Thyroid UK
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Where has my hypothyroidism gone???

Hi, I have just obtained results of my latest blood tests from the doc's. And apparently I have miraculously disappearing hypothyroidism. My only theory is this is related to me ceasing anti-convulsant medication (Carbamazepine) while in hospital, but I'd like to run it past you all in case I might be missing something.

I was first spotted as having subclinical hypothyroidism in early March this year. I had a 'classic' TSH of 5.2 and free T4 of 10. Fast forward to early June, 3 months later, and I still have TSH of 4.8 and free T4 of 13. Slightly 'improved', I think?, but not that dissimilar. Three DAYS later I suddenly only have TSH of 1.9 and free T4 of 11. The free T4 looks much the same, but what has happened to my TSH? How can it possibly have dropped so drastically in 3 days when 3 months had seen little change?

I haven't yet spoken to my doc about this, but the receptionist said it was "normal" and I know he will consider that there is now not a problem.

During those 3 days I was in hospital with severe low sodium and they took me off Carbamazepine because it can cause low sodium, so they wanted to be sure it wasn't the true culprit and, of course, to try and get my sodium back up without interference. Carbamazepine is known to cause "dysfunctional thyroid test results" so I'm thinking this may mean my subclinical hypothyroidism has been entirely caused by my Carbamazepine usage. Or at least has obviously been aggravated by it.

Is this a safe assumption, or is it possible something else may have been at play? In hospital I only had antibiotics and saline - nothing that would affect thyroid, as far as I am aware.

Am I right, that this is a Carbamazepine related effect, or am I missing something here? Is this now truly a healthy thyroid result?

Any insights most gratefully received. I'm blundering around like a headless chicken here and I don't want my doc to just dismiss this result if something else may be afoot. Many thanks!

18 Replies

Hah! Well done, Chancery. It sounds like one of those detective mysteries which is a double bluff, and the most obvious person did do it after all.

Is it a known side effect? Because I know you too well to think that you haven't gone through every single medication you've ever taken looking for raised TSH as a possible side effect.


OK, I know you've already read this but...


I hadn't actually seen that one, Asp, no, so thanks for that. I have seen similar studies though and they all seem equally vague: "It sends TSH up but it's not real" is the general gist. There seems to be a feeling that it messes with thyroid test results but doesn't actually DO anything to the thyroid, although this one seems to actually come out and say Carbamazepine can "precipitate" hypothyroidism, which kind of says it WILL produce the illness. They all seem to be hedging their bets. Not helpful....


I think you could become one of those single study reports. Hey! Anonymous fame! An oxymoronic triumph.

Good news though, if the next test holds up. As Emily Bronte used to say: "Poisoning doctors".


Ah, knowing Emily Bronte, she was actually recommending poisoning doctors, in her sly but blunt way (can you be sly and blunt at the same time?) But yes, if the thyroid tests do prove to improve (and now I'm rhyming) I will consider it a marvel of modern science, or at least the bleeding obvious result of giving up the worst drugs known to man, next to chemotherapy.


Carbamazi wotsit can cause neutropenia too. Emily Bronte just sent me a spirit message to let you know that. Also it's available as a research document.


Never seen that one either. You are either a more dedicated Pubmedder than me, or you are secretly a doctor of international renown, you sly dog. But tell Emily that I am only too well aware of Carbamaziwotsit's powers to do evil in the body. I am one of the lucky souls who had neutropenia before I went on Carbamazepine. Not that my doc bothered to check, or bothered to do the three-weekly tests that the lab told him to do in December last year. I have to chase him to check it every three months or so, and it's always got worse.

At last count, my white cells were marked as dangerously low, as well as my neutrophils, and every single one of the 'phils' had gone down - my doc neither noticed nor commented.

I'm afraid the infections have started too, with my recent hospital stay with cystitis that just wouldn't quit (first time I've EVER taken antibiotics for cystitis) and a toothache that I've just been given antibiotics for because although we can't really see anything on the X ray, it very definitely seems to be infected. I am now terrified of public toilets and badly cooked chicken! I've become an obsessional hand-washer.

