Thyroid UK
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Adding a little T4

About to start trial T3 only at a low dose of 2.5mg/day or 5mg every other day.

I suffer severe inner tension, which interferes with heart rate at times. To ease direct impact of T3, wondered if I'd hamper it's uptake by taking a small amount of T4 with it - say 1/4 of 25mg tablet?

Could then increase T3 as I can.

Whats your thoughts?

My serum T4 is middle of ref. range, my T3 is low end & appears I'm low T3 at tissue level.



5 Replies

Personally, I wouldn't add T4 as I found that it was levo which caused me palps/tachycardia. When I added T3 it calmed my whole system down and I switched over to T3 only.

This is a link re T3 which is self-explanatory and hope it is helpful. This is an extract

Dr. Lowe: I respectfully disagree with your endocrinologist. Studies indicate that T4 is of no use to anyone except, figuratively, as a storage unit for the metabolically-active thyroid hormones T3, T2, and possibly T1. When T4 ends its long ride through the circulating blood, it enters cells. There, enzymes convert it to T3, and, after a while, other enzymes convert T3 to T2. The T2 becomes T1, and eventually T1 becomes T0 (T-zero). T0 is just the amino acid backbone(called "tyrosine") with no iodine atoms attached. Because it has no attached iodine atoms, T0 is no more a hormone than is T4.

Rather than being a hormone, T4 is a “prohormone.” That means that enzymes have to convert T4 to T3 before T4 benefits us. T4 is no more a hormone than beans in an unopened can are a food. For all practical purposes, canned beans become food only when a can opener frees them so you can eat them. Hence, T4, like canned beans, only potentially benefits us, but actually does so only after being freed from its metabolically unusable form.

I do hope you benefit from T3 and can increase it till you are free of symptoms.


Shaws, Realy appreciate your time & info. Understand position T4. Just thought a little might lessen the impact of T3. Resting HR running 72/90.

Many thanks



Hi If complicated you should always see an endo for advice to GP re prescribing.I have always been on armour as cannot take T4 on its own. Since T3 came out, I have low Free T3, then I have had 20mcg T3 too. However I do always have Free T3 tested + TSH and T4. I also started T3 very very slowly., after a blood test, 5mcg first few days and took 2 weeks to get to 20mcg. which I split into 2, 12 hours apart. I have never had any problems with it a I do with a lot of drugs. I have just about every cardiac condition going, very complicated but my arteries are good ( better the other way round!) and 4 cardiac arrests, 2 MI`s etc etc. It is safe if you are very cautious and see an endo who looks after the whole body and understands the complications.

Best wishes,



Thanks Jackie,

So, you take Armour and T3 now? How Much Armour?

Have you considered dropping the Armour &, if not, why? If I mentioned T4 to Dr. he would jump at the thought.

He's not keen to prescribe T3 only, but agrees with low T3, it's needed. What affect on the HR did you experience when started T3 please?

With kind regards,



Hi Penny, first of all I do see a very good endo who treats the whole person, which does make a difference.When I started thyroid treatment , a long time ago. TSH, T4 and Free T3 was always tested for a proper diagnosis , now it is all about costs. I do still have these vital tests but I have to pay as the NHS here will never do them. I tried ,initially, different makes of thyroxine it made my AF ( atria Fibrillation ) very bad. and i could not take it., That was all I had . wrong with my heart then. My FT3 was very low, bottom of range. I need it at the top of range, but must be in range. I saw a thyroid doctor, very good but he only considered thyroid, as they do, big mistake. then I took 7 grains but tests till in range. TSH even lower than it was.before. My cardio, ( a new one) insisted with heart essential to be under an endo. Still no T3 available. She with my permission cut the armour down to 4. That was Ok but still lots of symptoms of low T3. Then T3 came out. Now my FT3 very near the top of range, TSH cannot be measured but always been very low. I now take 2 and half grains armour + 20mcg T3. She is exceptionally good. I know she thinks T4 and T3 the ideal but a lot of patients cannot tolerate that. next choice is armour etc, if not good she just uses T3 but that is the last resort. i ,like a lot of people need FT3 top of range and T4 top third of range. Starting T3 as I described I have never had any problems with taking T3 as well. In fact much better on it and not stable. before i went on T3 ,I did have 4 cardiac arrests, I have VT`s a major electrical problem and 2 MI`s, arteries are good. All the cardios I have seen in recent years say that as long a I see a good cardio and only have as much treatment to keep my thyroid sable with lots of tests ( I have them 6 weekly) that is fine. I do and have seen some of the top cardios I have autoimmune hypo. I hope that helps you. I really think slowly is the key as very strong drug Endo also discovered pancreatic enzymes a problem with drug absorption etc, that is sorted now.

I hope that helps, get back to me if I can help further.

Best wishes,



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