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Comment by phkahler | Hacker News Reader

I am increasingly convinced that the "thyroid hormones" T1, T2, T3, and T4 are simply a place to store iodine. When iodine is needed somewhere in the body it can be taken from T4, converting it to T3. But it's not the case that "T3 is the active form" as you'll read in the literature, it's that the removed iodine is the active or useful thing.

Changing the ratio of T3/T4 does cause a change in TSH (thyroid stimulating hormone) but that's IMHO simply a signal that the iodine is getting used, so please send us more.

There are other tissues in the body that need iodine, as evidenced by the sodium-iodine symporter present on those cells, so to set the recommended daily iodine intake based solely on what the thyroid can use is IMHO a huge mistake.

Some things with interesting iodine research: skin cancer, breast cancer, type 2 diabetes, asthma, polycystic ovaries, fibrocystic breast disease, other cancers. But yeah, it cures goiter...

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But it's not the case that "T3 is the active form" as you'll read in the literature, it's that the removed iodine is the active or useful thing.

Supplementation with T3 yields a rapid correction in bradycardia and hypothermia caused by hypothyroidism. We treat with T4 because it has a longer physiological halflife and thus yields more consistent serum levels; but the evidence is incredibly clear that it's T3 which is having an effect, not T4.

How does the T3 produce the result? Is it possible that conversion to T2 - liberation of iodine - is what does it? I have not head of this condition so I'll do some reading. Also, does simple iodine supplementation help?

The most common cause of hypothyroidism is the autoimmune destruction of the thyroid gland. No amount of Iodine helps; you need T3 (usually administered as T4 which is then converted to T3 endogenously).

https://en.wikipedia.org/wiki/Thyroid_hormone_receptor

https://www.thyroidmanager.org/chapter/cellular-action-of-th...

T3 hormone binds to thyroid hormone receptors in the cell's nucleus, which regulates gene expression. These TH receptors are present all over the place; thyroid hormone has wide ranging effects on the body.

If this were true, it would mean that people with hypothyroidism could simply supplement iodine rather than needing to replace the hormones.

For some symptoms it may be true, for others not? Some hypothyroidism can be fixed by supplementing iodine. Some are due to other causes. Also, some of the things thyroid hormone seems to do can also be achieved by iodine supplements, and some not. It's very complicated.

In that case the thyroid is not, in fact, “simply” a mechanism to store and distribute iodine, is it?

> Some things with interesting iodine research: skin cancer, breast cancer, type 2 diabetes, asthma, polycystic ovaries, fibrocystic breast disease, other cancers. But yeah, it cures goiter...

When I search for breast cancer and iodine, I find links that suggest iodine may help prevent that disease - and Japan’s low rate of the condition is potentially related to high consumption of iodine.

Are you saying that all those conditions are due to excess iodine?

Based on their third paragraph, I assume they mean that people are not eating enough iodine.

I interpreted that as the opposite - just because the iodine is getting used, it doesn’t mean it should have more.

I certainly find more on positive effects of iodine so I think I’ve misunderstood OP.

>> Are you saying that all those conditions are due to excess iodine?

No, the opposite. I'm suggesting they are due to low iodine intake.

... and congenital deafness, low length growth, neurological impairment, and other symptoms known as Congenital iodine deficiency syndrome.

The thyroid is by far the largest consumer of iodine. It stores iodine in thyroglobulin, which is the precursor to thyroid hormone. I don't know the numbers, but I wouldn't be surprised if the thyroid released more iodine by breaking down thyroglobulin than breaking down thyroid hormone.

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