The Dr Louise Newson Podcast - 28 - How synthetic hormones can rewire the female brain

Episode Date: October 7, 2025

For more than half a century, "the Pill” has been a routine part of women’s lives, prescribed not only for contraception but for acne, period pain and hormonal regulation. It’s so deeply woven into modern medicine and culture that most of us rarely question how it works or what it does beyond its prescribed use.In this episode, Dr Louise Newson speaks with psychologist, researcher and author Dr Sarah Hill about the untold story behind synthetic hormones and their impact on the brain. Together, they explore how shutting down natural hormone production and replacing it with synthetic versions can alter mood, motivation, cognition and mental health - changes that are often dismissed or overlooked in both medical practice and public conversation.Dr Sarah Hill also explains why progesterone remains one of the most misunderstood hormones in medicine. Far from being a simple reproductive regulator, it plays a vital role in neuroprotection, inflammation control and emotional stability with implications for conditions ranging from anxiety and depression to postnatal mental health and autoimmune disease.This episode challenges decades of cultural assumptions about women’s health and invites clinicians, researchers and patients alike to rethink what we know (and don’t know) about how synthetic hormones shape the female brain.LET'S CONNECT  Subscribe here 👉 https://www.youtube.com/@menopause_doctor Website 👉 https://www.drlouisenewson.co.uk/Instagram 👉   / @drlouisenewsonpodcast  Download balance app 👉 / https://www.balance-menopause.com/balance-app/ LinkedIn 👉     / https://www.linkedin.com/in/drlouisenewson/ TikTok 👉   / https://www.tiktok.com/@drlouisenewson Spotify 👉 https://open.spotify.com/show/7dCctfyI9bODGDaFnjfKhg LEARN MORE Join me on my upcoming theatre events in London and Birmingham 👉 https://www.nlp-ltd.com/dr-louise-newson-qanda/ Buy Dr Sarah Hill’s new book, The Period Brain 👉https://www.sarahehill.com/books/ Take my online education course, Hormones Unlocked 👉 https://www.learningwithexperts.com/products/hormones-unlocked-dr-louise-newson Sign up for my Confidence in Menopause Course 👉 https://www.drlouisenewson.co.uk/education---confidence-in-menopause  

I hope some of you will be able to join me at my two remaining theatre dates for World Menopause Month in October. I'm going to be at Birmingham Town Hall with Liz Earle on the 12th of October and on the 19th of October I'm going to be with Emma Barnett at the Rose Theatre in Kingston near London. They're live Q&As, I'm going to be questioned and then your questions in the audience are going to be answered by me. I'm really looking forward to meeting some of the questions. of you there. Dr Sarah Hill is the guest on my podcast today. She is a researcher, she's a psychologist and she's also an author. We talk a lot about the differences between synthetic and natural hormones and the impact that they can have on our brains, how contraceptives can have negative effects, but also how important progesterone is in our body and brains. Progesterone is still an underrated

hormone and so she talks a lot about it. So it's a great conversation that I just hope opens your mind a little bit more to the very beneficial effects of hormones. So Sarah, I have been stalking you for longer than you realise actually and you know your work is wonderful. Obviously you're a scientist, you're an academic and a researcher and this book, How the Pill Changes Everything and capital P for pill, by the way. So this is the contraceptive pill, which has become so common. And even quite soon after it, it was launched, people was just calling it the pill. And people know it's the pill. But actually, do people know what it is and what it contains? And the, you know, it's called birth control, but it's not just given to prevent pregnancies. So there's a lot really that really

resonated when I read this book with the way that I think. And I'm very, you know, very interested in the role of hormones on our brains. I'm very interested in neurophysiology, neuropharmacology, neuro pathology. The whole function of our brains, because as humans, our brain is the most important organ without shadow of a doubt, but it can be altered quite significantly by very small changes. And this is really what your book really talks about really eloquently, doesn't it? Oh, thank you. Yeah, you know, our brain, it is. I mean, it's like, it's what creates the experience of being the person that we are, right? And, and one of the things that it takes in to create that experience is our hormones. And so our hormones are, even though there is

this tendency for us to think of them as something that happens to us, like, oh, you know, hormonal or whatever, they're a key part of what our brain uses. is to create the experience being the person we are. And so when we change our hormones, that means that we change women. And this is something that I don't think that, you know, most people really had any awareness of, you know, because it's like when you take the birth control pill, a lot of times you're taking it for some specific end, whether it is contraception or whether it is to clear up acne. I know that it gets prescribed for that reason.

