Once the t-3 goes into the mitochondrion does there have to be proper functioning of the mitochondrion to care out the thyroid signaling from t3. One needs t3 to make the cellular energy work, but if the cellular is not up to optimal capacity then one would not get the desired from thyroid hormone. When you are referring to thyroid signaling are you referring to it on a receptor level or deeper with in the energy systems. If a person had a mitochondrial imbalance and t-3 was given with no response could make Dr think by giving more is going to resolve the issue when the real problem is at the cellular level? Dr's needs to look at giving substrates to help to support mitochondrial function such as ubquinol, acetly carnitine, citrates, iron to help make the ATP. In studies I have come across people with low thyroid hormones are also low in co-enzyme Q10 and iron, b-12. If these are low these could it affect the cellular signaling of the thyroid medicine.
So to summarize thyroid start to finish
1. Thyroid Absorption in to the blood
2. Thyroid conversion t-4 to t3
3. Thyroid receptor activation
4. Thyroid cellular signaling to make ATP.
5. Ability for mitochondrion to respond to increase thyroid demands.
So when a person that actually goes to see a traditional thyroid dr they are only looking at really 15-20% of the equation and leaving out the other 80-85%. These drs are totally ignoring the factors are what are effecting each one of these stages. This will explain why thyroid issues are missed 80-85% of the time. When I have time I will sit down and break each one of these down with what factors are affecting them. It should make a good sticky as well.