Confused by NDT to Levo Conversion

[flobaby]

I see people saying 1 grain of NDT = 100 mcg of levo. One grain of NDT contains

38mcg of T4

9mcg of T3

Multiply 9x4 (the usual conversion for T3 to levo) and you get this: 38+36=74mcg. Where are the extra 26mcg coming from?

[radd]

flobaby,

38mcg T4 + 9 mcg T3 is equivalent to 74mcg T4 using 4:1 ratio manuf. use.

They are not saying 38+9 adds up to 100mcg. They are saying the bioactive equivalent of 38mcg T4 + 9mcg T3 is equal to the same delivery, action & effect of medicating 100mcg T4.

[lucylocks]

Hi

I always thought the T3 was multiplied by 3.

Therefore 9 mcg. x 3 = 27mcg. but have just seen radd's reply, so whichever way it is multiplied one grain NDT is the bioactive equivalent to 100mcg. T4

[flobaby]

I don't understand the chasm in bioequivalence. I was taking 75Levo+15T3. Using the conservative 4x, that equates to 135mcg total.

If I used the 1grain=100Levo, my conversion would amount to around 1.25 grains.

However, if I use apples to apples (T4:T4 and T3:T3), then it's just under 2 grains. That's a huge difference.

The chasm is even wider if using a less conservative multiplier.

[Glynisrose]

You should not directly swap anyway if you want to start NDT then you should start low and build up over a few weeks. DON'T do a direct swap no matter what anyone says to you. I'm sure doctors will say to do a direct swap so they can say they ruled out NDT never mind how the patient feels.

[flobaby in reply to Glynisrose]

That goes against what I've read in that if you're already on T4/T3, you can do the direct swap. Starting low (from what I've read) is for those who've never had T3, since that can affect folks dramatically.

[humanbean]

Based on my personal experience I think T3 is 3 times as potent as T4.

So 1 grain of NDT which contains 38mcg of T4 and 9mcg of T3 would be equivalent to

38 + (3 x 9) = 38 + 27 = 65mcg T4.

Whatever the rights and wrongs of the various calculations people go through to decide what is equivalent to what, one thing I think most patients would agree on is that doctors massively over-value anything with T3 in it, whether it is NDT or T3 alone.

[flobaby]

Humanbean, I believe you are correct! Yesterday I ended up reading a ton of forum posts on inspire.com for Thyroid cancer survivors and the main posters there say the 100mcg conversion is totally wrong! That it's designed to protect those who've never had T3, to make sure they don't get into trouble. Their experience says 1 grain is equivalent to a 60-70 swap, which makes perfect sense.

I was on NDT for a short period of time before I'd ever tried levo, so I have some data points to work with, as well. I'm certain that if I was on 1.25grains NDT, I'd be in bad shape, that 2grains is the correct amount at this time.