Sometimes it gets prescribed for managing or trying to, you know, stop the symptoms of things like endometriosis and PCOS. But so it's like you take it for whatever the purpose is that it's being prescribed. But you don't think about the fact that you're shutting down your hormone production, right? So it shut us down women's own hormone production and then it replaces it with the synthetic. and of course that causes sweeping changes throughout the body, including the brain. And how did you first get into thinking about this and doing your research and writing about it? Yeah, it's funny because I spend most of my career just studying women and women's motivational states, so I'm a psychologist.

And one of the things that I had done research on and had published research on is, you know, the effects of women's naturally cycling hormones on motivational states and attraction and those sorts of things. And so I had an awareness of the fact that our hormones matter, right? And that women's hormones influence how they think and feel and experience the world. But I never thought twice about the birth control pills that I was taking every day and took for more than a decade of my life because I was on hormonal birth control for probably 11 or 12 years, give or take. And I didn't really spend any time thinking about them at all until I went off of them. And then within a couple of months of going off of them, all of a sudden, you know,

I started to recognize that I was feeling different. Like, I was like, you know, I had been downloading new music for the first time in a really long time on my phone. I was going to the gym again. I started growing my hair out again. I had more energy. I was like interested in sex again. I just felt like everything felt deeper and richer and more interesting to me. And I thought, oh, my goodness, like the pill.

Yeah. You know, and it was my experiences where it was like all of a sudden I had everything click into place where it was like, Of course, you know, I feel different when I went off the pill because, of course, it was different when I was on it. And so I finally was able to put two and two together. And I realized that if I had a blind spot with a birth control pill, right, being somebody who studies women's hormones and how they influence motivational states and the fact that it never even occurred to me that my birth control would be influencing how I feel and experience the world, I knew that most women probably also didn't know this information. And so I went to the research literature and I dug up everything that had been published on the relationship between birth control use and women's brains. And yeah, that was the birth of the book. It's so interesting.

And, you know, like you, I took the pill for many years as a medical student and junior doctor. I didn't even think about what it was doing to my own hormones. and I prescribed it for many years. And obviously I knew that it stopped ovulation because it was, you know, a contraception. But I didn't think that it's suppressing our own hormones. And so many people, even now, just think about, you know, women and periods, women in the womb, women and the hormones and our ovaries.

And, you know, even gynecologists sometimes are so focused on our pelvic organs, they forget that hormones, including progesterone, estradiol, testosterone, go in our bloodstream, go to our brain, but they're also made in our brain as well. You know, they have really important roles in our brains. So blocking them is one thing, but then also giving a synthetic hormone is, for some women, gives other sort of more detrimental effects or side effects that can really affect their mood and their cognition and motivation and everything, content? Yeah, for sure. I mean, you know, when you look at the birth control pill and the different types of side effects that are related to it, whether it's, you know, differences that we see in

mental health because we see that women on the pill have an increased risk of developing depression and anxiety. We also see that women on the pill have a greater risk of hypoactive sexual desire disorder and some of these other things when it changes sexual desire and it can change cognition and so on and so forth. And a lot of these changes. And a lot of these changes, is, you know, it's like when we look at why it is that women experience these side effects, it seems that there's kind of two big answers, right? The first answer is just by shutting down a woman's hormone production, which is what we do when we shut down ovulation,

because that's how female bodies make hormones, is that causes its own set of side effects. Because, you know, when you shut down ovulation and you shut down the production of estrogen and progesterone, this doesn't generally feel. very natural to women. Like it's not, our bodies are experienced as, you know, experiencing these beautiful rise and fall of our two primary sex hormones, estrogen and progesterone, and not experiencing that doesn't,

it's a weird state to be in and it can be related to things like low libido, for example, which is related to having relatively low levels of estrogen and low levels of testosterone because testosterone also changes in response to the birth control pill. But so that's like one, you know, so like some of the side effects that you get are related to the fact that you're shutting down your own hormone production. And the other set, as you noted, is the result of the fact that these synthetic hormones are a little bit funky.

