Thyroid UK
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T3 not getting into the cells

It seems I am converting T4 into T3 well and although I have lots of T3 it is not getting into my cells. As a result I still have lots of symptoms. I was on 200mcg Levo which didnt really do anything for me and I got a prescription today from my private specialist to try NDT.

I have high cortisol levels and v low vit D. I am taking vit D supplements.

My specialist said he doesn't really understand why my T3 isn't getting into my cells. He also said if there isn't an improvement on NDT 'we'll have to bring someone else in to look at you" whatever that means.

Anyone know what could be stopping my T3 from getting into my cells?

I'm depressed now because I'm scared in case NDT doesn't work either. I had all my hopes pinned on it and I don't know what to think about it all anymore.

16 Replies

hi Are you seeing an Endo? It is common ,if T4 is not converting sufficiently into FT3 to need T3 with T4 as fist choice, If the T4 was tolerated and the T4 blood test high and FT3 ( Free T3) test low,then this is clearly a case of needing less T4 and some T3 on a script. This is very common. It is only if this does not suit or not tolerated that the more expensive NDT is used.Also , most GP`s will not prescribe NDT unless very lucky which means you have to pay for it on a private script. \If seeing a private Endo or nHS one this is prescribed by the gP. at Endo`s instructions. Have you had the other autoimmune hormonal tests? Most Endos do these at the first visit and also more tests if considered necessary. These ae reverse T3, B12 \and Foliates, Iron/ferritin and Diabetes. Most of us are low in ferritin and need it to be quite high in range, likewise B12. This is all endocrinology

What are your TSH, T4 and Free T3 tests + ranges( all vary)? Without frequent tests ,especially with alterations in meds. it is dangerous.

I hope this helps, hard to be precise as not sure of your blood results.

Best wishes,


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Hi Jackie,

Yes I'm seeing a private Endo.

My T4 is converting very well to T3 but the problem is my T3 is just not getting into my cells. I've had some vitamin tests done which are within range apart from very low vit D and high cortisol levels 567nmol/1 (171-536). My surgery forgot to test my T4 but my free T3 is over the range 9.8pmol/L (3.9-6.8)

1 like

My ferritin level is 224ng/ml (34-528)

Serum vitamin B12 628ng/l (220-914)

Serum folate 16.2 ng/ml (2.6 - 20.1)


Hi They are fine. If you FT3 is that high, why does he say that your body is not converting? I would say, going by my own experience and my Endo that your FT3 is dangerously high, irrespective of your T4 ,which I suspect is too high Do you know that . Hyper symptoms can sometimes be the same as Hypo? I was overdosed by a private doctor and made very ill. What is he basing the fat that T3 is not getting into the cells on?The other tests you have mentioned are also fine, but unusually high if still Hypo.Have you had the best test for parathyroid ( PTH) ? Or the specific bloods for it, Am blood, done together, vit D, corrected calcium and PTH, if all high or 2 high and D high for you, then the investigations?f it was me I would be asking him a lot more questions.Have you had your reverse T3 done? Is your thyroid swollen, swallowing, voice or even visible or painful? In which case I would be asking for a thyroid ultra sound. Have you got your last tests of TSH, T4 and Free T3 results + if possible the fist ones you had. Have you had the 3 done before each rise in meds?Did you have corrected calcium tested before taking any vit D? Also again after 3 months?High cortisol could also be over treatment. What is he basing this opinion on?

Sorry about all the questions, just trying to get a full picture.

Best wishes,



I have read somewhere that HIGH Cortisol prevents the uptake of T3 at a cellular level. Possibly by blocking the T3 receptors on the cells....think satellite dishes covered with a blanket ! It is also one of many explanations for weight gain when you have UAT as T3 is needed to speed up the metabolism and burn fat - but when cortisol is high then this cannot happen. Reducing the stress hormones may help your absorption of T3.

It could be worth reading Paul Robinsons website He also has a book by the same name.....'Recovering with T3 '. He explains that T3 can help the Adrenals become balanced which in turn balances the thyroid hormones too. Paul is on this forum so you can find him in the Directory and have a read.

Don't be depressed about NDT - it's just another Thyroid Adventure and could work well for you. Do not be concerned until there is something for you to be concerned about - and then you can quickly write a blog and EVERYONE will be there for you......


What you describe reads like Reduced Sensitivity to Thyroid Hormone. Although it is unlikely to provide any usable answers, this link might help in trying to understand what is happening:

As always with Thyroid Manager, a heavy read in lots of ways. But sometimes there is very little real information available anywhere else.

Regarding desiccated thyroid - who knows? As none of us really understand why some people do so well on that but nothing else, obviously the only thing is to try it.

Vitamin D does appear to be intimately bound up with the whole thyroid hormone issues - but again, with little real understanding as yet. Do you know where you are in terms of getting D levels back up somewhere sensible?



