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I’m writing this post because there’s a quite a few clients that I have taking thyroid hormones and I think it’s likely making their condition worse.

What is Low T3 or Euthyroid Sick Syndrome?

Probably half of the clients I get have thyroid hormones on the low side.  It’s usually hovering either slightly below or slightly above the lower end of the reference range.

In the literature, this is called  ‘Euthyroid Sick Syndrome’ or ‘low T3 syndrome’ – when levels of T3 and/or T4 are at unusual levels, but the thyroid gland does not appear to be dysfunctional. (R)

Make Sure You Get The Right Tests

First, you want to get some basics out of the way before you come to other reasons why your thyroid hormones might by on the low side.

Many doctors only test for TSH, but this not an adequate enough test to see what your thyroid is like.  However, you also need to check your total and free T3.

There are also indirect ways to check for low T3.

Inflammation and Oxidative Stress are the Most Common Causes of Low Thyroid Function


Assuming you’ve taken the recommended tests, you’ll see if you have high thyroid antibodies.  If you do then this indicates an autoimmune condition and that’s the most likely reason your thyroid hormones are lower.  I’d recommend inducing tolerance if this is the case and going on a lectin avoidance diet for a few months.

If you don’t have thyroid antibodies, then the next most likely scenario is inflammation and oxidative stress.

Most people who feel fatigue and also have a lowish level of thyroid hormone think that this is the cause of their fatigue.

However, the likely truth is that low thyroid hormones are not the cause of their problems, but a side effect of a larger issue.

The real cause has to do with chronic inflammation more often than not.   IL-6, TNF, and other cytokines decrease thyroid hormones.  (R, R2, R3)

Cytokines like TNF and IL-1b also cause fatigue by suppressing orexin.

Therefore, inflammation is causing you to have a sluggish thyroid AND also feel fatigue.   Your thyroid isn’t actually the main cause of fatigue itself.

IL-6 also causes an increase in reverse T3 (an inactive form of T3). (R)

IL-1b and Interferon-gamma/Th1 dominance also decrease the enzymes needed to make T3 (IL-1b is more significant). (R)

IL-1b can make the thyroid hormones you do have become less effective because it decreases the receptors it binds to. (R)

What this means is your thyroid hormone levels can seem normal, but you’re still not getting the energy that you should from a given level of thyroid hormone.

This is possibly why taking thyroid hormones may make some feel a bit better even if their levels are normal – because they require more thyroid hormones to function at the same level as someone who has normal receptors.

Another study found that the reason IL-6 decreased thyroid hormones was because of oxidative stress. (R)

It also found that the decrease in thyroid function could be reversed by giving NAC, which increased glutathione. (R)

So what we see is that inflammation and oxidative stress are the root causes of thyroid problems, in the absence of antibodies.

People with thyroid antibodies usually have elevated inflammation in general, so it’s likely that these people experience a triple whammy of antibodies, inflammation, and oxidative stress.

It’s my position that it would be wise to get at the root of the issue before introducing thyroid hormones in as a confounding variable and which may also worsen your condition.

Once you get on, it’s not easy to get off.  However, having low T3 itself is unhealthy, so I’m not advocating that you stay in a low T3 state.

If you want to know what to do for the inflammation then click on the links.

My Experience With Low T3 Syndrome

I’ve experienced low T3 syndrome for years until I lowered my inflammation levels.  Most critical to this was my lectin avoidance diet.

Are You Tired Because of Low Thyroid Hormones?

Naturally, people who have health issues/fatigue will make the connection that since they feel tired a lot and their thyroid hormones are on the low side then it must be their thyroid is what’s causing their issues!

This is not an illogical connection because thyroid hormones are involved in metabolism/energy production.  Low thyroid hormones are associated with fatigue, but thyroid hormones themselves aren’t the principal system for wakefulness.

As an aside, the adrenal glands certainly aren’t involved in wakefulness.  See my post where I debunk the myth of adrenal fatigue.

Wakefulness is mainly controlled by the hypothalamus and it works by releasing the neurotransmitter orexin. Most of the wakefulness we experience is controlled by orexin.

Thyroid hormones can certainly contribute to wakefulness, but fatigue is more often at its core a hypothalamic/inflammatory issue than a thyroidal issue.

Many people with Hashimoto’s/hypothyroidism are fatigued, but find out after taking thyroid hormones that they still experience fatigue.  If you bring your thyroid hormones up and you’re still fatigued, this means that chronic inflammation is your main issue, not your thyroid hormones.

