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delicious thyroid! - helen-louise
baratron
baratron
delicious thyroid!
So now I'm terribly curious about whether or not I'm hypothyroid. I looked up the list of symptoms and could easily tick off more than half of them. I've been very tired all winter - unusually so even considering that I have SAD and chronic fatigue - and excessively cold, having to wear far more layers of clothes than other people just to stay warm enough. My skin has been very dry for months even before the itching started and despite all the cream and lip balm I use, and I've just noticed this week that my hair is falling out more than usual. I've also had concentration problems, total lack of motivation, weight gain and absolutely no sex drive - though these could be due to depression.

The problem is this: my TSH has gone from 3.81 uIU/mL in August to 5.16 uIU/mL now - but this is only just outside the range for "normal" in the UK, and the doctor's computer isn't bothered because it knows that carbamazepine can cause a falsely high TSH reading. So I did some research, and it seems that carbamazepine can mess up the results for just about all of the thyroid hormones (if the link breaks, it's pages 1253-1254). It can cause falsely high TSH and TBG (Thyroxine-Binding Globulin), and falsely low triiodothyronine (T3) in serum. And it can cause both falsely high and falsely low free thyroxine (T4) in serum! How do you actually confirm hypothyroidism if a medication you're on can mess up all the numbers?

There is also the question of how my TSH has gone crazy so quickly. Seems like a hell of an increase in 5 months. This article in Epilepsia. (1999), volume 40 issue 12, pages 1761-1766 suggests that carbamazepine "may induce subclinical hypothyroidism" (yes, in children treated for a long time, so not directly applicable), but goes on to say "This suggests a need for careful monitoring of TSH levels in children receiving CBZ" - implying that TSH is enough to monitor it, even though we know that TSH levels get screwed up by it. (Confused yet?)

This article in J. American Med. Soc. (1996), volume 275 issue 19 suggests a mechanism for how the serum levels of T3 and T4 get messed up - and goes on to say "Since currently available clinical tests will continue to show decreased free T4 concentrations in patients taking phenytoin or carbamazepine, clinicians should rely on serum TSH measurements to confirm the euthyroid status of these patients." Um... but we know that in patients on carbamazepine, checking the level of TSH no longer suffices as a test for hypothyroidism for patients suspected of it on clinical grounds" (if link breaks, it's page 122).

Endocrine Abstracts (2007), volume 14, page 318 is rather interesting - I'll reproduce the last paragraph in full. "In patients with no thyroid disorder, CBZ caused subtle hormonal changes of no clinical relevance, due to adaptive response. In hypothyroid patients with replacement therapy this adaptation is lacking, and CBZ may precipitate subclinical or overt hypothyroidism." Now... if hypothyroid patients can become even more hypothyroid on carbamazepine even though they're already on thyroxine, what could happen to someone who was borderline hypothyroid who went onto carbamazepine without thyroxine?

Alarmingly, I am currently reading an NHS document dated March 2007 which only recommends prescribing thyroxine once someone's TSH is over 10 mU/L. Before that, they only suggest a trial for "people who have symptoms compatible with hypothyroidism". Their reasoning is that "Each year, only a small percentage of people with subclinical hypothyroidism will become overtly hypothyroid. [...] People who are positive for antithyroid antibodies and those whose initial TSH concentration is greater than 10 mU/L are at greater risk of becoming hypothyroid. Some people return to having thyroid stimulating hormone level within the reference range." Also, "No evidence supports the benefit of routine early treatment with levothyroxine in non-pregnant patients with a serum TSH concentration above the reference range but less than 10 mU/L. Limited evidence indicates a risk of overtreatment, which may cause iatrogenic hyperthyroidism that could lead to osteopenia or atrial fibrillation." "These recommendations are based on a consensus guideline produced by the Association for Clinical Biochemistry, the British Thyroid Association, and the British Thyroid Foundation [BTA et al, 2006]. They are based on evidence from well conducted non-randomized clinical trials and expert opinion." Hmm.

The thing that annoys me in all this, though, is that there's a very clear link between thyroid dysfunction and bipolar disorder - to the point where some people have become asymptomatic with regard to mood swings once they are on thyroxine. If I do have a messed up thyroid gland then I probably won't get my bipolar symptoms sorted out until the thyroid is sorted out. And I'd much rather take a low dose thyroxine + low dose of mood stabiliser than the increasing number of psychiatric drugs I seem to be on at the moment.

This is just here for my reference: Epilepsia (1995), volume 36 issue 8, pages 810-816. "We conclude that normal thyroid function can be restored in patients with epilepsy by replacing CBZ with OCBZ." For some reason oxcarbazepine isn't licensed in the UK for bipolar disorder, even though it's just carbamazepine with the C=C double bond between carbons 10 & 11 replaced with an epoxide group. It's the metabolised form of carbamazepine.

