences in disease prevalence and treatment will continue to be important.