@Bridgette Thought I'd tag @arpie in as you wanted her to respond to your initial post. Just put a @ symbol before anyone's name & it will send a message to them!
Anyway, I was diagnosed in Dec. '17 & had surgery, rad treatment but i am on no medication.
I was diagnosed with Graves disease (over active thyroid) around 20 years ago & was put on a toxic drug that i was only supposed to be on for around 6 months. This was discovered around 3 yrs ago so i was taken off it & not put on other further medication as the endo was seeing if it would come back. Unfortunately, after my cancer treatment & further routine blood tests, it was discovered that my Graves disease had returned. I asked many different doctors if it was related to the cancer or the rad treatment & they all said no......so I put it down to a coincidence! Anyway, it was decided for me to have a radioactive iodine tablet which would treat my gland & now i am on thyroxine for the rest of my life but this is a very safe & common drug. I still wonder, like you, if there is a link so good luck in your findings & let us know if you discover a good doctor who knows the answer. Good luck xx