Normal TSH and T4 but low T3 cannot be hypothyr... - Thyroid UK (2023)

Normal TSH and T4 but low T3 cannot be hypothyroid?


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I have been prescribed Liothyronine T3 (20mcg per day) for the last 18 months which raised my FT3 from 3.7 to 4.8. I felt better, though not completely well, with less dizziness and brain fog, increased pulse rate from a very low level, reduced cholesterol and BP and no apparent side effects. Now my endocrinologist has retired and my new consultant has said that he wishes me to gradually reduce T3 back to zero and replace with T4 Levothyroxine.

He gave two reasons. Firstly, there is very little data on the long-term health safety of T3 (even though it has been around for 60 odd years...?) and secondly that with normal TSH and normal T4, T3 is not necessary. However, extensive tests by my previous endo showed that just taking T4 (up to 75mcg/day) raised my FT4 out of the top of the normal range with horrible side effects (24.5 vs a normal range of 9 to 23) reduced my TSH to almost zero but had no effect on my FT3 staying constant at a low 3.7. I have no wish to repeat these trials and go through many months of feeling unwell again or worse still to be forced to come off T3 altogether. Are there any other conditions or circumstances that could explain these results that I could discuss with him? Any help or advice appreciated. Thanks.

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  • TSH test
  • T3 test
  • T4 test
  • Levothyroxine
  • Liothyronine

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(Video) Causes of normal T3,T4 levels but low TSH levels - Dr. Anantharaman Ramakrishnan

We get most of our T3 by conversion of T4 to T3, the thyroid is responsible for about 15% of our T3 which is why levothyroxine monotherapy works for many patients. However, if fT3 is low it is primarily because T4 to T3 conversion is low, the amount of T3 from the thyroid is too little to explain why fT3 would fall to the bottom of its reference interval.

Endocrinologists invariably overlook the role of TSH in stimulating T4 to T3 conversion. If the thyrotroph (in pituitary) is secreting less TSH than it should then there will be impaired T4 to T3 conversion. If someone has low normal fT3 and normal fT4 we would expect TSH to be high, this would stimulate more T3 secretion and T4 to T3 conversion and so restore fT3 levels. This is why a high TSH can reveal a failling thyroid.

If however TSH is not high fT3 will remain low. If you give the patient levothyroxine it will drive TSH even lower and reduce T4 to T3 conversion even more. There will be more T4 to convert but a slower rate of conversion, hence fT3 will not improve much if at all. To make things worse the high fT4 reduces type-2 deiodinase (T4 to T3 conversion) which occurs close to the cell nucleus in organs such as the brain and skeletal muscles. These patients need T3 therapy, often at doses that give high or high normal blood fT3 levels.

grahamgraham in reply to jimh111

Many thanks for your very clear explanation of the conversion process. Having read it I can recognise what has been happening to me! I will certainly use this information to help steer my next conversation with my endo, so thanks once again. Graham


Hi, I was never good on T4, I saw aconsultant privatly some years ago who put me on 10ng T3 and 150mg of T4, I felt a little better. 11 years ago I moved to north Devon and the first thing my new dotor did was to remove my T3 until I saw a cosultant down here. It took 3 months to see said consultant who put me back on T3. Having been of it for 3months it did not have the same efect and said consultant put me on T3 only, firstly 30mg and later 60mg. I was very good on this dose. Another consultant said I was over medicated and reduced me to 40 mg and wanted to put me back on to T4, No way I now buy T3 my self. My GP rang me up a short while ago to say the CCG in this part of the world will not sanction any more than 10mg of T3 any more. I now buy T3 to make back up to 60mg. I refuse to take T4 anymore. the last consultant I saw said if I was 30 he would be happy to give me 60mg of T3 but because I am 70 he would only me 40mg. But that as been removed by the ccg. Best of luck in your area


(Video) Low Thyroid Lab Confusion With TSH, T3, T4, Hypothyroid and Hyperthyroid

grahamgraham in reply to Nigel

Many thanks for your reply NIgel. It seems as if it is a constant battle which sometimes you win and sometimes you lose. I hope your ccg will reconsider their position in the future. I will do my best in this area and then hope it lasts!! Graham


I am posting from my own experience, I was never ok on Levo and fought to get onto T3 after which I felt so much better- as though a cloud had lifted from me after 10+ years. When a couple of years ago the local CCG decided I shouldn't have T3 I amassed all the evidence I could- thanks to this site, contacted my MP, had a major row with a GP who knew better even though she did not understand the evidence. Long story short a wonderful endocrinologist took control and I am now getting it prescribed. I appreciate that it is very expensive- and I wonder on occasion whether the NHS supply is tampered with (this is a problem with the supply chain common to many drugs and T3 is very expensive in the UK), my main gripe is that I believe that the government should be challenging the hyper price of T3 which can be obtained across Europe for pennies. It is a scandal!

I am hoping to retire at some point and move away but I feel that I am under a cloud in terms of whether I will be able to if the CCG refuses me treatment. Also my Endo is planning to retire soon- some of his colleagues have been far from helpful over the years.

A big shout out to this site for their help, support, expertise and guidance.

Good luck Graham- stick to your guns.

grahamgraham in reply to Bolton70

Hi. I am so glad you have been able to receive the medication you need and I agree that pricing is an underlying issue which is often denied and therefore hard to fight. I will do my best as you have proved it is possible to have a successful outcome. Many thanks for your support. Graham

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