This is Your Brain on Hormones

Summary

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Radiolab – “This is Your Brain on Hormones”

Original Air Date: June 19, 2026
Hosts: Lulu Miller, Latif Nasser
Guests/Contributors: Molly Webster, Emily Jacobs, Laura Pritchett, Pavel Shapturenka, Gabby Santis

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Episode Overview

This episode dives into the little-understood, often misunderstood world of how hormones impact our brains—not just during the menstrual cycle, but in all humans. Inspired by a popular but controversial science fact, Radiolab investigates the true, measurable ways that hormones like estrogen and testosterone shape our brains on both a structural and functional level. The show upends long-held gendered stereotypes, explores state-of-the-art research, and asks how understanding our inner "chemical pulses" might show us a new way to look at mood, cognition, and what it means to have a changing brain.

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Key Discussion Points & Insights

1. The Big Question: Do Menstrual Cycles Change the Brain?

• Molly Webster: Opens with a fact she’s been repeating for years: that the brain physically changes during the menstrual cycle.
• Emily Jacobs (Neuroscientist/Neuroendocrinologist): Validates the question—recent experiments do indeed reveal brain changes over the cycle, but the story is even broader.

“I read that as you go through your menstrual cycle, the size or shape or makeup of your brain changes. And I remember reading that and thinking, wait, my brain actually physically is changing? Is that true?”
— Molly Webster [03:27]

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2. What Are Hormones, Anyway?

• Hormones are chemical messengers released by various glands (testes, ovaries, adrenals, thyroid) that travel via the bloodstream and affect almost every cell in the body—including the brain.
• Latif Nasser: Describes them as a "broadcasting system," using the body’s blood supply as a PA system.

“They’re like the PA for the human body, and they go everywhere your blood goes, including your brain.”
— Latif Nasser [06:33]

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3. Why Most Studies Omit Female Subjects

• Laura Pritchett: Observed in neuroscience courses that animal studies overwhelmingly use males, citing the perceived complexity of the estrous/menstrual cycle.
• This led Laura to her groundbreaking experiment: "28 and Me"—scanning her own brain every day of her cycle.

“I would pose this question of, why is this only males? And I would always get this response of, oh, well, females have an estrus cycle, you know, akin to the human menstrual cycle. And that's just complicated and it's just a lot. And I was like, what the fuck? …That seems pretty whack.”
— Laura Pritchett [09:53]

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4. The “28 and Me” Experiment

• Laura Pritchett:

  • For 28 consecutive days: collects blood and saliva, brain scans, daily mood logs.
  • Tasks included looking at food images, everyday objects (“like a Q-tip”), and even “still images of porn” during her MRI sessions.
  • Brain scanned in "resting state" and while exposed to varied stimuli.

• Findings:

  • Functional connectivity (how well brain regions talk to each other) peaks around ovulation as estrogen (estradiol) spikes.
  • Later in the cycle, as progesterone rises and estrogen falls, connectivity dims—like Christmas lights turning down but not off.
  • Not only functional but physical (morphological) brain changes: specific hippocampal subregions actually grow and shrink across the cycle.

“What we discovered is…we could see these structures of the hippocampus actually grow and shrink along with the menstrual cycle. I mean, like on a rapid time.”
— Latif Nasser [16:21]

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5. Birth Control and Brain Change

• Laura repeats the protocol while on common birth control that suppresses hormone fluctuation.
• Result: The cyclical brain changes disappear, directly tying the effect to natural hormone cycles.

“And the progesterone dependent changes that we saw in the hippocampus across the cycle were completely obliterated.”
— Latif Nasser [17:32]

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6. What Does It Mean for Behavior?

• The show cautions against over-interpretation: while structural and connectivity changes are clear, robust links to mood or cognitive performance remain elusive and highly individualized.

