Stress causes Chronic Fatigue Syndrome

A picture of stress: no water, little food, unrelenting heat.
What chronic stress does to you

(1) CFS
From the point of view of a lay-person trying to make sense of an article like this, the best name for the effect of persistent stress is “Chronic Fatigue Syndrome” (“CFS“), because that name tells you what the symptoms are: but CFS, although well described in terms of how affected people feel, is poorly understood.

The way that CFS develops is quite simple:
The thyroid gland makes a hormone with four iodine atoms (T4), which circulates in the blood so that it is available to all of your cells.
The cells absorb T4 from the blood and make T3 from it, by removing one iodine atom.
T3 is your body’s “accelerator”: without it, no cell can function efficiently.
Stress causes release of cortisol from the adrenal glands and cortisol removes T3 from your cells, producing a condition which doctors call “low T3 syndrome”.

The mechanism by which low T3 syndrome comes about is an enigma to most doctors.
So little is known about it that it has four other names: “Functional Hypothyroidism”, “Nonthyroidal illness”, “Subclinical Hypothyroidism” and “Euthyroid Sick Syndrome”. None of these names tells the whole story: the entire situation is super-confusing.

The best term for the syndrome is Intracellular Hypothyroidism, because that name tells you what the underlying problem is:
Intracellular Hypothyroidism (IH), is a shortage of the “efficiency factor”, T3, inside all cells of the body: the efficiency of every individual cell is thereby decimated.
Remember: here, we are talking about T3, the active thyroid 3 hormone, not “T4”, the raw material hormone which the thyroid gland makes.

IH produces a variable suite of “low thyroid” symptoms, depending on which organs in the body are most sensitive to “T3 starvation”.
The commonest complaints are feeling “cold, weak and tired”: there is a fatigue which is worse in the afternoon, with anxiety, “fuzzy thinking”, loss of motivation, poor sleep, constipation, mild depression and weight gain.

(2) Serious Illnesses caused by IH

Intracellular hypothyroidism doesn’t just cause CFS: over time, chronic IH is the root cause of many “autoimmune” illnesses.

The subject of autoimmune disease is huge: it is much too extensive and complicated to explain in a format such as this.
However I can give you a spectacular example: the worst condition caused by IH is also the easiest to explain!

The “broken heart syndrome”, properly called “Takotsubo Cardiomyopathy”, or “Dilated Cardiomyopathy” (DCM) is another condition which is poorly understood because doctors don’t think of IH:
DCM occurs following a stressful episode, such as the death of a loved one or any condition which produces grief.
In DCM, the muscle cells in the heart weaken rapidly, because they can’t get enough T3 to function properly.
Since they can’t contract properly, they stretch: the heart becomes swollen and is unable to produce pressure to pump the blood efficiently.
The result is heart failure, progressing to death in many cases: the person literally dies of a broken heart!

Doctors can prescribe drugs, to strengthen the heart and keep the person alive and if they are successful the person lives to get over their stress.
When the stress is gone, the supply of T3 inside the heart muscle cells is reinstated, the Intracellular Hypothyroidism which caused weakening of the muscles is resolved, the muscles recover and the heart works perfectly, as though nothing had happened.

The (admittedly circumstantial) proof that stress is the cause of DCM is that when the grief is gone, the heart goes back to normal, but if the person has another stressful episode, their Cardiomyopathy starts up and they get heart failure again.

Circumstantial evidence
Most illnesses, from depression to chronic fatigue syndrome, from high blood pressure to heart attacks, from obesity to diabetes, from cancers to neurodegenerative conditions, etc. etc. are more common among chronically stressed, poor and disadvantaged people than they are among those who are well-to-do and relatively stress-free.
The link between socioeconomic stress and chronic illness is a “no-brainer.

However, the most common example of illness brought on by stress is PTSD.

PTSD, the plague of military veterans, can result from any high-grade stress.
It can begin at any age and is often seen in abused children.
PTSD is actually a form of CFS: the basic problem is IH, but it’s hard to say whether what we see as PTSD is caused by the IH or whether the IH is caused by PTSD.*
PTSD may lead to virtually all types of noncommunicable illness, including autoimmune diseases and cancers, but its most frequent symptoms are those of IH.

  • My “take” is that physical or psychological trauma causes stress, the stress causes IH and the psychological symptoms of IH are interpreted as PTSD.
How stress causes low T3 syndrome (IH)

Stress raises blood cortisol, which blocks production of T3, the active thyroid hormone. Cortisol also activates an enzyme which destroys any existing T3 in the cells, so the cells end up with very little, if any, T3 at all.
All your cells need T3. They can’t function efficiently if they don’t have enough.
So to understand how stress produces illness, you first have to know how T3, your body’s “accelerator”, is made.

Thyroid hormone

The thyroid gland makes Thyroxine (“T4”), a chemical with 4 iodine atoms attached.
T4 is not actually a hormone: it is raw material for Triiodothyronine (“T3”), the “accelerator hormone”, which increases the efficiency of all our cells.

Deiodinase enzymes, the iodine removers

We have 3 completely different enzymes*, called “de-iodinases” (D1, D2 and D3), each of which can remove one iodine atom from T4.
D1: To make T3, all our cells (except in the pituitary gland) remove a special iodine atom from T4 with deiodinase 1 (D1).
D2: The pituitary cells do the same, but they use their own enzyme, D2. They don’t have D1 or D3.
D3: The body also has a “shutdown enzyme”, D3, which the pituitary does not have.
D3 removes the wrong iodine atom, converting T4 into a twisted T3, “reverse T3”.
D3 also takes an “I” atom off of any T3 it finds, producing T2 (see the graphic, below).
Reverse T3 and T2 don’t work: they are “garbage”. **

* An enzyme is a protein molecule in cells which works as a biological catalyst.[1] Enzymes speed up chemical reactions in the body, but do not get used up in the process, so they can be used over and over again.

