This is Your Brain on Hormones

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One of the reasons that I come to you is maybe 10 or 15 years ago. I read a popular science book. I'm not even going to say the title.

“So I think that it was like somewhat controversial afterwards.”

And I remember this fact. And I think since I read it, I have wondered if it was true. And I've also told everybody this fact. So this is like my live fact check, which is...

I read that as you go through your menstrual cycle, the size or shape or make-up of your brain changes. And I remember reading that and thinking, "Wait. My brain actually physically is changing. Is that true?"

Okay. There's so much to unpack here. Hey, I'm Molly Webster. This is Radio Lab. And today, I can go roll far back. And we're going hard on a question that I have been thinking about for years.

Totally. It's funny as I've been thinking about this topic.

“Everyone's like, "Una see, you should just talk to Emily."”

Oh. Emily is a neuroscientist and neuroendocrinologist to be precise. And she is on one of the teams that has been struggling to understand how hormones affect the brain. Because we had these glimpses.

These little flickers of what it could be doing. But to watch the full-pump cinematic view of how this is unfolding, that was a breakthrough. Very recently, Emily's lab came up with an experiment to so precise, so daring. It allowed them to pin down what hormones can do to our brains.

And here's the thing, even though the story starts with menstrual cycles,

it very quickly gets to the fact that women, men, whoever we are all at the mercy of a crashing, swelling, wash of chemicals inside of us. The chemicals we call hormones. So when we say a hormone, maybe we just define our terms.

When we say a hormone, that's a chemical messenger. It's a chemical that is released from an endocrine gland, like testes or ovaries. You have adrenal glands sitting at top of your kidneys. You have a thyroid gland.

And then once they start producing hormones, those hormones use your circulatory system. Your blood supply is their superhighway. They hit almost every cell in the body.

“When you think about like, why do we even have hormones?”

Why is that thing? Just make it complicated. Why do we have hormones? Because if you're a multi-cellular organism, if you have more than two cells, those cells need to know

how to communicate with one another. So that everything's working together and in sync. And natures figured out a really clever way to do that. There's several ways. But hormones are one way.

It just seems like a sloppy way to communicate. I'm going to wash you in a liquid. A synaptic connection where there's a fiber, a cable, and it's sending information from A to B feels like clean and directed and efficient.

So why would we choose this bathing method? I think because you can't have wires connecting every single cell to every single other cell. Yeah, it'd be like a scary motel. You see the wires around the walls.

Right.

So but we have this blood supply that feeds essential nutrients and oxygen

to all parts of our body. And so it's like hormones can just basically make use of what's already there in order to get your spleen talking to your heart talking to your brain. Think of it like a broadcasting system. They're like the PA for the human body.

And they go everywhere your blood goes, including your brain. Which brings us back to the brain question. What are hormones doing up there? The science is really, I'd say, my old one of the marathon.

Wow.

We are using pretty archaic methods to understand

the function of hormones in the brain. And a lot of it is correlational. Most of the studies take large groups of people and take one snapshot of their brain and take one blood draw. But that snapshot in time, that's not how the endocrine system works.

A fundamental feature is that it absorbs and flows over time. It is not static. In fact, all of its power comes from the dynamism of that system. Like my body doesn't care if I'm at 20 p.g. from a litter of extra dial. It cares that I came from zero and I'm going to 200.

So it's not the static level that matters. It's the change. And none of our experiments today were capturing that change. But something happened in the field of neuroimaging about 15 years ago where somebody was like, wait a minute.

I'm actually interested in how individuals change over time. This is a friend and collaborator at Stanford named Russ Poldrak.

And he completed a project where he basically scanned himself over a hundred times

and just collected everything you could possibly come to collect.

“Like how much caffeine did I have today and how well did I sleep?”