Have you had revelse t3 levels checked? It may be that the t4 is breaking down into reverse t3 as a method of reducing excess t4.

High reverse t3 will stop any free t3 from getting in to cells..... Get the rt3 test done alongside a free t3 test, and check that the ratio is more than 20...



I understand that for the conversion to work properly and for T3 to enter cells then the cells must have the correct nutrients and not be blocked by toxins. This is usually outside of Endos expereince and on the cutting edge or not recognised side of treatment. I found that Dr Myhill's website explains this well. She also does tests which she then comments on without you having to visit her. Toxins can be over exposure to PCBs in plastics, heavy metals like mercury, pesticides, other toxic chemicals. Maybe worth a look?

Good luck!



What is thyroid resistance?

Thyroid resistance, also called peripheral cellular resistance, is the inability of the cell to accept and utilize circulating thyroid hormone. This is similar to the plight of the NIDDM patient. Circulating levels of the hormones are normal and yet deficiency signs and symptoms abound. The mechanism of action in most congenital cases of peripheral thyroid resistance is an alteration in the c-erbAB gene. Mutations in this gene can lead to as much as a 97% reduction in binding of T3 to the nuclear receptor sites where transcription of beta-adrenergic receptors occurs.

Resistance may also occur in the form of elevated cortisol. High levels of cortisol can inhibit conversion of T4 to T3 and promote conversion of T4 to r-T3 (the inactive form). Dioxins and PCB's can also bind to transthyretin and presumably to nuclear receptor for T3, thus competitively inhibiting T3 binding. Other toxins that are known in animal models to produce decreased serum levels of T4 and increased rT3 include chlorinated paraffins, polychlorinated biphenyl, hexachlorobenzene, 3-methylcholanthrene, 3,3',4,4'-tetrachlorobiphenyl, 2,3,7,8-tetrachloro-p-dioxin and clofibrate. Drugs that reduce T3 and increase rT3 include; dexamethasone, propylthiourcil, iopanic acid (radiographic contrast agent), amiodarone, propranalol.

Down-regulation of T3 receptors also occurs in animals under conditions of prolonged fasting or illness, presumably to prevent catabolic wasting during periods of caloric deficit. A similar post-receptor effector mechanism defect is found in the ob/ob experimental mouse, leading to ob/ob mouse obesity.


There is also pooling of T3 which may be similar but I don't know much about that.


Thank you all for your replies. I really appreciate it. I believe now from what I have read from all your responses and my subsequent research that my cell absorption problem is linked to my high cortisol levels. I have been dealing with inhumane levels of stress my whole life (I am 53 now) so it makes sense that my cortisol levels are high.

I will make a start by getting my RT3 levels checked and check my free T3 again and look into trying to bring down my cortisol levels. I have started taking zinc as I've read that is good at bringing down cortisol.

My Endo wants me to contact him again in three weeks time and let him know if I am feeling any benefit from NDT.


Hi Karispitit,

I hope you don't mind me messaging you in this way but I'm wondering if I'm not absorbing T3 due to chronic stress. Do you have raised TPO antibodies, mine are 365? I have normal bloods, TSH 3.86 (so not great), family history and loads of symptoms. Debilitated and struggling to hold down jobs or even continue with volunteering.

Could you PM with details of any practitioners that could help? Where do you buy your T3 from?

Thank you


Hi Karispitit

Have you managed to resolve to your issue re getting t3 to work at a cellular level.I believe I have the same problem.I have seen many endos,but as we all know,as long as you have good levels of thyroid hormone in your blood,they are not interested as to why it s not working.Can you recommend a practitioner who looks at why the t3 isnt getting through to the cells.

many thanks



Hi Simon, My apologies for the delay in replying to you. I was on quite a journey as the NHS wouldn't take an interest in me as my blood tests always came back normal. I self medicate as I was desperate 3 years ago as I had a long list of symptoms. T3 turned out to be a miracle drug for me and I have been symptom free ever since. I don't know why my T3 is not converting properly and to be honest I don't have an interest in finding out as I'm just happy to be so well again. If I stop taking my T3 my body swells up and I get myxedema a lot so my T3 tabs stop that from happening. I used to see Dr Skinner but he died and I had no-one else to go to. I am happy to help you in any way I can. What are your symptoms? How long have you been suffering? Caroline


Hi Caroline

Thanks for your reply.I have good levels of both ft4 and ft3 in my blood.I still have hypo symptoms.Weight loss resistance,brain fog ,fatigue etc.I too have low vitamin D-now supplementing.I also have high cortisol from morning to night.Im convinced t3 is not getting to my cells.Im waiting for the results of rt3.Do you know of a practitioner that can help?i ve seen several people privately who have taken my money but hav nt been able to help.



Hello, I'm new here just wanted to gain insight into your T3 only dose and how long it took before you noticed the swelling starting to subside


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