Thyroid Health and Low-Carb Diets: What Lower T3 Really Means with Dr. Ben Bikman

welcome to the metabolic classroom I'm Ben bman a biomedical scientist and professor of Cell Biology and this is the podcast where we explore the fascinating science of metabolic health and how it affects our everyday lives I call it a podcast but of course as you may know by now I think of it more as a lecture thanks for letting me be your guest professor before we dive in um just as a matter of business I'm excited to share that I've launched Ben ban.com of course once again as you know by now bikman is spelled b

i k m n no C benman dcom that's going to be your new hub for all of my content at benman dcom you can subscribe you can become a member of the community at two levels an Insider or a pro- Insider as a subscriber at either of these levels you'll gain access to the show notes including the citations that I always reference in these lectures um and addition to some bonus podcast content especially at the pro Insider level and then you'll also get some Early Access to lectures that I'll be recording and sharing through the

website and some additional perks to help deepen your understanding of metabolic Health please visit the site benman docomo enic diet on thyroid function this topic often stirs some concern some claim that lower thyroid hormone levels observed on a ketogenic diet indicate thyroid dysfunction but is that the whole story we need to understand the reason why there might be changes in thyroid levels before we make any conclusions as to the health of the thyroid gland because perhaps the change in thyroid level is a reflection of thyroid resistance or changes in thyroid resistance perhaps it's an effect

of a change in glucose metabolism and a handful of other potential reasons so in the lecture today we'll discuss how thyroid hormones work so that'll be a bit of a fundamentals in physiology we'll explore the evidence from studies on ketogenic diets we will explore the concept of thyroid resistance as well of thyroid as well as thyroid hormones role in glucose metabolism and more all right now one of the topics I love to discuss is physiology that's one of the classes I teach as a professor so humor me for a moment while we take just a

few minutes to establish the basics I think you might appreciate just some deeper understanding of thyroid gland and hormone regulation to understand how a ketogenic diet impacts the thyroid and and in order for you to be able to put claims in context we do need to start with some of the basics here the thyroid gland is part of a system called the hypothalamic pituitary thyroid axis now you'll notice that I was deliberately kind of acting this out by counting down hypothalamus pituitary thyroid axis this is one of the ways we teach this axis regulation um

all of this is this uh all of these are three parts of this intricate pathway or what I'm referring to as an axis that decides how much we need of thyroid hormone it's it's essentially a way of fine-tuning the thyroid gland production or of of thyroid hormone it's kind of the thermostat if you will um and even the thermostat is a perfect example of a concept called negative feedback if you think about the thermostat you set the thermostat to a particular temperature it's winter here where I am in Utah so we need the thermostat to

help warm the home so let's say we set it at 69° and at 69° if the temperature starts to drop the thermostat will sense that the response will be to kick on the furnace then the central heating turns on within the home which brings the temperature back up to 69 and then it's turned itself off that's negative feedback So within all of this is the control center the affector the sensor these are all components Within the thermostat all of those components are in another way reflected within this axis of the hypothalamus at this what's called

a tertiary level the third tertiary level feeding a signal to the pituitary which is the secondary level which in turn is feeding a signal down to the thyroid gland itself the primary level so to say all of that another way the signal starts in the brain the hypothalamus produces thyrotropin releasing hormone this is just abbreviated as TR R this is the tertiary level of Regulation this signal tells the pituitary gland rather not down to here yet one little step down from hypothalamus to to pituitary um to in turn release a hormone called thyroid stimulating hormone

or TSH and TSH is a hormone that is always measured in the blood if you are looking at some markers of of thyroid function so TSH is going to be a commonly measured marker that if you've ever had a blood test that's measured thyroid hormone that's going to be on there now TR isn't because it is released in such low levels and only moves you know millimeters in distance and it doesn't flow into all of this systemic circulation of the body so if you were to take a blood sample from a vein in your arm

