T4 is NOT Needed in the Brain in Adults - New Research that Backs Up T3 Patients' Experience

This is a blog post to finally close the door on a question that we need T4 in the brain.

I have been told too many times that there is research that shows that our brain and central nervous system can only use T4. 

I have always argued that this is not true, as there are large numbers of people like me who are fit and healthy on T3 Only. 

We also have studies done that prove that there are no negative effects from long term use of T3-Only.

Well, to finally draw a curtain over this whole issue there is new research that has proven that adults use T3 in the brain and central nervous system very easily.

The new research is changing the entire understanding with its discovery of active transporters.

There are T3 transporters and they are more active in adult life, compared to fetal life.

So, circulating T3 is a source of T3 for the brain. It is not exclusively dependent on T4.

But this change of belief in transport, rather than diffusion, is relatively new, and more transporters are being discovered.

Older assumptions have been proven wrong.

The assumptions had to be wrong anyway - this is what I have been saying all along. 

So the people that say we cannot live without some T4 are wrong.

I have all the above on authority from thyroid researchers.

Here is the research:

Thyroid Hormone Action: Astrocyte–Neuron Communication by Beatriz Morte and Juan Bernal
Front Endocrinol (Lausanne). 2014; 5: 82.
Published online 2014 May 30. Prepublished online 2014 Apr 22. doi:  10.3389/fendo.2014.00082


Best wishes,


(Updated in February 2019)