Regenerous DIO2 Genetic Test - Wrong Test?

Lots of patients pay for this test based on the study by Vijay Panicker which found impaired psychological wellbeing. The results of the Regenerous test don't make sense to me, but I find genetics very difficult. So, I sent the following note to them in September and never got a reply, which is rather suspicious.

I have a question regarding your DIO2 genetic test. The study detailed in your documentation addresses the rs225014 polymorphism and compares patients with cytosine (C) and thymine (T) genotype. It finds that patients with the CC genotype have impaired well-being.

I have noticed that fellow patients who have carried out the test have received the response that they are 'homozygous AA'. Can you explain this please? It looks like the test is referring to adenine (A) rather than the cytosine (C). Does you test address the rs225014 polymorphism or something else?

Anyone with expertise in genetics who could assist with this?

60 Replies

jimh111 I hope you will push for a response as it's obviously important that patients should know exactly what they're paying for and whether it will enable them to be entitled to the appropriate medication from the NHS.

I organised my own test, through Thyroid UK link

My endo was extremely interested in the result and knew all about the DIO2 gene variation

Doubled my T3 as a result.

Also read another post last week by another member who sees Prof Toft, who doubled her dose after she tested positive

You can inherit from one parent - heterozygous

Or from both parents - homozygous

That person was me. He did indeed double my dose & accepted I have the DIO2 gene issue. My test was done by Geneva Diagnostics.

Are you heterozygous or homozygous?


Does this help?

rs225014, also known as Thr92Ala, represents a variant in the deiodinase, iodothyronine, type II DIO2 gene on chromosome 14. In dbSNP orientation for this SNP, the more common (T) allele encodes the Thr (threonine) and the somewhat less common (C) allele encodes the Ala (alanine) at this position in the DIO2 protein.

Very useful, I think. Will read it carefully when I have some time.

Is it a matter of strand orientation? So the AA result is equivalent to the TT genotype described in the paper?


Sorry it's too deep for me to understand.

Hi Jim, sorry I wasn’t clearer.

Your DNA has two strands and the sequence of one strand complements that of the other. So wherever there is a T on one strand there’s an A on the other (and vice versa), and wherever there’s a C on one strand there’s a G on the other (and vice versa). Some researchers and companies report on one strand, and some report the other, so a T in one report would be the same as an A in a different report.

I’m not sure that this is the reason for the discrepancy you’ve found, but it could be - it’s caused confusion in the past.

Sounds good but I'm still confused! The patients with the CC genotype do worse. I was thinking they get one C from each parent. So, I'm confused about 'strands', these the two halves of the DNA, one from each parent and it seems each base pair can be AT or CG. So I don't know where CC, TT (and CT, TC ?) come from.

At a guess, without much understanding, it could be that AA corresponds to TT and CC to GG if looking at the other strand?

Yes you’re right, an individual with a CC genotype for the trait in question would have had one copy from each parent. But each C would be (at the same position) on a separate chromosome, not on the DNA strands within a single chromosome.

I’ve been looking for a good diagram to illustrate the difference, can anyone recommend one?

If it's any help my positive results from Regenerus say :

Molecular Biology - Genetic polymorphisms implicated in various pathways

Result Deiodinase, iodothyronine, type II

DIO2 (T92A) rs225014 Heterozygous variant genotype TA

Interpretation : consequences of the detected genotype – decreased ability of the enzyme to generate the active T3 hormone

Clinical significance of the analyzed genetic polymorphism :

