Iodine and the Thyroid
Iodine is one of the key nutrients required for the formation of thyroid hormone, and for that reason, the thyroid requires more iodine than any other tissue in the body.
Because it needs it, it takes it: the thyroid “traps” iodine first, before any other tissue can get it. But if there’s not enough iodine to go around, the thyroid will swell up to try to trap it more efficiently. This is called a goiter, and it used to be really common, before iodine was added to salt in parts of the country too far away from the sea to have much iodine in the soil.
But there are other tissues that require a lot of iodine: the breasts, the ovaries, and the prostate.
Iodine and Estrogen
First, there are three main types of estrogen:
- Estrone, called E1
- Estradiol, called E2
- Estriol, called E3
Estrone is found in fat cells, and can convert into estradiol or estriol. Estradiol is the strongest of the estrogens, and responsible for most of what we think of as “estrogenic” symptoms, both in PMS and in menopause. Under the wrong conditions, it can be metabolized into 16-Hydroxyestrogen (16-OH), which is carcinogenic (cancer-forming).
Estriol, however, has been shown to protect against estrogenic cancers, decreases the risk of fibrocystic changes in the breasts, and can even help women with estrogen-related weight changes to drop the extra pounds.
Why this is relevant: Iodine helps to maintain the estrogen balance in favor of estriol.
(There are other ways to increase estriol, too, by the way: one great one is to increase your intake of cruciferous veggies such as broccoli, cauliflower, cabbage, and brussels sprouts, due to their high concentration of Di-indole-methane (DIM). Just make sure you wilt them first, or they may block uptake of iodine. Then you’ll be working at cross purposes!)
Why the Iodine Deficiency?
Now that we have iodine in our salt, why are so many of us still low in iodine? There are several reasons:
- Halides. These are competitive inhibitors of iodine, found in bakery products, flame retardants, pesticides, insecticides, and our water supply. Check out the linked article for more on this topic.
- Low concentration in the soil. To some extent this is natural (as you get farther away from the ocean), but it is also partially due to farming practices that deplete the soil of many nutrients, of which iodine is one. More on this in a future article.
- A less bioavailable form (iodide). The iodine added to table salt is generally a reduced form called iodide. Iodide works just fine for the thyroid, but not for the breasts, ovaries, or prostate. (And by the way, table salt isn’t the healthiest choice of salt for you anyway).
What to Do About It
Not everybody needs iodine, so get your levels checked before you start supplementing with large doses of it (what’s in your multivitamin is probably fine). Also get checked for antibodies against your thyroid, as iodine can make Hashimoto’s worse if it is present.
I recommend a urinary iodine test (ideally also testing for halides to see whether they are part of your issue), though I have had some success with a random serum test for iodine as well.