Thyroid UK
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Added T3 making T4 redundant?

I was wondering why I feel worse every time I add T3 to T4...

Can the newly-added T3 make T4 convert less to FT3 when the body senses that it can get active T3 directly, "the easy way". If it is not that, there is no logic why I feel worse on T4/T3 combo than on T4 alone...

21 Replies


My understanding is that adding T3 improves conversion of T4 to T3 and that is why some endos reduce T4 dose when T3 is added. FT4 level often drops when T3 is added and I think it is because the body doesn't need to hang on to high levels of T4 for conversion and because the T4 is used during the improved conversion.

You could feel worse on T4+T3 if your FT3 goes too high or perhaps because T3 doesn't suit. Not everyone does well on NDT or T3.


I feel worse in the sense that my hypothyroid symptoms increase although FT3 is high. My heart rate is slow, and all of my hypo symptoms deepen. I really don't know why.



Hypothyroidism encourages poor absorption & intestinal problems, metabolic problems in the liver where most thyroid hormones are converted and autoimmune antibodies that attack thyroid enzymes, receptors, or hormone precursors.

Although your previous TFT's where good, these are only representative of what is within the blood stream and can be be misleading when considering actual cellular activity but are a useful tool when completely lost with how we are feeling.

But what of the adrenals and immune system ? ? .. Even nutritional deficiencies can effect thyroid activity…. The pituitary gland can be a little more sensitive to the T3 we medicate ? ? ... and what about (as I suspect in my own case) a down regulation of the pituitary- thyroid connection after years of not being diagnosed and meaning I will only function best with a low TSH.

When biological stress is ongoing, your adrenals will eventually produce less cortisol after dropping from high and these low levels can cause chronic anxiety as thyroid hormones can pool high in your blood.

Many reduce their T4 on an introduction to T3 or maybe the T3 acceptance in your body is slower than the amount you have introduced......are you multi dosing ? ? ....

Fundamentals would include absolute optimal nutrients, iron, adequate cortisol levels and low thyroid antibody count...

Some members find taking pulse and temps to be useful tools to see progress.

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Radd, I am not multi dosing. I take everything at once upon waking up.

I found out I felt even worse when multi dosing.

I am taking pulse, keeping a log, I have one very potent hypothyroid symptom I can go by without even keeping a log (skipped heart beats), nevertheless I am keeping a log, and I am not getting any better at all.

Adding T3 has always made me more ill.

However T4 only does not help.



My heart was all over the place for over four years, banging hard and skipping beats on mono-therapy T4 too but I was lucky in that my body accepted T3 in very small amounts and when built up slowly.

However, any thyroid hormone//meds may not be accepted if other fundamentals aren't in place. However, the imbalance of these other fundamentals is often the prolonged low amounts of required thyroid hormone in the first instance.....

Iron is paramount as is Vit B12, folate and Vit D.

You may need to multi dose three or four times a day in minute quantities in order that your body may accept... and addressing all other issues will help the over all picture. Have you considered sex hormones that may be compromised through cortisol issues ? ? .. . All hormones depend on others and any deficiencies will show further up the line.

Good luck.


My sex hormones are fine. I have regular periods with 14 -day follicular and lutheal phase. I had a full panel and sex hormones were fine.

My iron is 23 (6-26), iron saturation is 43%, TIBC 51 (43-86). My ferritin is low but it was explained to me I cannot take iron since it will only build up in blood. I have a MTHFR mutation. My B12, folate, D are good, I am supplementing.

My heart skipping beats is my main guidance that I am hypothyroid.

I experience skipping beats 24/7...



I too have big MTHFR issues.

The ramifications can be huge, meaning we have difficulty in breaking down folate vitamins (of which folic acid is the precursor to), causing high homocysteine (increasing risk of coronary heart disease & BP conditions - jumpy heart ? ? ....) and effecting thyroid function.

Elevated homocysteine will be poorly converted to glutathione (chief antioxidant and detoxifier) making us more susceptible to stress and toxin buildup. ( I had all amalgam removed in 2015.) It will also convert less to methionine increasing the risk of arteriosclerosis, fatty liver degenerative disease, increasing free radical damage… and produce less SAM-e which can increase depression.

Are you supplementing methylfolate and methylcobalamin ? ? ....

Also another common mutation is on the CBS gene. This converts homocysteine into cystathionine, and removes sulfur containing amino acids. When impaired it can cause an excess of sulphur and low serotonin//dopamine, and chemical sensitivity.


"Are you supplementing methylfolate and methylcobalamin ? ? ...."

Yes, I am.

I haven't tested CBS gene.

