I'd be curious to know when your feelings of transsexualism most mild?

I don't think there's any information about prenatal hormones being linked to desire for gender "change". From what I know there's only initial data on prenatal hormones and "birth gender". I mean they can't do a blood test on the mother and determine baby gender - as far as I know. I'm using quotes here for terms I'm unhappy with.

"Increasing evidence confirms that prenatal androgens have facilitative effects on male-typed activity interests and engagement (including child toy preferences and adult careers), and spatial abilities, but relatively minimal effects on gender identity."

from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4681519/

Maybe paradoxically for trans to exist gender stereotypes/classic gender roles have to too - there's a leap somewhere to genitalia which I don't understand - maybe nobody does. Even if the behavior is unusual the body is male.