And in particular, the progestins that are in hormonal birth control are not biologically identical to progesterone. And progesterone has a, you know, and progesterone has a, you know, number of qualities that are really lovely to the brain and to the rest of the body. And when progesterone is being metabolized and broken down in the body, it releases this really powerful neuroceroid called alopregnolone. And it does things like help increase neuroplasticity. It helps to stabilize mood.

It's anti-anxiety because it has this really calming effect on the brain. It's part of how the brain is able to regulate emotional states. And naturally cycling women, when they release progesterone, are able to get all these really beautiful benefits of allopregnanolone. Because, again, when this is something that's released, when progesterone is being broken down in the body. And when you're taking the birth control pill, which contains these progestins, which are most of which are synthesized from testosterone,

So they're not synthesized from progesterone. They're made out of testosterone. When they get broken down in the body, they don't release alipregnolone because they, you know, they're not, that's not what they're made of. And so research finds that, for example, that women who are on the pill have much lower levels of alipregnantalone, which is probably also then, you know, contributing to some of these side effects like mental health problems, anxiety, feeling overwhelmed and unable to regulate stress. And so, like, you get some side effects like those, for example, that are the results

of the fact that these progestins are not biologically identical to progesterone. And you also get some weird things where, you know, these progestins, because they're synthesized from testosterone, and they're just kind of monkeyed with, so that way they'll also get picked up by progesterone receptors. Sometimes these hormones will still continue to stick. stimulate testosterone receptors. So it can lead women to experience things like hair growth, like facial hair growth, and some other types of losing their hair because of their testosterone receptors being stimulated by these progestins.

And they've also found that some of these progestins like to stimulate glucocorticoid receptors. So these are cortisol receptors, which essentially makes your body think that you're going through a stressful event because it's activating that cortisol. cell pathway. And so this also can contribute to feelings of extreme anxiety and overwhelm and ultimately mental health, you know, mental health related issues. Yeah, and it's so important. I did a recorded a podcast recently with my middle daughter and she talks a lot about her friends. And I see it a lot and I've seen it a lot over the years as a GP as well, that people have started on contraception, whether it's the pill or whether it's an injection or whether it's an injection

or an implant of a synthetic progestogen, and then they go on antidepressants. And, you know, it's this downward spiral and no one sort of really associates the two together. But it can really have such an effect. And a lot of people just feel very flat, very joyless, very demotivated. And then, you know, I see so many women who've tried three, four, five different types of contraception.

And they all have different side effects. and no one's really thinking about what's going on. And I certainly didn't either. I mean, I was taught at medical school that the contraceptive pill can reduce libido, but don't worry about that because young girls have high libido anyway, which is like it's just awful, actually. Like, why can't they enjoy their high libido? Like, it just seems like really terrible.

But then if they're on an SSRI and antidepressant, they're likely to have even more problems with low libido. which is like a double whammy for these poor people. And so I think there's one thing like not having your hormones, but there's another thing having a synthetic hormone that's altering the way that your brain and body and stress response work. Because it's hard enough for a lot of people just growing up, but to have these chemicals and then people aren't putting the two and two together. Yeah, no, totally.