And like, did I have an exome of flare-up? Like literally everything. This is like my dream. Yeah, yeah. And he, that study really launched this whole new way of thinking

about the use of MRI to understand dynamics of the brain. And so we, my group, you know, here we are sitting at UC Santa Barbara. And we're watching all of this great science unfold. And all of a sudden, it unlocks this. You know, this is sort of solves this major problem for us because we're like, wait a minute.

We can study an individual and track this change. And so I had this brilliant graduate student in the lab. Yeah. Laura Pritchett. Yeah, sorry.

Let me just, I'm going to modify my headphones a little. And she was like, hey, I have normal cycles. I have a summer to kill. I don't really have a life. I volunteer to do this.

Emily is a philosopher and I am a country bumpkin. That's why I describe myself. No better case subject than me. So our girl Laura is actually Dr. Laura Pritchett now. Now I'm in Philly for a postdoc.

But in 2018, she was a fresh-faced grad student in Emily's lab. She had just started studying neuroscience in her undergrad. And she was left feeling dissatisfied. I noticed for like a week after week after week, the papers we were having to read only included male animals.

“And I would pose this question of why is this only males?”

And I would always get this response of, oh, well, females have an extra cycle.

You know, the akin to the human menstrual cycle. And that's just complicated and it's just a lot. And I was like, what the fuck? Like, yeah. You're studying basic features of the brain.

You're also taking these findings and applying them to males and females. So the logic's not there. This doesn't make sense. And that seems pretty whack. At the same time, I remember my boyfriend at the time in college.

His mom was going through menopause. And I loved her. And she would just talk to me a lot about how she would walk into a room and forget where why she was there, where her keys were, you know, you put together like a human female going through menopause.

And then at the same time you're seeing study after study after study doesn't have females in it. Like, like, those two things connected for you? Yes, exactly. Then that led me to go, okay.

“Well, how do sex hormones influence the brain in ways that I can measure?”

And then you were like, I know who can be the perfect study sample. Yep, me. Yeah, I was like, I'll just to answer these questions. I'll just roll up my sleeves. And that's, you know, sort of how 28 me was born.

Laura named her experiment based on the 28 days. It roughly takes to complete a single menstrual cycle. And for each one of those days, she would wake up, go to the lab, spit in a vial. I did saliva. And then I would go get my blood drawn.

Mario, the flabotomist would poke her in the arm. We tried once to get my foot because I was a little too bruised up. And I almost kicked him in the face. Yeah. And then I would go straight to a two hour or so MRI.

They put her in a brain scanner. And she had to lie totally still. We 3D printed a foam head case custom to me. And I actually had them put sandbags on my legs. And takes straps and strap me in almost like a straight jacket.

Yeah, that's what I'm saying.

I'm going to wear it up. So Laura was in there. She was under this blanket of sandbags. And they would scan her entire brain while she was doing a series of mental exercises. We did a resting state scan meeting recording my brain as I'm letting my mind wander.

I would look at highly rewarding food for a block of, you know, a minute. I would look at very neutral images like a Q-tip. Then we looked at still images of porn. I remember they were like men taking selfies with a mirror. And I'm like, give me a romance novel.

Like this is not going to do this for me. But I did that every day. And Laura did this spits to scan spits to scan again and again for a month.

The hardest part was halfway through where you're like, I've done 15 days of this.

Oh my god, there's 15 more. And with every scan, they were taking a picture of what her brain looked like on each day of her cycle. And then with every task, they were looking at how her brain worked. Literally how it was firing as she moved through that cycle. Exactly.

“Did you, like, look at your data every day or did you wait till, like, the end to look at your data?”

Yeah, great question. I waited till the end. So we actually decided to start blind in a middle of a cycle so that I would, eliminate as much bias as possible. And I also didn't even know where I was at in my cycle.

And I remember her, I didn't even know when I was going to get my period. But I remember a graduate student had to come and give me, like, a tampon. When it was all said and done, Laura and her team had all of these images of her brain. And then alongside that, they had what her hormones were doing at the time the images were taken. And when they put those two things together, her data were beautiful.

