Is humanity approaching a catastrophic decline in fertility. Are hormone-hijacking chemicals to blame for falling sperm counts? Should we be concerned and what can we do about it?
In our first series we looked at endocrine disruptors - chemicals that disrupt our hormones - and the very real effect they might be having on human and animal health. And because they’ve shown to affect fertility in animal populations, one of the charges laid at the door of these disruptors is that they are also affecting fertility in humans.
No less an authority than environmental activist Erin Brokovich recently argued that hormone-disrupting chemicals were causing shrunken testicles and plummeting sperm counts, potentially spelling the end for humankind.
Certainly there are some troubling statistics: the birth rate is falling in many countries, and around a third of couples have some kind of trouble conceiving. So what’s causing this decline? Is it really down to rogue chemicals wreaking havoc with our hormones? And how worried should we be?
I’m Georgia Mills, and in this episode of Hormones: The Inside Story, we’re finding out there really is a fertility crisis, who it’s affecting, and what we might be able to do about it.
Just a note before we get going. We recognise that people’s gender identities don't always match up with their birth sex, but generally when we're talking about men or women we're referring to people born male or female, with the sex hormone profiles to match.
So, first things first - what’s going on?
Channa: So for women, I think that it's clear that there's a falling birth rates, but worldwide that's predominantly due to understandable and welcomed changes in social behaviour, such as increased participation in the workforce, and improved provision of education for women.
Georgia: This is reproductive endocrinologist Channa Jayasena from Imperial College. But, even as an expert on baby-making hormones, he’d be one of the first to agree that it’s not necessarily hormones that are to blame.
Once countries reach a certain point of widespread education and healthcare, an almost universal fall in birth rate occurs. This is partly because of the much lower child death rate - you don’t need to have so many kids to support the family if all of them are going to make it to adulthood - as well as access to and education about contraception. More broadly, there are also changing gender roles and attitudes towards women in society, meaning that motherhood is not the only option, or it’s something that can be put off until later in life. But that does bring its own problems...
Channa: And what that's done is resulted in the average age of first motherhood rising above 30 in the U.K. for the first time. And what that means is that because we're all less fertile when we're 30 or 40 than when we're 20, then clearly we are having fewer children overall and there will be more infertility around.
Georgia: But, as the song says, It Takes Two - making babies is a two player sport, and female fertility isn’t the only issue here.
Channa: Now, for men, it's a very different story. And there does seem to be objective evidence that over the last 40 years, sperm counts have dropped remarkably more than more than 50 percent in North America and Europe.
Georgia: We’ll come back a bit later as to the reasons why fertility might be falling, but before that let’s get back to basics with a bit of the birds and the bees.
Suman: Hi Georgia, I’m Dr Suman Rice, and I'm a reader in reproductive physiology at St George’s Hospital in London.
The biological act of baby-making starts when egg and sperm meet, so first let’s take a look at where eggs come from, with the help of Dr Suman Rice and some handicrafts.
Suman: And I'm showing you here my little knitted ovary that I've got - a crocheted ovary connected to fallopian tubes. And the uterus and the cervix so really actually when you think about fertility in a woman, you can't just think about the eggs produced here in this ovary. You've got to think about: are these tubes able to transport the egg all the way down and all the sperm able to travel up this tube to meet the egg because fertilisation occurs here and in this tube. And then the fertilised egg - known as an embryo - will travel down. And obviously the lining of the womb here has to be receptive, has to be at the right stage and thickness to receive that egg. And beforehand, the cervix itself here has to be able to allow the sperm to travel up and not kind of be a hostile environment for the sperm. So really, when we think about the whole of our fertility, it's this whole system has to integrate together.
Georgia: I love the crocheted ovaries. So the sperms have quite a long way to go down there.
Suman: Oh, massive, massive journey. I think some people have calculated it and in something like thousands of miles. And this is why we produce millions and millions of sperm because, again, it's survival of the fittest - who can make that journey and win the prize of fertilising the egg.
