Thyroid UK
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Are T3 and T4 made from animal by-products or laboratory synthesis?

I had never heard of T3, T4 or NDT until I joined this site.

I have been taking Levothyroxine (T4) for 30 years, and also took Liothyronine (T3) for a short while.

As I am now due to have a thyroidectomy, I have been investigating what changes may happen to my body and my treatment options

Natural Desicated Thyroid (NDT) seems to be loved and hated in equal measure by different patients and practitioners, but as it is made from the animal by-products of the food industry (pig or cow) I will not use it as I am vegetarian.

My question is - are T3 and T4 made from animal by-products or laboratory synthesis?

I don't seem to be able to find the answer to this on the net.


2 Replies

Levothyroxine (T4) and Liothyronine (T3) are manufactured in pharmaceutical plants using the usual tools of industrial chemical synthesis.

What I cannot tell you is where their raw materials come from - particularly the tyrosine (which I assume is usually an ingredient). Probably fermentation.


t4 and t3 are both synthetically produced

many people are only well on NDT so they have no option but to accept that

usually because they are chemically allergic as is the case for my Husband

Daughter and granddaughters

So for them T4 or T3 give them horrendous joint pains wheras NDT does not


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