Hmm. When she started to look at sort of relationships between that period when Esther dial peaks right around the time of ovulation, she saw this, like, massive increase in functional connectivity across most parts of the brain. Wait, what is functional connectivity?

Like, what am I visualizing when you say that phrase? This is really just a measure of brain regions that are talking to one another. Like, all the bits of the brain are talking to one another in a way that's more congealed. So it's like, everything is just, like, hyper connected. Imagine, like, let's say we wrapped the brain in a string of Christmas tree lights.

I don't know where this is now. I don't know where this is now. Do you guys love it? I love it. Try it.

Stay committed and keep it open. Okay. We're wrapping the brain in a string of Christmas tree lights. And when Estherile peaks, it's right around the time of ovulation. It's like, all the lights go on.

Like, the green lights are, like, really connected to each other and the red lights are all really connected to each other. It's like, they're all, like, working in sync.

“And then that's so, like, walk you through your menstrual cycle, right?”

Like, right after ovulation, you get this plummeting of estrogen and progesterone starts to dominate the scene. And during that moment, which is about a week before your period, you start to see, like, those lights dim a little bit. And it's not like the brain activity is dimming or, like, cognitive functions

or dimming, it's just a shift in the basic connectivity structure of the brain. It's kind of like the structure of the brain is the same. It's just not as in sync. But we also used a really high-resolution scan of the hippocampus. So this is the part of the brain that's, you know, really important for learning and memory.

What we discovered is that these, this region of the brain, and we can actually look at different subfields of the hippocampus. It's not actually one solid structure. It's got all of these little bits and bobs. And that we can see these structures of hippocampus actually grow and shrink

along with the menstrual cycle. I mean, like, on a rapid times, that one is actually physical. That one is physical. It's morphological. It is a change that literally, like, the brain structure is changing across the cycle.

Really? That's a thing people can wrap their head around. My takeaway here is that these liquid chemicals, into a here, is that these liquid chemicals in my body are washing my brain and changing it monthly, weekly, daily.

“But to be sure, you need to essentially squash the endocrine system.”

And if you squash it, you don't allow those rhythmic endocrine changes to occur anymore. Then let's see what happens.

So they basically do the entire experiment all over again.

But this time, Laura, I went to our student health center.

You're giving the undergrads. She went on a drug. That suppressed progesterone levels by 97%.

The birth control basically wiped out the hormones

in the back half of Laura's cycle. So that progesterone rise. And then she went back to the lab. It sticks can and the progesterone dependent changes that we saw in the hippocampus across the cycle were completely obliterated.

So it did give you a chance to say, like, look at the data. These bumps we're seeing are because of estrogen and progesterone cycling. Exactly, yeah. Okay, so if you're telling me, I can keep telling people that in different points of your cycle, your brain changes.

Yes. Wow.

“I think what we need to be careful is in the interpretation”

of that fact. So we don't know what it means in terms of behaviors. So that's where we have to draw the line. It's like, I don't know if this is good or bad. It's just different.

Well, it's funny. It's like, I can tell you what that feels like. In my body, it feels like you're making all these connections. And you're going so fast. And like, the world is like a little brighter.

And I'm quicker. Like, I'm like sent, sent, give me an improv troop. Like, yeah, send the shit out of the show. You know what I'm saying?

And then when the when what you're saying, the progesterone takes over and estrogen decreases and when I'm like right before I'm bleeding, I'm like, give me a cycle.

Like, yeah, like, what was your name? Like, oh, yeah. There were tears. That was a note. I was crying in the parking lot for some reason.

As part of the study, Laura was tracking her mood each day. Like, I was seeing the negative affect rise with progesterone rising. So I was seeing it across multiple days. And I was like, wow.

Like, this is real. And maybe for me, and maybe not for the female across from me. Laura and Emily did say they can't peg any particular person's mood

or cognition to these hormone changes. I mean, the body is freaking complicated. Like, estrogen affects dopamine. For me, that might feel really good to give that extra hit of dopamine.

