Poor[er] circulation might be contributing to cold hands when core body temps are low. If you have sweaty hands, that will make things worse. I used to have sweaty hands when young and when I worked with oak, it would get black where I touched it. Always felt cold easily then as well. No idea what was going on.
When iodized salt was introduced circa 1922 and other dates in other parts of the world, goiters and metal retardation were been eliminated, however increased rates of thyroid auto-immune disease and hyperthyroidism were observed. The first order response was to assign cause and effect and once 'in print' the medical community tends to set such things in stone.
But what was really happening was more complex and nuanced. The first thing to bear in mind is that the iodine deficient population had been suffering iodine deficiency for their whole lives and their thyroid glands had suffered the onslaught of high TSH for most of their lives as well.
In this population there would be individual with thyroid nodules caused by time+TSH and they were already technically hyperthyroid. But the thyroid glands and the nodules themselves were iodine starved and the iodine-->thyroid_hormone production was rate limited by low iodine levels. So it does not take much thinking to realize that feeding iodine to those thyroid nodules was going to lead to high thyroid hormone levels. I need to point out that thyroid nodules are sort of genetically modified in that changed gene expression, a local epigenetic change causes this tissue to be autonomous with refers to the fact that the nodules produce thyroid hormone independent of TSH levels. In such cases, ones T4, T3 can be high and TSH-->zero.
So for these "new" hyper thyroid cases, introduction of iodized salt uncovered pre-existing cases. The statistics show increased numbers of newly diagnosed and reported cases of hyperthyroidism.
Normal biochemistry in a normal thyroid produces free radicals that if left unchecked, create inflammation. That inflammation is a contributing factor to thyroid nodules. Higher TSH causes the thyroid to enlarge and that means increased levels of growth factors which may in combination lead to abnormal tissue structures [nodules]. Discussion of irritation, growth factors and inflammation resembles discussion of abnormal tissue generation and cancer genesis. And yes, tissue abnormalities in the thyroid do lead to thyroid cancers.
The above discussion started with hyperthyroidism and the interpretation of increased cases in populations when iodized salt was introduced. The above paragraph sets the stage for discussion of thyroid auto-immune diseases.
Carrying on and expanding the discussion of free radical production in the thyroid; we need to explore the role of selenium. In the thyroid there are enzymes that clean up these normally produced free radicals. When that fails, the free radicals create cellular damage and inflammation. And as expected, components of the immune system come in to clean up the mess. But things can go wrong and the immune system when cleaning up these damaged cells can misinterpret the wreckage as "foreign" and produce anti-bodies which then attack normal thyroid cells and you have an auto-immune disease. So what went wrong? We know that high TSH simply puts the processes that generate the free radicals running at a faster rate. Where are the cleanup enzymes are that are all the more needed? This specific enzyme, like most in the body, have a metal or metal-like atom in the enzymes catalytic reaction site. In this case, it is selenium, an essential trace element. Selenium deficiencies lead to this chain of events. So I always stress the need for selenium in ones supplements and that this is critical with iodine replenishment.
So back to the claims that iodine leads to thyroid auto-immune disease. When an iodine and selenium population has iodized salt introduced, thyroid glands have restored thyroid hormone production and the free radical generation could easily be increased.
And across all of this, when iodine was introduced to population and populations were watched to see the effects and benefits, many thyroid conditions would have been recorded that were previously ignored because there was no interest as this was simply what had always be happening in the population. This is a common problem where increased diagnosis and reporting creates uncertainty. If used to be that cancer deaths were under reported years ago because families and doctors kept secrets and cancer rates on death certificates was under reported. When people became more open about cancer in the last 50 years, there was a huge jump in recorded cancer deaths when the actual death rates were mostly unchanged. As thyroid conditions were studied and documented as thyroid health care and understanding of the biology progress, thyroid case diagnostic rates showed increases that were also deeply affected by increased reporting.
Lets take this back to something else we need to understand. Someone has a healthy thyroid, then the individual decides to use sea salt instead of iodized salt, or someone else in the household makes that choice. Sometimes it is because sea salt, or pink salts, are regarded as natural. Or they purchase non-iodized salt because it is in similar packaging and located on the self beside the iodized salt. TSH goes up and thyroid function goes down, T3, T4 are reduced. Thyroid gets enlarged and lumpy with nodules that start making thyroid hormones and as that progresses, thyroid hormones increase and TSH decreases and then becomes low and one is hyper. I have seen this happen with a woman that cared for her grandmother [GM]. GM's doctor put her in sodium reduced diet for high blood pressure mitigation. So salt was discontinued and GM later developed the predicable thyroid issues as a result of doctors orders, but if TSH<5.5 that is perfectly acceptable to the larger medical community. Meanwhile this woman was also iodine deficient because of that doctor directive and she learned to not use salt when cooking or at the table. At one point she lost weight and looked great, contrary to her genetic female family traits. Her thyroid hormone levels were high and accelerated her metabolic rate. The two trips to the emergency ward at the hospital, diagnosis, thyroid needle biopsy, radio active iodine uptake and imaging study etc etc. With iodine in her diet she has normalized decently and avoided having her thyroid destroyed with radioactive iodine and a lifetime of thyroid medication. So that is the story-progress line that I keep in mind when considering where someone might be. And in this story above, I need to repeat that all of that was subsequent to a doctor essentially doing harm by denying one's source of iodine. And I have never had a report of any doctor ever asking about iodine intake and iodized salt. And off the same consequences can follow one's choice to not use iodized salt, or whatever one's government source of iodine provides.
A further anecdote illustrating the problems with the medical community setting beliefs in stone instead of in [current] facts. When the woman discussed above had her diagnosis with radioactive iodine to study and image her thyroid, she was directed to avoid sources of iodine so her thyroid would not be iodine saturated then allowing her thyroid to take up the radioactive iodine. She was directed to avoid bread because that has been printed and reprinted over and over again. Iodine used to be added to bread in commercial bakeries as a dough conditioner, not for health reasons. As some point some doctors started to object saying that this might be harmful and iodine stopped been used in bread [USA, Canada and others]. So the medical community removed this source of iodine and then medical books kept reprinting that bread needs to be avoided when radioactive iodine is used for diagnostics or thyroid destruction. And with the internet, this will never be corrected. Meanwhile, commercial bakeries, not be outdone, started to use bromine, iodine's evil twin, as a dough conditioner. Bromine displaces iodine in the body and interferes with thyroid function. Bromine and it compounds are dangerous. Bromine in bread is a consequence of what the doctors did about iodine in bread. Did doctors cry out about bromine? - they do not care.