T4, when spoken off isolated, it imbibes our hypothalamo-hypophyseal axis so that efficient doses can be achieved.
Multiple studies refer to better tolerance but not higher efficiency.
The reflex of the Achilles tendon is replaced quicker
It prevents the formation of goitre
Improvement of the most ample symptoms
We achieve easier the T3 serum level (with T4 we have to give higher doses to reach the same level).
We achieve with more ease an adequate tissue level than we would with only T4 (studies in mouses)
The power of T3 is stable,T4’s varies
The stability of T3 is also higher than of the T4
The intestine absorption of T3 when connected to T4 is better than T4 on its own (95% against 35-67%)
There is inhibition in the conversion of T4 into T3
- With aging
- Hormonal disability (T3 deficit)
- Digestive disorders
- Deficits in various trace elements (selenium, iron, zinc)
So if we only give T4 we do not suppress the necessary quantity.
It is curious to observe that we need small quantities of T3 for the best conversion of T4 into T3. This way, we are able to suppress the minimal quantity of T3 at the same time as we favour the conversion of T4 into T3.
T3 is the most important hormone. Not T4.
5 times more T3 than T4 on the tissues
The level of T3 determines survival and not of T4, in studies of mortality.