March 22, 2023

A new study of over 600,000 thyroid patients from Taiwan suggested that thyroid patients taking levothyroxine have a 50% increased risk of developing cancer at any site. While concerning, the results of this study certainly do not prove that levothyroxine causes cancer but every thyroid patient taking levothyroxine should be aware of this potential connection.

Hey guys dr childs here today we’re going to be talking about the connection if there is any between the use of levothyroxine and your risk of cancer now this might seem like a funny thing to be talking about why would i be interested in talking about the connection between levothyroxine and cancer well there was a study that came out in 2021 so fairly recently

That included a large number of thyroid patients about six hundred thousand patients and showed that these thyroid patients who were taking levothyroxine had about a fifty percent increased risk of developing cancer at any site now this is pretty concerning information i wouldn’t say it’s alarming quite yet which is why we’re talking about it right not trying

To spread fear or cause fear in any single person we just need to talk about the information that is in front of us now my personal opinion on this is that we probably don’t need to worry yet and i’ll be talking about it right now and throughout this video but if you are somebody taking levothyroxine or any other thyroid medication for that matter then hopefully

You find this information helpful so what i will do is i’ll include the link to the study that i’m going to be referencing below and really what we’re going to be doing today is critiquing that study talking about why i don’t think you need to be freaking out if you are a thyroid patient taking level thyroxine but we do need to kind of talk about the results of

This study and what it means for you we’ll also be talking about some takeaways and so on so let’s talk about the study again the link will be in the description below now this was a retrospective study and it was done in the country of taiwan which will be important as we go later on and this study surveyed about 600 000 thyroid patients now in taiwan they have

This database of information it just includes a ton of health information of of patients not just thyroid patients of a lot of different people millions and millions of people but what it allows researchers to do is it allows research researchers to take certain criteria and look at that information backward in time and follow these patients and see well does they

Can ask questions right they can they can probe the data for for answers to questions that they may have so they might say hey do patients taking level thyroxine increase have an increased risk of developing cancer over some period of time now that’s just the question they asked for this study but they could have asked another question they could have said hey do

Women who are age 45 who drink alcohol have a risk of have an increased risk of developing breast cancer right they can look backwards in time with this data and really probe it for whatever they want to learn now unfortunately that doesn’t guarantee the connection between these two things which we’ll talk about in the future but it does send a signal that maybe

There’s something there which means that we should probably look into this a little deeper so when these researchers looked backward in time they looked at the six hundred thousand tired patients and i believe it was about two or three million um control patients of healthy patients you’ll have to look in the data to confirm that value so they looked at thyroid

Patients and healthy control patients they found that thyroid patients taking levothyroxine had higher risk of developing four specific types of cancer including brain cancer skin cancer pancreatic and breast cancer they also found that thyroid patients using levothyroxine had a lower risk of developing esophageal and cervical cancer and when you put all this data

Together it showed that about that thyroid patients taking level of thyroxine had about a 50 increased risk of developing cancer at any site you know when you when you account the much higher risk and the much lower risk that was sort of the average together so again what that’s just the data that’s just the information and now what i want to do is really critique

That information let’s talk about it let’s talk about why i don’t think you need to worry just yet and i’ll explain sort of my logic here and what how i’m looking at this data and how i’m interpreting it as we go so number one the first thing we need to talk about is the fact that this is what’s called a retrospective study now i won’t bore you with the details

Of talking about all the different ways that researchers can look and the different ways that they can create studies and research groups and groups of people and so on to follow them but what i will say is that retrospective studies they can be helpful but they don’t really show or prove anything when you when you use them and the reason is well there’s several

Reasons for this but one of the big reasons is that they’re looking backwards in time at data that has already been collected and already existed so this leaves a lot of potential problems now one of these problems includes a problem of data keeping and laboratory testing so when these patients are are first going in and they’re going to their doctor and they’re

Just having their data collected they’re not necessarily collecting it for any particular reason they’re just saying here come in get your yearly physical let’s let’s take a list of the medications you’re taking and let’s get your regular blood work and then we’ll just hold this data and then researchers can look at it in the future but in the case of thyroid cancer

And or level thyroxine and the potential increased risk of cancer we need to know more than just the regular stuff that they’re testing for right we need to know a lot about their thyroid lab tests we need to know about their personal history we need to know a lot of these things and so unfortunately because that wasn’t top of their mind when they were collecting

This data we don’t have a lot of good information that we would like to see in order to say that levothyroxine causes the cancer right now all we know is there is some connection we don’t know if it’s causal or if it’s just correlated right and that’s a big deal so the issue of data keeping and laboratory testing is important here number two we also don’t account

For confounding variables so what do i mean by that now imagine if we were looking at this group of people thyroid patients and we were trying to say that level thyroxine caused cancer in these patients well in order to do that we would have to rule out other things that could also cause cancer right and one big one would be something like weight gain right we know

That people who tend to be overweight which by the way a lot of thyroid patients suffer from this problem they have an increased risk of developing cancer because they are overweight not because of their thyroid but because of they are overweight so that’s a confounding variable right in other words it skews the data it makes it harder to tell which is actually

