Informational Posts

What’s in NDT?

What's in NDT?
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Originally published on 25th March 2016
Last updated on 3rd December 2018

Natural desiccated thyroid medication, made from real porcine thyroid gland, is controversial. Very few thyroid patients are lucky enough to get it prescribed and some, like me, even have to go private to get it. 

But what is actually in NDT?

Please note: calcitonin isn’t well absorbed orally, so may not have much benefit in NDT medications, and T1 and T2 are made outside of the thyroid gland, so are unlikely to be contained in NDT medications. However, this is disputed based on different thyroid information sources. It is worth noting that NDT manufacturers only list the T3 and T4 content on medication bottles and not T1 or T2, so this may suggest lack of content of these hormones. [1]

Unlike synthetic T4-only medicine such as Levothyroxine, NDT is from a natural source (porcine thyroid gland)  and gives you all the hormones your own thyroid would be giving you. As mentioned above, it is disputed whether they contain all five of the below, but many sources state NDT does.

According to a few books, such as those by Stop The Thyroid Madness and Dr Barry Durrant-Peatfield (The Great Thyroid Scandal..)the below are roles played by each of those five components of NDT.

T1 (disputed to be contained in NDT)

(also called iodothyronamine) is produced by the breakdown of the metabolites of T3 and T4. This hormone is thought to play a role in keeping your thyroid function in check and is believed to influence the heart by placing downward pressure on body temperature and cardiac output.

T2 (disputed to be contained in NDT)

(also called diiodothyronine)likely plays a role in converting T4 to T3, which is very important. It has an impact on the metabolism, influencing the burning fat and body temperature, and is effective in increasing liver metabolism and that of the heart.  It can also suppress TSH, which in turn reduces the production of T3 and T4 by the thyroid.


(also called triiodothyronine) is referred to as the ‘active hormone’ and has the greatest effect on the body’s energy levels and overall health and well-being. This is because it is needed for growth, brain health and development, metabolism, energy, body temperature and brain development. It is more active that T4. T3 is said to be linked to mental health, ability to coping with stress and emotional stability.


(also called thyroxine) is the ‘storage hormone’. T4’s main function is to convert to both active T3 and reverse T3. T4 is involved in brain function.


Calcitonin is secreted from the thyroid when blood levels are high in Calcium. It acts to lower levels of Calcium in the blood and stops the release of more Calcium from your bones in to the blood. Because of this, it’s said to be effective in the prevention of osteoporosis.

Armour Thyroid Medication

Different brands of NDT also contain fillers in addition to the above. Stop The Thyroid Madness have compiled  a list of brands and which each contain. You can see this here.


It’s hard to know which brand is for you, so have a good research and maybe reach out to patients who have tried different brands to get a feel for them.

I would always suggest working with a doctor to make any change to your health regimen, like switching to NDT. You may need to try quite a few doctors until you find one who is willing prescribe this medication, though.

Have you tried NDT?

You can click on the hyperlinks in the above post to learn more and see references to information given, but more info can be found on these links:

See also: What is NDT?

[1] Tired Thyroid: From Hyper To Hypo To Healing – Breaking The TSH Rule by Barbara S. Lougheed

About Author

Rachel Hill is the highly ranked and multi-award winning thyroid patient advocate, writer, speaker and author behind The Invisible Hypothyroidism. Her thyroid advocacy work includes writing articles, authoring books, producing her Thyroid Family email newsletters and speaking on podcasts and at events about the many aspects thyroid disease affects and how to overcome these. She is well-recognised as a crucial and influential contributor to the thyroid community and has a large social media presence. Her bestselling books include "Be Your Own Thyroid Advocate" and "You, Me and Hypothyroidism".


  • Marelize
    November 29, 2020 at 6:51 am

    I’ve been on Eltroxin, prescribed by GP, for 16 years. Then I developed goiter and went to a homeopath. After seeing her a year, and being on the AIP with lifestyle changes, she transitioned me to Thyroid S. Oh, it was perfect!

    Then came along covid and lockdowns with shortage of Thyroid S… so I had to resolve to another NDT – using it for a month now, but typically, being a woman, nothing is straight forward. Started my perimemopausal symptoms in this month too… So I am confused as to what is caused by or due to what.

    But I will never go synthetic again.

  • Caz / InvisiblyMe
    December 4, 2018 at 5:14 pm

    I wish you were a few years ago when I was looking into treatment options and learning about thyroid issues, this is fantastic! It’s so important to arm yourself with knowledge. Stuff like NDT is not given much/any airtime by docs & specialists, and yet it’s key to know what it does & what’s in it, and what the T3, T4, calcitonin aspects are all about.x


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