But if you're a person who already has a lot of dopamine, it could make you feel awful.

“So like, I think we still need the data to like,”

understand how that is tied to those aspects of cognition. If you're like a molly brain, when you first hear this research, you're like, oh, wow, it's so cool.

Like, every day that I have had my cycle since doing this story, I'm like, what's my brain doing today? But it also feels like, oh, my God, this is the exact thing that people

have been saying for millennia. Women are hormonal. Women change. Unlike men, women aren't reliable. When you like call somebody hormonal,

it's like almost always directed at a woman, right?

Like, it's a pejorative. But like, that belives the fact that like hormones are in all of us, these are ancient molecules, every vertebrates have like the, these are essential.

And, you know, men have them too.

“But it sort of comes right from the fact of like,”

ours females, however, you know, are changing on this 28 days cycle. It's like, I'm not saying like men don't have hormones, but I think there is a cycle

that women are running through. Right. I'm not sure if you're about to tell me like, well, guess what, men are going through a cycle too. Yeah, guess what, men are going through a cycle too.

Wait, really? Yes. That's right. We're not getting out of this episode without, the trending thing is boy cable, right?

A man. We're going inside the male cycle after the break. The fatal shooting of a teenager at a protest in Seattle has gone unsolved for six years. This is open in your face

to how are there no answers. Our investigation has uncovered new evidence

and witnesses who say they've never talked to police.

Did police ever call you? Not once. Listen to Weeky Bus Safe. A new true crime series on the embedded podcast from NPR. One of the reasons we did 20 in he.

Or does that what it was called? 28 in he? Yeah. Oh, that's hilarious. Fun fact, this was actually Laura's then partner now has been.

I met Laura first, an intramural softball in graduate school.

I am a scientist. Shout out to Pavel. The summer that we met. She had done prior that summer. The study on herself.

And I was just taking it back. Someone would do that for science.

“So just stick themselves in a huge magnet for a whole month every day.”

I mean, immediately I was kind of like, "Wow, I'm in love." You know? [laughs] So when Laura said, "Hey, so how do you feel about climbing into the MRI?"

Pavel said, "Yes."

But she would always be there by my side.

To your heart. Every morning they'd get in the car. I'd be pulling my saliva. Like, collecting it in your mouth. Like, don't talk.

Just gather spit. That's right. Yeah. He'd walk into the lab to posit his spit. And Mario would come and take some blood. I just love this character if Mario loves the bottom of this.

[laughs]

“Then just like Laura, he would lie in the scanner.”

Still as can be. But for his experiment, he did double duty. The first 15 days we had a morning scan and a morning blood draw. And then 10 days into that 30 day period. We also started a 15 day nightly scanning.

Why were you getting scanned twice a day? Whereas, you know, the main fluctuation of estrogen happens on a monthly time scale. Testosterone has sort of a daily rhythm. So it's diurnal.

It's super high in the morning. I don't know that. Okay, super high in the morning.

And then it drops by anywhere from 30 to 70 percent at night.

So for Pavel, we really kind of capitalized on this known circadian rhythm. Where testosterone and progesterone in estrogen are peaking the morning. They're dipping in the evening. And we said, "Huh, like let me have progesterone." Yeah, they have all the bits that we do.

It's just a different concentration. And these hormones cycle in men. And so we wanted to understand that.

“Is the male brain undergoing kind of a similar degree of change?”

After all Pavel's data was collected. Emily and Laura had their team combed through it. And they saw. The punchline is that, essentially, we see the exact same thing that we saw in Laura that like, when these hormones are peaking, you see the brain become more interconnected

with each other.

And then when the hormones dip in the evening, the brain becomes less interconnected.

