Ever wished that you could change your height? We investigate how hormones affect our height destinies, and what they have to do with the legend of the Irish giants.
This is Hormones: The Inside Story, the podcast from the Society for Endocrinology about the tiny things inside us pulling the strings.
Human height ranges a lot. The tallest person on record, Robert Wadlow, clocked in at an incredible 2.72 metres, or 8ft 11 inches in old money, while Dangi, the shortest adult, was just 54.6 cm or 1ft 9½ inches. More generally the average height changes through history, as anyone who’s bumped their head on a medieval door frame will know. It also varies by country, with the current chart-toppers the Netherlands having a nearly 8 inch height advantage over the shortest nation, Peru. And although there are some very tall women and some very short men out there, height also tends to track roughly with birth sex, with a typical global average male currently having a roughly 12 cm advantage over the average female. As for me, I am below average for the UK height, as I’m constantly reminded as people pick me up, so there have been moments precariously balanced on a stool to reach something from the top cupboard, where I’ve wondered if it’s possible to change my height destiny and get any taller.
I’m Georgia Mills, and in this episode we’re asking, can I hack my hormones to get taller?
Let’s start with the major hormone involved - and its name is a bit of a giveaway.
John: Growth hormone is what it says it is on the tin, it causes growth and it comes from a little gland in the head called the pituitary gland, which sits just behind the eyes. And it comes out in pulses often mostly at night. And it makes you grow and it makes you grow by stimulating the cartilage at the growing ends of the bones.
Georgia: This is Professor John Wass, he’s the chair of endocrinology at Oxford University
John: And it's a little bit more complicated than that because growth hormone actually stimulates the production of something called IGF one or insulin like growth factor one, which comes from the liver. And IGF one actually probably affects the cartilage more than the growth hormone itself.
So basically what the effect of growth hormone is probably not related to how much is being released. It's a question of the of the growing ends of the bones responding
And then, of course, you don't grow, grow forever. And so at various times in your life, you grow. Certainly from birth and then the most important thing about it is that you grow around puberty.
We grow a lot as babies, and then steadily get bigger, until puberty hits and WHOOSH - growth hormone and our sex hormones join forces to really get things going.
John: And then the two hormones work in concert so that basically growth hormone and oestrogen or testosterone caused this this growth spurt.
Georgia: so and then once we see what happens because we don't get to keep growing our whole lives
John: What happens then: at the growing ends of the bones there's cartilage before the end of growth. And at the end, these so-called fuse - that’s they join up. And so there is no longer any growing end of the cartilage in the bones, the long bones, which actually cause growth. And so that's what happens to stop growth. And then, of course, growth hormone production carries on. And what's interesting, actually, is that you'd think that growth hormone just causes growth and really isn't very important after puberty. But in fact, I hope and think that your next question might be, well, what happens and what's the purpose of growth hormone after puberty? And it doesn't cause growth at that stage, but actually is responsible for a whole host of other things which actually sort of maintain the quality of life.
Georgia: Why are some people just taller than others?
John: Well, and so there's something called the mid-parental height. And so if your mother and father are measured and in centimetres and they're totted up and for a girl, you take away 13 centimetres from the mean height of the mother and father and you divide by two, and that gives you an 80 percent prediction of a child's height so that if the father's tall and the mother's tall, then they're likely to have a tall son or daughter. And so the answer to your question is that it's a very genetic thing. So if your mother's five foot one or something, then you're unlikely to have a tall child. But if your father and mother are both tall, then the child will be tall.
Genetics are a big part of the story here. Height is one of the most strongly heritable human traits, with around 80% of the differences in height between people being down to variations in our genes. In fact, height is so hardwired into us that you usually guess what height someone will be once they are about two years old, as John likes to do with his own family.
John: It is quite interesting because, you know, you go around as the endocrinologist in the family predicting all your nephews’ and nieces' heights. And actually, you know, this was done a few years ago. And I think most of them are fairly accurate. Uncle John, they say this is what you predicted I'd be and I am. So it's rather nice.
Georgia: Amazing. You can buy clothes ahead of time.
And what about sex differences in height?
John: So the reason that girls tend to be shorter than boys is that actually girls go into puberty and get their growth spurt a year or two before boys do. And so girls go into their puberty, they start growing and then they actually stop growing probably a year or two before boys stop growing. And so that's why girls tend to be shorter than boys. And that's why around puberty, there's what's called the pubertal growth spurt, and that's because sex hormones stimulate the growing ends of the bones as well as growth hormone.
