This leads one to believe that "Iodine" is a catch all scapegoat in the world of medicine for thyroid issues when something else is really going on... maybe a halide imbalance of some kind, a co-factor issue, like selenium, or heavy metals.
Could be a malfunction in the regulation of thyroid hormones or in the TSH to begin with due to one of the above mentioned causes, or? Maybe the signal from the pituitary, adrenals or both is messed up.
I liked Corinthian's analogy of a waterfall... one action to the other; however, this is limited in that it would give one the impression of a linear action with a start and end, when in fact hormonal functions in the body are an endless feedback loop including multidirectional communications with all the other glands and tissues\organs of the body.