Girlie, yes you can still be iodine deficient if you have nice midrange thyroid levels (TSH, T4, etc...). There was a study testing school aged children for urinary iodine and they found (I believe 10-15%) some of them with great hormone levels yet deficient in iodine. Now here they used the current RDA values to determine if they are deficient or not. If they would've used other criteria the percentage would be much bigger.
The reason behind this discrepancy is that is 1. the thyroid seems to store iodine and hormones for its use and when you get low from the diet it can hold up for a while (not sure how long), HOWEVER, 2. the rest of your body also craves iodine/iodide (breast tissue, reproductive tissue, and immune cells like in this new research). So when you are low, the thyroid takes everything and leaves your immune cells empty handed. similary, even if your thyroid is doing good as far as iodine from diet, the rest of the body is also likley deficient (many tissues in the body can transport iodine inside of them).
The RDA is meant to prevent goiters and is not the optimal level that your thyroid needs and for sure not the optimal levels for rest of your body. For example there have been clinical trials with women with fibrocystic breast disease who had 60% symptoms reduction when they took 3-6mg of iodine for i believe was 3 months!
Like you said though, people need to be careful with iodine,and in particular are the ones who have anti thyroid antibodies. They should check with their doctor or functional medicine doctors, Otherwise some doctors swear by its safety.
In general terms, the word iodine means both (iodine/iodide) like in lugol's iodine. The body uses both forms, but the study looked at mostly iodide and only some iodine. Its worth mentioning that the body can convert iodide to iodine (molecular form).
Post Edited (Immunity) : 11/20/2017 7:24:53 AM (GMT-7)