switching from Levo to NDT

[RoseStar]

hi,

I’ve been prescribed NDT and have been told to start very low and slow as I’m sensitive to medication. We are starting to think about trying for a baby but I’m worried about my levels being too low and all my underactive symptoms coming back with the switch. Can anyone share their experience of switching with me and tell me what you did please?

[Jazzw]

I may not manage to come back to reply again until much later tomorrow but didn’t want to leave you hanging overnight.

How much levothyroxine are you currently on? I assume you’re still taking some? If it’s a decent-ish amount you may want to swap out some Levo for NDT and take both in the short term, slowly phasing out the levothyroxine and increasing the NDT over a number of weeks but it’s hard to advise without a few more details.

How much NDT have you been prescribed?

[RoseStar in reply to Jazzw]

thanks I appreciate that. I’m on 125mcg of levo (blood tests of my levels reflecting that dose from a month ago). I actually feel like I could do with a rise as the aches, fatigue and dryness are slowly creeping back in! I have been prescribed 1 grain to start with

Latest results on 125

[Jazzw in reply to RoseStar]

Ooh, ok.

Well, one grain of NDT is very sort of roughly (and yes, that’s a lot of “ish” words 🙂) equivalent to between 75 and 100mcg levothyroxine. It’s not an exact science because of the T3 element of NDT.

So one grain probably isn’t going to be enough in the longer term.

But Levothyroxine has a fairly long half life—give or take 7 days—which means it takes a while to wash out of your system and that might be why you’ve been prescribed one grain, because you’ll still have a good amount of levothyroxine on board for at least the first week or two during the switch.

There’s a few ways to do this. If you weren’t sensitive to medication changes I’d suggest a straight swap from 125mcg to 1 grain of Armour. Ultimately you’d need more Armour but it would take a while.

But you are sensitive, so I think what maybe I’d try is cutting my levothyroxine to 75mcg daily and adding half a grain of Armour. After a couple of weeks (if it’s going ok), add another quarter grain and drop to 50mcg levothyroxine.

Or… if that sounds a bit too scary, start really low and slow. Start with a quarter grain and cut your levothyroxine to 100mcg daily. After 2 weeks (if it’s going ok) up the Armour to half a grain and cut levothyroxine to 75mcg. After another 2 weeks, try three quarters with 50mcg etc, then 2 weeks later, 1 grain with 25mcg. At some point you’ll probably want to stop the 25mcg levothyroxine so that you can increase Armour instead.

[FallingInReverse]

If you are TTC, and therefore there’s a possibility you get pregnant, it is essential that you don’t let your FT4 drop.

From conception through mid-gestation (20 weeks) the baby does not make their own thyroid hormone and relies entirely on you.

The entire 20 weeks is important to keep your ft4 up.

But to put a finer point on it, week 5 is a particularly critical time for brain development where enough maternal t4 is needed.

Week 5 can easily be before any pregnancy test or missed period will tell you, and by the time one confirms pregnancy week 5 is upon you.

Please take care to test your t4 frequently if you choose to mix up your thyroid hormone replacement.