Instant Genius - What happens in our bodies when our hormones misfire

Episode Date: June 7, 2026

Every minute of every day, our bodies are flooded with a complex web of hormones – chemical messengers that travel through the bloodstream, coordinating everything from our blood pressure, body temperature, metabolic rate and even our emotions. When this system is functioning correctly, we barely notice its actions, but if it begins to misfire, it can lead to profound issues in everything from fluctuations in our energy levels or moods to the way our bodies develop as we age and even our appearance. In this episode, we’re joined by Dr Saira Hameed, an endocrinologist based at Imperial College London NHS Trust and best-selling author, to talk about her latest book Signal – The Inside Story of Our Hormones. She tells us how, despite being so tiny, the many hormone-producing glands situated throughout our bodies have a huge impact on our health and wellbeing, the many issues that can arise due to the overproduction or underproduction of hormones, and the new therapies in the pipeline we may be able to use to bring our bodies back into balance. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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in podcast form. Every Monday and Friday you'll hear world-leading scientists and experts talking about the most fascinating ideas in science and technology today. I'm Jason Goodyear, commissioning editor at BBC Science Focus. Every minute of every day, our bodies are flooded with a complex web of hormones, chemical messengers that travel through the bloodstream, coordinating everything from our blood pressure, body temperature, metabolic rate, and even our emotions. When this system is functioning, correctly, we barely notice its actions. But if it begins to misfire, it could lead to profound issues in everything from fluctuations in our energy levels or moods to the way our bodies develop

as we age and even our appearance. In this episode, we're joined by Dr. Syra Himede, an endocrinologist based at Imperial College London NHS Trust and best-selling author to talk about her latest book, Signals, the inside story of our hormones. She tells us how despite being so tiny, the many hormone-producing glands situated throughout our bodies have a huge impact on a health and well-being. The many issues that can arise due to the overproduction or under-production of hormones, and the new therapies in the pipeline we may be able to use to bring our bodies back into balance. So welcome to the podcast. Thanks so much for joining us. It's my pleasure. Thank you for the invitation. So in today's episode, we're talking about your latest book,

signals the inside story of our hormones. So I think before we really get going, so by trade, you're an endocrinologist. So I think, you know, if I have my Greek straight anyway, that's a medical practitioner who specialises in the study of the endocrine system. But some people might be like, well, I've heard that tone, but I don't know exactly what we mean. So first off, can you just explain what we mean by that, please?

The endocrine system is the body's internal communication system. system. It is made up of the body's glands. So you will have heard of the pituitary gland or the thyroid gland or the adrenal gland. Those glands are like radio transmitters and they transmit a hormone signal. The hormone travels in the bloodstream and it is destined for a target cell and it conveys a message. It conveys some information to that target cell and the target cell must carry out the instruction contained within that hormone. And as an endocrinologist, what I deal with are diseases or illnesses of the body's glands or its hormones. Three common scenarios. You might have too much of a hormone, and that makes you feel unwell because the message is essentially too loud to the body. You may be

producing too little of a hormone, and then the message is too quiet for the target cells to pick up, so something isn't working well. Or the body might become resistant. to that hormone message, that however loudly the message is transmitted, the information contained in the hormone just can't get through. So those are the three clinical scenarios we tend to see when it comes to hormone illnesses. So in the book, you split into chapters that cover different areas of endocrinology and different case studies. But before we start having a look at some of these that I've picked out, let's sort of take a little brief detour. and about an idea that's running through the book,

about the sort of practicalities if being a medical endocrinologist that you talk about, which I found was really interesting and, you know, really heartwarming. And it's the emphasis on trying to really figure out the bigger picture of what could be behind these certain issues that patients may be having. You know, perhaps things that aren't immediately obvious from things like various blood tests or scans. but from speaking to the patient, learning about them and building a rapport, you know,

it's sort of the human to human aspect of practicing medicine, which I don't think is really talked about that much. I think that's right. And particularly in the 21st century, there's so much G-Wizard re-associated with medicine that it's easy to believe that if I do this scan, if I do this test, that will lead me to the diagnosis. Medicine remains, despite the wonderful innovation, it's still. very much rooted in the art of taking a history and being able to listen to a patient story. I quote in the book a very famous physician, Sir William Osler, and he famously told his student,

I think it was at the beginning of the 20th century. He said, listen to your patient. He is telling you the diagnosis. And we might think, well, Oslo was practicing over 100 years ago. Surely things have changed by then. But actually, that remains the case today. So you're absolutely right. It's all about the storytelling. And what is so important about that is it will, A, not only lead you to the diagnosis, but should prevent you going down the wrong track, because it can seem that, oh, you know, if we just do every investigation, right, let's just cover all bases. And then we'll get to what's wrong with the patient.