The type II iodothyronine deiodinase (DIO2) is an enzyme which catalyzes the 5’ deiodination of thyroxine (T4) to generate an active thyroid hormone (T3). DIO2 is further known to be responsible for catalyzing the local production of T3 in specific tissues such as the developing brain, the anterior pituitary gland, the brown adipose tissue and also in human skeletal muscles. In the human thyroid the selenoprotein DIO2 is abundant at levels 50 150 times higher than in placenta and it is especially highly expressed in patients with Graves disease or with follicular adenomas. Exposure to the thyroxine substrate increases the degradation of DIO2, resulting in decreased DIO2 activity. Missense mutations such as the SNP T to C (rs225014) in the DIO2 gene cause the amino acid substitution Thr92Ala. In vivo studies showed that this substitution is connected to a decreased DIO2 velocity in skeletal muscle and thyroid biopsy samples, and is further associated to insulin resistance and obesity especially in patients with an additional Tr64Arg mutation in the beta-3 adrenergic receptor (ADRB3). It was shown that the level of circulating insulin is significantly increased in patients with a heterozygous genotype (Thr/Ala) and almost doubled in homozygous variant (Ala/Ala) patients. The Thr92Ala substitution may affect ubiquination of DIO2 impairing its ability to increase its activity in the presence of low T4 levels, reducing the ability to maintain homeostasis and increasing dependence on serum T3 as a source of T3 in the brain. Patients on T4 replacement monotherapy with genetic polymorphisms in the DIO2 gene might be affected in their psychological well-being while in comparison to patients on combination therapy T3/T4 who might show a slightly improved psychological well-being.

Deiodinase lodothyronine type II

DIO2 (T92A) rs225014

Heterozygous variant genotype TA

I think this means i have inherited from one parent but got 2 defective genes thats about all i was told by counsellor she really wasnt very clear on explaining it all,,, I am told to add T3 to lego to feel better, I had just been to an Endo before i received this test, he had reduced my Levothyroxine from 150mg to 100 and added 20mgs which is to be split into 2 doses taken AM pm... is the right dose for this gene or should i have more added, I do feel better on this mix but I think i have more room for improvement , my head is much clearer and energy level as better but still have a few muscular pains going on, I have only been on T3 this is my 6th day,, just wondered what others with this defective gene what they have been prescribed , is 20mgs enough or should i be getting more to reach the muscular pain ? or does that improve over time on dose im on now as its early days yet prescribed I will also put this in a new post as may not get seen in this Im a bit confused to what it all means tbh Is it i just cant convert Levothyroxine into T3 or is it something that affected me before I was diagnosed , as read somewhere that me blood tests would read normal with this gene ? sorry genetics i'm not at all familiar with and myRegenerus counseller left me even more confused

Pascha1 You really need to write a new Post on this forum to get the best replies, what you have written here will get lost as it's a reply to someone else's post. I have the defective DIO2 gene from one parent, and can only take T3. Any T4 (levothyroxine) made me really ill as the DIO2 gene means that it doesn't get converted into the usable thyroid hormone T3. All very complicated! I have been on 40mcg of T3 but everyone is different. Some are on much more, particularly men. It's good that you now know that you do have the defective thyroid gene.


Having DIO2 impairment is usually overcome by adding a little T3 to Levothyroxine. If you can't tolerate Levothyroxine that's a different matter, probably not related to DIO2.

Clutter please read my newly updated profile. Adding a 'little T3' to T4 kept me in an insane state. I'm beginning to wonder what actually was my correct diagnosis. I have Hashi's and DIO2 faulty gene. So thyroid antibodies + inability to convert T4 into T3. Any ideas why I went crazy when taking any T4 at all? Until I was on 40mcg of T3, I wasn't even near human

. The more I read the more I'm confused what is actually happening in my body.

Being now aged 66, I have remembered that I have a Unicornuate Uterus, ie my son grew inside half of a uterus. I did have 4 miscarriages but I got him in the end. However, I am now wondering........ both the thyroid AND the uterus are within the Endocrine System. I'm wondering if in fact I have half a thyroid as well. My mother had an x-ray whilst pregnant with me in 1951, so presumably it was that that stopped one half of my uterus from growing.


I've read your profile. As I said intolerance to T4 is not caused by DIO2 impairment. The DIO2 impairment is overcome by adding small amounts of T3 to T4. If you can't tolerate T4 that is a separate issue. Inability to tolerate a medication doesn't mean a diagnosis of Hashi's hypothyroidism was wrong.

I am thyroidless. I did well on T3 only for 3 months and felt poisoned when I was switched to Levothyroxine and physical and mental health declined badly. In addition, FT3 dropped below range despite suppressed TSH and upper range FT4. Adding T3 to Levothyroxine calmed the adverse effects T4 caused and raised my FT3 to healthy levels and I recovered.

