there are only three things that can make one ill. deficiencies. poisons. lies you might believe.
you are addressing a deficiency. probably a long term chronic deficiency. like any deficiency, the body must replace what the nutrient did with another process for life to continue. the body adjusts and processes that are not as efficient are used. some processes must stop. once these process changes are made they can become permanent even when the deficiency has been addressed.
one of the things i have heard and experienced myself is the therapeutic effect of mega dosing vitamins or minerals or other nutrients.
trust yourself. you know how you felt. and remember, Iodine might not be the only thing you are deficient in. your labs are not particularly relevant.