Causing the problem is it the weight gain is it the level thyroxine is it the thyroid right it confounds the pitcher it makes it a little more difficult now in this study we know that there were several factors not taken into account and i included one of those already one of them was bmi which is important another one that they couldn’t really account for was family

History of cancer now when you when you do studies like this you want to rule out those people who have a high who have a high higher risk than the average population of developing cancer because they can skew the results if you’re looking at a bunch of people who who happen to already know that they’re probably going to develop cancer because they have a long family

History of it well that’s not a regular control that you can use another thing that they really didn’t take into account was smoking history and then alcohol consumption as well which again both of these things can impact your risk of developing cancer so these confounding variables are important in so far as they kind of muddy the water a little bit number three

We have the data source now the data source obviously came from taiwan and which is another country and the reason that this is important is because people in different geographical locations across the globe have different risks of cancer based off where they live the environmental factors that they’re surrounding the the type of water you know whether that water

Is contaminated with certain minerals or heavy metals or whatever it is all of these things impact your risk or the people who are living there their risk of developing cancer so you can’t really take information from the from taiwan and apply it broadly to people who who let’s say live in the uk or to america as the case may be so that issue of the the people that

It was stead studying and testing for may not translate directly to other populations so that again is another thing to take to keep in mind and then lastly and very this is probably perhaps the most important thing we don’t have a lot of information on these patients on their dose of level thyroxine so if you were going to blame level thyroxine on causing cancer

You would need to see how each patient was taking it because here let me give an example let’s imagine that all these patients were taking level thyroxine but the standard by which they were dosed is completely separate there than it was in the united states so let’s say let’s say on average i’m just making this up but let’s say they were 20 under dose in taiwan

Compared to what the standard of care is here in america that would make a big deal right that would make a big difference because it’s not the medication so much as as it is the dose and that’s really really important here so we don’t have that information we don’t know how much they were taking and we don’t know how that dose impacted their tsh their free t3

Their free t4 all of these important thyroid hormone lab tests all we know is that these patients were taking levothyroxine for some period of time and they were allowed to be included into the study because they met the inclusion criteria so that’s the problem with the retrospective study it doesn’t doesn’t say anything about it doesn’t prove causation it just

Proves some correlation we don’t know what that correlation is so what that leads us to number two is that more research is definitely still needed now i don’t think that we need to freak out yet this is part of the reason why we why i want to say this as well it’s not quite time to freak out yet but it it is concerning this information that we’re we’re seeing

Here the research is a little bit concerning especially to thyroid patients so don’t be surprised in the coming years if we start to see more research related to levothyroxine use and your personal risk of developing cancer we’re probably going to see a lot of that coming out and it makes sense we would need to see that before we can definitively say yes it does

Or no it doesn’t number three we don’t have data on other thyroid medications so don’t freak out just yet because we don’t know does this only apply to level thyroxine does it apply to natural desiccated thyroid does it apply to all thyroid medications in other words is it related to the thyroid the medicine or some other factor right so that’s another reason why

We don’t have to worry just yet now i will say the fact that we don’t have information on these other medications is actually pretty good we’ll be talking about that in the takeaway section section in just a minute here and then number four the last reason we don’t need to worry just yet is because levothyroxine is bioidentical so another word for that is body

Identical and that just means that levothyroxine even though it is synthetic it contains the exact same hormones that your body would produce naturally now this is important because most of the time when we think about hormones and their impact on your personal cancer risk a lot of the times that these hormones cause problems would be because they are they are

Non-bioidentical in other words they are we call them i call them frankenstein-like hormones they look similar to the hormones that your body produces but they’re not the exact same so birth control pills would fall into this category they target estrogen receptors and progesterone receptors but they are not the same estrogen and progesterone that your body produces

Naturally and they do have an increased risk of cancer by the way if you look at the studies associated with birth control pills now typically hormones that are bioidentical which means they are body identical your body is used to producing these naturally they typically do not cause the same problems that these frankenstein like hormones do cause now having said

That you can still take too much of a good thing and it can cause problems so for instance one good example of this would be the connection between using high doses of estrogen and your risk of uterine cancer or breast cancer so there is a connection between the two if you use excessively high doses which again leads me to believe that this connection between level

Thyroxine and the supposed cancer risk is likely more due to the dose and how it’s being dosed than it is the actual medication itself so let’s talk about some takeaways so what does this mean for you going forward what should you do how should you respond to this how should you react and so on so number one i think this really this is probably the most important

Thing and that is don’t take thyroid medication unless you absolutely need to be on it now you might say i was put on thyroid medication i was told i have to be on it for life and that’s that that’s sort of true okay so i have some there’s been some studies that have come out more recently that show that about 30 percent of thyroid patients may not need to be on