If you want to fight fatigue, you need to activate orexin.  I discuss many ways to do this.  One way to increase Orexin is by increasing TRH, the hypothalamic precursor to TSH.  You can, therefore, indirectly check TRH by looking at your TSH levels.  If you have low TSH levels, that will indicate lowish TRH levels.

Don’t get me wrong.  If you have low thyroid hormones, you’ll feel fatigued from that.  The point I’m trying to bring home is that it makes perfect sense to still feel tired even after you’ve normalized your thyroid hormones.

Be Wary of a Thyroid Diagnoses if You’ve Got Low T3 Syndrome


In my consulting practice, I often see people making a big mistake by taking Thyroid hormones in response to fatigue.

People are influenced by what they read online, where others describe to have gotten better from thyroid hormones even though their levels were normal.

Thyroid hormones are stimulating, so it’s not too big of a surprise to get a bit of a jolt from it, especially if you have slightly low levels.

But just like I wouldn’t prescribe cocaine to someone who is depressed (it will help in the short term), I wouldn’t suggest taking thyroid hormones if that’s not the root issue.

In the alternative health sphere, Thyroid problems are one of the big over-diagnosed conditions.   Alternative health practitioners who specialize in thyroid disorders (who can prescribe drugs) sometimes tell people they have a thyroid problem even when their hormones came back normal.

As the saying goes, when all you’ve got is a hammer then everything seems like a nail.  The people who focus on thyroid function will dig up a thyroid issue when there is nothing actually wrong with your thyroid gland.

By Taking Thyroid Hormones You Might Be Making Your Condition Worse

What people don’t realize is that by taking thyroid hormones, you can actually be actually making you condition worse in the long term.

You see, inflammation (and T Cell proliferation) is closely tied to metabolism (the production of energy).

This means the higher our metabolism, the more inflammation we experience.

Our immune system requires massive amounts of energy to function and if it doesn’t have it, it will be idle.

The body is smart to become fatigued when we have inflammation.  This allows us to conserve energy for our immune system!

This is why mTOR, which increases metabolism, also increases our immune system and inflammation.  In the linked article, I listed a bunch of diseases that come from mTOR activation.

If you’re fighting a pathogen then revving up your immune system is probably a good idea (if you also use other means to kill it), but if your inflammation is from lectins or some other inflammatory agent, then it’s not a good idea to stimulate your immune system even more.

Indeed, one of the best ways to inhibit chronic inflammation is by inhibiting mTOR.

This pathway is particularly important to people with Hashimoto’s and Grave’s because both of these diseases originate from elevated Th17 inflammation, which is caused by mTOR activation.

Guess what? Thyroid hormones are activators of mTOR. (RR2)

Thyroid hormones can also elevate cytokines like IL-6 (dose dependent). (R)

Perhaps the worst effect of thyroid hormones is that they increase the worst kind of free radical: superoxide. It does this by increasing the energy production of immune cells (and others). (R)

Not only does it increase superoxide, but it also decreases the enzyme to break down superoxide (SOD)! (R)

That’s probably the reason why lower thyroid hormone levels are associated with longevity…. (R)

So Thyroid hormones are potent activators of metabolism.  We feel a boost of energy, but our chronic inflammation also goes up.

When we have chronic inflammation, the body is smart to lower our thyroid hormones a bit so that the inflammation is reduced.  It’s called homeostasis…

One client yesterday sent me an email of all of the supplements he’s taking and said this:  “T3/T4 cap 114 mcg/27 mcg – 1 cap AM (actually forgot to take this for two days, and think I actually felt better?)”

This client also said, “I did think it was unusual that the more my old doctor increased my thyroid meds, the worse my thyroid-related symptoms became”.

This client was duped into taking it by ‘progressive’ alternative doctor.  He’s still taking it even though he didn’t experience any benefit from it because it’s very difficult to get off.   And it made his condition worse.

Also, it would be wise to experiment with many other things first before turning to thyroid hormones.

If you’ve tried everything and you still have low thyroid hormones, then you can experiment taking it and only continue with it if you see a significant benefit (in the long run as well).

I would much rather people take TRH for a sluggish thyroid, although it is quite expensive.

My Own Experiments Verify This Theoretical Framework

Last year, I decided to take a high dosage of iodine supplements to see what it was like.   There were people who swore by it.