“We can't peg any particular person's mood or cognition to these hormone changes. I mean, the body is freaking complicated.”
— Molly Webster [19:14]

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7. Everyone Is Hormonal: “28 and He”

• Pavel Shapturenka (Laura’s now-husband) volunteered for the male version: 30+ days of scanning and testing.
• Testosterone (and other hormones) in men follows a strong daily (circadian) rhythm: high in the morning, dropping 30–70% by night.
• Finding: Male brains were also more interconnected during high hormone periods (morning) and less so as hormone levels fell (evening)—mirroring, but on a 24-hour timescale, the female 28-day cycle.

“Essentially we see the exact same thing that we saw in Laura, that like when these hormones are peaking, you see the brain become like more interconnected... and we see, you know, the brain is pulsing on this 24 hour scale.”
— Latif Nasser [26:42]

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8. Challenging Stereotypes of Variability

• Despite the “women are more variable” trope, research suggests male hormone levels (especially testosterone) are more capricious and responsive to social stimuli, producing more short-term variability.
• Key Example: Loss of a favorite sports team can cause a drop in men’s testosterone—something not mirrored by estrogen in women.

“Testosterone can spike and dip and it's super responsive to social stimuli... if they're just watching TV and their favorite team loses, you can see testosterone suppression.”
— Latif Nasser [29:18]

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9. Estrogen, Trauma, and Plasticity

• Recent mouse research: High estrogen opens the brain’s chromatin (DNA "unwinding"), increasing neuroplasticity, i.e., the brain’s adaptiveness—the “windows of enhanced neuroplasticity.”
• But a twist: High estrogen plus a stressor can result in long-lasting PTSD-like effects; low estrogen periods seem to confer protection against stress.

“What this work is suggesting…is that actually there may be sort of these protective mechanisms of having these beautiful but fleeting windows where you can drive plasticity, but then estrogen levels get a little bit lower and you are more resilient to these stressors.”
— Latif Nasser [33:47]

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10. Reframing the Cycle: Source of Stability

• The rhythm of hormonal cycles—whether daily or monthly—may serve as an organizing principle, not a biological “noise.”
• Having a cyclical, rhythm-driven brain is normal; refusal to acknowledge this is the real aberration.

“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?”
— Latif Nasser [36:00]

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11. Organizing Pulse: The Brain’s Rhythm

• The hosts liken hormone pulses to “the heartbeat of the brain.” This rhythmic action may be essential for cognition and learning.
• Envisions a future with real-time hormone monitors that could revolutionize both clinical care and neuroscience.

“Maybe this is the endocrine system…pulsing on these different rhythms, and then it’s creating these echoes throughout the rest of the body—that’s like, oh, cool, here’s the rhythm we get to dance to.”
— Latif Nasser [38:22]

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Notable Quotes & Memorable Moments

• “We are all at the mercy of a crashing, swelling wash of chemicals inside of us, the chemicals we call hormones.” — Molly Webster [04:13]
• “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 and Me was born.” — Laura Pritchett [11:09]
• “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.” — Molly Webster [30:01]
• “The brain likes prediction. It likes rhythm. It likes, you know, it likes rhythms…maybe that’s what hormones are doing. It’s like, laying down these…organizing principles for the brain that can, like, that help it function at its most, you know, at its highest level.” — Latif Nasser [37:11]
• “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.” — Latif Nasser [39:20]
• “I yelled at that person because I’m hangry and I don’t even know if I buy into free will. If I’m being totally honest, I don’t know…we are also just like big biological sacks of stuff.” — Latif Nasser [40:04]

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Important Timestamps

• [03:27] – The “fact check” about brain changes over menstrual cycles
• [09:53] – Why female subjects are omitted from animal research
• [11:19] – Birth of “28 and Me” experiment (Laura’s self-study)
• [14:07] – Discovery of heightened brain connectivity during estrogen peaks
• [16:21] – Physical (morphological) brain changes, hippocampus grows and shrinks
• [17:32] – Hormonal suppression erases cyclical brain changes
• [26:42] – “28 and He”: Male hormone cycle and brain connectivity
• [29:18] – “Testosterone…responsive to social stimuli” explains more variability in men
• [33:47] – Discussing new research connecting estrogen, plasticity, and trauma vulnerability/resilience
• [36:00] – Viewing cycles as sources of stability, not “noise”
• [37:11] – Rhythm as an organizational principle for the brain
• [38:22] – The “heartbeat” metaphor: hormone pulses as internal tempo

