I am in the middle of being diagnosed with ADHD (I'm 30). It was actually HN that prompted me to take action, but that's another story which I can expand on if anyone is interested.
I haven't read much about ADHD being linked to shyness and introversion, although I certainly haven't done enough research. But it describes me very well, could you possibly say a little more or point me to some resources? Everything I've read talks about impulsiveness and extroversion. I would guess that shyness and introversion are learned reactions to the impulsiveness.