Anyway, it induced a state of weakness and my pulse dropped to under 45 from 65.   I didn’t even take that much…

After some research, I realized that a high iodine dosage induces a hypothyroid state and this is what happened to me.

What was magical about this was that all of my inflammation practically disappeared – even after eating gluten or whatever.  No fatigue after meals.  I did this many times for experimental purposes.

Whenever I do any activity that stimulates my thyroid hormones (like walking for a long time), then the opposite occurs and I get a spike of inflammation from eating something that normally would only cause moderate inflammation.

So my own experience validates that thyroid hormone levels correlate with the inflammation I experience.

I am not advocating to cure your inflammation by being hypothyroid.  There are many downsides to being in a hypothyroid state.   I ate less and slept much more. I generally felt weak and my libido took a nose-dive.

What I am arguing is to at least not increase it or do so as a last resort if you’ve got no antibodies.

Low T3 and Heart Disease

Blood Pressure

Hypothyroidism is a very significant predictor of heart disease.  People who are hypothyroid are 4X more likely to get heart disease – even after adjusting for traditional risk factors.  (R)  Since heart disease is the number one killer in the US, this is very significant.

Low free T3 levels even within the normal range are correlated with heart disease and low T3 people also have a worse prognosis, even after adjusting for traditional risk factors (T4 was not associated). (R))

In a recent observational study, low T3 levels within the ‘normal’ range were correlated with heart disease. The level of free T3 was 4.0pmol/L (2.6pg/ml)  in the higher risk group versus  4.6pmol/L (3.0pg/ml) in the lower risk group. Free T3 was also lower in patients with severe heart disease when compared to mild heart disease. (R)

Hypothyroidism itself can increase heart disease risk by causing high LDL, excess homocysteine, blood vessel dysfunction, hypercoagulability, impaired fibrinolysis and platelet abnormalities. (R, R2)  It also increases LP(a), which is another risk factor for heart disease. (R)

Not only does hypothyroidism increase LDL, but it also increases oxidized LDL, which is much worse. (R)

However, inflammation and oxidative stress are perhaps the most significant drivers of heart disease, so I believe these are both increasing heart disease risk and also causing low T3.

Be Careful About Taking Iodine

My iodine recommendations are to get a total of 400mcg and make sure to take it with 50mcg of selenium (or more).

Getting more than 400mcg can be problematic for many and some would argue even that’s way too much.

Excess iodine increases Th1 and Th17 immune responses (R).

Excess iodine increases IL-17, IL-23, IL-6 and TGF-b and it decreases Tregs.

What this means is that it increases inflammation, especially the Th17 immune system.

It’s no wonder why high iodine intakes are associated with a higher likelihood of autoimmune thyroid disease. (R)

My recommendation is to experiment restricting or taking 400mcg.  Do what works for you.

Other Possible Causes of Lower Thyroid Hormones

Factors that affect thyroid function

Many supplements decrease thyroid hormones, but not too significantly usually.  The exception is iodine.

The most important factors are inflammation and oxidative stress.

While not as likely, it’s certainly possible other factors are at play and that’s why I’m bringing them down here.

Lifestyle/Diet factors that decrease thyroid hormones

Numerous toxins, including BPA, pesticides, mercury, and flame retardants such as PBDE, are shown to block tissue thyroid receptors and reduce T4 to T3 conversion

  • Calorie restriction (R, R2) – Significant… If you consume less than 2100 calories, then that’s a significant reason you’d have lower thyroid hormone levels.  You have to measure your calories for a week.
  • Yoga (certain types, subjective).  Significant, but only in the short term.  I don’t think it will influence your blood test.
  • Stress (R)/Cortisol supposedly blocks conversion to T3 and increases rT3….A study in healthy young men and women could only found that higher cortisol was associated with higher TSH, but not T3 or T4. (R)  A different study could not either find that cortisol decreases T3, even though exercise decreases it.  Actually, it found that a lack of cortisol spike decreased both T3 and  T4. (R)
  • Depression (R)
  • Low leptin (R) – leptin increases thyroid hormones.
  • Saturated fat
  • Low carb diets
  • Low Estrogen (R) – decreases T3 and T4 and increases TSH
  • BPA/Estrogen mimics (R)
  • Insulin Resistance (R),
  • Chronic pain (R)- suppresses Type 1 deiodinase, which lowers T3
  • Low Testosterone (R),
  • Low Growth Hormone (R) – decreases the conversion of T4 and T3,
  • Alcohol,
  • Toxins: Fluoride, BPA, lead, mercury, Pesticides, radiation,
  • Tea, Cruciferous veggies, Soy, Millet, Fenugreek.