I'm not questioning the diagnosis of firstly Hypothyroid in 1981 then Hashimotos in 2017 by doing a private blood test. Are you saying that there is 'something else going on' here in my body? I'm just needing a bit of help understanding why I was in such an incredibly bad state of health for such a long time, despite being on 30 - 40 mcg of T3 a day.

Deiodinase can be impaired for many reasons, not just this polymorphism, often to a much greater extent that caused by the polymorphism. You may never discover the reason, so it's best to concentrate on what resolves clinical signs and symptoms without causing over activity.

Thanks jimh111 I'm starting to think that I should not really have been born.... the egg and/or sperm I came from must have been extremely strong. But along the way, my mother had an x-ray whilst pregnant with me in 1951, which I presume was what knocked out half of my uterus giving me a Unicornuate Uterus. I inherited a DIO2 gene - which you are saying Isn't really that important anyway. I have been incredibly ill for36 years, have fought and fought to recover, and now I have done it. During those 36 years I have seen 4 Professors of Endocrinology, 3+ endocrinologists, a whole variety of alternative therapists, 2 consultant psychiatrists and hundreds of hours of GP time.

It's very frustrating, had these doctors trialled L-T3 all this could have been avoided. Looking to the future it's important to document your current health status, what you can now do which you couldn't before. You might need this evidence if they try to stop your L-T3.

It was the wonderful Dr Peatfield who changed me from levo onto T3 only in 1995. He had read old medical papers and knew immediately that I needed T3. He said "you can't convert T4 into T3 Dahling". So, what was his premise for that?


Low TSH, high (in range) FT4 and low FT3 indicates poor conversion.

I never ever had low TSH - around 8 after paying for all my medical records. Also my FT4 and FT3 were low or just inside the bottom of the range. I think I must be an alien in disguise !! :-)

A TSH of 8 with fT3 and fT4 near the bottom of their reference intervals is low. Most patients with fT3 and fT4 near the bottom of their reference intervals would have a higher TSH. This is why endocrinologists say TSH is a sensitive marker for primary hypothyroidism. They are correct, it is sensitive in most cases but not all cases, as your case shows.

As I noted earlier I believe TSH promotes D2 and as your TSH is lower than it should be that could be the cause of your impaired T4 to T3 conversion. We can't be certain but I think it is much more likely than the DIO2 polymorphism.

I'm drifting off topic so will stop there.

jimh111 You say "as your TSH is lower than it should be" ............... My TSH was HIGH until I was on 40mcg of T3 a day.

With due respect, you are confusing newbies and me also. I am not a newbie, my brain is now 100% functioning all guns blazing but you are confusing me. You say one minute you are a geneticist then the next you say you do not understand genetics. Please make up your mind. Perhaps Regenerus will read your posts and replies and sue you for slander.

Marigold22. You wrote "I never ever had low TSH - around 8 after paying for all my medical records. Also my FT4 and FT3 were low or just inside the bottom of the range."

A TSH with low fT3 and fT4 is unusual. Normally TSH is very high when fT3 and fT4 are low, assuming you are not taking T3 medication and leaving a long time between the last dose and blood draw.

I am absolutely not a geneticist, I've never suggested I am. I do find genetics a difficult subject. I asked Regenerus to explain their test but they did not reply. The results they supply are not consistent with the study they reference.

This post is : -

Regenerous DIO2 Genetic Test - Wrong Test?

(Sorry about the wrong spelling of 'Regenerus')

I raised this query because the reports Regenerus produce do not match those from the DIO2 polymorphism research and I am unable to get an answer from Regenerus. Some patients have given helpful replies regarding possible explanations.

I ask that we now limit this discussion to the topic I raised.

jimh111 May I please ask you, respectfully, do you have Hypothyroidism or Hashimotos Thyroiditis? If not, what qualifications do you have to assist those who do to recover their health?

"Normally TSH is very high when fT3 and fT4 are low, assuming you are not taking T3 medication". My TSH is HIGH, my FT4 and FT3 are LOW when on any dose of T3 lower than 40mcg. OMG

I think the whole world has gone totally insane. As I said to jimh111 , Clutter , I always had HIGH TSH, very LOW FT3 and very LOW FT4 before taking an adequate dose of T3.