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Final Thoughts

The episode brings empathy and nuance to a topic mired in cultural myth and scientific neglect. By exploring both personal journey and groundbreaking science, Radiolab illuminates the reality that everyone, regardless of gender, lives at the mercy of beautiful, rhythmic internal chemistry. These cycles are not chaos, but potentially a deep organizing principle—and understanding them further might one day let us control, or at least appreciate, our own wondrous biological pulses.

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For Further Listening or Data Access

• Explore raw data: openneuro.org
• Learn more: radiolab.org/thelab

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Transcript

[Lulu Miller]

Hey, friends. Lulu here. I have been working in public radio for over 20 years. I feel so lucky to get to do this job. And this is a moment unlike any other. Nearly a year ago, Congress eliminated our federal funding, and so many of you stepped up to support Radiolab at that time. Thank you. Thank you from the bottom of our hearts. Thank you. But the truth is, we just aren't out of the woods yet. There's no sign of federal funding coming back, and New York Public Radio, our home station, is currently facing an ongoing shortfall of nearly $3 million. And so I'm coming to you to ask for support. If you are one of those listeners who has never given. We see you, we make this for you, we don't want you to have to support it. But again, this is a moment that is really different. If you appreciate our weekly dollop of wonder, of stories that we hope make you see the world anew, that give you some dinner party fodder or just some quiet escape, please consider supporting us by joining the lab. And in return, we will ship you a fan favorite T shirt with the design of a pro tool session on the front. You know, with little sound waves kind of layered on top. It is peak sound nerd, but the audio ain't peeking. Little sound joke for you there. Anyway, for real, I am so proud that Radiolab is a show on public radio. We are not beholden to any institution. We can report on anyone from Facebook to the government to, you know, the secret underwater sex lives of aquatic animals that they don't necessarily want us to know about. We go there. We are beholden to no one but you. So we're asking you, be the public in public radio. Join the lab for the T shirt. The other perks like bonus content and sponsor free episodes or just do it to keep the show going. To join the lab and see the T shirt and check everything out, just go to Radiolab.org join or you just text the word lab to the number 83763 to make your donation. Thank you so much. And on with the show.

[Latif Nasser]

Oh, wait, you're listening.

[Lulu Miller]

Okay.

[Geico Gecko (Voice Actor)]

All right. Okay. All right.

[Latif Nasser]

You're listening to Radio Lab.

[Molly Webster]

Lab. Radio Lab from wny.

[Lulu Miller]

See y.

[Molly Webster]

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 because 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 makeup of your brain changes. And I remember reading that and thinking, wait, my brain actually physically is changing? Is that true?

[Gabby Santis]

Okay,

[Latif Nasser]

there's so much to unpack here.

[Molly Webster]

Hey, I'm Molly Webster, this is Radiolab. And today I can go real far back. We're going hard on a question that I have been thinking about for years.

[Latif Nasser]

Totally.

[Molly Webster]

It's funny, as I've been thinking about this topic, everyone's like, honestly, you should just talk to Emily.

[Gabby Santis]

Aww.

[Molly Webster]

Emily is a neuroscientist, a neuroendocrinologist, to be precise. And she is. Is on one of the teams that has been struggling to understand how hormones affect the brain.

[Latif Nasser]

Because we had these, like, these glimpses, these little flickers of what it could be doing. But to watch the full cinematic view of how this is unfolding, that was a breakthrough.

[Molly Webster]

Very recently, Emily's lab came up with an experiment 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.

[Latif Nasser]

So when we say a hormone, maybe we can just define our terms. Like, when we say 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 on top of your kidneys. You have a thyroid gland. And then once they start producing hormones, the. Those hormones use your circulatory system, your blood supply as their superhighway. They hit, you know, almost every cell in the body. And that's when you think about, like, why do we even have hormones? Like, why is that a thing?