** A very recent article describes the actions of T2 made from normal, T3 and separately, “reverse T2”, made from reverse T3. This is not of clinical interest at this point in time, but when it has been completely investigated, it may prove to be important.
If you are interested, click HERE.


This was copied from
Cardiomyocyte-specific inactivation of thyroid hormone
in pathologic ventricular hypertrophy: an adaptative response or part of the problem?”,
by Christine J. Pol, Alice Muller, and Warner S. Simonides, in “Heart Fail Review”, Nov 24, 2008).

Diagram, showing the action of DI ordinances 1, 2 and 3 on Thyroid hormones
D1 (in the Body) and D2 (in the Pituitary) make T3 from T4. D3 makes rT3 from T4 and T2 from T3, BUT NOT IN THE PITUITARY, where no D3 exists.
Cortisol and stress

Stress causes low T3 by increasing production of cortisol, the “stress hormone” (perhaps cortisol should be called “the shutdown hormone”).
Cortisol blocks D1, so inside the cells, T3 production stops.
Cortisol also turns on D3, so inside the cells, T4 is converted into reverse T3.
D3 also takes an iodine atom from any T3 in the cells, making T2, which is also inactive.
Therefore the effect of cortisol is to almost completely remove T3 from your cells.

The cells of the pituitary gland are unaffected

The pituitary uses D2 . It doesn’t have D1 or D3.
So it keeps on making T3 for its own use and it doesn’t make reverse T3.
It doesn’t notice that anything is wrong, because it has enough T3 in its cells.
So it keeps on making TSH (thyroid stimulating hormone), according to how much T4 is available to it, and the patient’s blood TSH and FT4 are normal.

What’s the diagnosis?

As detailed above, I call this situation, where stress causes low T3 in the cells, “Intracellular Hypothyroidism” and thyroid-savvy practitioners call it “Functional Hypothyroidism”.
But traditional doctors have given it various names, like
“Low T3 syndrome”,
“Euthyroid Sick Syndrome”,
“Nonthyroidal illness”.
Also, some writers don’t realise that stress causes low T3: they talk about Chronic Fatigue Syndrome (CFS), CFS/ME, “Long Covid” etc.

All these conditions cause the symptoms of “true” Hypothyroidism.

These illnesses cause the same symptoms as hypothyroidism.
In both true hypothyroidism (when the thyroid gland doesn’t produce enough T4) and intracellular hypothyroidism, the cells have the same problem: they don’t have enough T3 to work efficiently (IH symptoms are worse, because the T3 starvation is more severe).

What’s the connection to aging?

Aging doesn’t cause intracellular hypothyroidism by itself.
However as you get older, your hormone production (including your T4 production) goes down, so your cells may not be working properly in the first place.
In old age, the cells are already “dragging along”, with less internal T3 than they had when you were young – that’s why old folks are always tired.
So it’s that much easier for low-grade stress to push elders into severe “T3 starvation”, producing the hypothyroidism symptoms mentioned above.
Thus the effects of stress, physical or psychological, tend to be worse in older people.

What’s the connection to other diseases?

Every serious injury, every life-threatening disease and every life-changing condition, causes stress.
Starvation, obesity, depression, social or economic pressures, abuse, PTSD, severe injury, burns, major surgery with complications, grief etc. cause stress.
The stress increases cortisol production.
Cortisol blocks T3 and intracellular hypothyroidism starts.
So low intracellular T3 is a feature of all admissions to Hospital ICUs, all cases of heart failure, psychological shocks, abuse, catastrophic weather and all stressful situations.

The doctors don’t know what’s happening

Your MD doesn’t know that stress causes low T3 and won’t notice that anything has gone wrong.
The only way to diagnose intracellular hypothyroidism is to test for T3 and rT3 and figure out the T3/rT3 ratio.
So tests for TSH, T4, T3 and reverse T3 should be done in every serious illness.
But T3 and rT3 aren’t tested:
Doctors are told that TSH is the only valid test for thyroid function and
the system threatens to “discipline” them if they do “unnecessary tests”.

Treatment for Intracellular Hypothyroidism:

There is no way to block cortisol production, but you can supply your cells with the T3 that they are not making, by taking T3 capsules until the stressful period is over.
This works very well and the stress-related symptoms go away quickly.

However if no life-threatening disease is involved, simply eliminating the stress might reduce cortisol production, allow T3 generation in the cells and relieve the symptoms.
This is why meditation and relaxation help some people with CFS, Fibromyalgia and Long Covid.

What you can do

If you are simply weak and tired from stress, or if you have a serious disease plus fatigue, what you can do is:
(1) Read and learn about intracellular hypothyroidism, via this website.
(2) “De-stress”: listen to music, dance, meditate, take a nap, walk (or sit) in the woods.

A picture of relaxation, with zero stress.

I’m stress-free–how’re you doin’ ?

(3) Consult with a functional medicine physician for analysis of your hormone balance, including tests for TSH, T4, T3 and reverse T3 and for treatment with T3 if you have IH.
(3) Follow that physician’s instructions re. correction of your T3 and other hormones.

A search, on stress relief.

Of the many websites which purport to solve the problem of “stress” and chronic fatigue syndrome, most peddle patent remedies of one sort or another.
However I have found one very well-designed website which gives considered advice in a tasteful and pleasant, non-capitalistic way.
Check the website below, for stress-relieving ideas:
go to

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