So the most well-known of these structures is the bed nucleus of the striae terminalis. The size and number of a specific type of neuron in that region is highly predictive of the gender of the individual, with very high reliability. Postmortem, you can count these neurons and be very close to sure what the sex of the dead person was.
Not only do trans individuals have the structure of the gender they identify as, but there were several interesting controls done to double-check.
First, they looked both at trans people who had undergone different stages of reassignment and compared them to trans people who had not initiated treatment at all. There was no difference, so HRT, etc, is not the cause of the structural differences.
Then they went to a sample of men who were sufferers of specific types of penile/testicular cancers that required a large number of feminizing hormones during the treatment process. Still no change in the striae terminalis.
And then they went back a couple years later and repeated the same experiment, with the same result.
This was all done close to 20 years ago. We’ve known this for a long time.
Fun addendum: there are a couple types of penile cancer that, sadly, requires the penis to be excised. In 70% of these cases, the men involved experienced phantom penile sensations (phantom limb syndrome). So what’s the rate of phantom penile sensations in MTF post-operation trans people? Almost 0%.
And that video is 12 years old. From my quick search to try to find the original sources just now, it seems even more studies have been done on it in the meantime.
Just managed to skim the paper and watch the video. That is a really interesting lecture and clearly he is interested in the science as he addresses caveats and the political nature of the studies. But that is actually really interesting findings. Thanks a lot for sharing this.
It’s so much more fascinating than just that!
So the most well-known of these structures is the bed nucleus of the striae terminalis. The size and number of a specific type of neuron in that region is highly predictive of the gender of the individual, with very high reliability. Postmortem, you can count these neurons and be very close to sure what the sex of the dead person was.
Not only do trans individuals have the structure of the gender they identify as, but there were several interesting controls done to double-check.
First, they looked both at trans people who had undergone different stages of reassignment and compared them to trans people who had not initiated treatment at all. There was no difference, so HRT, etc, is not the cause of the structural differences.
Then they went to a sample of men who were sufferers of specific types of penile/testicular cancers that required a large number of feminizing hormones during the treatment process. Still no change in the striae terminalis.
And then they went back a couple years later and repeated the same experiment, with the same result.
This was all done close to 20 years ago. We’ve known this for a long time.
Fun addendum: there are a couple types of penile cancer that, sadly, requires the penis to be excised. In 70% of these cases, the men involved experienced phantom penile sensations (phantom limb syndrome). So what’s the rate of phantom penile sensations in MTF post-operation trans people? Almost 0%.
Hey can you share some sources on this I’d love to know more.
Sure! I learned about it from this Harvard neurobiology lecture by Richard Sapolsky.
INAH: https://youtu.be/LOY3QH_jOtE?t=4412
Bed nucleus of the stria terminalis: https://youtu.be/LOY3QH_jOtE?t=5035
These time stamps are from the same video, so you can start at the first one and he’ll just move right into the second one.
This is the study he refers to by Simon Levay (you might be able to get a copy through an open access site somewhere, I don’t know though): https://www.science.org/doi/10.1126/science.1887219
This is the study he refers to in regard to the stria terminalis is: https://www.nature.com/articles/378068a0
Here is the replication study for the stria terminalis: https://academic.oup.com/jcem/article/85/5/2034/2660626
And that video is 12 years old. From my quick search to try to find the original sources just now, it seems even more studies have been done on it in the meantime.
Just managed to skim the paper and watch the video. That is a really interesting lecture and clearly he is interested in the science as he addresses caveats and the political nature of the studies. But that is actually really interesting findings. Thanks a lot for sharing this.