Georgia: And how you hear this and you hear people now and in the past, I might have been a bit of a giant back in the day. So why do you think that is
John: that you're asking some stupid questions? So in the reign of Henry, the eighth two things. Number one, the children were a lot shorter and Henry VIII, of five foot eight, was taller than most of his people in his court. So that was one thing. But I think it was thought that nutrition was less good in those days. And so I think that one: nutrition is better nowadays. So nutrition is important. And that's one of the reasons why it's thought that people are taller now and then the other thing is that puberty was actually much later. It's interesting that puberty was much later. So in the reign of Henry VII, the periods didn't usually start till around 18 and now they normally start 11 or 12. And so it's very different. And those are the two differences. So the answer to your question is, why are we taller now than we were? And I think that's largely nutrition.
Georgia: And as we get older, we start to lose a few centimetres.
John: Oh, yes, our poor old queen. And so basically this is why. So this has nothing to do with growth hormone. What it is, is that you actually get sort of what's called kyphosis or bending of the back, and you can actually get thinning of the bones and can collapse vertebrae in the back. And so a lot of people who are older have a curvature of the back and lose height. And that's nothing to do with growth hormone. It's related to their bones and things actually changing in shape so that there's more of a curvature of the spine.
Georgia: So to summarise - growth hormone is released throughout life, and it causes the creation of another hormone, IGF 1. Before puberty it acts on the ends of our bones, making them grow longer. Once puberty hits, enter the sex hormones which cause a further growth spurt. And then once puberty ends the growth party is over and the ends of the bones are effectively sealed off, so there’s no more bone growth, even if there’s more growth hormone sloshing about.
And in fact because growth hormone does other things, if you were to take growth hormone it could have lots of unintended consequences.
Georgia: If you get a pituitary tumour that causes an excess of growth hormone post puberty, you still get the growth hormone increase, but its effects are very different, leading to what’s known as acromegaly.
John: The prevalence is 40 to 60 cases per million of the population and those new cases of four per million of the population. And this has a whole load of different effects that can affect hands and feet. It causes people to sweat more often and it can give headaches and so on. And so there are a number of different symptoms with which people can present, and then they gradually change their facial appearances over the years. Post puberty, the bones are carrying on growing. They don't, as I say, get longer, they get wider. And you can see a patient who's got growth on excess, sometimes in their hands, because their hands are bigger, their rings change size the ring, the rings need enlarging.
So as an adult, growth hormone won’t make you taller, but might have side effects. But what about pre puberty? This is where growth hormone increases can make a massive difference.
Márta: And if you have too much of this growth hormone, then you develop quite severe symptoms. And if this happens in childhood, you begin to grow faster than you supposed to be through, and that for you can grow to be a giant.
Georgia: This is Márta Korbonits, professor of endocrinology at Barts and the London School of Medicine and Dentistry at Queen Mary University. Her work has involved tying science to legend in a way that has changed lives.
Márta: Yes, there is an interesting link with giants and Ireland.
There is even a legend that is the Irish legend of Finn MacCool, so popular folklore suggests that. The Giant’s Causeway was built by Finn MacCool, as stepping stones to Scotland so as not to get his feet wet. He also once scooped up part of Ireland to fling it at his Scottish rival, but it missed and landed in the Irish Sea. The clump became the Isle of Man and the void became all of Lough Neagh. And for me, the story started when I heard that there is a medical museum in London called the Hunterian Museum. And my professor of endocrinology who trained me here in London, Professor Michael Basser, suggested that I visit the museum because there is a skeleton there of a giant and he's called the Irish giant
Just like that, the Irish giant.
He actually had a name. His name was Charles Byrne. But everybody just mentioned him as the Irish giant.
So Charles Byrne was born at the end of the 18th century and he started to be tall in his childhood. So much so that sooner or later he was exhibited in markets and travelled around in his area. And then he became so tall that he was quite exceptional. And therefore he started travelling around not just in Ireland but also in Great Britain.
Georgia: Marta knew from her work that pituitary tumours can cause massive increases in growth hormone - leading to excessive height. But for a very long time it was unclear what caused these tumours.
Márta: So I was interested that we had quite a lot of patients with this disease and got interested that could there be a genetic background. And then in 2006 a publication appeared with describing a gene in some patients from northern Finland with this particular disease and identifying a mutation in a gene called AIP. So soon after I started to test these families, which I had by then, whether the harbour a change - what we call a mutation - in this gene and indeed the very first family in my kind of collection called Family One, they had a mutation in this particular gene. So I was extremely excited that this is indeed something which can be identified in patients.
Georgia: And Marta noticed that some of them came from an area in Ireland very close to where Charles Byrne was from. So Marta got wondering, could all these cases be connected?