[Molly Webster]

Just to make it complicated.

[Latif Nasser]

Just to make it complicated, like, why we have hormones. Because if you're a multicellular organism, if you have more than two cells, those cells need to know how to communicate with one another so that, like, everything's working together and in sync. And nature's figured out a really clever way to do that. And there's several ways, but hormones are one way.

[Molly Webster]

It just seems like a sloppy way to communicate. Like, I'm gonna wash you in a liquid, like a synaptic connection, where there's, you know, 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?

[Latif Nasser]

I think because you can't have wires connecting every single cell to every single other cell.

[Molly Webster]

Yeah. It would be like a scary motel where you see the wires around the walls. Yeah, Right.

[Latif Nasser]

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.

[Molly Webster]

Which brings us back to the brain question. What are hormones doing up there?

[Latif Nasser]

The science is really, I'd say mile one of the marathon. No. Inch one.

[Molly Webster]

Inch one.

[Radiolab Sponsor Announcer]

Wow.

[Latif Nasser]

We are using pretty archaic methods to understand the function of hormones in the brain. And a lot of it is correlational. Like, 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 ebbs 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 picograms per milliliter of estradiol. 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 to date 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 collect. Like, how much caffeine did I have today? And how well did I sleep? And, like, did I have an eczema flare up? Like, literally everything.

[Molly Webster]

This is, like, my dream.

[Latif Nasser]

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 and this, you know, it 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. Yep, Laura Pritchett.

[Laura Pritchett]

Yeah, sorry, let me just. I'm gonna 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.

[Latif Nasser]

I volunteer to do this.

[Laura Pritchett]

Emily is a philosopher and I am a country bumpkin.

[Molly Webster]

That's how I describe myself.

[Laura Pritchett]

And no better case subject than me.

[Molly Webster]

So our girl Laura is actually Dr. Laura Pritchett now.

[Laura Pritchett]

Now I'm in Philly for a postdoc,

[Molly Webster]

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.

[Laura Pritchett]

I noticed for like week after week after week, the papers we were having to read only include 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 estrus cycle, you know, 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, 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.

[Molly Webster]

Oh, 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 those two things connected for you.

[Laura Pritchett]

Yes, exactly. Then that led me to go, okay, well, how do sex hormones influence the brain in ways that I can measure.

[Molly Webster]

And then you were like, I know who can be the perfect study sample.

[Laura Pritchett]

Yep.

[Gabby Santis]

Me.

[Lulu Miller]

Yeah.

[Laura Pritchett]

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 and Me was born.

[Molly Webster]

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, go to the lab,

[Laura Pritchett]

spit in a vial, I did saliva, and then I would go get my blood drawn.

[Molly Webster]

Mario the phlebotomist would poke her in the Arm.

[Laura Pritchett]

We tried once to get my foot. Cause I was a little too bruised up. And I almost kicked him in the face.

[Gabby Santis]

Yeah.

[Laura Pritchett]

And then I would go straight to a two hour or so mri.

[Molly Webster]

They put her in a brain scanner and she had to lie totally still.

[Laura Pritchett]

We 3D printed a foam head case, custom to me. And I actually had them put sandbags on my legs and take straps and strap me in almost like a straight jacket.

[Molly Webster]

I can't believe that made you feel better.

[Laura Pritchett]

Yeah, that's what I'm saying. I'm a weirdo.

[Molly Webster]

So Laura was in there. She was under this, like, blanket of sandbags. And they would scan her entire brain. While she was doing a series of mental exercises, we did an arresting state

[Laura Pritchett]

scan, meaning recording my brain as I'm letting my mind wander. And 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 there were, like, men taking selfies with a mirror. And I'm like, give me a romance novel. Like, this is not gonna do this for me. But I did that every day.

[Molly Webster]

And Laura did this spit stick scan, spit stick scan again and again for a month.