Thyroid medication forever so it’s a pretty that’s a pretty good chance 30 so what i would recommend is if you don’t have if you no longer have a thyroid and if your thyroid has been ablated or you are in nsage hashimoto’s then you’re going to have to take diary medication forever but if you don’t fit into those three categories it may be worth exploring whether

Or not you need to be on thyroid medication forever right you and i have resources that can help you with that i have videos that go over that so i’d recommend if this is you know a little bit concerning to you if you’re hearing this even though it’s in its infancy i don’t necessarily think you need to freak out yet but if you find yourself concerned that would be

Oh that’d be okay you might want to consider this option consider looking into whether or not you have to be on third medication because thirty percent is a pretty pretty big number uh as far as people go right it’s about one and three or pretty close to it so don’t take it unless you absolutely have to number two another consequence of this is that it’s probably

Going to be more difficult to get on thyroid medication from here on out now doctors already made it kind of difficult to prescribe thyroid medication because a lot of patients who felt that they were hyperthyroid were hypothyroid were actually in a subclinical hypothyroid state so they weren’t truly hypothyroid now a lot of doctors could sort of be pressured into

Giving you thyroid medication in these instances now i think that that’s probably going to become less likely because if you are a doctor and you’re seeing this information you’re going to be like well if you don’t really need it i’m not going to prescribe it because if there’s even a little bit of risk of developing cancer even though again it’s probably not quite

That simple that they could use that as ammunition to then say let’s not give it out to you now this probably won’t impact most of you watching this because most of you are probably taking it already because you really do need it but there will be some people who are kind of on the cusp especially in the case of let’s say early hashimoto’s who could maybe strong

On their doctor into giving them medication early and that can have a positive effect on on certain patients with hashimoto’s and as a result of this study that may no longer be the case so we’ll have to see kind of how that plays out but i’m guessing that it’s probably not going to be as easy as this information gets disseminated out number three this is another

Big takeaway and that is optimizing your dose of thyroid medication is more important than ever and it’s more important than whatever thyroid medication you’re taking so if you’re listening to this and you’re freaking out because you’re thinking well i’m on level thyroxine and i have to be on level thyroxine so if that’s the case don’t freak out too much because

You still have control over your dose now remember one of the most important things that this study did not take into account was the impact of that dose on thyroid function so what i would say to you if you’re if you’re a little bit worried is focus more on the dose that you’re taking and less on that medication so if you’re taking level without accident maybe you

Need more maybe you need to uh maybe you need a little less but focus on how that level thyroxine is impacting your tsh your free t3 your free t4 and your reverse t3 as you optimize for those those values those uh free thyroid hormone values i think you’ll feel not only feel better but i also think you’ll reduce any risk that may be associated with underdosing which

Is probably what’s happening underlying here number four even if again you are a little bit upset about this or freaked out or a little bit scared there are still things that you can do to reduce your own risk of your own personal risk of cancer so things like making sure that you are eating healthy foods right there’s never a bad idea to go on a whole food diet

Which is what i’m constantly recommending diary patients to do it’s never a bad idea to make sure you’re lowering your stress to sleeping enough to eating healthy um to doing all these things that can normalize your body weight which will you know balance your hormones reduce insulin resistance reduce leptin resistance make your thyroid medication more effective

All of these things can be done and they should be done by you right now regardless of whether or not you’re hearing this but let’s say you have been holding off on doing this for some reason well now maybe is the time to start doing these things so now more than ever i would say make sure you focus on the things that are within your control so that these things

Because these things can have an impact and will have an impact on your potential future cancer risk and then number five this has already happened so i know that this has definitely happened to at least one person but some person who read the article i wrote on this which by the way if you want a more in-depth um sort of overview of this uh study i’ve written

About it as well my blog so you can check that out and one of the one of the people on that blog left a comment said that as a result of this she she basically requested that she get switched from level their oxygen to another thyroid medication so that may be a positive as a result of this study so you might be able to use this study as ammunition so to speak to

Help your doctor or not help but basically to say hey i don’t feel comfortable taking level of thyroxine because of this study do you mind giving me level three or do you mind giving me armor thyroid or np thyroid or some other combination of thyroid medication so that might be a good thing that comes of this study because most thyroid patients feel better when

Taking ndt thyroid medications or combination t4 and t3 thyroid medications so that might be worth a shot as well if you’re feeling a little bit you know if you’re just feeling a little bit worried as a result of this information but i do want to reiterate i don’t think it’s time to worry just yet yes this is concerning but no it’s not freakout time or anything

Like that for all the reasons that i’ve saved previously now if you have any questions about this study again you can find the full link to the study in the description below and i have also a more detailed write-up of the study and the critique of all the things that are going on and i go into a little more detail there this is just really an overview of that

So make sure you check that out if you have any questions but if you do you can also leave them below and if you haven’t already make sure that you download my free thyroid pdf resources i have tons of information all designed to help dire patients like you feel better so make sure you check those out as well if you haven’t and otherwise i’ll see you guys in the next one

Transcribed from video
Does Levothyroxine Cause Cancer? Study of Over 600,000 Thyroid Patients Explained By Dr. Westin Childs