I got my GP to sign the DMV paperwork, but that was in California.
My endo kept checking the box for a temporary gender change on my license, even though he promised that he would mark it permanent as soon as I had my top surgery. After my surgery, he did this two or three times. I finally got sick of it and went elsewhere.
Oh, and in CA, the recommendation has to come from an MD (not a PhD) if you want a permanent change. So I never asked my therapist at all.