This accessible paper reviews the various environmental factors that affect TSH, FT4 and FT3 levels. Quite a large compendium.
Mirjana Babić Leko, Ivana Gunjača, Nikolina Pleić and Tatijana Zemunik
Int. J. Mol. Sci. 2021, 22, 6521. doi.org/10.3390/ijms22126521 Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels
Thank you, once more, kind sir! Much appreciated.
Thanks. My hypothyroidism was caused by PBDEs which are briefly mentioned. They are more similar to T3 than T4 with negligible effect on TSH, fT3, fT4 but can affect peripheral hormone activity. I don't want to drift off topic, just highlighting that hypothyroidism can occur without abnormal blood tests.
wow yes a lot of info. i guess it shouldn’t be surprising that so much of it is conflicting considering the vast number of studies it attempts to compare and summarize. some surprising conclusions like smoking increases ft3 and olive oil decreases it (except when used to cook food)?! taking those with a grain of salt all considering.
Only one human study of olive oil and thyroid. This one study suggests olive oil marginally lowers T4 and T3 levels, overall function of thyroid untouched. (Was there a mention of cooking food? )Not a conclusion per se - a report of the findings of one study - and nothing to be concerned about!
thx you’re right, conclusion was the wrong word. finding is more accurate. and thanks for looking into the study - i wasn’t concerned enough to even do that 
(i’d assume any effect of olive oil is accounted for by blood level results and thus treated appropriately). just thought the olive oil and smoking findings were especially unexpected (despite the effect being small in the case of olive oil). i know PUFAs have long been considered by some to be detrimental for thyroid functioning, but always assumed monounsaturated fats were fine. (i wouldn't consider slight lowering of t3 as leaving thyroid functioning “untouched”though, unless i’m i missing something)
somewhat unrelated but interestingly, this reminded me of some info i came across a few years ago that found that women who smoked and didn’t use facial sunscreen regularly were less affected by certain types of hair thinning than those who didn’t smoke and did use sunscreen.
Table 1 is where I they list vegetables cooked with olive oil as being associated with increased T3
i think it’s already fairly well known that it’s best [to clarify, i mean for hypos] to avoid soy, millet, and uncooked cruciferous veggies as a general precaution. personally didn’t see anything else new (in browsing this article quickly) that would nec warrant dietary restriction, but would be interested to hear your perspective - sounds like you’ve perhaps looked through a bit more thoroughly!
I must be looking at a different paper - I see Fig. 1 but I don't see a list of vegetables cooked with olive oil. I think, too, the finding in the cited paper was that T3 levels were lowered in those consuming more olive oil and at least 2 servings of veg. Not raised.I'm not sure what you mean by ''i’d assume any effect of olive oil is accounted for by blood level results and thus treated appropriately)''
Anyway, the cited paper took a couple of hundred southern Italians, none of whom had been diagnosed as either hypo-or hyperthyroid and all of whom were classed as either overweight or obese. The participants self-reported their diet. The authors concede that while none of the participants were on any medication, they had all been recruited for the study when attending hospital appointments - 'so must have had a reason for being there'. ( might even had undiagnosed thyroid problems??)
All T3 and T4 levels were still within reference ranges. I guess we can't assume, either, that all participants had observed the requirement to fast...
So all in all, I just felt that it was a bit of a ropy study.
It's open access too so you can read it here: mdpi.com/2072-6643/12/10/31...
have a lot of brain fog/difficulty concentrating/mental fatigue atm and prob don’t have any business commenting on (or maybe even trying to digest) research right now or trying to articulate myself so may not be doing a good job.i’ll try again but if unclear don’t worry about it
table 1 is in the original paper. you’ll see what I mean. not a listing of different vegetables just a reference to a separate finding (diff study) about vegetables cooked in olive oil. its not important though.
yes what you describe sounds like the kind of poorly designed study i would only expect when it comes to thyroid research. hence why i’d said i’m taking findings with a grain of salt
what i meant when i said any effect of olive oil lowering t3 would be accounted for in blood tests was that, to the extent that any dietary factors affect levels of free serum thyroid hormones, that would show up when we get our blood results done, and we would dose our thyroid hormone meds appropriately thus compensating for those slight effects. not sure how else to explain.
I'm not really concerned about minor effects (which may or may not be real) but the obvious thyroid- affecting candidates are much more important.
yes the paper would have been much more helpful if the authors would have taken an approach similar to what examine.com does with its supplement reviews and laid out contextual info regarding their findings in terms of degree of the effect (eg minor, moderate, major) and the quality of the studies reporting the effect
Thyroid receptors quote