No, I wasn't saying anything else is going on. I was simply saying intolerance to thyroxine is NOT due to DIO2 impairment.

So sorry Clutter to continue this..... but what could intolerance to thyroxine be due to then, if not DIO2 impairment?


Some people are simply intolerant to some medication. It just doesn't suit them. That's why some people do badly on thyroxine but are okay on NDT. Some can't tolerate any amount of T4 so take T3 only. Some very unfortunate people can't seem to tolerate any thyroid medication.

Clutter How do you know that intolerance to thyroxine is NOT due to DIO2 impairment. I thought that was the whole idea of the DIO2 test. To prove that my body cannot convert T4 into T3 adequately, therefore I need to take T3 and not T4

Clutter, I'm sure abnormally low TSH reduces D2 activity although it is difficult to prove. I've started to dislike the term 'suppressed TSH' because it presumes the very low TSH is caused by suppression rather than insufficient stimulation by TRH. Clutter, in your case it would seem your TSH is 'insufficient' rather than 'suppressed'. This would reduce D2 and explain your low TSH, low fT3 and high fT4. If you increase your levothyroxine TSH will fall further thus reducing D2. When fT4 levels are high D1 takes over producing more T3 but this is counterproductive as D1 produces equal quantities of reverse T3. This increase in D1 at high fT4 levels appears to be a mechanism for mitigating thyrotoxicosis by producing rT3 and reducing the T4 available for D2.


My TSH is suppressed <0.1 to avoid cancer recurrence. On 200mcg FT4 was 35 and FT3 top of range. On 125mcg FT4 was within range but FT3 had dropped below range. When I came off thyroid meds for 4 weeks TSH rose to 107.5 so any suppression is clearly due to thyroid meds.

Clutter, I see, makes sense. I prefer the term 'very low TSH' or something similar because 'suppressed' is presumptious, could be suppressed or insufficient.

Your TSH is suppressed. It depends on what your TSH was when you were on 125 mcg but the low fT3 then could be because your pituitary (specifically thyrotrope) had not recovered. When you came off thyroid hormone it's possible your thyrotrope picked up.

The problem with measuring fT3 is that we don't know where the T3 is coming from (except for any T3 from tablets). Is it coming from D1 or D2? D1 increases as we approach thyrotoxicosis and also produces rT3. It's therefore reasonable to assume D1 has anti-hyperthyroid effects which might explain why you felt bad on 200 mcg L-T4. D2 increases in low hormone situation and so seems to be the 'good' deiodinase for hypothyroid patients.

By the way it's worth checking whether you still need your TSH suppressed from a cancer point of view. I believe they are able to assess this much better now and many patients need less suppression. Assuming you would be OK on a lower hormone dose.

(edited to change 'could be suppressed IN insufficient' to read '... OR sufficient'.


Suppressed is the term commonly used to described TSH <0.1. Mine is exogenously suppressed. It has been <0.01 on *60mcg Liothyronine, and Levothyroxine 200mcg down to 100mcg apart from when I came off thyroid meds on three occasions.

My endo would like my TSH less suppressed at 0.05. Hard to see what benefit there may be from such a small rise but 3 dose reductions over 13 months didn't budge TSH although FT4 and FT3 dropped considerably. I began to feel unwell so I declined further dose reductions. I'm yet to be convinced that exogenously suppressed TSH causes either atrial fibrillation or osteoporosis.

*edited to correct 180mcg to 60mcg.

Clutter, I've recently become averse to automatically calling all very low TSH levels 'suppressed' simply because sometimes it is not due to suppression. Your TSH is clearly suppressed. Can you confirm you are on 180 mcg liothyronine, that it wasn't a typo.

High levels of thyroid hormone do increase the risk of AF although it depends on the patient. Some patients appear to have resistance to thyroid hormone but this usually involves the beta-1 receptor. The heart has predominantlly alpha-1 receptors. So, if you take sufficient hormone to overcome the beta-1 resistance it will be too much for the heart.

Raising TSH (from <0.01?) to 0.05 is quite a big change as there is an inverse exponential relationship between TSH and thyroid hormone levels. Going from 0.01 to 0.05 is similar from going from 1.0 to 5.0.


