Circadian Rhythms & Fertility: Sleep, Hormones, and Reproductive Outcomes

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In this episode of the Love & Science Fertility Framework, Dr. Erica Bove explores how circadian rhythms influence reproductive function and fertility outcomes.

Circadian rhythms regulate hormone secretion, ovulation, inflammation, and implantation physiology. When sleep schedules are disrupted — whether from shift work, long call hours, or chronic stress — the reproductive system is directly affected.

Topics discussed include:

• GnRH pulse generator disruption and anovulation

• Brain–ovary signaling and altered hormonal secretion

• HPA axis activation and cortisol elevation

• Stress physiology and reproductive suppression

• Melatonin production and uterine receptivity

• Clock genes and light exposure

• Sleep disruption and testosterone levels

• Inflammation and implantation outcomes

• The impact of chronic sleep irregularity on fertility

Dr. Bove reviews the physiologic mechanisms linking sleep disruption to ovulatory dysfunction, implantation challenges, and miscarriage risk — and discusses why circadian stability may be particularly important for women in high-demand professions.

This episode is part of Season 1 of The Love & Science Fertility Framework: The Biology Beneath the Surface — a clinical series examining the physiology that drives reproductive outcomes.

Transcript

Hello, my loves, and welcome back to the Love and Science podcast. Today, we're going to talk about a very important topic, which is circadian rhythms and the influence on the reproductive system and the reproductive function. So circadian rhythms, we learned about them in medical school. For those of us who are physicians, what are they? Basically, they are biological processes which reflect a 24-hour cycle. So this can pertain to things like sleep,

like core body temperature, like blood pressure regulation, and also even hormonal secretion and regulation. And so when we think about many of us, whether we're physicians or maybe attorneys or engineers with jobs at late hours, right? Like many of our bodies are not allowed based on our work schedules to have a regular schedule.

And one of my good friends, Dr. Funke Brown, she is a sleep doctor, sleep specialist. We talk all the time about the really intimate interplay between hormones and sleep and how important that is. So I wanted to review some of the mechanisms and the data regarding circadian rhythms and reproductive outcomes. So why are these circadian rhythms so important?

Well, when we have altered sleep schedules, for instance, long call shifts, or maybe, you know, shift work that varies from day to day, month to month, this can have tremendous hormonal effects, right? We know that women who have irregular sleep cycles and circadian rhythms, they can have an ovulation and amenorrhea because what happens is that the pulse generator gets affected. The GnRH hormone secretion is altered that affects the pituitary hormones that affects.

the ovaries and so thinking about it you know we know that there is these clock genes right super interesting to think about there are these genes that are influenced by the light exposure that we have you know perhaps even the humidity right we have these different changes in seasons and also even our eating patterns can signal our bodies about you know what they're supposed to do next and so

In the hypothalamus, there's this area called the suprachiasmatic nucleus. I remember learning about it at medical school. I was obsessed with neuroanatomy, right? And what happens is that these areas get dysregulated when we have alterations in.

the light that we see, right? Even the invention of a light bulb affected our overall health, which is fascinating. And also even like whether we eat breakfast or not could have an influence on some of these functions as well. So thinking about how in women, right, how ovulation can truly be affected by hormone changes related to sleep disturbances, I think that's really powerful.

And also we know that testosterone levels are lower, both in animals and humans for men where there are sleep disruptions. And I think that's just really powerful. There was even data to suggest in rodents that the semen analysis is worse when rodents' circadian rhythms are disrupted. And I think that's quite powerful, right? Everyone's like, why are sperm numbers decreasing around the world, right? So maybe there is a link between the worst sleep that we're getting and...

also the secretion of these hormones and the ultimate effect on the sperm quality. Just a thought, but just think about it. There's some biological plausibility there. So that's really the first mechanism is alteration in hormone secretion, right? The second mechanism is how when we don't have regular sleep patterns and our circadian rhythms get messed up, that then activates our hypothalamic pituitary adrenal axis, right?

