Natural solutions to optimize the brain, thyroid and adrenal connection


Natural solutions to optimize the brain, thyroid and adrenal connectionBy Dr. Justin Marchegiani

Today’s talk will address how important nutrients and nutrition are for healthy thyroid, adrenal and brain function. I’ll do a brief overview of how the thyroid works just so you’ll have some foundational information. And then I’ll cover what you need or what you may be missing that’s preventing your thyroid from functioning optimally on the nutritional side. So let’s dig in.

Overview of Thyroid Hormone Production

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 thyroid stimulating hormone (TSH). Our TSH is coming from the brain, particularly the pituitary, and it’s telling the thyroid to make thyroid hormone.

From there, our thyroid spits out some T4, and about 20% of that T4 actually gets converted to T3 at the thyroid, 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, and 60% of that 80% actually happens in the liver.

Factors to consider in thyroid hormone production

Factors to consider in thyroid hormone production


A healthy liver function is very important. If we’re getting toxins, chemicals, and various plastics in our food, then we’re not getting enough sulfur-based amino acids or antioxidants in our diet to run those pathways. Our liver may be 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 de-iodinate means pulling an Iodine off, and that’s why it goes from T4 to T3, because we’re pulling 1 iodine molecule off it, and 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, which we’re going to need for that liver enzyme to work. Selenium is also a strong precursor to glutathione. So selenium also helps with our detoxification, also supports the liver. Liver is very important for thyroid hormone conversion.

Gut Bacteria

Next we see gut bacteria. We need good, healthy gut bacteria because about 20% of conversion happens 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 (SIBO), that can throw off the balance of your gut bacteria, and that can decrease your gut’s ability to activate thyroid hormone.

Adrenal Glands

The adrenals are profound and 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. I count the adrenals as being a 20% contributor of activating thyroid hormone. They do it a couple of ways. If the body’s under too much stress, cortisol is too high. If we have high cortisol, we’ll have more reverse T3s.  And reverse T3 is inactive T3.

How this happens is that the reverse T3 molecule gets in the receptor site in the cell. It doesn’t 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 blanks in the magazine. When you fire that gun, the effect that you’re looking for is for that bullet to come out, but all you hear is the noise. And you don’t get the actual end result, same thing. 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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So on that note, we need healthy levels of cortisol for thyroid conversion to happen. So the adrenals are also affected because high levels of cortisol, stress, etc.—these can actually affect TSH. TSH levels can go off with an extreme amount of stress via cortisol, and if we’re depleted, if our adrenals are so dysfunctional that our cortisol levels are now low like at a stage-3 adrenal fatigue level (cortisol levels <23), then we’re not going to have enough cortisol to make that conversion happen. We need cortisol to really activate that thyroid hormone.

When we do thyroid temperature testing, we’ll see chronically low temperatures with low thyroid function. When we see adrenal stress, we’ll see aberrations in temperature greater than 0.3 degrees Fahrenheit. So what we’ll see when we have adrenal and thyroid issues is if this is the threshold we want to be at temperature-wise, we’ll have a low temperature but we’ll have aberrations in that low temperature. If it’s just a straight low temperature, that’s a thyroid dysfunction. If it’s low and aberrant, that’s thyroid and adrenals. And if it’s normal and aberrant, that’s just adrenal function. So that’s a great way that you can use temperature to assess whether you have a thyroid issue, adrenal issue, or both.

Nutrients and Thyroid Hormone Activation

3 Nutrients and Thyroid Hormone Activation

Now that you have a good background of how the thyroid gland converts a lot of the T4 and T3 into active hormones, let’s talk about some of the nutrients that are involved for activating thyroid hormone.


Our TSH is the signaler. So TSH is an inverse hormone. It goes high when thyroid hormone is low, and it goes low when thyroid hormone is high essentially. So if I’m yelling at someone and I’m not getting their attention, I’ll have to raise my voice louder until I get that person’s attention. Think of that as what TSH is doing: the brain is yelling down to the thyroid to make hormone, and if it’s not high enough, it will increase the amount of TSH. TSH 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 need to be looking at the actual active hormone downstream, the T3. This is much more important and much more indicative of an early-stage thyroid issue. A lot of times people may have healthy 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 have to be very careful. We actually have to look at TSH, T4 free and total, T3 free and total, and maybe even look at reverse T3 and the thyroid antibodies.

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. And, again, if we have a gut issue, you can see that nutrition isn’t just a given. If we take in nutrient-rich foods, but we have a gut issue, malabsorption, low stomach acid, dysbiosis, and infection, you can see how that may impede the absorption of these nutrients, thus causing deficiency even though we have a really good diet. So keep that in mind: we always need 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. The process known as iodination involves iodine and tyrosine being cleaved together. The T in T4 and T3 stands for tyrosine (an amino acid), and the 4 and the 3 stand for the number of iodines. We don’t need too much iodine to have this healthy conversion and activation.

Iodine  Dosage

There’s a lot of debate out there that we need more iodine, into the high milligram range. Some say we only need the recommended daily allowance (RDA), 250 or so micrograms, to make our thyroid hormone. We have to be careful because iodine can be a strong stimulator of autoimmunity, and 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 Autoimmune Conditions

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

Getting iodine and not having selenium there by its side can definitely be a recipe for destruction. So with iodine, be very careful. Make sure you’re working with a functional medicine doctor. Make sure you’re not autoimmune or have any autoimmune symptoms before you give iodine at higher levels. About 200 micrograms will probably be okay, but double-check with your functional medicine doctor.


This is really important. If you have a microcytic, hypochromic anemia, that’s going to be a major issue. Low iron—we need iron to make thyroid hormone. But we also need iron to help carry oxygen throughout our body.

B vitamins

B6 is super important because B6 helps with dopamine activation, and if we look at the hypothalamus, which is the top part of the brain, we actually need dopamine from the hypodopamine production to actually stimulate the hypothalamus to make thyrotropin-releasing hormone (TRH). 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.


So Iodine, Tyrosine, Iron, and your B vitamins are really important for energy, for making the Krebs cycle go around. Vitamin C is a really important antioxidant and helps the adrenals as well. Vitamin D 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 100. So be very mindful if you have an autoimmune thyroid. Make sure your vitamin D levels are up at 70 to 100, just to make sure you have that therapeutic immune balancing effect.

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

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

Woman holding neck suffering from thyroid issues

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Thyroid Testing

Thyroid autoimmunity is a big issue—40% of people that test for thyroid autoimmunity actually are a false negative. This means they come back negative, but they may still have a positive thyroid autoimmune condition. So make sure you get your thyroid looked at either by palpation and/or by ultrasound. Just to make sure there are no nodules or inflammation in the thyroid that could be caused by Hashimoto’s.

So outside of that, if you have a thyroid issue, nutritional issue or neurotransmitter issue that could be affecting your thyroid, and you’re not quite sure of the next step to take, click here to schedule a consult with me to dig deeper or get my Thyroid Hormone Balancing Series for more information on how you can get your thyroid back into balance.

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The entire contents of this website are based upon the opinions of Dr. Justin Marchegiani unless otherwise noted. Individual articles are based upon the opinions of the respective author, who retains copyright as marked. The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information from the research and experience of Dr. Justin and his community. Dr. Justin encourages you to make your own health care decisions based upon your research and in partnership with a qualified healthcare professional. These statements have not been evaluated by the Food and Drug Administration. Dr. Marchegiani’s products are not intended to diagnose, treat, cure or prevent any disease. If you are pregnant, nursing, taking medication, or have a medical condition, consult your physician before using any products.