Recently I had enzyme testing through Nutritiongenome.com in the US, and although my DIO2 enzymes were normal, I was heterozygous for the DIO1 enzyme. I am 59 yo and have had Hashimoto's for 15+ years, and became very hypothyroid on levothyroxine only. Also I became very sick with a suppressed HPA axis after epidural steroid shots for ruptured discs. After my endocrinologist on 11/18 said she would not prescribe more than 20 mcg/d of T3, I switched to T3 only medication in Jan 2019 and gradually worked up to 120 mcg, following Paul Robinson's protocol. I feel so much better!! Wonder if I should stay on T3, which I take 5 times/d, or at some point try to go back to adding NDT? Anyone have any advice? ( PS I believe my nutrition is optimized now including Vit D, ferritin, folate, B12, selenium.) Thanks!
Significance of DIO1 gene mutation? T3 only - Thyroid UK
Significance of DIO1 gene mutation? T3 only
I am going to be both very helpful and utterly unhelpful - all in one link:
The link gives a huge amount of very technical information about DIO1. Almost completely way above my head.
Somewhere on that page is mention of GeneRIFs: Gene References Into Functions. In turn that lists 38 papers which refer to the DIO1 gene and its functions. This is the link (actually a search, so the number might vary over time):
ncbi.nlm.nih.gov/gene?db=ge...
I wish you the very best in reading through it all. 
Some of those links might even be readable.
Thanks! I will dive into those soon!
Good news that you are feeling well!!
If you feel completely well on T3-only I don't see any reason to mess with that and go onto something else!
Has someone told you it's better to be on NDT long term? We have a few forum regulars taking T3 only and doing well.
Good point! I guess I was hoping to not have to take a medicine 5x/day by adding a longer acting thyroid replacement. But compared to what Type I diabetics have to do with insulin shots, I do feel grateful I can manage this autoimmune condition with oral medication. Thanks!
If you want to you could try having 4x a day and see how you feel (keeping the overall daily dose the same, but splitting it into 4 instead of 5). You might be able to get away with it. Some people take all their T3 in one big dose!
Do you leave a gap between food each time? I take 3x doses, and the worst bit is not being able to eat for most of the day.
You are taking the equivalent of 360 mcg of T4. That is too much T3. You may find weird symptoms starting up after a period of time. I get alot of strange brain symptoms and my glucose goes out of control when on too much thyroid hormone. It does take some time, usually 2 or 3 months before you start feeling very strange. If I were you I would reduce your T3 intake down to around 40mcg per day or lower.
I have tried taking less T3 at one time, like 22 mcg, and after a couple days the old hypothyroid symptoms return. My adrenal system was severely suppressed 2.5 y ago after a series of epidural steroid injections (my morning ACTH was not detectable, cortisol was 6-lowest limit of normal, but ACTH stimulation test showed adrenals were responding OK), so maybe that's why I need a higher dose of T3. Paul Robinson says he knows some people who take 200-300 mcg/d. Maybe some thyroid resistance? Every person is unique. I follow the protocol in Paul's CT3 method to adrenal recovery.
A mutation on the Dio1 gene means you cannot convert T4 to T3 very well. I have it homozygously, which explains why i was so ill but got pretty well instantly better when i started taking T3.
Testing for DIO1 and DIO2 gene defects
t3 only
Hydrocortisone and T3 only
T3 only, high RBC, haemoglobin and hematocrit 