Márta: I kind of jokingly said to my colleagues, “could there be a link with the Irish giant in the museum, you know, in the Hunterian museum?” And they just laughed at me. But I actually took my own silly idea quite seriously and wrote a letter to the museum saying that I have a family from Ireland and I would like to study the DNA from the Irish giant.
So by the time I got permission from the Hunterian Museum to actually study the DNA from the 18th century skeleton, I was practically sure what I would find.
Georgia: Sure enough - a sample of Byrne’s bone from Byrnes revealed that he had the same genetic mutation Marta was seeing in her patients. Could this be the root of a - literally - gigantic legend?
Márta: We did these calculations and realised that this mutation is in Ireland for quite many years and actually. Probably explains all the Irish giant stories and folklore and historical kind of description of these giants based on this single family.
Georgia: Not only is this a piece of fascinating folkloric and genetic detective work, but it means that we now have a way of identifying families in this area who are carrying this genetic variant and are therefore at risk of developing pituitary tumours, so they can be offered preventative surgery or drugs.
Márta: The main issue is that we need to look at these families, look at the young people and the children screened. If any of them would have the mutation and the ones who have the mutation would be followed. And this is not a very complicated follow up. They just need to be measured at least once a year and see if their growth is normal over the years. We now had quite a few cases which we identified this way. Cases means that patients who started to develop high hormone levels and started to develop a tumour in the pituitary gland. And several of these cases have been operated on. And according to our last kind of assessment, which was published in 2020, we found that all the cases which were identified in this prospective way were a lot milder than the cases which were identified based on their symptoms, suggesting that the screening is working. It has a clinical benefit.
So my motto would be that: no more giants.
So it's totally devastating to be a giant. I mean, patients are very wary that they are looked at on the street. There are stats that they are teased at school. It's something which is really horrible. So it's very important from a psychological point of view to avoid this as well. But also the medical point of view, because a lot of the complications, such as on the heart, on the bones, on the soft tissues, on their on their jaw, you know, any part of their body there are at disadvantageous complications.
Georgia: If anyone’s listening to this and feels tempted to try and get hold of some growth hormone to boost their height, alas, your bones aren’t going to get any bigger, and it probably won’t do your health much good. But it’s a different story for kids who seem to be slow to sprout.
Helen: Slow growth in children is a really sensitive indicator of health and well-being. So any kind of insults or impacts on a child can cause them not to grow
Georgia: This is Helen Storr, a professor in paediatric endocrinology at Queen Mary University of London
Helen: But one of the commonest things that you may hear, one of the most common hormone problems is growth hormone deficiency. And that's one thing that as a paediatric endocrinologist, we diagnose and treat.
Georgia: As for your role in the clinic, how do you know when someone is just a little bit short because there is natural variation and how do you know when treatment is required?
Helen: Yes, so. I mean, there are two categories of children with short stature, you can get normal variance or short stature, so that's when a child is short, but they might be normally short. So they might have a problem. That is it's not caused by underlying pathology and they end up catching up and they have normal adults predicted height. So those children, we can usually measure them in the clinic, look at the family measurements, look at how they're growing over a period of time. In some cases, we may do some basic blood tests or some other tests, and then we can usually reassure them that they're fine and their growth is going to be appropriate for their family's height.
Georgia: And is it common, because tall people are more likely to get into positions of power. I think they earn more and they're more likely to be on sports teams. Do you ever get people who are within natural variation, but they want to go for them to be taller than they would have otherwise been?
Helen: Yeah, we do. I mean, we do see a lot of concerned families. And I think one of the problems is that in the UK, we're not very good at screening children and measuring children. So in many European countries, this is a natural part of public health. Children are measured and weighed and reassured. So I think many children, you know, may get to a point where, you know, they're concerned or the parents are concerned. And we do see a lot of those children and often with, you know, with careful measurements and explaining, you know, that they may have some growth to come. For example, if it's a child who isn't yet in puberty, a lot of people don't understand that in puberty you have this big pubertal growth spurt and sometimes children have, you know, a lot a lot more growth to come. And that often does reassure people. But people do hear about growth hormones and they do think that sometimes it's something that might help their growth. But actually, growth hormone is something that is only prescribed for very specific reasons. There's only a license for very specific conditions.
Georgia: So, can you hack your hormones to get taller? If you’re an adult, the answer is a definitive no. The best way to be tall is to have tall parents, access to good nutrition growing up - and maybe a good pair of platform shoes.
Thanks to our guests, Marta Kobonits, Helen Storr and John Wass.