While there are multitudes of sperm, the egg is bigger with more resources in it, so there is usually only one released each month - but these eggs are made very very early on.
Suman: have been laid down when you were a baby in your mum's womb.
Georgia: That's quite mind blowing. And it's and it's I guess that brings us to the idea that we have a finite reserve. We're not making new ones as we go. And that’s tick, tick ticking away.
Suman: Exactly. So unlike sperm, which can be made ad infinitum, so to speak, though, of course, there are challenges now we're beginning to see with older fathers, so to speak. But yes, for women, we have this finite fertility which is determined by this ovarian reserve. So once we're born and once puberty is established, we're losing follicles all the time, naturally by what we call atresia, which is just a process of cell death. We estimate that we only have about 400 cycles. So you'll ovulate only 400 eggs out of those half a million or a million that you are born with. And of course, once you've depleted all those follicles, we enter into menopause. So you can see that your age when you with menopause and also your fertility potential is determined by that ovarian reserve.
Georgia: I’m in my 30s, and like many women my age I’ve heard that female fertility falls off a cliff when we hit 35. So while I’ve got Suman here, I have to ask is this really true?
Suman: Thinking about the cliff, so now there's no doubt that we lose primordial follicles, as I said, throughout your reproductive life. And what do I mean by reproductive life? Reproductive life is your reproductive lifespan could be considered the age of menopause, minus the age of menarche. So when you started your periods
Actually, it's not that one thing, but really is that cliff face as steep as it is out? For me personally, I think of it, it's more of a gradual decline rather than a steep drop off. But the issue is that the gradient of this decline can vary from woman to woman, because the ovarian reserve will greatly vary from woman to woman.
And some years ago, as part of my research project, I used to collect tiny biopsies from the cortex, the outer edge of the ovary, when women were having elective caesarean sections and all the primordial follicles in this outer edge. And then we would be able to do research on this. And one of the things I was doing was counting the amount of follicles and doing some modelling. And it was really interesting that in the women who were in the 30 to 39 age bracket, some of them would have the number and stages of follicles like a woman in her 20s, and some would be like women in their 40s.
Georgia: There are a few things we know can affect our store of egg follicles, including exposure to certain chemicals - including those found in cigarette smoke. And there can be hormonal conditions too.
Suman: Polycystic ovary syndrome, as we said, is the most common endocrine disorder affecting women of reproductive age. And it's been very kind of a long journey to get it first diagnosed properly and for a consensus on the diagnosis. And I think some of the problem also comes from the name, unfortunately named polycystic, because there are no cysts. They are actually just the big follicles that have stopped growing. And many things can affect these. We know what is disordered is that they have excess androgens, the male hormones, are produced from the ovary in excess, which can, of course, then result in a lot of other issues that women with PCOS have. Like they can get male pattern baldness, they can get excess hair on the contrary, they can get a lot of acne. And that's all caused by this excess androgen. So it's very multifaceted and multi complex. And part of the problem is that it can manifest in teenage years, but often it's not picked up by GP's or people treat it symptomatically. So in the early stage, a lot of young women are more concerned by the aspects of excess hair and the acne and things like that. And they're not necessarily thinking about their fertility. So the treatment is all symptomatic. So to treat that. But then, of course, as they get older and by the time they think up a baby, then that's the problem.
PCOS affects around 1 in 10 women in the UK, and researchers are still trying to discover the cause of this hormonal error, and it’s a battle for many women to be diagnosed.
So, let’s take a look at the sperm.
Georgia: So that’s eggs, but what about sperm?
Rod: When it comes to sperm, nature has a few surprises for us. If you take the sperm of an elephant and you compare it to that of a mouse, you'll see that the elephant sperm is much, much, much smaller than that of the mouse. But perhaps even more surprising is if you take the sperm of a fruit fly and you stretch that sperm out to its full length, you'll find that that sperm is actually five centimetres in length, which, compared to the size of a fruit fly itself, is somewhat remarkable.
