There are three reasons that I am aware of as to why a Hashi sufferer wouldn't be able to tolerate NDT.
The first is with regard to a patient who hasn't medicated T3 before. The rate of T3 acceptance in their body may be slower that the rate of increased NDT required to keep TSH suppressed. Depending on the immune state and the type of thyroid antibody present, suppression may be required to discourage thyroid activity and a possible Hashi attack.,
The second reason (similar but for differing reasons) is if a patient has hugely elevated thyroid antibodies putting their immune system into a high state of response. The NDT dose required to suppress the Hashi attacks may exceed that of the hormone amount actually required for replacement.,
The third is nutrient deficiencies, especially iron and cortisol hormone. This would be the same for all hypothyroid patients medicating NDT but as most of them are Hashi sufferers, it makes sense to include it..
Many Hashi sufferers take NDT and appear to achieve well being. However, I constantly see members on the forum who start NDT but can not raise quickly enough to suppress the imminent antibody activity and have to switch back to their previous meds.
Elevated thyroid antibodies can make the patient more susceptible to allergies and intolerances. It may be assumed that after so many years our thyroid glands are totally shrivelled up like an old dried up pea - LOL ...(mine is, I saw it on the scanner last year ! ! ...) ... and so not capable of being attacked but it only takes one tiny living thyroid cell to instigate an attack. Also the antibodies will attack the glandular proteins which may be seen as an enemy, similar to the molecular mimicry scenario of gluten.
I was medicating T4 for four years and was a complete mess until adding T3 June 2015. I have spent a year working to improve all nutrients, iron (of which I am usually in excess of ! ! ..) .. and adrenal health. I was planning to investigate NDT in about another 6 months but the withdrawal of my National Health T3 has kinda forced my hand. I could buy T3 but suffer a weird mouth problem and want to get off Levothyroxine anyway to see if it improves.
I think if you wish to try NDT, ensure the fundamentals are in place .. .. absolute optimal nutrients, iron, adequate cortisol levels and low thyroid antibody count...then you stand as good chance as anyone in tolerating it and hopefully gaining lots of benefits.
As an after note - I now read that T2 (included in NDT) is becoming more recognised as having a stimulatory effect on the 5’-deiodinase enzyme activity, encouraging further production of T3, so enabling less meds to be administered and inhibiting TSH.....It also increases metabolism in brown adipose tissue (brown fat where surplus calories are burnt away rather than being deposited in fat stores ... yahoo ! ! ..).