Have PhD, MS in Ops Mgmt and Supply Chain, and I teach as a tenure track professor to MBA (and undergrad) students, present research at conferences, and consult in industry. Lots of talking, definitely blocking and repeating and face contortions, but due to the exposure, it has improved a ton (but it's never gone). Had to redo my Dissertation proposal because the stutter was so bad the committee couldn't understand what I was presenting on. Talk about embarrassing... to a level I cannot describe. Eventually got it done, and I say to those who wonder... whatever it is, yes you can! You just have to pay a different price, and/or take a bit longer to get there than the easy talkers. Just do it. Pay the price, it's worth it. Lots of great, supportive people on the way, and you'll need to be one of them for yourself. The tendency to retreat will need to go, and it won't be easy.