Actually, going down those alleyways can harm a patient. If you do the wrong test, you might get a false positive, and then you're on track for for something the person doesn't have. So not only you're not detecting what is actually one with them, but now you have started a sort of conveyor towards something that's the wrong route. So just, you know, ticking all the boxes and trying to do things through tests alone is not the answer,

even in 2026, even in modern medicine. Yeah, absolutely. So let's have a look at some of the ways that our hormones affect our health that you talk about in the book. in the first chapter you kick off with talking about somebody who was struggling with tiredness. I think that's a great place to start because I'd venture a good proportion of listeners, obviously will have felt tired at some point in their lives. But there can be various reasons for this.

Maybe we've got a new baby or something. Maybe shift patterns have changed at work or something. But sometimes it's difficult to put your finger on exactly what is going on. So in this particular case study that you talk about, you talk about the role of cortisol. So if most people have heard of this, I probably think, oh yeah, I know what that is. That's the fight or flight hormone. So what role is it, does it play in these feelings that some people get from deep fatigue? So you're right, cortisol has taken on these two different monikas.

One is the stress hormone, and that's biologically correct. It's also the energy hormone. And it operates on a very specific. 24-hour circadian rhythm, so that just before your usual wake-up time, probably about half an hour before, your adrenal glands pour out cortisol into your bloodstream, and that is essentially your jump start for the day. Blood pressure goes up a little bit, blood sugar rushes to your muscles, brain cells become very alert, very active. And if you compare the feeling to, you know, how did you feel when you got into bed?

the night before. Really ground down, exhausted, just couldn't answer another email, just absolutely everything was too much, I've just got to get into bed to the feeling when you wake up of like, yeah, I can do this, kind of welcome the new day. There are lots of explanations and, you know, I'm sure you've had many sleep experts on, but cortisol is one reason why you get that bam in the morning and you can get out of bed. So cortisol is a great thing. We need it for our energy and our pep and our sharp thinking and then to feel really good. And you're absolutely right to say there's tons of reasons why people might be tired. Cortisol deficiency is rare, but we do sometimes need to think about it, particularly if there are other parts of a patient

story that seem to be pointing in that direction. Yeah, so you mentioned adrenal glands there. And of course, as you said earlier, glands are just a huge part of this entire conversation. But so adrenal glands, you know, we've probably heard of that at some point from another, but where are they in our bodies and what do they do? The adrenal glands sit one apiece atop of each kidney. If you were to ask somebody, put your hands on your hips and where your thumbs would be pointing to in that sort of a pose, that might be very roughly where your adrenal glands are to be found. They're quite small. They're about the size of a grape, each one of a of them, but they produce these hormones, including cortisol, which are fundamental to life.

And as you'll have read in that chapter about cortisol, if we don't have enough cortisol, it could even be fatal. Yeah, so that's fascinating. One thing that I thought, like running through this whole story is that these very tiny parts of our body can have huge effects on our health. It is kind of mind-blowing because you think, you know, you think that somehow maybe the effect of an organ or a tissue should be proportionate to its size. But another gland I talk about in the book is the pituitary gland. And to orientate listeners, that's a gland to be found in the brain that is instrumental in controlling many of the body's hormones. pituitary gland is the size of a pea. And even though I've looked after many patients with pituitary illness, I've seen petuitaries on MRI scans, sometimes, Jason, if I am pouring out frozen peas for my kids' dinner, I will sometimes look at one of those peas and think, how can

the pituitary be that size and yet be such an essential part of the body signaling system? So let's stick with the adrenal glands for the moment. And this particular, case, somebody you eventually discovered had a dysfunction in the glands. So, you know, what was happening there? And, you know, how did you discover that? The adrenal glands can fail for a variety of reasons, but the commonest reason we would see in the UK would be the body launching an autoimmune attack against the adrenal glands. And the autoimmune disease essentially means that the immune system is there to fight off viruses, bacteria and so on. But sometimes, and for reasons that aren't completely well defined, the immune system will turn its might, will turn its force on a part of the

