Sounds like Graves - the uptake scan can help confirm cause of hyper and see if I-131 is a good treatment option. Meds are usually first line these days, with I-131 or surgery as back-up. I don't think I-123 scan, I-131 treatment or anti-thyroid meds would likely impact your IC, but you should check with your urologist.
Please go to a endroconolist who is a specialist to get the correct diagnosis
i have had graves disease for 25 yrs and i am 55 years old. with grave disease
they need to tpo antibody test, and i am still on heart medicine, i also had rai three time in last ten yrs, i am on tapazole and levethyroxin too, on me the rai didnt work 2 times and 3rd time i am severely hypothyroid and still
get the hyper symptoms, my tpo is 150, i am hypoglecimic, high cholesteral,
and have fibromyalgia, i have lost 20 pounds and it is still severe and now they are telling me i have hashimoto disease, so i would seriously think of not getting rai or surgery, and get a second opinion, the general doctors sometime overlook and think that if it is normal range it is not because you have symptoms that need look closely by a specialist. i am still having problems