[Laura Pritchett]

The hardest part was halfway through, where you're like, I've done 15 days of this. Oh, my God, there's 15 more.

[Molly Webster]

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.

[Laura Pritchett]

Exactly.

[Molly Webster]

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

[Laura Pritchett]

Yeah, great question. I waited till the end. So we actually decided to start blind in the 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 I didn't even know when I was gonna get my period. But I remember a graduate student had to come and give me, like, a tampon.

[Molly Webster]

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

[Latif Nasser]

together, her data were beautiful. When she started to look at sort of relationships between that period when estradiol peaks, right around the time of ovulation, she saw this, like, massive increase in functional connectivity across most parts of the brain.

[Molly Webster]

Wait, what is functional connectivity? Like, what am I visualizing when you say that phrase?

[Latif Nasser]

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 hyperconnected. Imagine like, let's say we wrapped the brain in a string of Christmas tree lights. I don't know where this analogy is going, but we're gonna try it.

[Molly Webster]

Stay committed and keep.

[Latif Nasser]

Okay.

[Lulu Miller]

Okay.

[Latif Nasser]

We're wrapping the brain in a string of Christmas tree lights. And when estrile peaks, it's right around the time of ovulation. 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 working in sync. And then that's. So to walk you through your menstrual cycle, right, like right after ovulation, you get this plummeting of estrogen and progesterone starts to dominate the scene.

[Molly Webster]

And during that moment, which is about a week before your period, you start

[Latif Nasser]

to see like, those lights dim a little bit. And it's not like the brain activity is dimming or like cognitive functions are dimming. It's just like this shift in the basic connectivity structure of the brain.

[Molly Webster]

It's kind of like the structure of the brain is the same, it's just not as in sync.

[Latif Nasser]

But we also used a really high resolution scan of the hippocampus. So this is the part of the brain that's really important for learning and memory. What we discovered is that 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 of and bops and that we could see these structures of the hippocampus actually grow and shrink along with the menstrual cycle. I mean, like on a rapid time.

[Molly Webster]

And so that one is actually physical.

[Latif Nasser]

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.

[Molly Webster]

My takeaway here is that these liquid chemicals in my body are washing my brain and changing it it monthly, weekly, daily.

[Latif Nasser]

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.

[Molly Webster]

So they Basically do the entire experiment all over again. But this time, Laura, I went to

[Laura Pritchett]

our student health center and I said, prescribe me the most common birth control packet you're giving the undergrads.

[Latif Nasser]

She went on a drug that suppressed progesterone levels by 97%.

[Molly Webster]

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. Spit stick scan.

[Latif Nasser]

And the progesterone dependent changes that we saw in the hippocampus across the cycle were completely obliterated.

[Molly Webster]

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.

[Latif Nasser]

Exactly, yeah.

[Molly Webster]

Okay, so you're telling me I can keep telling people that at different points in your cycle, your brain changes?

[Latif Nasser]

Yes.

[Molly Webster]

Wow.

[Latif Nasser]

But I think where we need to be careful is in the interpretation of that fact. So we don't know what it means in terms of behavior. 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.

[Molly Webster]

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, send, send. Give me an improv troupe. Like, I will, yes. And the shit out of this show. You know what I'm saying? And then 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 sec. Oh, like, yeah. Like, what was your name?

[Latif Nasser]

Like, oh, yeah, there were tears.

[Laura Pritchett]

I remember that was a note. I was crying in the parking lot for some reason.

[Molly Webster]

As part of the study, Laura was tracking her mood each day.

[Laura Pritchett]

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

[Molly Webster]

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 get that extra hit of dopamine, but if you're a person who already has has a lot of dopamine, it could make you feel awful.

[Latif Nasser]

So, like, I think we still need the data to like, understand how that is tied to those aspects of cognition.

[Molly Webster]

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. Are hormonal. Women change. Unlike men, women aren't reliable.

