Thyroid nutrition for optimal thyroid health – the adrenal, gut, brain and thyroid connection

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By Dr. Justin Marchegiani

There are certain nutrients essential for thyroid health, yet often times doctors are not checking to see if they are a root cause of a person’s thyroid issues. Today's talk is going to be on nutrition for your thyroid, how important nutrients and nutrition are for healthy thyroid function. We’ll do a brief overview of how the thyroid works in case you haven't seen any of my past videos on the thyroid. Just so you’ll have some foundational info so you can see how healthy thyroid works. And then know what you need or what maybe you're missing that's preventing your thyroid from functioning optimally on the nutritional side.

Overview of Thyroid Hormone Production

So let's outline how the thyroid hormonal cascade or domino rally works.  The first step we have is really the brain signalling down to the thyroid.  This pathway is known as our TSH or our thyroid stimulating hormone.  Our TSH is coming from the brain particularly the pituitary and it's telling the thyroid to make thyroid hormone.

Now from there, our thyroid then spits out some T4. About 20% of that T4 actually gets converted to T3 at the thyroid and about 20% and we'll review some of the nutrients that we need to help that conversion.  So 20% actually happens in the thyroid gland. The other 80% actually happens peripherally.  So we look down at that 80%, 60% of that 80 actually happens at the liver.

What do we need for optimal thyroid function?

Liver Health

Healthy liver function is very important.  So if we're getting toxins in our food, chemicals, various plastics, we're not getting enough sulfur-based amino acids or antioxidants in our diet to run those pathways. Our liver maybe burdened and that may affect our body's ability to convert and activate thyroid hormone.

One of the enzymes that’s responsible for thyroid conversion, the 5-deiodinase enzyme–you break it down 5-deiodinase. De-i is taking an iodine off.  So the T and the number 4 stands for how many iodines there are.  The 4 stands for the number of iodines.  So where de-iodinate something, we're pulling an iodine off and that's why it goes from T4 to T3. It's because we're pulling 1 iodine molecule off it.  We're doing it with that liver-based enzyme known as the 5-deiodinase enzyme, which is selenium-based.

So things like egg yolk, seafood, nuts, seeds–things like that are going to be very rich in selenium. We're going to need these for that liver enzyme to work.  And selenium is also a strong precursor to glutathione.  So selenium also helps with our detoxification. It also supports the liver.  Liver is very important for thyroid hormone conversion.

Gut Health

We need good, healthy gut bacteria because about 20% of conversion is responsible in and around the gut with acetic acid or the various sulfatase enzymes. And these enzymes are important at taking inactivated T3 and activating it.

So if you have dysbiosis or imbalances in gut bacteria from various infections, pathogens, or even small intestinal bacterial overgrowth, that can throw off the balance of your gut bacteria. In addition, it decreases your gut’s ability to activate thyroid hormone.

Adrenal Health

The adrenals are profound. It's very, very important for activation of thyroid hormone. Mainly because of the fact that if we're under adrenal stress, that can increase our reverse T3 levels.

So really simple, I count the adrenals as being a 20% contributor of activating thyroid hormone.  It does it a couple of ways.  If the body is under too much stress, cortisol is too high and if we have high cortisol. We’ll have more reverse T3s. And reverse T3 is inactive T3. If we have our receptor site for the thyroid hormone and reverse T3 molecule gets in it, that does not have the same metabolic effect of the T3.  The T3 can't make its way into the receptor site because the receptor site is blocked.

So that's kind of how reverse T3 works.  It’s like taking a gun and putting bullets in the magazine to that gun that are blanks.  So you got to fire that gun and the effect that you're looking for is that bullet to come out. But then all you hear is the noise. You don't get the actual end result. Metabolically, we see a hormone in that receptor site.  But it's a hormone that doesn't have the same type of stimulation that thyroid hormone does at the nuclear receptor site level.

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Thyroid nutrition


We need healthy levels of cortisol for thyroid conversion to happen. So the adrenals are also affected because of high levels of cortisol, stress, etc. This can actually affect TSH. TSH levels can go off with extreme amount of stress via cortisol. And if we’re depleted, if our adrenals are so dysfunctional where cortisol levels are now low, like at a stage 3 adrenal fatigue person, then we're not going to have enough cortisol to make that conversion happen. And we need cortisol to really activate that thyroid hormone.

Thyroid Temperature Assessment

When we do thyroid temperature testing, we’ll see the following:

So that’s a great way that you can use temperature to assess whether you have a thyroid, adrenal issue, or both.

Nutrients for Thyroid Hormone Activation

Now that everyone has a good background of how the thyroid gland is converting a lot of these T4 and T3 into active hormone, let's talk about some of the nutrients that are involved for activating thyroid hormone.

Vitamin A, Zinc, Amino Acids

The brain needs vitamin A.  It needs zinc, it needs B vitamins, it needs protein, asparagine, the various amino acids to make our TSH.  That’s the signaller.  So TSH is an inverse hormone.  It goes high when thyroid hormone is low and it goes low when thyroid hormone is high.

If I'm yelling at someone and I'm not getting their attention, I’ll have to raise my voice louder until I get their attention.  Think of that as what TSH is doing.  The brain is yelling down to the thyroid to make hormone. If it's not high enough, it will increase the amount of TSH. This is a very bad indicator to use for thyroid dysfunction because it's so late stage.  It comes on so late in the game, 5 to 10 years down the road, we really want to be looking at the actual active hormone downstream, the T3 that’s activated down here.

