- We've often known that for quite a while, menstruation and exercise are linked together. But today we're gonna talk about an article that suggests they're even more intertwined than we previously thought. So let's dive in. Welcome back to the Building Lifelong Athletes podcast. Thanks so much for stopping by, I really appreciate it. For those who don't know me yet, my name is Jordan Wrennke. I'm a dual board certified physician in family and sports medicine. And the goal of this podcast, to be active and healthy for life through actionable evidence informed education. In today's episode, we're gonna talk all about article in the British Journal of Sports Medicine about menstruation and female athletes. So let's dive in. So first let's take a look at what the actual paper is. So the paper here, as you can see, it's titled "Hypothalamic Pituitary Ovarian Axis Suppression is Common Among Women During US Army Basic Combat." And it's by Pop et al. And it's a recent one here. And that's a mouthful here. We're gonna talk specifically about the HPO axis or hypothalamic pituitary ovarian axis. Let's talk what that means. Let's take one step back, basic training. So basic training in the military, it can be anywhere from about six to 13 weeks, depending on your level or your officer enlisted and your prior experience, what medical degree do you have? When I saw me perfectly in my military, mine was like a six weeks, five weeks, six weeks course. And so the general training is usually a little bit longer, right around like eight, 12 weeks, something like that. And we do a previous record of knowing that women in the military have menstrual disruption. It's pretty common. About 53% of American Academy cadets have dysfunction of their menstruation within the first three months. So 53%, more than half of the females coming into the Academy. So the academies are right after high school, it's going to West Point Naval Academy, Air Force Academy, they have disruption from the first three months. And about 86% of women have some sort of disruption during their basic training in the army. So we're looking at well over half of the cadets and 86% of women having some sort of menstrual disruption. That is huge. But why do we care about that? Well, we care about that because the HPO or hypothalamic pituitary ovarian axis, it regulates reproductive function. And suppression of this HPO axis can lead to altered hormonal patterns and can lead to cessation of periods, so stopping periods. And this can have long-term consequences on things like infertility, impaired bone health, makes your bones weaker, and increased risk of heart disease. And so let's dive in just a little bit here into the physiology. So physiology here, right here, you can see this is a diagram of the hypothalamus, the anterior pituitary, and then the gonad. So essentially looking at the hypothalamus as a portion of the brain, it secretes something called GnRH. Then this acts on another portion of the brain called the anterior pituitary. This then makes hormones LH and FSH. And these go, specifically here, we're gonna talk about the ovaries to females, and then they make estradiol and progesterone. So make estrogen and progesterone. And this is kind of the general how the flow works, right? They're very similar for males, except it goes to the testes, but for females, this is what we typically have. And this is the axis in general. And then if you look here, this is the feedback loop. So we can see, once again, hypothalamus here releases GnRH, then goes to the anterior pituitary, releases LH and FSH, and then the ovary from there makes estrogen and progesterone. And you can see estrogen then feeds back, comes all the way over here, the hypothalamus can shut things down. So this is what we call the feedback loop. So when we say the HPO axis, that's what we're talking about, this axis saying, hey, your body does this with a ton of hormones. And you can have regulation as you produce these things. If you have more of the end product, that circles on back and says, hey, we're good, slow it down, we don't need as much. And vice versa, if there's not enough down here, then you'll make more of the initial start products to then produce that hormone. So that's what I mean, HPO axis. This whole thing can get disrupted, and that's why we care about it so much. And on top of that, let's just real quick review our menstrual cycle. So the menstrual cycle in females, broken down into about two phases, kind of three, depending on what we're looking at here. But you have this first phase here, which is the follicular phase on the left. So this follicular phase is here, and then we have the luteal phase on the right, and then we have ovulation happening in between there. Some people call it their own stage, but typically about 14 day periods here. So the follicular phase is about 14 days, and luteal phase is about 14 days. And typically a follicular phase is happening before the egg is released. So this is like starts day one of menstruation. This is what we think of like, this is preparing to release an egg. Usually it's supposed to be about 14 days. And in this, as you can see up here, estrogen, progesterone are typically low. So this causes shedding of the endometrium, which is the lining of the uterus and menstruation begins. And so just to step back there once again, estrogen, progesterone are typically low. This is causing a shedding of the endometrium and leans out. And then on top