[Latif Nasser]

When you, like, call somebody hormonal, it's like almost always directed at a woman. Right. Like, it's a pejorative. But, like, that belies the fact that, like, hormones are in all of us. These are ancient molecules. Every vertebrates have them. Like, these are essential. And, you know, men have them too.

[Molly Webster]

But it sort of comes right from the fact of, like, our females, however, you know, are changing on this 28 day 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.

[Pavel Shapturenka]

Right?

[Molly Webster]

I'm not sure if you're about to tell me, like, well, guess what? Men are going through a cycle too.

[Latif Nasser]

Yeah, guess what? Men are going through a cycle too.

[Molly Webster]

Wait, really?

[Latif Nasser]

Yes,

[Molly Webster]

that's right. We're not getting out of this episode

[Pavel Shapturenka]

without the trending thing is boy kibble, right?

[Molly Webster]

A man. We're going inside the mail cycle after the break.

[Lulu Miller]

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[Latif Nasser]

One of the reasons we did 28 and he, we're just like, oh, is

[Molly Webster]

that what it was called? 28 and he, yeah. Oh, that's hilarious.

[Latif Nasser]

Fun fact. This was actually Laura's then partner, now husband.

[Pavel Shapturenka]

I met Laura first an intramural softball in graduate school.

[Molly Webster]

Okay.

[Pavel Shapturenka]

His name is Pawel Pavel Shapturenka. I am a scientist.

[Latif Nasser]

Shout out to Pavel.

[Pavel Shapturenka]

The summer that we met, she had done prior that summer this study on herself. And I was just taken aback that someone would do that for science, would 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,

[Molly Webster]

I've climbed the Eiffel Tower. So when Laura said, said, hey, so

[Pavel Shapturenka]

how do you feel about climbing into the mri?

[Molly Webster]

Pavel said, yes.

[Pavel Shapturenka]

She would always be there by my

[Molly Webster]

side to your heart. Every morning they'd get in the car,

[Pavel Shapturenka]

I'd be pulling my saliva, like collecting

[Molly Webster]

it in your mouth. Yeah, like, don't talk, just gather spit.

[Pavel Shapturenka]

That's right, yeah.

[Molly Webster]

He'd walk into the lab, deposit his

[Pavel Shapturenka]

spit, and Mario would come and take Some blood.

[Molly Webster]

I just love this character of Mario the phlebotomist. Then, just like Laura, he would lie in the scanner still as can be. But for his experiment he did double duty.

[Pavel Shapturenka]

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.

[Molly Webster]

Why were you getting scanned twice a day?

[Pavel Shapturenka]

Whereas, you know, the main fluctuation of estrogen happens on a monthly timescale. Testosterone has sort of a daily rhythm. So it's diurnal, it's super high in the morning.

[Molly Webster]

I did not know that. Okay, super high in the morning and

[Pavel Shapturenka]

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

[Latif Nasser]

So for Pavel, we really kind of capitalized on this known circadian rhythm where testosterone and progesterone and estrogen are peaking in the morning, they're dipping in the evening. And we said, huh, let's wait.

[Molly Webster]

Men have progesterone? Progesterone, yeah.

[Latif Nasser]

They have all the bits that we do at just at different concentrations and these hormones cycle in men. And so we wanted to understand that like, is the male brain undergoing kind of a similar degree of change?

[Molly Webster]

After all Pavel's data was collected, Emily and Laura had their team comb through it and they saw the punchline is

[Latif Nasser]

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 like 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, is pulsing on this 24 hour scale. So when hormones are high, it's a little bit bigger at evening, it sort of like tightens up a little bit. And we get. The crazy part is that we can literally see this, you know, curiosity, 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.

[Molly Webster]

That's crazy.

[Latif Nasser]

So it's like these hormones are having the same size effect whether it's happening on a 24 hour timescale or across the 28 day menstrual cycle.

[Molly Webster]

But wouldn't women also be doing this circadian?

[Latif Nasser]

Yes, that is true.

[Molly Webster]

So we're getting circadian 24 and 28 across time.