This is much more important and much more indicative of an early stage thyroid issue. And a lot of times people may have fine levels of TSH because T4 feeds back into the brain better than T3.  We could have normal levels of T4 but have low levels of T3. And it may not even be reflected in the TSH.  I see that all the time in my patients.  That’s why we got to be very careful.  We actually have to look at TSH, T4 free and total, T3 free and total. Maybe even look at reverse T3 as well, and the thyroid antibodies.

Gut issue

We talked about the nutrition, vitamin A, zinc, various B vitamins, and protein for healthy thyroid hormone function knocking that first domino over which is TSH.  If we have a gut issue, you can see nutrition isn't just given.  If we take in nutrient-rich foods, but we have a gut issue and a malabsorption and low stomach acid and dysbiosis and infection, you can see how that may impede the absorption of these nutrients, thus causing deficiency even though we're having a really good diet intact.  So keep that in mind, we always got to look deeper at the gut, deeper at the liver, and deeper at the adrenals.  We can't ignore these three body systems.


Iodine is an important nutrient for thyroid hormone creation.  So the process known as iodination involves iodine and tyrosine being cleaved together.  The T actually stands for in T4 or T3, it stands for tyrosine. That’s an amino acid.  The 4 and the 3 stand for the number of iodines.  So we don't need too much iodine to have this healthy conversion and this activation.  There's a lot of debate out there that we need more high milligram range.  Some say we only need the RDA, a couple hundred micrograms, 250 or so to be exact to make our thyroid hormone.

Iodine and Hashimoto's

Again, we got to be careful because iodine can be a strong stimulator of autoimmunity.  There’s a great deal of research showing that excess iodine can actually stimulate Hashimoto's.  It activates TPO or thyroglobulin antibody that can increase thyroid destruction.

Iodine and Selenium

A lot of people say that the reason why iodine’s a contributing issue with autoimmune condition is because people also are very, very low in selenium. And when iodine is being fused to thyroid hormone via this process known as iodination, what happens as a result is hydrogen peroxide gets kicked out.  This hydrogen peroxide can be very inflammatory and can cause our B cells to come up and infiltrate and start attacking the thyroid tissue.  So that's why if you're giving any amount of iodine, you want to make sure there are adequate levels of selenium there. Because selenium comes in and it actually neutralizes the hydrogen peroxide, pulls an oxygen off it and makes it H20 which is water, which is very benign.

You can see giving iodine and not having selenium there by its side can definitely be a recipe for destruction.  So with iodine, be very careful of it.  Make sure you're working with a functional medicine doctor.  Also, make sure you're not autoimmune or have any autoimmune symptoms before you give iodine at higher levels.  A couple hundred mics will probably be okay, but double check with your functional medicine doctor.

Again, you can see iron is really important.  If you have a microcytic, hypochromic anemia, that's going to be a major issue.  We need iron to make thyroid hormone but we’d also need iron to help carry oxygen throughout our body.

B Vitamins

B vitamins–B6 is super important because B6 helps with dopamine activation. And if we go up one stream here and we look at the hypothalamus, which is the top part of the brain, we actually need dopamine from the hypo–dopamine production to actually stimulate the hypothalamus to make TRH.  And TRH is important at stimulating TSH. So dopamine is essential and a lot of people may have neurotransmitter issues that need to be fretted out doing an in-depth organic acid test.


Summary of Nutrients

Iodine, Tyrosine, Iron

B Vitamins

Your B vitamins are really important for energy, for making the Krebs cycle go around.  I did a video on the mitochondria recently.  Take a look at that video to get more info on B vitamins.

Vitamin C

This is a really important antioxidant and helps the adrenals as well.

Vitamin D

This is really important for immune function.  A lot of people with Hashimoto's and hypothyroid autoimmune issues tend to have a vitamin D polymorphism at the receptor site of the vitamin D receptor and they need higher levels of vitamin D, 70 to a hundred.  Be very mindful if you have an autoimmune thyroid.  Make sure your vitamin D levels are up at 70-100, just to make sure you have that therapeutic immune balancing effect.


We already talked about the nutrients needed for our T4 to T3, that selenium is essential, also for the autoimmune effects of helping to neutralize the hydrogen peroxide into water.


Zinc is important for thyroid conversion. It is also essential for sex hormone production, esentially for making testosterone. And then also it's an important building block for making hydrochloric acid.  If we don't have hydrochloric acid levels adequate enough, we won't keep a nice low pH in the stomach.  So if we don't have that nice low pH, we won't be able to break down protein and fat adequately. We’ll have a harder time ionizing minerals.  And we need to ionize minerals and hit them with hydrochloric acid, so then we can then take them in our blood and they're not like rocks floating in our bloodstream.  We actually want to ionize them so they're absorbable.  So that's really important.  If we have issues with these nutrients, we may see other problems in the thyroid hormone chain that could be happening as well.

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Thyroid Testing

Like I mentioned, a thyroid autoimmunity is a big issue–40% of people that test for thyroid autoimmunity actually test–they are a false negative.  They may come back negative but they may still have a positive thyroid.

So make sure you get your thyroid looked at either palpation-wise and/or if you need, get an ultrasound run just to make sure there are no nodules or inflammation in the thyroid that could be caused by Hashimoto's.

Outside of that, if you have a thyroid issue or nutritional issue or neurotransmitter issue that could be affecting your thyroid, and you're not quite sure the next step to take, click on screen.  Again schedule a consult with me, subscribe to the videos, and get my Thyroid Hormone Balancing Series for more information how you can get your thyroid back into balance.

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