I was originally prescribed *60mcg Liothyronine for 3 months, then switched to 200mcg T4 in 2012.

I am now prescribed 75mcg Levothyroxine + 30mcg T3 but have only been taking 25mcg of the T3 despite telling endo I wouldn't reduce. My annual TFT isn't until May so I won't know whether the 5mcg reduction has made the slightest difference to TSH or FT3.

*edited to correct 180mcg to 60mcg.


I've just realised I've been saying 180mcg T3! Of course, it wasn't, it was 3 x 20mcg T3. I'm so sorry. My brain is addled!

Clutter Where do you get that theory from? ie If you can't tolerate T4 it's a different matter and probably not related to DIO2 faulty gene

I think I've explained this to exahaustion. The DIO2 polymorphism is minor. There are many ways deiodinase can be impaired. Intolerance of L-T4 may be due to impaired deiodinase or just intolerance of the excipients in the tablets. Subjects with the polymorphism (40% of the world's population) do not have a faulty gene. It's just a minor variation, like having blue eyes or straight thumbs instead of bent thumbs.

You need to give it time to settle

My endo only reduced my T4 by 25mcg. Initially 10mcg split dose. Increased to 20mcg split dose after 6 weeks and no further T4 reduction.

In fact after 4-5 months I increased T4 back, initially by 12.5 and now at 6 months T4 back to 25mcg, (where it was before T3 added).

Probably needs further increase I am now more active and able to walk. I find if I try to have an active day like a normal person, I still run out. Have to take it quieter next day to recover

As I understand it the DIO2 gene affects the brain as brain needs T3 and can not convert T4. Seems to affect pituitary perhaps?

In healthy subjects the brain uses mainly T4 and converts it to T3 via D2. If you have the DIO2 polymorphism D2 will be a little less efficient. Whether this has much effect I don't know but I assume any effect is very small as we would have noticed if 16% (homozygous) or 40% (heterozygous) of the population were mentally subnormal!

The pituitary relies on D2 to convert T4 to T3. So if the effect of the polymorphism was substantial subjects with the polymorphism would all have high TSH levels.

Whereas my TSH never rose much even when absolutely dire and in wheelchair.

But vitamins where incredibly dire too - so I guess because there was unused thyroid hormones floating about TSH feedback doesn't work

I DID HAVE HIGH TSH - originally 76, then 12, then 8 , then perhaps 6

If you took high dose hormone for some time, such that it suppressed your TSH it can down-regulate your hypothalamic pituitary thyroid axis which means your TSH will from then on be lower than in a normal person. If you want to discuss this further it would be better to raise a separate post as it is off topic.


20mcg T3 should be plenty to overcome what will be a slight impairment in the conversion of T4 to T3. You should have a thyroid test including FT3 6 weeks after adding T3 to make sure FT3 remains within range.

T3 isn't an instant fix. 6 days is no time at all to expect improvement in symptoms. It will take up to six weeks to metabolise the T3.

The last two posts are helpful, thank-you. I don't really understand them but they do help. If I've got it right the polymorphism is caused by a replacement of a A T base pair with a C G base pair at a specific locus on the DNA. If I've got this right (don't hold your breath) this would mean that if your test came back as CC or GG you have the polymorphism that affects DIO2 activity. I will go away and read up on genetics sometime. This is really heavy stuff so please treat all my comments here as speculation. Just one comment I'm sure of, the above note from Regenerus mentions DIO2 is present in the developing brain. In fact, in healthy subjects not on hormone treatment most brain T3 comes from D2 conversion of T4.

On just T4 I always, (from day one almost), had this weird sensation like the centre of my head was becoming rigid, like lots of tight taut tendons, with much groaning and crunching if turning head .....(try explaining that to an endo!!)

Since starting T3 all this is less evident, though it comes back if I over do the physical output......and then my legs stop working too (trifle inconvenient!)

jimh111 I have only just seen your reply to my reply here about my Regenerus results. My own brain is now much recovered over the 2 month period since you wrote it. I am now able to comprehend a lot more - and grateful you pointed out that DIO2 is present in the developing brain. I guess it's obvious really, as it's a gene. I should be grateful if you could take a look at my newly updated profile. I consider now that I was a chubby child, only grew to, with ADD. I just about 'got through' life until a whole series of events - septicaemia in my 20s, 4 miscarriages, and I was born with half of a uterus only.