body, and the adrenal glands can be one of those targets. And so you end up with this autoimmune kind of wipeout of your adrenal glands, and your adrenal glands no longer produce cortisol. And that's when a person will start getting symptoms. Yes, you know, absolutely deep exhaustion, but also other things as well because cortisol isn't just about managing our energy levels. Another sort of fascinating thing that you mentioned about this is, you know, the kind of visual symptom of this particular patient that was kind of a tell tale that they were suffering from this particular condition, you know, so what was that? The adrenal glands are essentially the cortisol.

production factory. But they're doing as they're told. They don't really have a say and how much cortisol they're producing. They are under the control of this P-sized gland that we talked about a few minutes ago, the pituitary gland sitting in the brain. And the pituitary gland will send out its own hormone signal to the adrenal glands and tell them make and produce cortisol, release cortisol. and the reason that the patient I describe in that chapter looked unwell or didn't look quite right was that the hormone signal sent out by the pituitary. One of the precursors can be involved in a tan of the skin, in increasing pigment within the skin. When your adrenal glands are failing and they're not sending out enough cortisol,

the pituitary is very, very smart. It picks this up. It's like a factory foreman. because what's happening? Why has the factory production? Why isn't it churning away what's going on? Petuitary picks this up. And so it tries to stimulate or get the adrenal factory going again by pummeling the adrenals with this get-going hormone. But because one of the sort of side effects you could say of this signal is increasing melanin in the skin, if you're way overproducing this pituitary go-ahead signal, you might end up very tanned. Yeah. So one, Once you identified this issue, what sort of treatment options do you go for? You know, how do we sort of address these glandular dysfunctions?

So there's sort of two paradigms in endocrinology. If there's not enough hormone, which is the scenario we've just talked about, cortisol deficiency, you replace it. Flipside, too much hormone suppress it. In this scenario that we're talking about, there's not enough hormone. We're going to replace it. Now, before the early 1930s, there was nothing to replace it with. We didn't have medicinal cortisol replacement.

And people with this condition, it was fatal. And the breakthrough came, I think in the early 1930s, when it was worked out that we could extract these hormones from bovine adrenal glands, inject them into humans who couldn't make enough the hormone themselves. And it was like magic, that person got better. Obviously today, the patients we're seeing now, we're not injecting them with cow, sort of pulverized cow adrenal glands. I'm happy to say treatment has moved on. So we now have synthetic medicines we can use that mimic sort of cortisol and patients will take a tablet every day and then get on with life. Yeah. So let's move on to another of the areas that you talk about, which I think maybe some people, it wouldn't, when

you know, talk about hormones, it wouldn't come to your mind immediately. And that's our physical growth, the way that we mature, which is all sorts of things, you know, our bones, our muscle development, all sorts of things, you know. So what role does our endocrine system play in our maturation? It's such a good question, because on the one hand, we instinctively understand. that we change and we change from, if you look in the family photo album, from this kind of grainy fetal ultrasound, we look a sort of curled up little kidney bean, to sort of 20 years later a fully fledged adult human. So we all kind of appreciate that change is going to happen. We're going to grow taller, our physical characteristics change. That's totally driven by your

hormones because what are we doing? We're just living our lives. We're not really in control of that and our hormones are pinging around the body making that happen. A few that are really essential in that process. There's growth hormone, which is one of the nicer hormones in the sense that it does what you think it's going to do. It's like a name as it's as it is on the tin kind of a thing. So growth hormone is released again. We come back to the pituitary, this pea size gland in the brain and it releases growth hormone. And that message is destined for many tissues, but it has a particularly stimulatory effect on bone. And that's how our bones elongate through childhood.

But eventually, so the reason that we stop growing and we hit our final adult height is that eventually there's no more growth potential in the bone. So the proliferating bone kind of hits a hard stop and then that's it. And then you've reached your final height. Your feet stop growing because I still remember being a kid and I was like so frustrated. I love those trainers.