you're not going to get any TR because it's not making it that far in contrast TS H from that secondary level of the pituitary does have to migrate down to the thyroid gland and to do so it spills into the blood and so you can measure TSH in the blood and so that brings us to The Next Step so TSH from the pituitary gland is the secondary level and then it travels to the thyroid gland signaling to the thyroid gland to produce thyroxin which is T4 and a smaller amount of the hormone triiodothyronine three iodines

triiodothyronine T3 in fact that's the difference T4 has four iodine molecules on it T3 has only uh three and now this at the level of the thyroid gland is considered the primary level and of these two thyroid hormones T3 and T4 T3 is the active form of thyroid hormone this is the one that is eliciting the actions that we typically think of when we think of thyroid hormone it regulates metabolism and the rate at which every cell is doing its business that's one way I often describe this is that the general effect of thyroid hormone

T3 in particular is that it will regulate the rate at which a cell is doing whatever that cell is doing so when someone has hyper thyroidism everything is happening more and so they're hotter they're Twitchy their nerves are actually working faster than they were before um they have a hard time calming down everything is their heart is beating harder and faster everything is just sort of turned up a bit because thyroid hormone if it's elevated is elevating the rate at which everything's happening it sort of sets the idle of the engine if you will um

now as I noted thyroid gland produces a lot of T4 and a little bit of T3 and then a lot of that T4 will get it almost acts as a reservoir of T3 because T4 will get converted to T3 throughout the body most especially in the liver the liver is the main site of pulling in this less active form T4 and then spitting back out the active form T3 and then back to this concept of negative feedback and the thermostat and this Loop or at this axis when T3 levels especially are sufficient um when they're

at a good level they are flowing through the the blood and going back to the hypothalamus and the pituitary gland telling them hey I'm at a good level now you can kind of turn down your signals and this is very important and it's a concept I'm going to touch on later to help put in perspective some of the findings that people will often claim support the idea that a ketogenic or a low carb diet somehow damages the thyroid gland we need to look at this entire axis in order to really appreciate what what's going on

all right to so to sum this physiology primer up if T3 is in a normal range then TSH will be in a normal range if T3 is low because of some primary problem with the thyroid gland then you would think think through this in fact this is the kind of question I ask my students in my physiology class if T3 is down because of thyroid damage then there's less to turn these upper components off so now the hypothalamus and the pituitary gland are thinking hey there's a there's not enough thyroid hormone coming from the thyroid

gland we need to kick it into action and so what would you think would happen to TSH levels because remember you can't measure TR in the blood so I won't even ask that one what would happen to TSH if the primary signal is down if thyroid hormone is down especially T3 what is the pituitary going to try to do to kick it into action it's going to release more TSH so TSH would be high this is very important to keep in mind to understand and to remember again if the thyroid gland is struggling to produce

T3 then TSH would be higher however if the thyroid gland is producing a proper amount of T3 whatever that amount may be for the given body then TSH would sense hey everything's normal there's no reason to react and to try to turn anything up or down we're just going to stay in our normal level because T3 is at its normal level based on what our needs are that's important to note all right now let's get into some of the studies that people will claim support the idea that a low carb or ketogenic diet somehow damages

the thyroid gland one particular study was published in the journal plus one plus is an acronym P plus1 examined and they examined how a ketogenic diet affects thyroid hor hormones now as a reminder um for you to get the citations and all the show notes you have to be an Insider so go to benman docomo the community I would love for you to do that um but that's something I'm happy to offer to you there all right so in the trial they took 11 normal weight adults and they were put under two different diets a

high carb lowfat diet and a low carb ketogenic diet each diet the each patient or subject we use the word sub subject when referring to a study I'm not a clinician so I don't use patients I use subjects or participants each subject was put onto the diet for three weeks and then they had one week off and then they were moved on to to just revert to their normal diet and then they were put onto the other diet in a random order now what did they find this is one of the most ofs sited Studies

by people claiming that it damages thyroid because they found that T3 levels dropped significant l in this study on the ketogenic diet T4 levels were unchanged but TS H levels were also unchanged now this is very important I'm going to say that all one more time T3 levels dropped a lot so thyroid hormone went down but TSH levels were in a totally normal range think through the concepts I just taught you if this if this reduction in T3 was a sign or were a sign of thyroid gland damage what would TSH levels have responded I'm