of that though, at this time, FSH levels usually slightly increase, which stimulates the development of the follicles. And so you can see FSH kind of creeping up here a little bit. If you're looking at the chart right here, creeping up just a little bit here, starting to go and that's kind of preparing the follicle. Then once that does happen, so FSH goes up, prepares a couple of follicles, and then it does have a decrease. And then when it decreases, only one follicle kind of remains. And that follicle then hangs around and produces estrogen. So estrogen still increases. So once again here, as you can see, FSH goes up and then it starts to go down. And as it goes down, we have one follicle remaining and that tends to lead to an increase in estrogen. So that's what we're happening here in the follicular phase. You know, we've kind of had an increase here of the FSH go up a little bit and then down again. Then we have remaining follicle that's creating the estrogen. That's typically what's happening early on. Then we have the egg release, which is around day 14. Here we see a surge of LH and FSH. And LH stimulates egg release. And it happens about 16 to 32 hours of after that surge. And then estrogen decreases during the surge and progesterone increases. So you can walk up here and say, "Hey, yep, LH going through the roof, estrogen starts to go down and then progesterone starts to go up." All that's happening prior to kind of around releasing that egg. And once that releases, we're moving to the luteal phase. And the luteal phase usually happens days 14 to 28. We see a decrease in the LH and FSH. Up here you can see markedly here, we have that LH, FSH just plummeting down as you see that progesterone going up. And then you'll start to see that estrogen also start to creep back up as well. 'Cause a lot of what happens is, you know, once the ruptured follicle, it becomes something called the corpus luteum. So the corpus luteum kind of hangs around and that creates progesterone. So we have lots of progesterone. And then estrogen is also high. And then estrogen and progesterone help keep the lining of the uterus thick to help prepare for fertilization. That's the ultimate goal. However, though, if we have no fertilization, the corpus luteum then breaks down and then progesterone, estrogen decrease and the cycle is started over. So once again, you can kind of see here on the pictures, it gets ready, we have progesterone, and estrogen increasing, getting ready for fertilization, right? Or for implantation saying, "Hey, this is what's gonna happen. If it doesn't happen, then they go back down. Then we restart at the follicular phase." And so that's a whole lot of physiology. And you're just like, "Well, Jordan, that was super boring. Why did you do that to me?" Well, we care because it actually matters in terms of overall health, obviously reproductive health, but then also for our athletes as well, it's really important to understand what is normal, right? So what is a normal period? It's really important for this article we're gonna talk about here. What's normal so we can understand abnormal. And so when that gets disrupted, it can lead to things, as we mentioned before, poor bone health, cardiovascular issues, lots of things. And so how do these disruptions happen? Well, there's multiple ways. So specifically, there's lots of ways you can do it. Most of the time we talk about things like sleep or stress or nutritional deficiencies are the biggest reasons why we have it. Most common is probably decreasing calories or low energy availability. And typically we'll see weight loss or body fat loss in this as well. However, it's really, really hard to track energy expenditure in like non-controlled settings, right? So specifically for people who are in a controlled environment in some sort of experiment, you can control their calories, like how much is coming in, how much is coming out. You can't really do that at basic training. That's gonna be really hard to do. It's really hard to, you're not gonna know everything they eat and everything they're burning. And so what they do here, and we'll talk about it, you can track kind of proxies for that. So you can use blood markers like leptin, thyroid hormones, and IGF-1, which can reflect short-term low energy availability. So usually within about three to six days, we'd see a decrease in those. You can also use different lab markers, body mass and body composition as a proxy for energy status as well. And the goal of this overall study was to characterize HBO access function in incoming US Army trainees by measuring daily hormonal measurements through their training. And their hypothesis is that the HBO access suppression would occur in about half the trainees. And this was gonna be defined by shortened luteal phase or anovulation, meaning they're not having the menstrual cycles anymore. So once again, they thought about half the people would have disruption, and they're gonna measure that by the luteal phase shortening or not having any sort of period whatsoever. And so going on from the introduction, then we're going over to the methods here. The methods design, this was a prospective observational study of US Army trainees enrolled at basic training. Prospective meaning we're looking forward, right? Observational meanings, we're not doing anything. There's no intervention happening here. We're just seeing what happens, we're observing it. And typical training includes lots of