Nutrient Deficiencies and T4 to T3 Conversion

A deficiency in any of the following can lead to lower thyroid hormone levels.  T4 is converted to T3 by Type 1 deiodinase.

  • Iodine – Significant, but not common.
  • Selenium (R) – Needed to convert T4 to T3.  Protects against autoimmune thyroid conditions (R). Too much Selenium (300mcg) lowered T3 in men in one study (R), but a larger study couldn’t replicate the results (R). Selenium also increases chromium excretion, so make sure to take chromium as well.  I recommend 150-250mcg from all sources daily. (RDA is 55mcg)
  • Zinc (R) – higher levels were associated with lower free and total T4 in males. (R)
  • Iron (R) – needed for TPO.
  • Chromium,
  • Copper – higher blood levels were associated with free and total T4 in males and both total T4 and T3 in females (R).
  • Vitamin A (R) – in obese women, vitamin A increases T3 and lowered TSH.   There’s a decent chance that this will work in others.
  • B Vitamins: B2B6B12,

Supplements that decrease thyroid hormones

The Takeaway

The takeaway from this article isn’t that you should try to induce a hypothyroid state to reduce inflammation or that thyroid hormones can’t benefit you.

Thyroid hormones are critical for sex drive, cognitive function and gut function, among many other things.

Even if your low thyroid hormone levels are from inflammation, taking thyroid hormones can still get rid of some of your symptoms.

What I’m saying is that you should only take thyroid hormones after you’ve tried everything else because it’s not so simple to get off of it.

Don’t you want to see how much you can get better before taking this possibly irreversible move?

I’m also saying that you should pay attention if you feel better in the long run from thyroid hormones, not only the day you took it.  If you don’t notice an improvement then taper off of it as soon as possible.



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  • lilly bolton

    Im on levothyroxine 150 I had under active thyroid since I was a baby .but it makes me feel so tired during day but I also suffer from anxiety and depression and Im on 150 sertraline medication aswell. Its hard to loose weight and my hair falls out . I have intimacy problems and im embarrassed go doctors about something like that is that how it can make you feel when you take levothyroxine .

  • Andy V

    where are the references for potassium iodide and curcumin decreasing thyroid hormones?

  • Donna

    I had low t3 and was put on thyroid meds. I felt horrible, but this was also when I became pregnant and had a baby so I chalked it up to motherhood. I began losing my ability to sleep and my memory. I was wired with stress all the time. I told my doctors that the thyroid meds made me feel bad, but they dismissed it to fibromyalgia. Thirteen years of taking that poison (yes, my thyroid levels were in range) and I was almost incapable of working due to memory loss and inability to concentrate. I assumed I was getting dementia. Then I finally had a high t3 reading with a new doctor. I quit taking the thyroid meds and slowly got my mind back. It’s been 4 months off thyroid meds and my levels are perfect. God knows what damage thyroid meds did to me long term. Scary!!!

    1. Nattha Wannissorn

      Glad you finally got better. They should’ve rechecked it sooner.

  • Fritz.Harber

    You wrote what to do to decrease thyroid hormones, but what do you do to decrease them? I have a really low pulse and feel cold very often. What are the best ways to increase thyroid hormone production?

  • Ella

    Hi! I did an experiment yesterday taking x10 iodine just for the hack of it. Now I feel like shit ( a similar feeling that I feel when I get out of ketosis by mistake and do not have any meal after). What do you recommend I do now apart from restricting iodine for awhile?

  • lordlol

    iodine reduced your inflamation that much?
    65 pulse to 45 are you for real/?
    what dosage did you take? i want to try this.

    1. Joseph M. Cohen

      Yup, why?

  • Jean

    This is a great article, Joe. I found that zinc was responsible for my hypothyroid problems. I took 150mg of optizinc for about a week and started to feel normal. My fingers and toes were warm for the first time in my life. Reduced sleep a lot and libido went up the roof. Started to see very clear also – this fog disappeared from my vision. People tend to focus too much on iodine.

    1. Jean

      150mg daily*

    2. Joseph M. Cohen

      Did you check it before and after or you are assuming because you felt more energy?

      1. Justin Long

        I think this article is irresponsible. You should recommend people load iodine for an experiment. EXACTLY how do you know that it decreased your inflammation? You state your observations with no test results to prove this is even fact. Readers beware…

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