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Current Mood: confused confused? yeah, me too.

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Comments
tirnoney From: tirnoney Date: 13th January 2009 10:56 (UTC) (Link)
This is what a sympathetic GP is likely to be thinking if presented with the above even though they will never say it (I won't write what a less sympathetic one would be thinking):

These symptoms are very vague and non-specific but this girl is very fixated and obsessed with them. Maybe I would be too if I had those problems. I'm sure that being fixated on them is not helping but then I don't know of anything I can realistically do about that. So what to do?.... hmmm....

Well her thyroid function is borderline, but then she is on carbamazepine so that's likely to be messing with them. She also has depressive issues and there is a certain overlap. Some of it could also be side-effects. So, do I give her thyroxine and see if it helps? Well, if I don't treat then she gets annoyed with me and stays obsessed with the symptoms and continues to be tired etc... and if it is hypothyroidism the symptoms may become more florid in the future and be more clear cut on the tests. After all, the reference ranges by definition only include about 95% of the normal population anyway. If I do treat she may get better or she may flip into AF and have a cardiac event and die. In which case I think my decision to give her thyroxine would be medically indefensible so goodbye job and hello GMC fitness to practice panel. So what I really need to do is wait until the symptoms outweigh the risks and I have some laboratory evidence to back up my decision to treat.

If only she could just accept that there are things I just can't fix and learn to live with them. If only I could get her to see that when it comes to medicine, the condition has to be pretty bad before the side-effects and risks of the treatment are an improvement. Of course, then there are the people who ignore blood coming from their arse for two years and rock up to the surgery, moribund from terminal metastatic cancer, and say 'sorry to trouble you doc, if you could just give me bit of a tonic I'll be fine.' If only we could all find the happy medium and know what we need treatment for and what we're just better off living with.

Right, better put on your best doctor front and say something confident, she's starting to look at you like you're stupid....or worse still, like you don't know what you're talking about.
baratron From: baratron Date: 13th January 2009 16:41 (UTC) (Link)
Thing is, if I was in the US, I'd have been treated for hypothyroidism in August. There they treat it if TSH is above 3.0 uIU/mL. The American association of endocrinologists (I forget their exact name) states that more than 95% of euthyroid people have TSH between 0.4 and 2.5 uIU/mL - very different from the conservative British endocrinologists. When I have more free time I'll look up the "normal" range for different countries to see how it varies.

The main reason I'm obsessed with it is the link between thyroid function and bipolar disorder. In other countries bipolar patients are treated with thyroxine even if their TSH is within the range of normal - with monitoring to make sure it doesn't drop too low. The belief is that high TSH = depression, and low TSH = mania. I really want to get my brain working better because the way it is now just isn't good enough. I can't cope with being stupid.

The question remains how do you confirm hypothyroidism if a medication you're on can mess up all the numbers? I couldn't find that anywhere. Do you ask for T3 & T4 tests to be done, knowing those can be fucked up as well and get the doctor to look at all the numbers together? And then wait another few months and get them all done again, and see what's changed? That's what I honestly want to know. My mother was hypothyroid for so many years and now her thyroid has failed altogether, and her life is miserable. I don't want to get to that stage.
tirnoney From: tirnoney Date: 13th January 2009 18:46 (UTC) (Link)
'euthyroid people have TSH between 0.4 and 2.5 uIU/mL - very different from the conservative British endocrinologists.'

The reference ranges are highly dependent on laboratory techniques. Even different hospitals in the UK have different reference ranges depending on who manufactured their assay.

'In other countries bipolar patients are treated with thyroxine even if their TSH is within the range of normal - with monitoring to make sure it doesn't drop too low.'

If you have guidelines or a substantive body of medical opinion to support that, even if from another country, then that counts as backing to do something which may not be the routine way of treating it. When a doctor stands before the GMC, being able to show that 'substantive body of medical opinion' is almost always sufficient defence. I doubt your GP would be willing to do that though, but present an endocrinologist with such evidence/arguments and you might get somewhere.

'The question remains how do you confirm hypothyroidism if a medication you're on can mess up all the numbers?'

You then have only the clinical picture to go on, something an endocrinologist might be more willing to work with. Perhaps get a referral, given that your situation is complicated with the carbamazepine. Sometimes you just have to be pushy.
artremis From: artremis Date: 13th January 2009 11:55 (UTC) (Link)
you don't seem like omangel is when she gets hypothyroid (or like my Mum but there is so much stuff going on there it's hard to work out what's what - but you not being like my Mum i a good thing generaly!)
nitoda From: nitoda Date: 14th January 2009 10:40 (UTC) (Link)
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