Selenium is a key component of the enzyme thats required to make T hormones. Unless your multi has 400mcg to 800mcg of selenium, that very well could be your problem.

In my short time researching Iodine supplementation ive seen mentioned countless times supplementing one without the other can actually cause problems that didnt exist prior to supplementation.

Just how much selenium do you need to supplement? That seems to be very personal based on diet and where you live. Some regions are notoriously low in selenium so if your eating a lot of local foods you will be deficient.

Most multis have around 75-150mcg selenium, which may be enough if your diet is already rich in selenium may very well may not be if your region of the world is deficient in soil selenium.

I invite your to simply google selenium AND thyroid, even check youtube, there are quite a few video lectures by docs etc who are big proponents of selenium supplementation, many of which dont seem to be big proponents of Iodine and many of them have people running 600-1000mcg selenium. The key to finding how much you need would be an RBC mineral test, supplement for a while, retest and adjust as needed. Im not saying to go out and take >100mg of selenium like is often done with Iodine because a little goes a long way but as I stated earlier selenium seems to be an often overlooked piece of the puzzle around here among those who are having problems with iodine.

I can't seem to post links, so if you'll PM me, I'll send you all the links I have...or try to.