And we see, you know, the brain is pulsing on this 24-hour scale. So when hormones are high, it's a little bit bigger. And evening, it's sort of like tightens up a little bit. And we get the crazy part is that we can literally see this, you know, periodicity, this wave, if you will, happening every single day throughout the entire,

you know, he did 40 sessions across 30 days. So it's just this, like, beautiful rhythm that exists. And we can, we can measure that. That's crazy. So it's like that these hormones are having the same size of fact,

whether it's happening on a 24-hour timescale or across the 28-day menstrual cycle. But wouldn't women also be doing this circadian? Yes, that is true. So we're getting circadian 24 and 28 across time.

That's right. And men are more locked into the 24. That's right. That's right. Um, I feel contradictory then because somehow,

in you trying to be like, look at men are part of this equation too. It actually just leaves me feeling like, wow, my hormones are even more up and down than I thought. Oh, yeah. Meaning that, I mean, like, it's like a surprise that you have a circadian cycle on top of.

Yeah. Like you're absolutely right in that this myth of female variability and this idea that we have this kind of like pet. Emily said that even though females have these two cycles, studies have shown that they're not inherently more variable than males. In fact, it might be the opposite.

Here's where stuff gets, I think. Funny. It's like, you know, women have this menstrual cycle and for most women for most of our lives, it's as steady as the tides. Like, you know, maybe until we start to get to menopause or if there's like a reproductive condition, like short of that, like it's, it is, you know, this sort of rhythmic event again.

It's this kind of predictable thing. That is not so true for male-dominated hormones like testosterone, which are famously capricious. So testosterone can spike and dip and it's like super responsive to social stimuli.

and you get these like testosterone surges and then if they're,

“they lose a fight, you get like testosterone suppression.”

It's true in humans who aren't even engaged in like, you know, fist-to-fist combat if they're just watching TV and their favorite. Team loses, you can see testosterone suppression. But that's not happening with like estrogen. Yeah, not as much. It's really, you know, again,

every, you know, every sex has every hormone is just the proportions that are different. But in, you know, testosterone, which is like on average higher in men, it's, it's, it's much more fickle. Wow. So it's just funny to me that women are the ones deemed as this like unknowable, you know.

It turns out all of our brains are oscillating with these hormones.

Whether it's monthly or daily or fickle or regular, all of us have estrogen and testosterone flowing in, and the brain gets bigger and more connected. And then estrogen and testosterone flow out, and the brain gets smaller and less connected.

Brains are built to change their built to learn their built to adapt, and here we have this mechanism, this hormonal mediated mechanism that's allowing our brains to do that. If brains did not change, that would be the pathology of interest.

“So I think my takeaway is that the brain is opening in some way,”

when it's bigger or when it's firing in that stronger Christmas tree light,

like analogy you gave, like when it's when it's speaking to itself better that it's opening. Yeah. So like these estrogen rhythms are opening up these windows of, of enhancing our plasticity, and it's that's. Neuroplasticity, you probably know this is this idea that the brain is malleable. It's open to change.

And Emily said all sex hormones, including estrogen, can go into the brain down to the level of the DNA and open it up. So DNA is organized in this chromatin structure, right? So it's actually like pretty tight and closed up. Like wound, tightly wound.

Like tightly wound. And then the helix is like exactly tight. It's really tight, right? Yeah. But estrogen is one of the factors that can actually like loosen up the DNA.

It just, it's like it just relaxes a little bit. And it can promote, you know, the production of proteins, and then that's the pathway by which learning and all of these great things happen. Okay. But this paper that I just sent you was like, I got it like five minutes for the interview.

So I have no idea what it says. I know. Okay. So this is work from Tally Barron. And oh my god, it's blowing my mind because this is what the study asked.

What happens if during that brief fleeting window where estrogen is flooding the system, your chromatin is all loosened up. It's like it's getting ready for its massage. It's on the table. It's warm.

It's like, let's go. And then you introduce a severe stressor. You know, blasting loud music. You know, you're sort of shaking the animal. You know, introducing it to odors of its predator.

