Thyroid UK
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Thybon T3 compared to Armour


Just wondering which could be stronger, Thybon is synthetic whilst Armour is "natural". My Endo said Thybon was 2.5 times the strength of T4. Armour is often quoted as 4 times the strength of T4 but I don't think it's that strong for me anyway (I'm guessing more in the range of 2.5-3.0 stronger)

Also is the T4 in Armour equivalent to T4 in Synthroid/Exltroxin? I recognise these are hard questions to answer but still trying to get my head around this.

Just to add I think I convert T4 to T3 reasonably well - even though I had a TT I went hyper on 2 grains. I'm very sensitive to the drugs and need a lowish dose. Also went hyper on 75mg T4 & 20mg Thybon (and also 125mg T4 only) so it's consistent. My iron and adrenals are fine.


The Hoggle

6 Replies

The Hoggles, the potency of T4 and T3 is the same whether tablets are synthetic or NDT. Interesting your endo says that T3 is 2.5 x more potent than Levothyroxine, many are still saying it is 5:1 which can leave patients undermedicated. I usually work on 3:1 as per this research

The NDT manufacturers say that 1 grain NDT is bioactively equivalent to 100mcg. That is the manufacturer's 'safe' estimate to avoid people overmedicating when switching from Levothyroxine. Members have said the equivalence feels nearer to 75mcg Levothyroxine.


What's interesting is that if t3 is 3x stronger then 1 grain would be closer to 65 t4 I think?


TheHoggle, the manufacturers ratio is just over 4:1 which means the 38mcg T4 + 9mcg T3 is equivalent to 75mcg T4 but they are suggesting the bioactive equivalence of the combined T4+T3 is 100mcg.

The equivalences are really only a starting guide and can be tweaked according to symptoms and bloods.


When you say you went 'hyper' on T4/T3 and on T4 only. Did you feel you were hyper or did the GP say you were due to your TSH result as sometimes that's what they believe.

1 grain of NDT is equal 'in effect' to 100mcg of levothyroxine. Due to it containing T3 so you would have taken the equivalent of 200mcg with 2 gr.

NDT contains all of the hormones our healthy thyroid gland would provide. Some of us are more sensitive to synthetic hormones and may not convert T4 to sufficient T3, the active hormone that's needed in our receptor cells. than 'natural' products.


No I felt hyper on both occasions my tsh on t4 only was 0.3 the previous week and then I could feel a surge of thyroid hormone and went hyper. On t3/t4 I didn't get a blood test just went hyper in two weeks. I had been on 125 t4 for six weeks previous didn't know at the time that it was too much


If you reduce your dose down gradually, till you get no hyper symptoms and feel well you will have reached the optimum dose.


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