Cellular T3 & cortisol

I must add the following edit since I have researched this question after links were kindly provided - this is what I now understand:

Low cortisol causes T3 to work less effectively within the cells. This is because T3 and cortisol are partners within our cells. High cortisol also causes problems and can reduce the effectiveness of T3 within the cells, hence thyroid patients with high cortisol often complain of feeling hypothyroid even when they appear to have reasonable FT3 levels. When patients try to raise T3 levels in the presence of low cortisol, they may find that the body compensates for low cortisol by producing more adrenaline. This can cause anxiety, rapid heart rate, the feeling of heart palpitations etc. This is usually the adrenaline response rather than a direct issue with the T3. Very often, it is the low cortisol that is at the root. (Paul Robinson website)

I am currently reading Peatfield’s book.

He suggests that low cortisol can make thyroid medications either

a. Ineffective

b. Make things worse.

It explains that cortisol facilitates T3 access to the cell, this is the reason given for why low cortisol causes problems. 

However, how can thyroid hormone make things worse if there isn’t access to the cell? Surely T3 is either in the cell, or it’s not. And if someone suffers negative reactions from t3 containing medications (as I do) then surely this suggests that the t3 is indeed getting into the cell, otherwise how come a reaction at all? I’m confused.

I’ve come across many resources that site the same, along these lines: 

Whatever you may be told, adrenal insufficiency in thyroid disorders is very common indeed and should always be considered at the onset of treatment. Failure to respond to thyroid supplementation, or actually feeling less well, is likely more often than not to involve the low adrenal reserve syndrome. (Peatfield “how to look after your thyroid”)

If, upon starting NDT, you experience symptoms, including anxiety, insomnia, shakiness, sweating, dizziness, feeling spaced out its a strong sign that you may need adrenal support. (Tpauk website)

So, I’m confused… in the case where T3 is causing MORE problems (and over medication and raising too fast is ruled out) how can it be low cortisol preventing T3 to access the cells? Surely where more problems are appearing, the T3 is almost certainly getting access to create these symptoms.

All wisdom welcomed!