Hello Mary,
Welcome to the Pain Management Forum. I am sorry to hear that on top of Chronic Pain you have also been DX with Graves Disease. You've asked a good question.
I have a close friend that has this condition. He has not noted any difference in the effectiveness of his medications. I have what's called "Dumping Syndrome" meaning that everything I ingest gets rapidly put through my system. This only appears to effect any medications that are absorbed in my small intestine, such as an enteric coated tablet. So it's not exactly like your faster metabolism but similar.
This is an excellent question to ask of your PCP or Specialist. You may also want to post in our Autoimmune Forum. Here's the link:
http://www.medhelp.org/forums/Autoimmune-Disorders-/show/174
I wish you well and hope that you will share with us what you learn ... as we all learn from one another. I'll be interested to read your updates.
Take Care,
~Tuck