I'm not worried - far as auto-immune disorders, which is what Hashimoto's is, Iodine is taking care of problems I have in that area.
I haven't any symptoms of hyper- and my hypo- symptoms are disappearing. If I was going hyper I would adjust my dosage or take a break.
And I know what hyper is - lived with a guy who was abusing synthroid (legitimate scriipt, just taking more than prescribed) to "give him an edge", LOL!