[Latif Nasser]

That's right.

[Molly Webster]

And men are more locked into the 24.

[Latif Nasser]

That's right, that's right.

[Molly Webster]

Um, I feel contradictory then because somehow in you trying to be like, look it, 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.

[Latif Nasser]

Yeah, meaning that. Meaning I'm surprised that you have a circadian cycle on top of.

[Molly Webster]

Yeah, yeah.

[Latif Nasser]

Like you're absolutely right in that this myth of female variability and this idea that we have this kind of like pest.

[Molly Webster]

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.

[Latif Nasser]

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. Right. 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 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 super responsive to social stimuli. So you can study this in animals who get in a fight and you get these testosterone surges and then if they lose a fight, you get testosterone suppression. True in humans who aren't even engaged in fist to fist combat. If they're just watching TV and their favorite team loses, you can see testosterone suppression.

[Molly Webster]

But that's not happening with estrogen.

[Latif Nasser]

Yeah, not as much. It's really. Again, every sex has every hormone. It's just the proportions that are different. But in testosterone, which is on average higher, in men, it's much more fickle.

[Radiolab Sponsor Announcer]

Wow.

[Latif Nasser]

So it's just funny to me that women are the ones deemed as this like unknowable.

[Geico Gecko (Voice Actor)]

You know,

[Molly Webster]

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.

[Latif Nasser]

Brains are built to change. They're built to learn, they're built to adapt. And here we have this mechanism, this hormonally mediated mechanism that's allowing our brains to do that. If brains did not change, that would be the pathology of interest.

[Molly Webster]

Wait, can I just ask a question? 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 speaking to itself. Better that it's opening.

[Latif Nasser]

Yeah. So, like, these estrogen rhythms are opening up, these windows of enhanced neuroplasticity and neuroplasticity.

[Molly Webster]

You probably know, this is this idea that the brain is malleable. It's open to change. And Emily said, I. All sex hormones, including estrogen, can go into the brain, down to the level of the DNA and open it up.

[Latif Nasser]

So DNA is organized in this chromatin structure. Right. So it's actually like, pretty tight and closed up.

[Molly Webster]

It's, like wound tight. Like, everyone see the helix and then the helix is, like, tight.

[Latif Nasser]

It's really tight. Right. But estrogen is one of the factors that can actually loosen up the DNA. It's like it just relaxes a little bit, and it can promote 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,

[Molly Webster]

like, five minutes before the interview, so I have no idea what it said.

[Latif Nasser]

I know. Okay, so this is work from Tali Bahram. And, oh, my God, it's blowing my mind, because this is what the study asks. 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.

[Radiolab Sponsor Announcer]

You.

[Latif Nasser]

You know, introducing it to odors of its predator. If that happens during this period, you create a PTSD like phenotype in these animals.

[Molly Webster]

Wow.

[Latif Nasser]

And it's. It is long lasting.

[Molly Webster]

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 asked the question, okay, well, what happens in moments of low estrogen?

[Latif Nasser]

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 fleeting windows where you can drive plasticity, but then estrogen levels get a little bit lower and you are more resilient to these stressors. Again, pure speculation at this point, because the science is so young.

[Molly Webster]

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 wanna 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.

[Laura Pritchett]

If you have really high connectivity between regions of your brain that's really energy dependent, that's.

[Molly Webster]

Laura again.

[Laura Pritchett]

You could be exhausted.

[Molly Webster]

It is funny. Maybe part of what is opening up for me is like, there's so much about, you know, I just finished my period. There's like so much about it where you're like. But I'm like, just thinking about it in a different way. Like as it. As it's almost. It's like a way my body is like, taking care of itself.

[Laura Pritchett]

Yeah, I think that's a beautiful way of thinking about it. And I think, you know, if I teach a class or guest lecture, I say what comes to mind when I say estrogen, and it's like Zooey Deschanel's character, new girl crying and, you know, eating ice cream. And it's like, we can move from those stereotypes and be like, wow, hormones are just fucking powerful and they serve a purpose and they're neuroprotective.

