Levothyroxine and lung cancer - study

[zerendipity]

I wonder what happens now.

ncbi.nlm.nih.gov/pmc/articl...

[greygoose]

'Levothyroxine (LT4) treatment can lead to iatrogenic hyperthyroidism'

That's a very misleading statement!

Firstly, you take levo because you are hypo, for whatever reason. That means that your thyroid cannot produce enough thyroid hormone to keep you well. In 99.9% of cases (that figure is a guess, I don't have anything to back it up, but the huge majority of cases) it is irreversible. And, you need thyroid hormone to stay alive.

Secondly, levo is not a cure. It is thyroid hormone replacement. It doesn't suddenly - or even slowly - make the thyroid well enough to make sufficient hormone to keep you well. Even less does it make the thyroid 'go hyper' - i.e. over-produce hormone. It just replaces the hormone that the gland can no-longer make in sufficient quantities or at all.

Thirdly, you can over-medicated, of course. But, if testing is done regularly, and properly, that won't happen.

So, although it can, in a worst-case scenario, lead to over-medication - or what doctors refer to as 'going hyper' - it doesn't automatically have to be that way.

[helvella Administrator]

zerendipity,

Well, nothing much has happened in the four years since that was published to change what happens in the real world.

The conclusion:

Despite the common knowledge that LT4 is a life-saving drug, some concern has to be addressed for its prescription. The findings based on the sales of LT4 in Italy are consistent with the hypothesis that there is a direct correlation between this drug and lung cancer, whereas there is no correlation with breast, colorectal and gastric cancer. However, the clinical background of hypothyroidism, which is the main reason for prescribing the drug, might also be involved in the development of lung cancer. Specific epidemiological studies should be conducted to test these two hypothesis.

One obvious question, does the same apply to liothyronine?

There have been several threads here, such as:

healthunlocked.com/thyroidu......

[zerendipity in reply to helvella]

From what I understand the problem is high T4 and low T3 levels, which results in oxidative stress. So if one has optimal levels of both there is no risk.

The problem of course is that hypo patients are mostly given T4 medicine and their T3 levels are not checked. I was thinking of mentioning this study to my doc since she told me to stop taking T3 (claimed it's dangerous) but I am afraid she'd only use it as an excuse to refuse any treatment.

[helvella Administrator in reply to zerendipity]

zerendipity,

I agree that is logical - but they zero-in on LT4 very specifically. And the T3 question is very definitely not part of this paper as they say:

This means that the amount of LT4 reaching the lungs following an external supplementation cannot to be transformed into LT3 as in the other tissues, and make lungs very vulnerable to possible toxic effects of LT4.

That, though, raises the possibility of inadequate LT4 being an important factor - if there is enough to ensure adequate blood FT3, the proposal inadequate T3 as a cause might not then apply?

This sentence throws into question everything we have read and heard about once-a-week dosing:

During the therapy with LT4 even at the steady state condition a peak of the hormone is evident a couple of hours after the administration and may cause a temporary condition of hyperthyroidism and a further increase of oxidative stress.

If the daily stress has an impact, how much greater a weekly dose?

[humanbean]

One of the things that I realised as a smoker is that smoking a cigarette perked me up a tiny bit, in much the same way that a cup of coffee or tea might.

Perhaps there are others like me who discovered that smoking perked them up a bit so they kept on smoking. And how many of them were undiagnosed or under-treated hypothyroid?

I stopped smoking a few years ago and my untreated hypothyroidism got substantially worse. I got my first treatment for hypothyroidism about four years after I stopped smoking. However, if I get lung cancer in the coming years I'll blame my decades-long smoking habit not my thyroid meds.

.

Finding a correlation between Levo intake and incidence of lung cancer does not indicate causation. Correlations can be found between all sorts of things that are completely unrelated. See this site for several examples :

tylervigen.com/spurious-cor...

.

An example of spurious correlation in the health field is the subject of HRT and heart disease. In the 80s it was believed, based on observational studies, that HRT was hugely beneficial in preventing heart attack and stroke in women.

In the 90s scientists finally decided to test the effect of HRT on heart attack and stroke with a proper rigorous randomized controlled trial. To quote "Doctoring Data" by Dr Malcolm Kendrick :

"Analysis of hazard ratios showed that after 5.2 years there was a 29% increase in coronary heart disease risk, including an 18% risk of coronary heart disease mortality and a 32% increase in risk of nonfatal myocardial infarction. There was a 20% increase in the risk of fatal stroke and a 50% increase in the risk of nonfatal stroke in women assigned to HRT"

Dr Kendrick then goes on to say :

"So a 42% protection in an observational study turned out to be a 29% increased risk in an interventional study. A complete turn around. Findings that swept away everything that everyone thought they knew. Oops."

[helvella Administrator in reply to humanbean]

humanbean,

With respect to smoking - yes, absolutely, quite similar.

With respect to causation, yes, no proof there.

Questions abound - and none appear to have been answered in the intervening years since the paper was published. Not least whether having been hypothyroid, possibly for many years, itself is a causative factor?

[humanbean in reply to helvella]

I would strongly suspect that being hypothyroid is a causative or contributory factor in just about any disease known to man (or woman).

It is my understanding that T3 is needed for the proper functioning of every cell in the human body, at least at some point in the life cycle of the cell. What happens to cells which are short of T3 throughout their life cycle? There could be any number of faults which develop in cells of all kinds, including lung cells. And it seems likely that cells which are not performing well, or which are under-powered, or have some other issue, could well become cancerous earlier than they might in a healthy population with healthy cells.

Another thought that crosses my mind - If people are hypothyroid and undiagnosed and/or untreated for decades I wonder if they are more likely to have become smokers?

I always felt that physical activity was difficult. Apathy and lack of motivation have bedevilled me all my life as well. I was an excellent sprinter in childhood, but ask me to run more than 100m and it was as if I was running under conditions of higher gravity than normal. I so often felt as though I was wading through treacle. I could have been a poster child for TATT (Tired All The Time). I suspect low T3 could have been an issue for me since birth.

.

I have just noticed that the paper refers to levels of T3 and T4, so I am assuming that they were measuring Totals and not Free T3 and Free t4. I'm not sure what ramifications that will have, if any.

[Zephyrbear in reply to humanbean]

I totally agree with you humanbean! I smoked for 35 years (20/day) and having a fag not only picked me up, but also calmed me down when stressed... I was finally diagnosed hypo after I'd stopped, although I believe I was hypo long before that! I was on T4 monotherapy for 7 years before it became clear that it was not having very much effect and my dear (now sadly retired) endo put me on to T3 and I haven't looked back since! Both my dad and my brother died of lung cancer, so I think there is probably a genetic link there too but, should the worst happen, I would ascribe any lung cancer to those poison sticks I lit up 20x a day too, not my thyroid hormone replacement therapy!