I doubt it is limited to the brain
My understanding is there are lots of ways biological sex can conflict such that genetic sex and physical sex don't match up at some point in the body.
Some people want sex reassignment surgery and others only want hormones. I'm all for letting people decide this and I'm not interested in gatekeeping people out of doing what they want to their own body.
But I think it would be nice to have data on "x biological profile typically benefits from thus and such hormones" and it would be easier to get access to hormones if it was medically established that these biological mismatches impair immune function.
Not wanting this information "because transphobes will start murdering us/aborting us/whatever" is letting the transphobes win without a fight. I'm interested in improving medical care for this population.
I'm frankly not interested in even focusing on the gender identity per se. You think and feel and present how you like.
I'm interested in helping people address what I believe is a sex hormone syndrome so they can be healthier. That's what this blog is about.