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Have you tried taking the low doses of T3 yet ? You are taking about 20mcg T3 in one go i think plus your T4.

why don't you try a simple thing like a tiny amount of T3 to start with = 1/8th tablet. See how this goes in the morning and then 4h's later take another 1/8th. Then 4h's later another 1/8th. IF you are feeling any positive signs later in the day hold off the T3 and see how long it continues for.

You need to experiment a little more than what you are doing. You seem to have done a lot of research and know your body well, but you are still ill.


Marsaday, I have built up T3 to 20 mcg in 25 days in tiny amounts, and I feel no difference at all. At the beginning I was taking 3-4 mcg at a time - 1 in the morning, 1 at noon, and 1 in the evening - no difference, still very ill. When it was clear to me that taking T3 in this way makes no difference to how I feel, I started taking 10 mcg in the morning in one go and 6 mcg in the afternoon - still no difference. Then I left only the morning dose and build up to 20 now.

I know my body very well, indeed, but everything I have tried so far thyroid-wise has failed. It seems that there is no right hormone or hormone combination for me.

I have never felt any positive sings from taking T3, ever. Not a single positive sign! I still have thousands of skipped beats every day, and bone and muscle pain, and fatigue, and everything.

People report feeling burst of energy after taking T3 or at least feeling a bit better for an hour or so after a T3 dose. I feel practically nothing, as if I am drinking water instead of T3..

Oh, and although I really know my body very well, I am keeping a thorough log with signs and symptoms for the respective day and with listed T4 and T3 doses taken. And I cannot improve, I even get worse on T3/T4 combo, but my bloods say otherwise: FT3 is 6.85 and I am feeling the same way I was feeling when FT3 was 5... In case I forget I have my log to remind me. FT4 level has stayed the same -19.25 vs 19.33.

I think I might have a pooling problem...


Yes it is pooling. As my endo told me years ago "the T3 is being spat back out from the cells and so staying in the blood" (he didn't though have the answer why, but i knew it was adrenals). This is why the Ft3 level is nice and high.

Looks good on paper, but the T3 is not doing what it should be doing and going where it needs to. Your tissue levels of T3 must be low, hence you feel so ill. We can't measure tissue levels though.

So if you are pooling it has to be cortisol related (other aspects seem to be ok according to your replies). What have you done to help adrenal performance? For me things changed when i started low dose progesterone. I take 6mg per day and this has helped improve cortisol balance. I can only guess what is happening because i don't have blood tests to help navigate.

So a few things could be happening:

getting more cortisol

making less cortisol

DHEA production has increased. This spares cortisol so it goes up or it helps create a better cortisol / DHEA balance. They want to be around a ratio of 4:1. When we move away from this ratio our bodies get out of balance.

Have you looked into pregnenalone usage in LOW doses coupled with low DHEA usage. Taken together they work much more synergistically. You also don't get as many negative side affects. But you must take the lower does. 10mcg pregnenalone and 5mcg DHEA.

Your metabolism is out of balance and thyroid is part of the solution.


No, we don't have these drugs here, so I cannot buy them. I cannot even get a prescription. Doctors don't treat adrenals. I haven't done any tests.

However, I was doing OK only six months ago on T4 alone. Can adrenals become so ill so quickly?

I will stop using T3, it does not help me at all, and I think it makes T4 convert less to FT3. I was feeling better on T4 alone. Maybe I will have to put up with feeling ill for good.


Levo is T4 alone. Try to forget numbers and concentrate on YOU and how you feel.


Are you gluten free?


Yes. And my antibodies go higher even though I am gluten-free....


You may have other food sensitivities. Might be worth a spell on the PAI protocol to see if you can identify any other problem foods:


I have done that and don't eat some foods.


Stress is another major factor, does this affect you? Important to make time for relaxation such as meditation, yoga, long baths, listening to music, walks in nature etc.


I am not particularly stressed. It is not that.

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It is a no brainer to stop the t3 and focus on t4 only. If you feel better then it is positive. Now you have to look into other metabolic aspects to try tweak health.

Your issue is not t3 production but the absorption of the t3. You can buy lots of stuff from the USA or U.K. If you have the money. Or you could look into Chinese herbal support for adrenals and these may be sold in Bulgaria


I never feel completely well on T4 only as well. However I feel better than on T4/T3 combo. Currently I am under antibody attack, it may be that that I am pooling. I really don't know...

The first time I took 12.5 T3 two months ago I went to give bloods 2-3 hours after taking the T3. As an experiment. And my level was 21 something which is very high, most people's reaches 14-15 after a T3 dose...

I might have some sort of thyroid hormone resistance per se.


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