Can T3 Therapy Stress the Adrenal Glands?

This is a question I have heard far too many times. Here is an answer that hopefully will deal with this and can be used in response to this in future.


The language of 'stress the adrenals', or 'adrenal fatigue' or 'weak adrenals' is language that you see all over the Internet and it is flawed and out of date. It is a type of expression that continues to get spread around the Internet unfortunately. Thyroid patient's get advice like, "You need to take HC to rest your adrenals", or "You have adrenal fatigue, so use adrenal glandulars until they are less tired" or "You may have weak adrenals, that's why you have low cortisol", other such rubbish.

Let me attempt to be very clear:

1) The adrenals don't get 'stressed'. They are simple, robust organs that rarely have any issues. If they become issues at all, it is usually due to an autoimmune condition that eventually develops into Addison's disease. All the adrenals need is cholesterol and enough ACTH signal from the pituitary. This is why thyroid patients with low cortisol often pass a Synacthen (ACTH Stim Test) very easily. This brings me to point 2.

2) Hypocortisolism does exist of course. This is usually due to the hypothalamic-pituitary axis not working. Often, this is due to far too little FT3 through the night and in the daytime, as the pituitary effectively 'runs on' T3.

3) T3 actually stimulates the pituitary-hypothalamic system more than any other form of thyroid hormone. So, for low cortisol, raising FT3 is a great solution in many cases. T3 therapy does this more effectively than other thyroid treatments. 

Note: If T3 is used and the hypothalamic-pituitary system cannot respond, then adrenaline can get produced. This feels like high heart rate and anxiety etc. This can happen in a few situations e.g. long-term use of anti-anxiety drugs or anti-depressants, Lyme disease are some reasons for this. But if it does happen, it still is NOT the adrenals getting stressed - they cannot get stressed. In most thyroid patients the adrenals are capable of working well. It is simply that for one reason or another the hypothalamic-pituitary system has not responded well. In these cases, persevering with some T3 can sometimes correct this over time. LDN use can sometimes help also. Obviously, addressing any other significant issues is essential.

Here is some further information:
and my books:
The Thyroid Patient's Manual Chapter 5 and 7 at least
Recovering with T3 Chapter 16 (Updated Edition 2018)
The CT3M Handbook

Hope this helps.

My website blog (and books) are there to provide this information and a lot more besides:

Best wishes,