My thyroid was underactive (tsh 5.2 mU/l, free T4 10.4 pmol/l) there has never been any other tests done, the main symptom i could base on that my thyroid was underactive was my stool (constipation, very little condensed stuff), i out of my own initiative knowing that if i had hashi or something i would probably make it worse started with iodine supplementation.

At first i just added iodized kitchen salt here and there, which in terms of iodine content is basically nothing, but after a week consistently doing that my stool was good for the first in a year, but after a week that was over.. then i took a supplement which was 150mcg a drop.. again after a week consistently taking that it was good again, but more and more drops were required, somewhere in there i picked a day when i knew it was good and got my blood levels tested, and it was indeed good (better: tsh 2.9mU/l, free T4 11.8 pmol/l), eventually i took 16 drops a day before the supplement was gone, then i bought a 5% lugols solution, which i till this day take 1 or (accidentally) 2 drops a day from which has worked for a while, but now is starting to not work so good anymore it looks like.

As far as i know stress, physical and mental stress plays a role, elevated stress hormones take down the thyroid hormone production.
But i'm wondering what would happen if now i wouldn't take any iodine at all.. would my TSH skyrocket and T4 plummet?