And increasingly, you know, they're being used, like you say for, for actually. Now, there are lots of other reasons why people get acne. It's not just their hormones. And if it is a hormonal imbalance, then we should be thinking about the natural hormone imbalance, not giving something synthetic as well. So I just think it's really important that we know this difference and look at the science, because there is a lot of science and evidence. It's just been ignored, actually, for many years. But also thinking about hormones being ignored, like you talked about projection. and how important progesterone is. And I think this is a really, really under-recognised, underspoken about hormone because people always think that estrogen is the female hormone. Testosterone is the male hormone, which absolutely is wrong. But progesterone is just something to protect the lining of the womb if you're on estrogen. And I didn't really know too much about progesterone when I was like growing up as a junior doctor.

but it's so important because it's actually progesterone is the precursor, if you like, for testosterone and estradiol, but also for our cortisone and cortisol, so that help with inflammation, but like you said before, stress. So I know you've written a lot. I've got a copy. I haven't got the beautiful copy because it hasn't come out yet. It will when we do the, put the podcast out, the period brain, which is your other. book and you talk a lot about the power of progesterone in this book and you know just explain a bit about why progesterone is so important as you noted culturally we tend to think about women and that their sex hormone is estrogen right it's like men have testosterone women have estrogen and then that's the only hormones that matter but that's just not true as noted you know it's women have two primary sex hormones, right?

We have estrogen and progesterone. And the reason that we have two primary sex hormones is because our bodies have to do two different jobs to reproduce, right? So men only need to do one job for reproduction, and that's have sex, right? And so they've got one sex hormone. Women have to have sex, right? And we have a hormone for that, and that's estrogen. And when we are at a point in the cycle, when sex can lead to conception and estrogen is being

released, it orientes our brain and our brain. our body to do all of the things that are necessary in order to attract mates and have sex, right? It increases libido. It makes us smell better, sound better, look better to men. It makes us more sexually interested, and it sort of gets all of our body marching, you know, in the direction of wanting to do things that are going to lead to conception, right? And so that's what estrogen does. But women's bodies also have to do a second thing to reproduce, and that is give a pregnant, right? And so allow for an embryo to implant and then get pregnant. And so we need a second sex hormone whose job it is to coordinate the body and get everything marching together in that

direction. And that's what progesterone does. It shifts our body and our brain from being in, you know, in a state that's optimized for sex and attraction. And it shifts us into a state that is optimized for implantation and pregnancy. And this, you know, creates a whole cascade of changes within the body and within the brain. And so it does things, like, for example, because we're having to build and differentiate the cells in the endometrial layer, this raises our metabolism. Right. So women's metabolism increases by like 8 to 11 percent, which means that we need more calories

during this part of our cycle than we do during other parts of the cycle. It shifts our immune system away from a pro-inflammatory to an anti-inflammatory state to help allow implantation of an embryo without having the immune system go crazy and try to attack it. It changes the threshold by which our brain sort of detects danger and makes us more cautious. So it's like our brain is quicker to alert danger signals because, again, this is a hormone that's getting our, body and our brain oriented toward, you know, things that will help promote a successful pregnancy. And because pregnancy is a time that's very vulnerable for women, they're more vulnerable to their environments, it does make us more alert to the possibility of social dangers and

also physical dangers. And so women tend to notice more things that can potentially be threatening even within the context of their relationships. and sometimes even especially in the context of their relationships, because of course historically women have been very dependent on men in their provisioning ability to promote a successful pregnancy. And so women are attuned to threat so that way they can be able to better address them. We experience changes in libido where libido actually decreases in that phase in the cycle

because pregnancy is not possible from sex or conception is not possible from sex And sex is, you know, it creates a physiological inflammatory response in the, you know, cervix and vaginal area in response to foreign material. And that can be suboptimal for implantation. And so, you know, women experience this whole shift that occurs as our bodies are transitioning from the state optimized for attraction and sex and then moving into the state that's optimized for implantation and pregnancy. and not really having any discussion of this, right, and not understanding what progesterone does.