[Latif Nasser]

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.

[Molly Webster]

Geez, are you ever, like, Damn our brains? 24 hours a day it's going up and down, up and down. Then every other day it's going up and down, up and down.

[Latif Nasser]

But I think it's like an organizing principle of the brain.

[Molly Webster]

It's creating sounds tiring. But you're saying it's not. I know.

[Latif Nasser]

Is it tiring for the waves to, you know, happen on this rhythm? I don't know. Or is it like, organizing the system in some really helpful way? I don't know. Those are the questions that I want to dig into that like, man, we have just, like, scratched the surface on scientifically.

[Molly Webster]

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? Why would brain changes be organizational?

[Latif Nasser]

The brain likes prediction. It likes rhythm. It likes, you know, it likes rhythms. You know, like, 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 they can put themselves to bed whenever 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 flow 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.

[Molly Webster]

Yeah, yeah, yeah, but.

[Latif Nasser]

But now we get to at least ask the question of, like, is that pulse doing anything that the brain likes or that, like, helps us in some way?

[Molly Webster]

Yeah. Wow, that's a. That's a cool word. Pulse. Like. Like brain pulse. Like, it's. It's working out up there.

[Latif Nasser]

Yeah. It's like the heartbeat of something. Right. It's like the vital sign.

[Lulu Miller]

Yeah.

[Latif Nasser]

This. It's like, you think of, like, the cha chunk, chunk cha 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 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 then the whole body to get in sync to.

[Molly Webster]

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 a way in which it just has a. It's all powerful. And so then when I hear something about the brain changes, I'm, like, immediately, like, wow. Like, awestruck.

[Latif Nasser]

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 suggests 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 I yelled at that person because I'm hangry and I don't even know if I buy into free will. If I. I'm being totally honest, I don't know. I mean, I think that there's ways we can gain free will. But like by and large we are also just like big biological sacks of stuff. And I hope that being that I'm

[Molly Webster]

a big biological sack, but if I know that if I say it out loud, then I could maybe do a little bit more with the sack. Like I could push it to the left and push it to the right, even if only an inch maybe. I hope that's my wish.

[Latif Nasser]

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 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 this like grainy little blip in the, you know, in the sky. And now we can see the individual like craters and 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.

[Molly Webster]

This episode was produced by Mona Medgalker and me, Molly Webster. It was fact checked by Diane Kelly. I want to thank Soren Wheeler, Pavel Shapdurenka, Emily Jacobs and Laura Pritchett. Emily hangs out at the University of California, Santa Barbara. You can find Laura and Pavel at the University of Pennsylvania in Philadelphia. And you can also find all of Laura and Emily Pavel's data online. Go to openneuro.org that's open n e u r o.org props to Laura for making all of her data public. Also a huge shout out to Catherine Woolley whose 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 the lab 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 Radiolab, and the next time I see you, I'm going to ask where are you at in your cycle?

[Gabby Santis]

Hi, I'm Gabby. I'm from the Bay Area, California. And here are the staff credits. Radiolab is hosted by Lulu Miller and Latif Nasser. Soren Wheeler is our Executive editor. Sarah Sandbach 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 Gable, Maria Paz Gutierrez, Sindhu Nainasambandan, Matt Kielty, Mona Maudgauker, Annie McKeown, Alex Neeson, Sara Khari, Natalia Ramirez, Rebecca Rand, Joanna Strogatz, Anissa Vitze, Arian Wack, Molly Webster and Jessica Young, with help from Gabby Santis and Maya Appleby Melamed. Our fact checkers are Diane Kelly, Emily Krieger, Natalie Middleton, Angeli Mercado and Sophie Semay.

[Molly Webster]

Hi, I'm Aubrey calling from Salt Lake City, Utah. Leadership support for Radiolab's science programming is provided by the Simons foundation and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.

[Geico Gecko (Voice Actor)]

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[Lulu Miller]

It feels good to get good news. It feels good to GE.