The Flawed Concept of ‘Resting Adrenal Glands’ for Thyroid Patients

So much is written on the Internet by thyroid patients and thyroid patient groups about the idea of ‘resting the adrenal glands’.

This concept is based on the idea that when a thyroid patient is suffering from low cortisol that their adrenal glands are the root cause.

It is rooted in the idea that adrenal glands get tired and exhausted due to stress or some other reason.

The way in which this ‘rest’ is proposed by some thyroid patient groups and some doctors is often to suggest the thyroid patient uses hydrocortisone (HC) or adrenal glandulars.

The idea is to ‘take the strain off the adrenal glands’ and ‘rest them’.

It is based on the idea of ‘adrenal fatigue’, i.e. the adrenal glands have got tired of making cortisol, and that is why it is now the thyroid patient has low cortisol now.

I no longer believe in ‘adrenal fatigue’. 

The adrenals are very simple glands with ample capability of producing high levels of cortisol, indefinitely.

In the majority of people, all the adrenal glands require is a good ACTH signal from the pituitary and adequate cholesterol.  ACTH stands for adrenocorticotropic hormone, and it stimulates the adrenal glands to make more cortisol and DHEA.

The above goes a long way to explaining why people with Cushing’s syndrome can go for years and years with extremely high cortisol levels. Their adrenal glands never get ‘fatigued’ because undamaged adrenals do not get fatigued. 

I believe the majority of cases of low cortisol are due to hypothalamic-pituitary dysfunction (HP dysfunction) and the lower level of ACTH that results from it. 

Some people do have Addison’s disease, which can be usually be discovered via an ACTH Stimulation test (Synacthen test).  Addison’s disease is caused through adrenal tissue destruction, often through an auto-immune attack. It requires hydrocortisone (HC) replacement for life.

But for the typical thyroid patient with low cortisol, it is likely to be HP dysfunction causing the low cortisol. Many things can cause this, e.g. prolonged stress, toxicity etc. The result is the same – low cortisol. 

Sometimes the cause for the HP dysfunction cannot be discovered and the patient may require some HC or adrenal glandular support.

However, it is often caused because the thyroid patient no longer has a working thyroid gland, and no longer has a normal 24-hour cycle of thyroid hormones, i.e. because they are on thyroid medication.

Why Can the Use of Thyroid Medication Cause HP Dysfunction?

The pituitary has the highest concentration of Free T3 (FT3) in the body. It makes its own D2 deiodinase enzymes. It converts around 80% of the FT4 present in its cells to FT3, and it keeps most of this T3 inside itself. The pituitary gland ‘runs on T3’ for fuel.

Why? The pituitary gland needs a good supply of FT3 to function well of course. If anything lowers FT3, e.g. a conversion problem, the pituitary may suffer, and ACTH could be lower. 

With lower ACTH comes low cortisol. This has to happen. Cortisol cannot be made by the adrenal glands without enough of an ACTH signal (and enough cholesterol – which comes from the diet).

By the way, lower pregnenolone or progesterone is not going to be a problem in making cortisol. Cortisol is made in adequate amounts if there is enough of an ACTH signal and enough cholesterol (and most people have enough cholesterol).

What can cause a lower level of T3 in the pituitary gland? 

Factors include: Hashimoto’s thyroiditis, thyroidectomy, a DIO1 and especially a DIO2 enzyme defect (which affects the internal pituitary conversion of T4 to T3), or anything else which lowers T3 levels.

Taking thyroid medication in the daytime only is also likely to lead to lower levels of FT3 by the night time when the pituitary begins to crank out a lot more ACTH.

Treating HP-dysfunction with levothyroxine or Synthroid is often not going to work. It needs extra T3 to bring the system back to normal. In some cases it needs T3-Only.

‘Resting the adrenals’ with steroids is an Internet myth and a fallacy. 

The adrenals won’t miraculously recover through ‘rest’, as there is usually nothing wrong with the adrenals themselves. It needs a better, smarter approach.

Using more T3, and the Circadian T3 Method (CT3M) can often help resolve the HP-dysfunction and raise cortisol levels back to normal. 

Click on the following video for more information on CT3M:

For those that want to dig deeper into CT3M, please read Recovering with T3.

A companion book, The CT3M Handbook, is also available if you need even more information on CT3M.

Best wishes,


(Updated in February 2019)

Paul Robinson

Paul Robinson is a British author and thyroid patient advocate. The focus of his books and work is on helping patients recover from hypothyroidism. Paul has accumulated a wealth of knowledge on thyroid and adrenal dysfunction and their treatment. His three books cover all of this.

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