Why have grown out of them? That's really annoying. And now suddenly, you know, as an adult, unless your shoes wear out or whatever, you know, your shoes will always fit. It's kind of cool. So there's growth hormone, but there's also what we call the sex hormones. So there is estrogen in females, testosterone in males. And that's obviously intimately involved with puberty and the development of adult characteristics. Yeah, so that leads on nicely to what you talk about in the book, the case study, about a young boy who sort of started having issues with his vision. they noticed and then he was a lot shorter than his brother and they just thought, oh, well, maybe, you know, that's just a matter of fact thing.

It's who he is. But once you've looked into it more deeply, it was actually a hormonal issue. Could you talk us through that? Exactly right. So this patient had a sort of slow onset of things, which, as you say, at the time, you can kind of explain away. you can come up with a counterfactual. And quite often that counterfactual might be correct that, yes, some children hit

a great spurt later than others. Some children will go through puberty later than others. And all of those things you can sort of explain away. But then, as you say, when his vision changes, it becomes apparent note. This isn't just a sort of slow onset of puberty. This is something else. And what that case really, I think, shows to readers is the important. of a gland called the hypothalamus. So we've talked about the pituitary, and it might sound to listeners

at this point, oh, the pituitary is super important. I'm not going to dispute that. The pituitary is super, the pituitary is not the boss. The pituitary is carrying out the orders of what is typically called an endocrinology, the master gland, and that is another gland in the brain called the hypothalamus. Again, tiny, the size of an almond. So you've got the almond hypothalamus and the peopetuitary and gosh these things are so important yet absolutely minute and what the case of the boy shows us because you know don't want to give too much away but essentially it illustrates to us that when the leadership of the hypothalamus is felt it really has a very catastrophic effect on somebody's life yeah so sort of you've mentioned there puberty and sex hormones so let's have a

look at testosterone sort of coming off the back of that because you know a lot of people people will have heard this and they think of it in the sort of context of aggressive males or sort of big muscular sports players or something. But that's just not a complex enough way of looking at what is an incredibly complex hormone, which is also involved in our physical development as we grow and as we age. So what can we say about that? Yeah, absolutely. So testosterone is, when it's working well, you're not aggressive or any of those things exactly as you spelled out that can be some of the sort of hype that's out there. Testosterone is essentially needed to lead a regular life, be that to go through puberty as a male

to maintain what we call your secondary sexual characteristics. What does that mean? It might mean, for example, facial hair, body hair. Men need it for libido, they need it for healthy erections, and so on. So they need it for their muscle health. They absolutely need it for their bone health. So testosterone is doing many, many things in the body. If men don't have enough testosterone, that will lead to illness because, as we've just said, it does all these essential things in the body. And when you don't have enough, you become quite unwell, whether that's to do with your bone health, whether that's to do with your fertility and so on. So a bit like we said with the cortisol example, if a man doesn't have enough testosterone, then we replace the hormone.

That same paradigm again. If you don't have enough, we replace it. Yeah, so let's have a look at another thing that our hormones affect. That's how emotional states. So I think people will sort of glibly say things about hormones in emotional states. But again, the real picture is much more complicated to the level where it can cause things like extreme anxiety you talk about. So I found that really fascinating because, you know, again, there's all sorts of manner of causes for people feeling anxiety. But one potential cause

is, again, it goes back to our hormones. Yeah, I think that's right. I think firstly, hormones are often invoked in a negative sense when it comes to emotions. So there's this idea, you're hormonal, I'm hormonal, he's being very hormonal and I don't think we're meaning that as a compliment. But actually, hormones in health play a key part in mood regulation and us feeling calm and okay and, you know, in an upbeat mood and so on. What's a really important point to get across is we've said the brain produces hormones. We've talked about the hypothalamus. We've talked about the pituitary. Obviously, the body produces hormones. We've talked about the adrenals, for example. Where the connection comes in is the hormones from the brain control,

the body and the hormones from the body control the brain and there is this interconnectivity. We call it neuroendocrinology. There we go. So that's this idea that the two are in full communication. And when all is purring along really well, we don't notice our hormones. There's this quote I use in the book from the 20th century surgeon, a French surgeon called René LaRees. And he says, health is life in the silence. of the organs. So the idea that when everything is, you know, all your hormone signals are