This is Rod Mitchell, Professor of developmental endocrinology at the Centre for Reproductive Health in the University of Edinburgh.
Rod: My main interest is in fertility in males and particularly focussed on the development of the testicles in males and how things that might go wrong or impact on that development in early life, either foetal or during childhood, can then determine what happens for that individual when they become an adult male. So it's really developmental issues on reproductive function.
Georgia: And you say you're interested in male fertility are female fertility and male fertility, I was about to say bedfellows, but that's probably the wrong turn of phrase. I mean, are they completely different fields? Is there any common ground between the two?
Rod: So the hormones that drive male and female reproductive function are essentially largely the same. They don't always do the same things in males as they do in females. And I think, there are other similarities between reproductive function, but at the same time, there are major, major differences.
I think when it comes to male fertility, I think we are now coming to a general consensus that there is a reduction in male fertility. And here we're talking about really sperm counts in adult males. And whilst there are still some people who would disagree with that, I think the main question we're facing now is actually: to what degree is this decline? And probably equally as importantly, where are we headed with this? So is this going to be something that is going to continue and are we going to start to see more and more harmful effects of this over time?
Georgia: An expert in the field, Shanna Swan wrote a book called countdown, in which she underlined the worrying trends of declining sperm counts - are we approaching a world without sperm?
Rod: The book largely talks about that if we continue our trajectory in declining sperm counts, then we'll end up with sperm counts of zero by somewhere in the region of 2045. And the question really is, is that what will happen in reality or will there be some kind of, if you like, almost compensation for this reduction in sperm counts that will allow us to retain and maintain fertility over the long term? And I think that is a good question. So I'm not convinced that we are facing Armageddon when it comes to sperm counts. But I do believe that there is a reduction in sperm counts. And I do believe that it's something that we need to be aware of and look into the reasons why and also think about how we can do something about it.
Georgia: And just before we get into why this might be happening, why is sperm decline a problem in fertility? Because the one thing most people know about sperm is that there are lots and lots of them to begin with.
Rod: Yeah. So when we look at sperm counts, essentially, we know that there are millions of sperm in an ejaculate. And we also know that once you reach a certain level of sperm that anything above that doesn't necessarily increase your fertility. So there is a kind of a critical threshold where once you fall below that, then the risk of infertility increases quite substantially. So it's really ensuring that we maintain sperm counts above that threshold to know that we will have, if you like, normal fertility. And if we drag everybody down and we start to reach that threshold on a more regular basis, then that's when we're starting to see the major issues.
Georgia: Although only adult males make sperm, these problems with fertility actually seem to start much much further back in life.
Rod: So we're now starting to understand that that it may well be development of the testicle right from the very early stages. So right from foetal life that can be potentially impacting on that adult's future reproductive function. And this is something that's become more widely recognised over the last sort of 20 to 30 years or so. But knowing exactly what those causes are is more difficult. And so what we think is that we think that this is very much likely to be environmental and lifestyle factors that are behind it that would make sense in terms of things happening over a relatively short period of time, i.e. decades. But what are those environmental and lifestyle factors and how can we actually prove that these are the things that might be affecting fertility? And that's a big question, I think, for the field at the moment.
Georgia: Do we have any likely candidates?
Rod: The common things that you will hear talked about are certainly lifestyle factors. So obesity, smoking, alcohol, these types of things, these are very commonly spoken about in relation to how they might impact on fertility. And the other big group of factors that people look at are what we now see in our industrialised world. So we're talking here about chemicals, particularly synthetic chemicals that might be interfering with hormone development either during foetal life or as development progresses. And you'll hear many factors talked about, so for example, plastic, it's not that infrequently that you'll open up a newspaper, read an article online about bisphenol A or phthalates, these types of chemicals and whether they're associated with fertility issues. So these are really the main factors that people propose. But what we're starting to recognise now is that perhaps it's not just things that we're exposed to at very low levels like these chemicals, but actually maybe even medications or pharmaceuticals that individuals are taking that might be affecting fertility.
