What, if any, is the biological difference between a trans woman and a cis woman?

Christine Penn
4 min readJul 17, 2023
Photo by Annie Spratt on Unsplash

This question was asked on Quora and I answered it. You can use the link below to see the original question and others responses. I think the answer I provided is worth sharing here as well.

My Answer

Wow, I’ve read some of the responses here and can’t believe them. Biology is much more diverse.

First — the starting point. While science is well aware of how transgender people can be created through a variety of means, they are also well aware that they likely have not discovered them all yet. However, of the ones we know about, it presents a picture that things can go down different paths during fetal development that can cause different areas of the body to develop differently from a sex standpoint. This can result in brain structure differences, hormonal balance differences, etc. (Trans people explaining having female brain into a male body is actually something that really happens.)

This is made possible by the simple fact that all bodies have the instructions to build both traditionally male and female structures/organs/etc. It’s just a matter of what got activated or deactivated during development. And then also that development also occurs in stages; not all at once. (Not only during initial development, but then also puberty later.)

And then you add on top of that what can be made/activated later. This forces you to evaluate the body piece by piece. Some components, for example ovotestes, have an one way path. Once made into an ovary or a testes, there is no converting back. (Lets leave building new from stem cells out of the picture for now). But others can still be activated independently on their own. For example, breasts can still be grown simply by introducing hormones into the body at any time. Once created, they too become a one-way street as well. So, trans women can grow breasts with the introduction of hormones, trans men will have to have them removed.



Christine Penn

Trans woman, parent, cyclist, software engineer, author, chef, and many other things.