That's considered a stressful circumstance, right? Our bodies are trying to stay in a rhythm. They're trying to respond to the environment, but the body sees that as a potential threat. And when our HPA axis gets engaged and activated, that increases our corticosteroids. And we know that that has the effect of...

decreasing the sex steroid secretion and also increasing inflammation. And so, yes, it is good that our HPA axis can get activated in times of stress, but when we are chronically sleep deprived, when we are burning the candle at both ends, so to speak, when we are going into the hospital and maybe getting out at 2 a.m. and then the next day we have a different shift, that's very confusing to our bodies, which like predictability and no bodies know when it's a stressful time, right? We know this from data.

When our bodies are stressed out, the body's like, oh, it's not a great time to be getting pregnant. So even if we're overriding things with IVF, the body knows and these disturbances can really affect the HPA access and what that does with the interplay with our reproductive system.

There's also evidence that when we have disturbed circadian rhythms as pertains to sleep, that that can decrease our melatonin production and that can affect a lot of the peripheral systems. And so the way that it works with the clock genes is that it affects that nucleus in the brain, right? And then there are both neuronal and hormonal influences on these more peripheral circadian.

target organs and so you can see effects in the liver you can see effects in the kidneys you can see effects in the heart you can see effects in the reproductive organs because you know we are wired we are one system right we're not just the sum of all these little parts like we truly are connected whole human beings and so you know really really interesting to think about how our melatonin is important and that helps us with our sleep and when we have less

melatonin production, there's actually some evidence that has suggested that that is related to increased risk of miscarriage and also reduce uterine receptivity. And so this question of why are my high quality embryos not implanting? You know, we think, oh, we can do, you know, we could just keep working as hard because we got to serve all the people.

I think there may be a good argument for reducing call, having more regular schedules, all those different things that would actually take good care of ourselves to restore our circadian rhythms as we were trying to get pregnant. Okay, so let's talk about stress for a second. I know this is a very controversial topic, but...

stress alters the circadian clock it just does and so people always say you know what's the role of stress infertility well yes stress infertility is inherently stressful but that also affects the certain circadian clock when the circadian clock is affected then that

then increases truly not just our emotional stress, but our body's experience of stress. And so if we're thinking about it, what can we do to optimize our outcomes? What can we do to feel better? Even in the setting of IVF, like I said, where we're overriding a lot of these things, there's really good evidence that if we can get better sleep, our bodies can have more predictable schedules. There's even some evidence that eating breakfast can be helpful to the overall process, right? Because it helps our circadian system stay in check.

that that can then decrease the HPA activation, reduce inflammation, remind our body that we're safe, provide our body that's a good time to be pregnant, right? Like it's sort of truly decreases our stress response and allows our physiology to work better. So if you're listening to this and you do have a schedule that is irregular or unpredictable, or maybe you're an OBGYN and babies are born, we know at all different hours, you know.

And you're trying to get pregnant. I mean, I think in general for overall health, it's good for us to try and get regular sleep as much as we can. Obviously there's good data for that, but in particular on the fertility journey is it is very, very important to do the best we can. And that might mean setting boundaries. That might mean talking with our supervisors because.

really we get one shot at this, right? Like we have our reproductive years and then they're over. And my job is to empower you to make the best choices that you can. So I hope this, this little talk about the clock genes and those circadian rhythms was educational. I always learn when I prepare for these talks, but I really think there's definite links to the reproductive system, both in terms of hormone secretion, HPA activation, inflammation.

And likely even, you know, implantation issues as well, as well as increased risk of miscarriage. And this question of like, why do female physicians have worse outcomes compared to, you know, non-physicians? I think this may be part of the picture. So thank you for listening. As always, tell me what other science-y topics you want to hear about, because I will go to the literature and I will bring some clarity to the situation. You know how much I love you. Bye.