going to keep that open sort of as a hypothetical question all right because I think you've been able to think through that answer all right now given that TSH I'm kind of answering it now myself given that TSH levels stayed normal that is I would say absolute conclusive evidence that there was no thyroid damage because if the thyroid gland Were Somehow producing less thyroid hormone than the body needed TSH would have gone up that the hypothalamus and the pituitary would have sensed this as a problem and kicked more of their products manifested as elevated TSH

up that didn't happen this then suggests that in the ketogenic diet these bodies simply needed less T3 that is a very valid conclusion very rational conclusion it's certainly the one I come to I propose and we'll spend a little time going over this that there are two reasons for this one is a change in thyroid sensitivity and that concept involves a little bit of speculation because unfortunately there's no solid evidence that uh to address this there's no studies that have asked that question and then second changes in glucose metabolism itself all right so the first

of these Concepts let's discuss thyroid horm hormone resistance a potential hidden factor that can explain some metabolic problems in people all right so thyroid hormone resistance as the name suggests is simply a condition where the tissues fail to respond adequately to thyroid hormone there are ways in fact to measure thyroid hormone resistance although there are no studies that have done this in the context of a ketogenic diet that I'm aware of and I have sought Dil ly in trying to find them I want you to be familiar with these two tests because perhaps you can

measure them on your own looking at your own blood tests I actually don't love these two tests and perhaps I need to help create a new one um and I'll explain why after but these are the two tests that are used one is called the thyro thyroxine resistance index abbreviated as TT T4 RI this index assesses how the pituitary gland responds to free thyroxin and thyroxin is T4 it's calculated by looking at TSH multiplied by the amount of three T4 and then the number the higher value the higher that number is the more it suggests

A reduced sensitivity to thyroid hormone then the other one is the thyroid stimulating hormone resistance index or TSH RI it's essentially the same it's just a slightly different variable but it's using the exact or a slightly different formula but it's using the exact same two metrics namely T4 and TSH and it's calculated by TSH divided by um free T4 and the higher the number the greater the thyroid hormone resistance now again as I noted while I'm going to cite some studies that just show you that thyroid resistance is a real phenomenon I'm going to do

that in just a moment unfortunately there are no studies that have used these metrics to measure uh thyroid sensitivity uh in in the context of a ketogenic diet so there's no study that looked at overweight unhealthy metabolically unhealthy individuals with thyroid resistance and I'm going to cite some studies in a moment that do show that wouldn't it be great if they'd taken those people put them on a ketogenic diet and then measured those same outcomes that's never never been done that's why I noted at the outset of this little segment that this involves some speculation

on my part all right now what is there is is thyroid hormone resistance even a thing you might not have even ever heard of that concept but it is a thing as I just noted there are in fact clinical tests that people will use and and there are multiple studies that show that this is a real phenomenon now I just remembered a moment ago I mentioned some of what I don't love about those tests I don't love that they use T4 remember T4 is not the active form of thyroid hormone thyroid hormone in its active

form is T3 I wish that there were some formula that used T3 instead of T4 again as I noted perhaps my lab needs to be among those that help figure that out all right so some evidence of thyroid resistance in metabolic disorders or people with metabolic syndrome there are several studies that have explored thyroid hormone resistance including these measurements I just mentioned in the context of obesity and metabolic syndrome okay the first is a paper that was published in a very good journal the journal of clinical endocrinology and metabolism and they found that individuals with

obesity often exhibited elevated TSH with elevated levels of T3 and T4 so this pattern does suggest and you could cite those metrics I mentioned earlier those formula that despite sufficient thyroid hormone production uh in fact it was elevated the tissues may be resistant and the study concluded that thyroid hormone resistance is a significant factor linking obesity to impaired metabolic Health another paper was published in Diabetes Care another very good Journal highly cited high impact factor This research linked higher thyroid hormone resistance in disas these two metrics I mentioned for example to obes OB metabolic syndrome

