The Power of The T3 Thyroid Hormone

I had a conversation with a patient recently who had begun to have symptoms of hypothyroidism again after an inadvertent, slight reduction, in her T3 medication. This had occurred due to switching T3 brands. It made me realise that I probably need to say a little more about how T3 works and why even very small changes can make such a large difference.

Well over ten years ago, I wrote in one of the early drafts of Recovering with T3, in Chapter 14, that T3 could be viewed as a wave. This is what I wrote:

“Imagine a sandy beach, which is sheltered from the sea by large rocks. Only a wave that is large and powerful enough is capable of striking the rocks and sending a spray of seawater over them, to drench the sand beyond.

Each T3 divided dose is like a wave, the intracellular targets of T3 are akin to the beach and the rocks represent all the possible biochemical barriers that the T3 has to overcome. I do not believe that this is just some idle analogy. This is definitely how T3 replacement appears to feel and work within my own body. A small dose of it (2.5 or 5 mcg) might not do very much, because only some of it became properly active within the cells.

A little more might enable more T3 effect to occur.”

I also wrote in the protocol chapters that it was important to only change one dose at a time by 2.5 to 5 mcg at most, OR change a timing. I already knew that a small change could cause profound effects.

Way back then, I knew that T3 affected the cell nuclei and caused the basic function of cells (through gene transcription) to work and speed up. I also knew that T3 caused the mitochondria to work more efficiently and to multiply within cells. I found research that proved that the number of mitochondria per cell decrease in the presence of low FT3, and increase with increased FT3. The mitochondria improve their performance and provide more cellular energy (ATP) when T3 and cortisol are at good levels. I also knew that T3 increased cortisol.

Very shortly after the Recovering with T3 book was published I began to see the research that showed that T3 improved the level of cortisol through the hypothalamic-pituitary system being more stimulated, thus enabling the adrenals to make more cortisol.

We now know that cortisol works synergistically with T3. Without enough T3, cortisol does not work well. Without enough cortisol, T3 does not work well. Both cortisol and T3 work at the cell nuclei and the mitochondria.

As you can see – there are a lot of connections. So, when one key hormone is low, there are a lot of systems that are affected, i.e. there is a bit of a ‘snowball effect’. 

So in summary, T3 – works to improve the performance of:

  • Cell nuclei.
  • Mitochondria.
  • Hypothalamic-pituitary system – thus helping to improve cortisol production from the adrenal glands and
  • Cortisol-effect itself within the cells (just as cortisol helps to improve the effect of T3).

T3 thyroid hormone is potent and needs to be handled carefully. My protocol for using T3 recognised this potency when I first developed it 15-20 years ago, and when I wrote about it in my first drafts over ten years ago. 

It is not just the effect of T3 on cell nuclei. But it is the combined effect of an increase in T3 on the nuclei, the mitochondria, the hypothalamic-pituitary system and how cortisol and T3 enhance each other’s effect.

This is why so many thyroid patients are sick. They are deficient in T3 at all the key sites. This is also why T3 needs to be handled with some degree of reverence and care. A good protocol needs to be used. I think that the safe and effective protocol that I created and wrote about in detail in the Recovering with T3 book is still the safest way to use T3. I would be happy to enhance this protocol if I ever had some new information – but that has not happened yet. 

However, when patients do not respond to T4 therapy or to T4/T3, or NDT therapy, more T3 or even T3-Only therapy can be truly helpful.

Used skillfully, T3-Only can have profoundly good effects and help someone who is still very ill with hypothyroidism to recover.

I hope you found this short blog post interesting.

Best wishes,


p.s. for those who do have to switch T3 brands I suggest reviewing this blog post:

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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