physical activity, calisthenics, running, marching, more marching, combatives, and they average about 16,000 stats per day. That was kind of on average. This wasn't necessarily this group. They weren't counting that, but just from previous studies, that's what they mentioned. The participants here, there were 104 female trainees. There were a couple of things they could not have had restrictive physical activity, meaning being on a profile saying, hey, you can't run. So they'd exclude them for that. They'd exclude them if they had an endocrine disorder, if they're pregnant, or if they're using hormonal contraceptives or have PCOS. Just because they weren't sure what that would do to their numbers, they said, hey, all those people unfortunately were going to kind of exclude from there. They also gave questionnaires then. They filled out these questionnaires at baseline and then each week, and they asked about things like their demographics, their lifestyle, sleep, and menstrual history. They determined their baseline menstruation status, which this was determined by self-reported number in previous year, meaning, hey, how many periods do you have in the previous year? And then each week they reassessed if they had their period or not. And the final week they reported if there's any menstrual cycle differences compared to the year prior. And that's kind of how it looked at the menstrual cycle, just from a subjective perspective. And then also to assess the HBO access, they assessed urine studies. So they got urine studies looking for LH, FSH, and then estrogen and progesterone metabolites. And of those people, one thing they did mention right away is 49 of the 100 women had less than 60% of the urine samples collected in more or more than four consecutive missing days, meaning, hey, life got busy, right? It happened to basic training, they missed it, who knows what happened. So, but almost half had some disruption in there. So we had to think about that. And then when we're looking at the HBO, we're also looking for evidence of luteal activity. This is an estimation of ovulation, right? So this luteal activity or length is kind of saying, hey, what's going on with ovulation? And to define having luteal activity, you had to hit one of these criteria, which is a three times increase in progesterone metabolite concentration above the nadir lowest level for three straight days. So LH getting that surge, right? That's gonna indicate it's coming. So three times higher or a corresponding rise in FSH, LH or estrogen metabolites. So as we talked about before, that's why I mentioned all those things like the different metabolites and what's going on. We see the FSH, LH and estrogen all rise. Those are one of those two things we're looking forward to say, hey, yep, you've hit it. They also did measure their body composition. They calculated their BMI and they used DEXA to determine the body composition. And they also took blood samples as well. They got a, once a week they got fasted morning samples looking for IGF-1, which is insulin growth factor one, cortisol, T3, T4 and leptin. And they got those at weeks two, four, six, eight and post training as well. And they also got a baseline testosterone. And so moving on to statistics now, they looked at changes in body mass, body composition, BMI, sleep and testosterone, and also just different HPO markers. They looked at those within luteal activity groups and then outside luteal activity groups. And they compared them by T tests and ANOVA analysis. And just a nerdy step back here, a paired T test. This compares the mean between pairs of measurements to determine if there's a difference or not. And then an ANOVA is analysis of variance, which is used to analyze the difference between the averages of multiple groups to see if they're statistically different. So those are the kind of the overall statistics they use. Once again, we're not statisticians here, but we're kind of looking to say overall, this is the model we wanna use. Hey, is there a significant difference between these groups? And so from a results perspective here, I do wanna break it down. There's three total groups that ended up being discovered. So the evidence of luteal activity or ELA, as you'll hear me talk about, or there's no evidence of luteal activity, which is any LA, and there's indeterminate saying, ah, I don't know, put your hands up, who knows. For baseline characteristics on average, they're 22 years old and had a normal BMI. They averaged about seven and a half hours of sleep before basic training, that certainly changed. And everyone, but one had normal testosterone going in. Age of menarche was younger in the luteal period group. So the ELA group, it seems like on average, had to have, or seem to have a little bit younger in their age of menarche. And looking at a table here, these are lots of baseline characteristics. I'm not gonna go into every single one of them, but you can see here, this breaks down the cohort into their ages and specifically looking at their height, weight, fat mass, all those things, age of menarche, going in there, that's something we can consider and look at as well. But looking at the HPO access function, about 42% of women reported regular menstrual cycles during training, so less than half, but only 12.5% exhibited normal cycles during training based on your measurements. So 42% said, "Yep, I still had my cycle." And the lab work said only 12% of them had normal cycles. And even