and type 2 diabetes and they their findings suggest that impaired sensitivity to thyroid hormone could contribute to energy imbalances and metabolic dysfunction I have previously spoken about the connection between thyroid hormone and Insulin receptors particularly on fat cells I don't want to take the time to revisit that now although now that I'm mentioning it I can't help but want to talk about it a little bit we'll see how I feel in a moment whether I revisit that idea but I have before you can look through some of the previous metabolic classroom episodes and in fact

for the sake of time I won't but there are Direct effects of thyroid hormone on insulin receptor expression on fat cells which is a direct regulation then of how thyroid hormone can through insulin receptor impact the growing in the shrinking of fat cells briefly very very briefly when thyroid hormone levels are down insulin receptor expression on fat cells goes up so that means the fat cell is responding more and more to insulin and what does insulin tell a fat cell to do it tells it to grow in contrast when hormone when thyroid hormone levels are

elevated insulin receptor expression on the fat cell goes down meaning the fat cell is less responsive to any given amount of insulin and thus it's going to be more inclined to shrink now there's a third study that was published in a journal obesity surgery once again finding similar findings that uh reporting that the individuals with higher thyroid resistance indices these metrics I mentioned earlier had a greater prevalence of overweight of being overweight and obese so the researchers noted that metabolic disorders mediated the relationship suggesting that thyroid hormone resistance is both a symptom and a driver

of metabolic dysfunction okay so that just helps establish the idea the concept that thyroid resistance is real now let's bring this all back to the point which is how does a ketogenic diet affect thyroid function and thyroid levels what does it mean for the ketogenic diet if thyroid hormone resistance is common in metabolic disorders improvements in metabolic Health like those seen on a ketogenic diet May enhance thyroid sensitivity this could explain why lower T3 levels on a ketogenic diet are are not a problem again if there were a problem we would see an elevated TSH

we do not see that TSH is normal that suggests that as far as the upper levels of Regulation are concerned everything is fine here's another layer of relevance T3 is heavily involved in glucose metabolism it upregulates glucose Transporters like the most abundant glute 4 GL glucose transporter Transporter 4 and it enhances insulin's ability to stimulate glucose uptake on a ketogenic diet where glucose intake is minimized we're eating fewer carbs so there's less converting into blood glucose the body's demand for T3 May simply be lower this isn't a sign of dysfunction it's an example of the

body adapting to a new metabolic State now let me talk about that because I think it's the second pillar of our understanding of why thyroid hormone levels may be coming down on a ketogenic diet the first was that it's likely a sign of improved insulin uh thyroid sensitivity if thyroid hormone is working better we simply need less and far from it being a sign of thyroid damage if it were then TSH would be elevated it is not suggesting that there's no crisis everything's fine we just need less of it now because it's working better there's

improved thyroid sensitivity ity this second pillar then the second part of this understanding is this concept of glucose metabolism where when we are consuming less glucose we need to clear less glucose from the blood and perhaps once again this is another reason why thyroid hormone goes down when we talk about metabolism thyroid hormone is often considered one of the primary conductors of this multi-piece Orchestra among thyroid hormones many roles one of its roles is regulating glucose transport in response and and Insulin signaling both of which are Central to maintaining energy balance especially in the context

of appropriate glucose metabolism all now let's break this down a little bit first thyroid hormone particularly the active form T3 directly impact glucose transport into cells T3 enhances the expression of glucose transport proteins like glute 4 and glute 4 is the main insulin response of glucose transporter and it is found in the biggest tissues of the body skeletal muscle and fat tissue so by mass those tend to be the biggest tissues on the human body and glute four is what abounds in them glute four as I noted is an insulin sensitive transporter meaning it facilitates

glucose uptake into tissues in response to insulin by regulating glute 4 T3 ensures that glucose can efficiently enter the cells reducing blood glucose more easily allowing the glucose to be burned for energy or stored for later use in the form of fat or glycogen however the relationship between thyroid hormone and Insulin signaling is in fact a double-edged sword as happens so often in the body there can be too much of a good thing while normal levels of T3 can support glucose transport and insulin sensitivity if thyroid hormone is excessively on like a case of chronic