But that 'only when it falls below 500/m3', or whatever it is in your paper, is most unhelpful - what the hell does that mean? My test ranges look nothing like that!


Were the blood draws at same time of day?

Were the tests all processed in the same lab?

There are, as you well know, no safe assumptions! :-)


Except the assumption that there are no safe assumptions!


No, Rod, they weren't. First test with high TSH was done at mid - late afternoon, then the second one (almost as high TSH, but not quite) in the hospital at 8 in the morning then the one 3 days later (with low TSH), at the docs, at 2.15 in the afternoon.

I should just point out that the two high TSH tests, although they seem to be far apart in time aren't really because when I had the first one done I was in the habit of rising between 1 - 2 pm, so really that was morning for me. SO really they are both morning tests, while the most recent one is an afternoon test, since my time of rising has changed quite drastically.

Sorry, that's complicated. Hope it all makes sense!

They were all processed at the same lab, as far as I know, although the hospital one MAY have been done in situ.


What is the range for that FT4? 11 sounds as if it might be very low. TSH is meaningless by itself. It's the FT4 and FT3 that really say if you're hypo or not. Do you have antibodies? I can't remember. As Rod asked, were all these blood tests done at the same time of day? Had you eaten before any of them?


Hi GG. The range for the FT4 is 9 - 21 pmol/L, so it's at the low end of the spectrum at 11, yes. It was the first time too, at 10, but the TSH then was substantially higher at 5.2. It's that sudden TSH drop that mystifies me. I had exactly 3.5 antibodies when they tested me, out of a range of 0 - 50, so that's a big no for antibodies!

I had eaten before the first test, with high TSH, and before the last one, with low TSH, but not before the hospital one (also high TSH), so that's not very consistent either! The whole thing's baffling...


But you must know that the TSH is irrelevant. Your FT4 is low, so your FT3 is probably low, too. You cannot say you are no longer hypo without testing your FT3, because it's low T3 that makes you hypo, not high TSH. You can still be hypo with low TSH if your FT3 is low. Surely you know that.


Nope, GG, I didn't know that, but I do now! I'm afraid I find all the various 'ratios' of the thyroid hormones difficult to deal with. The drugs I'm on make it difficult to retain information and I think the thyroid combinations just defeat what little retention I have!

Given these new figures, I can't imagine I stand a snowball's chance in hell of getting my doc to retest FT3, so I guess I'm stuck with this. Hopefully, it's a good sign though and this may improve as I leave more Carbamazepine behind. If it doesn't, it looks like I'm going to be another thyroid statistic, because I just don't have the energy to work this out.


How are you. Do you feel better now you TSH is reduced or the same. If you are better you will feel better.


Hard to tell, Mandy. I've got so much going on, with bacterial infections from neutropenia and I'm on drugs (with side effects), of course, so they confuse the issue too. I am more exhausted recently, for some inexplicable reason. I've put it down to the drugs, but I should be used to them after a year. I am messing about with the dose though so maybe it's that, but who knows?

If forced to answer the 'do you feel better?' question I'd have to say not particularly, no.


Central Hypothyroidism - not Primary could be a consideration....


Hi Marz. I don't think central is likely because I've never has any pituitary damage, or any indication that it might be malfunctioning. I suppose it is just possible that an opposite Carbamazepine effect has occurred, as in my day and a half of missing Carbamazepine has actually caused an artificially LOW TSH to be recorded and in actual fact the higher earlier tests are the more accurate ones.

Either way, I think I'm just going to have to sit it out and wait another three months or so till, hopefully, I have got rid of this Carbamazepine and then I can test it again and see what's actually happening.

Honestly, it's a bit of a pain because I am awfully exhausted right now - terrible trouble getting going in the mornings, and the 'waking up with the horrible black anxiety moods' has returned. I'm fighting it manfully, but I wish I understood what was going on....


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