I was never ever going to return to good health on Thyroxine (T4). In fact it made me feel worse than before I took it in 1981.

I'm a bit confused! I don't understand the homeopath stuff - clone T3? The DIO2 polymorphism has minor effects and would not explain your severe symptoms. It's also not clear what thyroid hormone you are now taking. Perhaps start a separate post if you want to go into detail.

An update. I managed to make contact with Regenerus. They have contacted the company who makes the test, Laboratoires Reunis who are based in Luxembourg. Unfortunately they just sent their standard comment about the rs225014 polymorphism so I've asked for a more specific reply. Hpoefully my note will get to a technical person.

Unfortunately, I used the wrong e-mail address in my first e-mail. I used a right to left 'cut & paste' to select the address next to the envelope icon just above the map in their contactus web-page . This gave In my second e-mail I guessed the address should be If you look very closely you can just see an 'i' next to the envelope but it tends not to get picked up with cut & paste. I've suggessted a web-page change which should make it much clearer.

I will post another note when I get further information.

I've just realised Regenerus have not replied to my follow-up on 11th December so I have sent them a request to chase it up.

I just got a DIO2 result back from Regenerus and have made a post similar to this thread to query the result. Mine came back as follows:

DIO2 (T92A) rs220514 Heterozygous variant genotype TA

I am seeing my GP tomorrow and hoped I could blast him with some studies, but it seems they all relate to TT/TC/CC genotypes. I have now read this thread so it seems I'm not the only one who is confused! I would be very interested to hear if/when you get a response from them! Do please let me know....

I got a response, I'll try and put it here later today. I need to work out how to write it in understandable language!

I've clarified this with Regenerus after they contacted the lab in Switzerland that carries out the test. Here is a summary of the DIO2 enzyme, the genetic test and how the results are reported by Regenerus:

There are three deiodinase enzymes D1, D2 and D3 controlled by genes DIO1, DIO2 and DIO3. D2 converts T4 to T3 and is responsible for local T3 generation in organs such as the pituitary and brain.

A DIO2 single nucleotide polymorphism (SNP) rs225014 is associated with impaired baseline psychological wellbeing and enhanced response to combined T4 / T3 therapy . In this SNP the possible base combinations of thymine (T) and cytosine (C) are TT, TC and CC. Patients with the CC base pair have impaired psychological wellbeing and respond to combined T4 / T3 therapy. i.e. patients who have inherited the C allele from BOTH parents.

Note that there is no difference in T3 levels between subjects with or without the polymorphism, probably because D2 activity in the brain controls local T3 levels not circulating T3. Patients who think this polymorphism is causing low serum fT3 levels are mistaken. Blood T3 levels are not changed by this polymorphism.

Now to explain the confusion!

Rs225014 is also known as Thr92Ala. The T allele encodes the Thr (threonine) and the less common C allele encodes the Ala (alanine). You can report TT, TC and CC or you can report ThrThr, ThrAla and AlaAla, depending on whether you report the base pair or the resultant amino acids.

Regenerus report the amino acids. Unfortunately, they incorrectly describe them as alleles and use the abbreviations T and A instead of Thr and Ala. This becomes even more confusing as there are four types of bases found in a DNA molecule: adenine (A), cytosine (C), guanine (G), and thymine (T).

So, where Regenerus report a T it corresponds to Thr which comes from a T allele and where Regenerus report an A it corresponds to Ala which comes from a C allele.

Patients with the CC alleles have impaired baseline psychological wellbeing and respond to combined T4 / T3 therapy. This corresponds to an AA result on the Regenerus report.

So helpful jimh111, many thanks for your persistence. Following your detailed responses, I finally felt equipped to delve into my 23andme tests for this SNP. I am TT so do not have the polymorphism. I am also on T3 only and cannot tolerate levo so I guess I'm looking for another reason other than a 'DIO2 polymorphism'.

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