One of my colleagues has answered a question of mine regarding what iodine deficency can result in, in chronic deficient regions. This is yet another expression of thyroid function under stress.
I see a lot of patients suffering from arrhythmia due to high-T3 syndrome (e.g. resulting from iodine deficiency). These patients have normal TSH and FT4 concentration but isolated FT3 elevation, and this condition has clinical consequences. This is another understudied situation.
Just to reiterate what I think is being said...
If someone presents with in-range TSH and in-range Free T4 but over the range Free T3 then they are suffering from iodine deficiency or it is just one of several possibilities?
On the forum people have generally assumed this pattern of results is common in people who are in the first stage of developing hypothyroidism.
Should we be suggesting that patients ask doctors for urine iodine non-loading tests? (We'll get told NO, I can practically guarantee it.)
To do them privately is expensive.
medichecks.com/products/iod... £97
gdx.net/uk/product/urine-io... £71
regeneruslabs.com/products/... £78.75
In iodine deficiency, it is advantageous, because of the struggling thyroid ( which can become goitrous), to try to boost T3 production at the expense of T4. But it seems to go over the top with some patients. There's a control lost somewhere and it would be useful to find out what this is.
Were the old 'Trades Description Act' applied today to Endocrinilogy... 😅👽🥃
This is my situation. High T3 only. Do you have other resources I can read?
Just to add a note that although the UK has traditionally (last 80 years or so) been seen as iodine-replete, this might be changing.
(There always would have been some individuals who were deficient, but as an overall population, we got enough.)
However, the move to non-dairy is having a significant impact. Most, possibly all, non-dairy milk-replacement products do not contain any iodine, or at least nowhere near as much as real (dairy) milk.
This is not a reason to go and buy lots of iodine-containing supplements. But it is a reason to consider more often the possibility of iodine deficiency in those who have changed away from dairy in their diets.
Also veganism. A number of iodine researchers are concerned about impact on young women, children and potential impact on pregnancy/ developing baby.
This same situation appeared in a Canadian Patient Support Group 2 days ago.
The answer might be in here: Dayan, CM & Panicker V (2009). Interpretation of Thyroid Function Tests and Their Relationship to Iodine Nutrition-Chapter 5:Changes in TSH, Free T4, and Free T3 Resulting from Iodine Deficiency and Iodine Excess. In Comprehensive Handbook of Iodine (pp 7-54) Elsevier Inc.
Low TSH but normal Ft4 & Ft3
Low FT4 With Normal FT3 and TSH?
Normal TSH, FT3, FT4, Very high TGAB
High TSH, T4 within range 
Low fT4, but midrange fT3. Feeling cold, brain fog.
