Thyroid UK

By what mechanism do low cortisol and hypothyroidism interact?

Hi, I'm writing a letter for my GP as she needs to write to an endo for me and I want to explain the catch 22 situation that can arise with low thyroxine take up and low cortisol. I understand the idea that as every organ needs T3 to function adrenals will slow down if not enough T3 in cells, plus the stress of this long term to the body also raises the demand on adrenals however, could anyone explain to me how low cortisol in it's turn prevents efficient thyroid take up? By what mechanism does this happen? Thanks you

9 Replies

Hi Sorry I cannot help but I am exactly the same.



Have you googled 'cortisol thyroid connection'? There's loads there.

Mostly they are saying that inadequate thyroid hormone causes a rise in cortisol production. Basically it seems that the adrenals try to compensate for poor metabolism as a result of inadequate T3 by pumping out more cortisone. This raises blood glucose in order to optimise cell function in the 'fight or flight' situation. Then because your blood glucose is raised, insulin is raised which drives 'excess' glucose into the cells where it is converted to fat. Hey presto! - you have weight gain, and eventually insulin resistance which is the first stage of type 2 diabetes.

In young healthy subjects raised TSH was found to correlate with raised cortisol. So,, if there isn't enough T hormone about, the body will try alternative strategies to keep things going.

Now in reality our adrenals can't compensate for inadequate T3 indefinitely and give up the struggle eventually, which leads to adrenal fatigue and eventually potentially to adrenal failure or Addison's disease. In writing to your doc I would suggest you use the term adrenal insufficiency rather than fatigue. Docs have trouble understanding that just as the thyroid gland doesn't wake up one morning and refuse to work at all, the adrenals can underperform due to chronic overwork!

There is also an interesting article here

that I haven't fully absorbed yet!

When you have finished your letter, would you mind posting it here? I am sure lots of folk would be very interested.

1 like

Thank you I will look at that link. I haven't found anything that explains why once cortisol has crashed it is so hard to increase thyroid meds without getting symptoms.

I won't post my letter it is a rather long chronology of all the health hells that have happened to me since 1994 that she wanted to help her write to an endo. If I find the answer to my question I will post that.


I can't remember the whole mechanism now, but there is a warning on thyroid meds, all of them and the doctors all should know this..they are not to be used in someone with low Cortisol. Cortisol should be checked first before starting Thyroid meds..but it is rarely done.


Wow I've never seen that on my meds. Dr p says treat adrenals for two weeks then add thyroid meds, but what do u do if already on meds, stop? I am on t3 only I wonder if that makes a difference?


I wouldn't stop the Thyroid meds. You would be on nothing and who knows what would happen. Can you ask Dr. P what to do? The t3 would be out of your system in like 3 days, which would be pretty scary.

1 like

Hi Sulamaye,

The little understanding I got came from reading "Stop the Thuroid Madness" and Dr Peatfield's book.

Here's a quote from "Stop the Thyroid Madness"

"cortisol raises your cellular level of glucose which works with your cell receptors, ATP and mitochrondria to receive T3 from the blood to the cells."

So my understanding is, when the cortisol level is low, there's not enough T3 getting from the blood to the body cells hence continuous hypo symptoms. Link below

Dr Peatfield says something similar in his book "Your Thyroid and how to keep it healthy"but he adds that the T3 receptors in the cells might become dormant or may disappear or may become resistant due to low cortisol/adrenal insufficiency.

So the end result again is T3 not getting to the body cells and us staying hypo.

Hope this helps and good luck


1 like

Thanks Joyce - I've read Dr P's book but couldn't identify the mechanism that causes what he is talking about. I am waiting for STTM to arrive. I wonder what that means for the body, having raised celullar levels of glucose. Wow if I ever get well enough I'm going to see if there's an Open University course on Endocrinology!


If you look up info on t3 or t4 meds, they will tell you the contraindications? to using the meds. It is also in The Physicians Desk reference ..the book the doc's use for guidelines for treatment. They should be sued!

1 like

You may also like...