And, you know, and it does have these, like, really beautiful anti-inflammatory effects within the body. It's got anti-inflammatory effects within the brain. It increases neuroplasticity. It does all kinds of really wonderful things, but not having, you know, any awareness of the fact that our body is shifting gear. and that sometimes the things that we need to do, like we need to change the way that we treat ourselves. Like, for example, we do need more calories in the second half of the cycle than the first because our metabolism increases. That can make us feel awful. And so a lot of, you know, what women tend to think of as like, you know, PMS and feeling bad in the second half of the

cycle, a lot of that is the result of, you know, just not acknowledging that. that like our bodies needs change, right? So for example, if you're not eating enough, because you've been told you should have X number of calories on a given day, and then you're in the second half of the cycle, when your calorie needs are higher, you're going to feel like you have food cravings and that you're hungry and that you're grumpy and that you're tired

because you're not eating enough, right? And that if we understand that the rules for our bodies change, and then we treat ourselves, you know, we do the things that we need to do to best take care of ourselves during this time, I think that a lot of women can feel a lot better. And then the other answer is, you know, kind of getting at something that you had touched on, and that is that in our current environment where people do have more sedentary lifestyles and they're eating more processed foods and they don't have the large social support networks

that humans really thrive under, all of these things can erode our cellular plasticity and our resilience to hormonal changes. Because, you know, as we experience big hormonal changes, it can, some women are very sensitive to those hormonal changes, and it makes them feel terrible. And these are the women who have really severe PMS and PMDD, oftentimes because the ludial phase, which is, you know, the second two weeks of the cycle,

it's characterized by larger hormonal swings than what we see in the first half of the cycle. And so women who are sensitive to hormonal changes, it can make them feel out of sorts. And one of the reasons that we see so many women with hormonal sensitivity is because there are a lot of things in our environment that really do erode our resilience to those hormonal changes. Because it shouldn't feel like falling off a cliff, you know, as your hormones are changing. Instead, it should feel more like riding a wave. Yeah, and some people are just a lot more sensitive to these changing hormone levels. Like you say in the Luteal phase, the second half of the cycle, we get a really big peak in progesterone, far higher than eustodial,

and then it does drop quite quickly before people have their periods. And some people really are very sensitive to the changing levels. And we see that a lot, obviously, in perimenopause as well, when hormones can shift a lot. And a lot of people think it's all eustodial that's shifting and changing, but aren't thinking about the progesterone as well. Yeah, no. Well, what's kind of interesting is that when you look at the research literature, it seems to show that people who are sensitive to hormonal changes within their cycle are also the ones

that are at a greater risk of developing postpartum depression. And they're also the ones who are at the greatest risk of experiencing depression. during paramedopause. And so, you know, there are people, right, if you're one of those people who has that sensitivity to hormonal changes, that's like really important to know because you do need to build in extra support for those big transition times like postpartum

and parametopausally. Yeah, and we see this a lot. Obviously, I see a lot of perimenopause that are menopausal women, but I increasingly see a lot of younger women in my clinic. But what really saddens me is that I see a lot of women with quite severe, often very severe mental health history who've been under psychiatrists for many years. And when I take a really detailed history from them, and these are now menopausal women, when I say to them, how did you feel when you were having your periods? Did you feel any

different throughout your menstrual cycle? They'd say, oh yeah, just before my period, it was just awful. And then my period came and I would just get a bit of break. And it would be like night and day the difference. And then I, if they've had babies, I always say to them, how did you feel when you were pregnant? And they would grin from ear to ear and say, do you know what, it would be the best time. I would wish I could have that time again. But then they've often had postnatal depression or psychosis and often didn't want to talk about it to anyone because they were scared their babies would be taken away from them. So they'd often not gone for treatment at all. And then when you realize these big hormonal shifts that occur, especially postpartum,

it's so obvious that it's related to hormones, especially progesterone, but I can't find any guidelines that say that we should be giving progesterone to women who have postnatal depression. It's always the antidepressants and it just doesn't feel right. Right. No, I mean, and there is some research now because, of course, they've found a patentable product that, is that is uh it's it's essentially alopragnanolone it's it's like a and and and so they're they're using that for um for postnatal depression and and it seems to be working pretty well and um but you know that's like the end product of progesterone and it's a lot more expensive right and like why not just give the hormone right exactly yeah like yes yeah no progesterone is um it's so it's so funny because

it's so underappreciated and I just learned for the very first time that most women or most doctors who treat women and are giving them hormones for for a paramenopause and menopause that they only give them like progesterone if they have a uterus and that they're doing it because you know they want them not to get overproliferation within the uterus but um and And it floored me to learn that. So did you not realize that? That's really interesting. No, I didn't.

