Iodine complex effect on Thyroid gland
When thre is excess Iodine in the circulation it will be entrapped by thyroid follicles and subsequently organized and coupled to be released as T4 & T3 in excess amounts.
With time, build up of greater amounts of Iodine within the gland will lead to inhibition
of many steps involved in T. hormone synthesis (transport, coupling and even release of hormones).
This happens in a way somewhat similar to the down-regulation process in receptors; when u give an acetylcholine agonist, e.g. Physostigmine (Cholinestrase inhibitor), in therapeutic dose there will be improvement of muscle contraction while in overdose it will cause flaccid paralysis by accummulation of Ach in synaptic cleft.
- & Hypo
thyroidism ----------both r caused by Iodine
-----------both r caused by Ach
Keep in mind that Radiocontrast media contains Iodine and can affect the thyroid by the same mechanism.
I don't know if there is direct effect of Iodine on the TSH or TRH release, anyone knows about that??