If that happens during this period, you create a PTSD like phenotype in these animals. Wow. And it's, it is long lasting. This study, which was done in both female and male mice, was an attempt to understand why some people record more trauma than others.

And one of the takeaways was high estrogen plus stress can produce PTSD.

“Then they ask the question, okay, well, what happens in moments of low estrogen?”

What she is suggesting in her data is that actually, if you look at the low estrogen periods of the female menstrual cycle that they were immune to these stressors. Like they had almost like this armor on. What this work is suggesting, which is so profound, is that actually there may be sort of these protective mechanisms of having these beautiful,

but then estrogen levels get a little bit lower and you are more resilient to these stressors.

Again, pure speculation at this point. Yes, the science is so young.

“I think for me, the thing with this study is that when I think about my period,”

the moments of high estrogen are the ones that I feel really good in. And the moments of low estrogen are the moments I want to get out of as fast as possible. But maybe at a deep biological level, those moments when we feel our worst. So for me, during my period, maybe for you at the end of the day, those might be moments that are worth sitting in.

If you have really high connectivity between regions of your brain, that's really energy dependent. That's Laura again, you could be exhausted. It is funny. I maybe part of what is opening up for me is like,

there's so much about, you know, just finish my period. There's like so much about it where you're like, but I'm just thinking about it in a different way. Like, as it's almost, it's like a way my body is like taking care of itself. Yeah, I think that's a beautiful way of thinking about it.

And I think, you know, if I teach a class or guess lecture, I say, what comes to mind when I say estrogen? And it's like Zoe Deschenels, character, new girl crying. You know, eating ice cream, and it's like, we can move from the stereotypes into like,

wow, hormones are just fucking powerful.

And they serve a purpose and they're not protective. And if anything, you know, why are we trained to think of the cycle as a source of noise? When in fact, I think it's a source of stability. You know, hormones guide behavior and they do so through this rhythmic action, whether it's across the circadian cycle for males and females,

or whether it's across something like the menstrual cycle for females. Are you ever like damn our brains 24 hours a day? It's going up and down, up and down, up and down. Then every other day it's going up and down, up and down. But I think it's like an organizing principle of the brain.

It's like, it's, it's creepy. It's not tiring, but you're saying it's not. I don't know.

Like it's a tiring for the waves to like, you know,

happen on this rhythm. I don't know where is it like organizing the system in some really helpful way. I don't know. The, those are the questions that I want to dig into, that like, man, we have just like, scratched the surface on scientifically. So what make, like, just the fact that you could even suggest something like,

is it organizing us in a certain way? I'm like, ooh, why did you choose the verb organizing? What, what, why would brain changes be organizational? The brain likes prediction. It likes rhythm.

It likes, you know, like it's, it's like providing a scaffolding or a structure. It's the same thing like if you have kids and you let them just like, you know, there's no rules in the house and like put themselves to bed, whatever they want or they can eat whatever they want. Like it is high chaos in the house and nobody's happy

and nobody functions well, but like you put a little bit of structure. You put a little like organizational structure and then all of a sudden, like shit flows better.

“And maybe that's what hormones are doing. It's like laying down these like,”

fundamental rules. These organizing principles for the brain that can like, that help it function at its most, you know, at its highest level. I don't know. I'm totally speculating here, but yeah.

But, but now we get to at least ask the question of like, is that Paul's doing anything that the brain likes or that like, helps us in some way? Yeah. Wow. That's a cool word, Paul's like brain pulse. Like it's working out up there.

Yeah. It's like the heartbeat of something, right? It's like the vital sign. Yeah. It's like you think of like the chunk of like the heartbeat monitor.

Like maybe this is the endocrine system. It's like it's pulsing on these different rhythms. And then it's creating these echoes throughout the rest of the body. That's like, oh, cool. Like, here's the rhythm we get to dance to.

“And it's, that's what I mean when I am thinking about this sort of organizational framework.”

