ALSO: I've been tying myself in knots over the equivalence charts between NDT and T3 & T4. This short paragraph from the Thyroiduk,gov website sums up my confusion nicely:
NDT comes in grains. Generally, 1 grain is 60mg and contains 38mcg of T4 and 9mcg of T3. Some brands have 65mcg. Equivalence charts show that 1 grain of NDT has the approximate equivalence of taking 100mcg of levothyroxine.
I've been working under the assumption that 100mcg of Levothyroxine contains 100mcg of T4. But the only way I can interpret this paragraph is that each Levo tablet must contain just 38% of T4. Similar rules must apply to Liothyronine and T3 (in this case, the ratio appears to be 36%).
I will write to ThyroidUK, but as I'm seeing my endo tomorrow, I would be grateful if someone here could advise me.
Many thanks
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PillJunkie
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Thank you for the link, it's very interesting to see the various excipients.
Yes, it would have been sensible for me to examine the PIL before writing my post - apologies for that. It doesn't tell me what proportion of the dose is made up with excipients, but I think it may be safe to assume it is 62%. Rather a lot, but it's the only logical answer to my question.
Surely - all this is saying is that 1 grain NDT is roughly equivalent to 100 mcg T4 - as to it's ability to relieve symptoms of hypothyroidism.
The issue is of course - based on the assumption that the patient can utilise and convert the T4 content - whether it be the T4 in Levothyroxine or the T4 in NDT. and that there are no other underlying complications - which presumably there are - and why you need to see an endocrinologist.
A fully functioning working thyroid would be supporting you on a daily basis with trace elements of T1. T2 and calcitonin + a measure of T3 at around 10 mcg + a measure of T4 at around 100mcg -
with T3 known to be the active hormone and around 4 times more powerful than T4 which is pretty much inert until converted as and when by the body into T3.
I believe the paragraph in question says that 1 grain of NDT is equivalent to 38mcg of T4 and equivalent to 100mcg of Levothyroxine. The difference, I can only assume, is that excipients take up 62% of a Levo tablet.
A typical levothyroxine tablet weight something like 100 milligrams.
But the dose is just 100 micrograms.
That means, that only around one thousandth of a levothyroxine tablet is the Active Pharmaceutical Ingredient (API). To illustrate this, something like one crystal of sugar.
There are something like 100 crystals in the attached photo. Just one of them would be the entire levothyroxine content in a tablet.
A 100 microgram levothyroxine tablet contains 100 micrograms of levothyroxine.
(Or very close. The MHRA imposed limits are between 90 and 105 micrograms but I think they'd be concerned if real tablets were at either end of that range.)
And a 20 microgram liothyronine tablet contains 20 micrograms of liothyronine.
NDT comes in grains. Generally, 1 grain is 60mg and contains 38mcg of T4 and 9mcg of T3. Some brands have 65mcg. Equivalence charts show that 1 grain of NDT has the approximate equivalence of taking 100mcg of levothyroxine. Ensure that you discuss dosages with your clinician.
[There is a typo in there - on the Thyroid UK page.
One grain of desiccated thyroid contains either 60 or 65 milligrams of Thyroid USP.]
One grain of desiccated thyroid will contain 38mcg of T4 and 9mcg of T3 (or close to that).
It is impossible to make a reliable conversion formula between desiccated thyroid and levothyroxine.
Start by assuming (as many do) that T3 has four times the effect of T4 - per microgram.
Then do the arithmetic:
38 T4 plus four times 9 T3 = 74.
That would make one grain approximately equivalent to 74 micrograms of levothyroxine. Which seems more reasonable but I still wouldn't place a bet on the results.
The equivalence charts over-estimate the equivalence.
In one person, one grain of desiccated thyroid is likely to be between, say, 60 and 90 micrograms of levothyroxine. But there are lots of factors hidden in that which could push the number up or down a bit. Things like absorption. And issues with converting T4 into T3.
Thanks helvella; I must admit that you lost me a couple of times there!
Can I rewind? I went to a highly respected endo when I was on 3.5 grains of NDT and T3 & T4 near the bottom of their ranges. He took me off the NDT and replaced it with 100mcg Levothyroxine and 20mcg of Liothyronine. My T3 & T4 dropped further.
I am trying to understand:
1. How much T3 & T4 I was obtaining from the NDT
2. How much I am now obtaining from the Levo & Lio
I know that my endo knows his job, but from the various figures I've studied it appears that I am either on fractionally less, or considerably less, T3 & T4 than when I was on NDT. What is your view?
If you were in my situation, what would you be looking to get out of your next meeting with your endo?
Sorry if that is an unfair question; I'm not trying to put you on the spot, it's just that I need to know my objective and to have the knowledge to support it.
For me that equivalence 1 grain to 100 mcg levo seemed about right, except NDT (1.25 grains) resolved my symptoms but 125mcg levo did not and anything higher made me very agitated. 125mcg was the best it ever got and it was still utter pants.
That's what I originally thought the calculations were, but subsequent posts appeared to suggest otherwise. Perhaps I misunderstood. I don't want to underplay my hand with the endo.
Hi PillJunkie - I used to be on 100 mcg levothyroxine and felt terrible. I started very gradually on Armour NDT and I'm now up to between 2.75 and 3 grains per day. I'm a bit shakey on 3 grains but all my other symptoms feel much better on that dose. My T3 levels are much better on NDT. I can't do all the maths with percentages per grain etc, I've been guided by my doctor, by how I feel and by thyroid blood test levels. Probably everyone is different in how they respond to Levo or NDT.
I was on 3.5 grains of NDT and my T3 and T4 barely moved. My endo switched me to 100mcg Levo and 20mcg of synthetic T3 and my T3 and T4 plunged! I'm now up to 150mcg Levo and 30mcg T3. I only started this yesterday. My endo converts NDT (per grain) @ 38mcg Levo and 9mcg T3 - no other adjustments. Using his calculations, I'm now on a little less T3 and a little moreT4 than when I was on 3.5 grains of NDT, and feeling rubbish. I wanted to go up to 40mcg of T3, but he wouldn't have it.
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Results
first time post (test results)
NDT dosage replacing Thyroxine
thyroid test results
