Well, estrogen does change hair on every other part of the body, so why not on the scalp? I can't say that I've noticed this effect myself, but then my hair always was exceptionally fine. It's hard to imagine it getting any finer, but these days if a strand hangs over my face, I can't see it. I thought it was just my vision getting old, but it could be that the hair is just too fine to see.
Hmm, maybe that explains why it is so thin on top. It's probably still there, just to fine to see. Yup, that's my story and I'm sticking to it! 😄