hyper thyroidism this would be something like Graves disease for example that can lead to insulin resistance this occurs because the chronically elevated thyroid hormone starts to increase so much lipolysis that there's so much free fatty acids that now you actually are coming to this idea of um the Randle cycle or the glucose-free fatty acid cycle but of course on the flip side hypothyroidism can impair glucose uptake by reducing glute four expression so there's simply not enough glute for these doors that open up on the cells of muscle and fat most especially allowing the glucose to

come in all right now let me just kind of state all of that again what to me seems likely is that with less carbohydrate consumption there's less less of a need to stimulate glucose uptake into tissues in the body like muscle and fat in the ketogenic diet those tissues are more reliant on fat for fuel or ketones for fuel and they are thus less reliant on glucose in other words with greater carb consumption comes a greater need for assistance for for assistance to clear that glucose from the blood and thyroid hormone can help with this

but of course as carbohydrate consumption drops blood glucose isn't chronically elevated the body does not need any extra help to clear the glucose and thus one of thyroid hormones effects is now unnecessary and and thus no surprise the thyroid hormone levels may go down now as a final thought on this lecture let's compare this thyroid regulation to the pancreas and insulin regulation because I don't know why a person can't look at a study that shows low thyroid hormone levels and why conclude that's a problem and yet look at another study that shows lower insulin levels

and conclude that's a good thing now let me elaborate a Hallmark of improved insulin sensitivity is that the body requires less insulin to regulate blood sugar levels effectively when insulin sensitivity improves the pancreas doesn't need to work as hard to secrete high levels of insulin the fasting insulin levels naturally decrease insulin is simply working better so this is not evidence of pancreas damage or dysfunction rather it's a clear sign that the body is functioning more efficiently and responding to the insulin that is being produced so it needs less insulin because the insulin is working better

and and because there's less of this constant spiking of glucose you simply don't need it as often drawing a parallel then to thyroid health I submit a similar logic applies when we see lower levels of T3 in certain contexts such as during a dietary change like a ketogenic diet why do we conclude that T3 levels going down is a problem so instead of interpreting reduced T3 levels as a sign of thyroid dysfunction or damage I believe it is more reasonable to consider this is simply a reflection of improved thyroid hormone sensitivity just as lower levels

signify better insulin action when insulin levels come down and just simply less need lower T3 levels May simply indicate that the body is using thyroid hormones more effectively requiring less of the active hormone to maintain metabolic function in this light lower T3 is not necessarily pathological but simply a physiological response to a healthy indeed a healthier metabolic State suggesting improved metabolic efficiency at least in response to thyroid hormone so what does all of this mean for you lower T3 is not automatically bad if you're on a ketogenic diet and your blood test reveals a reduction

in T3 it does not necessarily indicate harm I'm not your clinician of course just your friendly neighborhood scientist but if TSH is normal and you don't have any signs or symptoms of hypothyroidism like weight gain or you're cold or you're lethargic and you're slow in your thinking and actions then your thyroid is likely simply adapting to improved thyroid sensitivity and reduced glucose demand your body doesn't need the assistance of thyroid hormone to help clear these chronic elevations in blood glucose all right so to wrap it all up a ketogenic diet may lead to lower T3

levels there are studies that show this there are also studies to show no difference in thyroid levels but regardless it does not suggest I don't believe that there's harm it may simply reflect improved thyroid sensitivity and reduced metabolic demand for glucose clearance combined with evidence of thyroid hormone resistance in obesity and metabolic disorders these findings do highlight the adaptability of the thyroid in response to dietary changes I hope all of this has helped you gain a deeper appreciation of the majesty and Miracle of the human body and perhaps even give some direct insight into some

things you've been thinking about or some things you may have even noticed in your own lab tests or clinical outcomes that have changed thanks for joining me on the metabolic classroom today until next time more knowledge Better Health