It's like, I think it's creating that rhythm for them. The whole body to get in sync, too. Hmm. I think I'm having this question of, the brain is such a regal and like commanding object, right?

Like, you kind of know how much work it's doing in your body. Even though it's part of you, it kind of feels like other like there's there's a way in which it just has up. It's all powerful. Hmm. And so then when I hear something about the brain changes,

Like, awesome. Yeah. Oh my god.

“I think that that idea that the brain is like this regal thing is a myth.”

I actually think it's an organ like every other part of our body.

Like, I think the way we can show that hormones influence aspects of the brain suggest that, I don't know, we're all just kind of these like, you know, big buckets of chemicals walking around and we think we have control, but like, no, we don't like me. I yelled at that person because I'm a hangry, and I, I don't even know if I buy into free will. If I'm being totally honest, I don't know.

I mean, I think that there's ways we can gain free will. And by and large, we are also just like big biological sacs of stuff. And I think that I'm a big biological sac, but if I know that, if I say it out loud, then I could maybe do a little bit more with the sac like I could push it to the left and push it to the right, even if only an inch.

That's my, that's my wish.

“I do think an understanding of the system allows us to control it.”

In fact, I was just on a call earlier this week talking to,

there's this incredible researcher out of Caltech.

And he's developing continuous hormone monitors. So we, you know, we have the glucose monitor where we can track. Yes, and now they're starting to develop technology where either from sweat, which seems difficult, but even in like interstitial fluid, you can create a glucose like monitor that can just give us this kind of constant readout.

Of hormones. I mean, imagine if we could get like a second by second or even just hour by hour readout. We can just watch and observe and see the patterns play out. But that's so huge. I mean, think about the images of Pluto that we had a hundred years ago,

“where it's just like grainy, little lep in the, you know, in the sky.”

And now we can see the individual like craters. And then you like this idea of let there be light, like, like, being able to see a phenomenon in, you know,

incredible detail is the start where all of the breakthroughs happen.

This episode was produced by Mona Medgalker and me, Molly Webster. It was fact checked by Diane Kelly. I want to thank Soren Wheeler, Pauval Shepterinka, Emily Jacobs, and Laura Pritchett. Emily hangs out at the University of California, Santa Barbara.

You can find Laura and Pauval at the University of Pennsylvania in Philadelphia. And you can also find all of Laura and Pauval's data online. Go to openneuro.org. That's openneuro.org, props to Laura for making all of her data public. Also a huge shout out to Katherine Woolie, who's original research on sex hormones

and the brain was foundational to all the stuff we're talking about today. If you find yourself with some spare time, go to radiolab.org/thelab and sign up for our members only access. You'll get ad-free listening, special content. It's fun over there. And that's it. I'm Molly Webster.

This is Radio Lab and the next time I see you, I'm going to ask, where are you at in your cycle? Hi, I'm Gabby. I'm from the Bay Area California and here are the staff credits. Radio Lab is hosted by Lulu Miller and Latif Nasser. Lauren Wheeler is our executive editor.

Sarah Sandback is our executive director. Our managing editor is Pat Walters. Dylan Keefe is our director of sound design. Our staff includes Jeremy Bloom, W Harry Fortuna, David Gabel, Maria Paz Gutierrez, Sindu Naina Sambandon, Matt Kilti, Mona Modgalker, Annie McEwen, Alex Nisan, Sara Curry, Natalia Ramirez, Rebecca Rand, Joanna Strogetz, Anisa Vizza, Arian Wack,

Molly Webster and Jessica Young, with help from Gabby Santis and Maya Applebee Milamid. Our fact checkers are Diane Kelly, Emily Krieger, Natalie Middleton, Angelie Mercado, and Sophie Semi. Hi, I'm Aubrey, calling from Salt Lake City, Utah. Leadership support for Radio Lab Science Programming is provided by the Simon Foundation

and the John Templeton Foundation. Foundation support for Radio Lab was provided by the Alfred P. Sloan Foundation.