Georgia: It’s going to be a tricky task to unpick all the elements of the chemical soup that surrounds us, to discover which of them might be impacting our fertility.
Rod: There are so many different chemicals, you know, we are exposed to thousands and thousands of chemicals all the time in our environment. All of the chemicals will have their own specific combination of actions. Some of them will overlap. Some of them will be specific. And they might not actually be always hormone pathways that they're affecting. They can affect other types of signalling mechanisms. I don't think it's a case of one particular mechanism or hormone that is affected by all these different things. I think it's actually could be or is likely to be a variety of different mechanisms.
Georgia: mean, if we do find out “blank” is causing this problem, you mentioned that it's very likely to be problems in development that are causing these problems infertility later in life. So does that mean that we've got a bit of a lag in any sort of solution we can come up with? It might be 18 to 25 years before we start to see an improvement?
Rod: Yeah, I think that that probably is one of the difficulties. If this is a developmental thing, then you do have maybe 15 to 20 years from an exposure to an outcome in terms of fertility. You obviously can't measure a sperm count until an individual reaches adulthood.
So there IS a problem. And it is not an easy one to fix. So is there anything we can do? Channa Jayasena
Channa: Well, short of, you know, the really important climate change and environmental lobby that we all know about in society that I think need to change. There is a lack of treatments that we have. So, for example, we know that pollution can provoke asthma, but we have excellent treatments for asthma. And I'm saying it's the solution. But for people who have already been affected, then we currently have a situation whereby there is absolutely no approved drug or treatment for a low sperm count. So a low sperm count is one of the most common reasons for a couple not being able to have a baby naturally. And yet there is no drug to treat it. And that's either because it doesn't exist, will never exist, or more likely that we just haven't invested enough time to look into those. So, where I work, that's one of the things we're trying to do. We're trying to discover this tranche of drugs that can help us to complement changes in policy, which are really important, to also help people who have been affected.
And something else that might help is reframing how we view fertility - it’s so often seen as a woman’s worry, and this framing, alongside stigma - has held up research.
Channa: I think it's really unfair. And I think if you look at society, you know, women have always been blamed and given the responsibility of starting a family, whereas clearly it takes both partners. And what we have at the moment is a perfect storm where it's the male infertility that's particularly suffering. And we know very little about it because we have ignored it. We haven't done enough research into it. And it's difficult to do because historically there's been a stigma associated - that's changing - but it will take time for us to develop the same level of treatments and support for men as we do have for women.
It’s a problem we really need to fix, whether you want children or not.
Rod: I think this points to potentially wider issues. So we certainly know that fertility, sperm counts, hormone production, reproductive hormone production are also associated with other health problems. So it might be that even if you're not concerned, particularly about this from a fertility perspective, it might be pointing to general other health issues that we're facing today and that might be considered perhaps by some as more serious. So, I think it could be very much a warning to us, if you like, the canary in the coal mine, almost as you often hear about.
Georgia: So is spermageddon really approaching? Some definitely think so, while others are more optimistic about the future of humanity’s baby making abilities. We can pin some of the decline in global birth rates on changing societies and personal choices, but there does seem to be something else going on too.
Again we return to the problem we discovered back in series one, that endocrine disrupting chemicals are everywhere. The complex interplay between our hormones, fertility and the wider environment means that it’s not going to be easy to fully understand the problem - and also that it’s likely to be hard to address it.
Even so, the lessons from the past and the discovery of the impact of endocrine disruptors on wildlife populations tell us that this is definitely something that researchers around the world should be keeping a close eye on.
Thanks to my guests, Channa Jayasena, Suman Rice and Rod Mitchell
This show was produced by me, Georgia Mills. Kat Arney is the executive producer and it was made by FIRST CREATE THE MEDIA. Thanks for listening, and goodbye.