No, I had no idea. I'm like, how in the world, like, why in the world would a doctor think that this only matters for the uterus? Well, isn't it interesting? Yeah. Somehow estrogen affects everything, but that progesterone only affects the uterus. I mean, it's like. Yeah, well, you see, this is where, like, as doctors, we're blinded because I was always

taught that. taught you only give progesterone if a woman has a womb. And so if you're taught it, that's it. You don't question it. You just do it. And that's what a lot of the pathways and guidelines say. Right. Yeah. But then recently, obviously, I've read a lot more about progesterone. I've read physiology, you know, basic things I should have known for many years. And so now we do give progesterone to women who've had a hysterectomy or if women have a marina coil in, you know, an IUS that's a coil that contains synthetic progesterone. I'll often give progesterone as well, because it will get into the blood and go to the brain, everything else.

And most weeks I get letters from doctors to my clinic to say, how dare you prescribe progesterone? This isn't in the guidelines. We don't have evidence. And it's like, well, hang on, it's a basic hormone. It's really interesting that common sense often is forgotten in medicine. Yeah, no, that's crazy. And I think that you're ahead of your time on that. And I think, but I think it's smart.

So we're actually doing a study right now where we're going to be looking at supplementing micronized progesterone to women on hormonal birth control to see whether or not we can minimize some of these unpleasant effects that women get from it because there is. Yeah, it's very interesting. Yeah, I bet. I bet that that's true. Yeah, no, you're ahead of your time. I'm impressed. I think that's great. I love that you're doing that. Yeah, well, I just, you know, I suppose in medicine, I'm quite inquisitive, but you always just look at the reason. And, you know, I don't want to put sticking plaster on things for patients. I don't want to be giving them antidepressants if they don't need to. So I think, you know, working with people who a scientist and thinking beyond the box

is really, really important. And, you know, the birth control has been out for decades. Progesterone we've known about for nearly 100 years. And I feel like the conversation is only just beginning, really. So I'm really grateful just to have the opportunity to talk to you. And I really wish you a lot of luck with the book because I think it's going to help people to understand a bit more about our natural hormones and why we are, who we are and what shape us, but also what we can do if we're struggling,

the big message is really talk to someone who understands hormones as well. So before I end, there's always three take-home tips. But I would just like to ask you three things about progesterone that you think everybody, and men as well, because men produce progesterone. So three things that we should all know about progesterone as a hormone in our bodies. Okay.

So number one is that it doesn't make you feel bad. I think that a lot of people, because progestins, those terrible, you know, those synthetics and birth control make people feel so awful that they assume that progesterone and because, you know, women do sometimes experience PMS and PMDD, they think that that progesterone is this like feel bad hormone and it's just not. And so that's one. Number two is that progesterone matters for cells in the body that are outside the uterus, including the brain.

Number three is that progesterone is beautifully, wonderfully anti-inflammatory and neuroprotective. And so it has all of these really wonderful, these wonderful characteristics in the body in terms of being anti-inflammatory and sort of orienting you more toward an anti-inflammatory response. In fact, it's even been argued that one of the reason that contemporary women have so much autoimmune disease is because our ancestors spent so much time pregnant that they were constantly having this really powerful break on the very inflammatory female immune response. And that lacking that break is the reason that we're seeing these types of inflammatory diseases and women.

So it's beautifully anti-inflammatory and it is neuroprotective. It's used in traumatic brain injury to actually prevent people from getting brain damage from excitotoxicity. And so it's got these really beautiful effects within the brain and the body. Amazing. Thank you so much for sharing some of your knowledge and it's been great connecting with you. So thank you so much. Yeah, thank you for having me.