pinging around beautifully, you don't think about them because your life just feels good. So let's have a look at other of these organs, these glands in our body that you mentioned earlier that, again, lots of people have heard of, but won't really know what it does. And that's the thyroid. Yes. It's one of those things, is it, that you sort of, oh yeah, I've heard of that word, but, you know, so let me fill you in. The thyroid is, is a gland that sits at the front of your neck, just in front of your windpipe, about the size of a butterfly,

and it produces thyroid hormone. Thyroid hormone we can think of as the metabolism hormone. It is driving metabolism in the body's cells. Metabolism is the way in which a cell changes the fuel that comes into it, the sugar or the fats or the amino acids. How does the cell change that sort of, incoming fuel into something else. That's what metabolism is. And the cell can either burn the fuel and produce energy, or it can use that fuel to build with, to build neurotransmitters or enzymes,

for example. And all of these metabolic processes are highly under the control of thyroid hormone. Now, we have 30 trillion cells, and each of them are very metabolically active. So you can imagine that if thyroid hormone goes wrong, either you have too much or too little, and metabolism is, either too high or too low accordingly, boy, can you feel really unwell. Yeah, so what are some of the symptoms? Again, like you said, it could be overactive, underactive. So say my thyroid's underactive, what are some of the effects that can have on my health and my body?

Your metabolic rate slows down. It's a bit like, I always think of the thyroid as being a bit like a sort of factory stoker in the olden days of sort of, you know, got cold. fire and, you know, it would be loading the fuel into the furnaces. Well, if your stoker goes AWOL and those processes sort of diminish and your metabolism dwindles to a flicker, that's your mesabolic rate slowing down, you can feel very tired, you can feel very low in mood, you can develop other manifestations, essentially the body working too slowly, things like constipation, for example. things like hair loss and hair not being replaced.

So it's almost like the body has gone into this kind of hibernation mode. And very, very important if people have symptoms to, and it's quite a simple blood test to diagnose this. You can diagnose an underactive thyroid on a blood test. Your GP can do the blood test. Once again, if you have too little, you replace it. So you take a thyroid hormone replacement tablet. So how about on the flip side, continuing this metaphor, if the stoker's putting too much fuel

in via the thyroid, what happens then? It's a great metaphor to continue. Essentially, you can imagine the furnace is roaring and just burning in overtime. So metabolism's going too fast. You lose a great deal of weight. A byproducts of metabolism, just like our furnace example, is heat generation. so you feel sweaty and uncomfortable and really, really hot. And like the example in the book, it's December,

and you're wearing a T-shirt and you're opening windows. You can get diarrhea, your heartbeat can speed up. You can feel very, very anxious, very difficult to sleep. Your hands can become tremulous. So it's one of the more dramatic presentations in endocrinology. So we've covered an awful lot there, and we've established the huge effect that, hormones have in our bodies. But sort of looking into the future, you know, what are some roles

that hormones are playing in our bodies that perhaps we don't have as good an idea of, you know, what's the sort of the next five or ten years? What are some of the targets that we'd like to figure out with our endocrine systems? Where we are at the moment, so we mentioned in the adrenal gland example, that autoimmunity often plays a big role in the body's gland not working well, an autoimmune strike on the adrenal glands or the thyroid gland, let's say. And as endocrinologists, what we're doing is we treat the outcome of the problem. We replace the hormone, let's say. But where I would love to see the direction of travel in this specialty is how do we address

the root cause and how could we even reverse that root cause, if possible. Sometimes a gland is wiped out. There's not much you can do. But it would be fascinating to think that rather than just treat the end damage and to say to somebody, well, then you have to take this hormone replacement, this cortisol replacement, thyroid replacement, whatever, for the rest of your life. And, you know, if you stop taking it or you can't take it for a while, whatever, you can become really ill, how do we actually go to a root cause and try and think, well, A, why is this happening? Could we

identify people at risk before it happens? Are there markers or some way to identify people? And how could we maybe either protect a gland or prevent that damage happening. So that I think would be a game changer. Thank you for listening to this episode of Instant Genius, brought to you from the team behind BBC's science focus. That was Dr. Syra Himede. To discover more about the topics we've just discussed, check out her book, Signals, The Inside Story of Our Hormones.

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