Thyroid UK
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I have been on levothyroxine for around 5 years, and now have to change to natural thyroxine. What is the difference?

Low T4 diagnosed by Dr. Myhill, so been on levothyroxine for 5 years and got back to part time work after 8 years on incapacity benefit. She is now unable to write prescriptions after a GMC hearing, and the NHS GP practice will not prescribe it. So Dr. Myhill is sending natural thyroxine.

a) what is the difference, and how will it affect me?

b) are there any campaigns to get the NHS to test for T4 (they won't in Shropshire) and to recognise the need for this?

c)What support is Thyroid UK giving to Dr. Myhill?

I am fortunate in being able to pay a private specialist. What about those who can't?

thanks for allowing the rant!


2 Replies


The difference between desiccated thyroid and levothyroxine is significant.

The thyroid hormone content – levothyroxine is only T4; desiccated contains T4, T3 and uncertain amounts of other thyroid hormones.

Other constituents. Desiccated also contains everything else that is present in the porcine thyroid – whatever that is – probably largely thyroglobulin. But I have never found a proper analysis.

The other ingredients () vary between all the various brands of desiccated thyroid, though probably they are less variable than the many levothyroxine brands.

The dosage is very different. Desiccated comes in tablets in traditional grains. (Actually, some are 64 mg grains - very nearly the traditional value, while others are 60 mg ‘modernised’ grains.) One grain contains around 38 mcg of T4 and 9 mcg of T3. Using the conventional scaling of T3 being four times as potent as T4, that works out as 38 + ( 4 * 9) = 38 + 36 = 74 mcg T4 equivalent. This is only a way of estimating a suitable dose. You might find it seems somewhat more or less potent than this.

Although all the desiccated thyroid brands are very similar in declared potency, people do find that the various brands (e.g. Erfa, Nature-Throid, Armour) are not identical. It seems very sensible to keep to one brand. (Obviously it isn’t always possible in the early days when trying to find which is best for you.)

Another issue is that we see people talk of the half-life of T4 being around 7 days; that of T3 somewhat less than a day. This means that you might notice a bit of a roller coaster effect. That is one reason many people split their doses of desiccated thyroid (or other T3-containing medication).

And the difference it will make to you? Very difficult to guess. Some people prefer it; others prefer levothyroxine. And quite a few who have tried find some proportion of levothyroxine and desiccated works best for them.

As for testing for T4, the policy round here appears to be they will automatically test T4 if your TSH is significantly low or high. But if you are well in the reference range they will not.

As for campaigns and Thyroid UK support for Dr Myhill, you might care to look at their website. For example:

And your question was far too tame to qualify as a rant. Try harder next time. :-)

All the best



thanks for reply. Trouble is, I have too warped a sense of humour to rant properly. Must practice harder. (maybe if I didn't take the tablets I would be more bad tempered!)

thanks for link to campaign. Agree that patients need to get together and Rant Loudly. But the GMC is unlikely to listen! MPs?

Look forward to hearing/supporting any campaign that thyroid uk actions.



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