all seven that had normal cycles had measurements that did have some sort of shortened luteal phase. So it wasn't even completely normal. And women who had evidence of luteal periods also did have higher estrogen, pedestrian, LH levels as well. And this is a graph as well looking at here. This is kind of from their paper saying, "Hey, self-reported before training, 78% of females said they had regular menstrual cycles. That went down to 42% during basic training." So pretty significant there. You see a huge jump in that. And then urine measurements, you can see here, indeterminate was 12.5%, evidence of luteal activity was 12.5%, and then no evidence was 75%. So looking in there, the vast majority of people had some sort of disrupted urine measurements when it comes to HPO access. And that's pretty substantial. That's one of the big takeaways here is like huge, huge gap in our knowledge thinking that, "Oh, if you have your period, it's just normal." We'll talk more about that, but those are big findings there. And they also looked at changes in body mass, composition, and sleep. And on average, trainees gained body mass by gaining lean mass and lost fat mass. And the reported hours of sleep per night decreased from baseline, which is the least shocking news ever. If anyone's ever been in any sort of military training, that's their whole goal is to get you sleep deprived. And so no surprise there. And these are kind of the body composition characteristics that we look at as well. This looks at the specific change in body mass in BMI, all that stuff. You look at the cohort, the ones who had there, and those are kind of stats we can look at if you wanted to, but it's not really that important. And then moving on to fasting blood markers. There was quite honestly all over the place here. There's leptin numbers were higher in the NALA group, which was pretty much all points. T4 was lower from baseline at all time points. Cortisol seemed to spike for all groups towards the end. And overall, it was a hot mess. So if you see on screen, we're looking at different things. So this is leptin. You can see in that NALA group, the ones that did not have no evidence of luteal activity, sky high leptin at the end there. And then if you look at even the other ones too, even for the luteal groups, they're still higher than the baseline, which is interesting. T3 overall, not too much different from a lot of different people, maybe going down a little bit here. And then determinate group, nothing crazy. For IGF-1, we see lots of spikes going on here. Overall, nothing insane. And then looking at here cortisol, you can see all of them pretty much have a higher cortisol, which cortisol is usually like a stress type hormone. And so the thought is that, okay, maybe it's not that weird or unsurprising that we're having a disruption in cortisol in people who are super stressed. And so that's kind of the takeaway, but they're kind of all over the place. They weren't like definitively really, really reproducible results. But going into the discussion then, there is a surprising amount of suppression, I would say is like the overall takeaway here. Overall, there's a significant suppression of the HBO access seen throughout basic training. Many trainees reported menstrual bleeding, but did not show a sign of hormone profile sitting there having the actual luteal period. So once again, they were saying that they had their period, but the lab results are saying that their luteal phase was still disrupted. So that's something to talk about. Almost all the trainees also failed to achieve a progesterone surge indicative of ovulation and normally productive function. So they weren't having the surge. And that means that self-reported menstrual status may not be the best indicator for HBO dysfunction. And overall, pituitary hormones and lean body mass gains indicated they had adequate energy intake, or at least that's what they thought. They're saying, hey, your hormones weren't that disrupted. Yeah, the cortisol is up a little bit, but the thyroid hormones weren't that bad. And you gained lean body mass, so there must have been decent amount of energy available. But overall, the authors said that these are unexpected results for them. The researchers did not expect to see this much suppression. However, it's not unprecedented though. There were previous studies of the UK Royal Military Academy, which showed 24 females all reporting a menstrual cycle, but in their lab work, only 14 of the 24 had laboratory evidence of ovulation in the first 30 days. And then looking at recreational and competitive athletes, there was another study that actually showed that 25% of people reporting regular cycles were an ambulatory by hormone measurement. And so the important take-home point there is substantial suppression was seen at basic training, and it happened really quickly. That's kind of the thing you don't think about. You know, it happened within a couple of weeks where they're saying, hey, they're just kind of shutting down things. And there are definitely ramifications to this as well. There's metabolic ramifications as well. Lapton was elevated throughout, which usually signals adequate energy. So that's one thing saying, hey, maybe this wasn't totally just energy availability causing a decrease in menstruation, which was kind of interesting. On top of that, T3, free T3, IGF-1 were only low at two time points and otherwise baseline or higher. And once again, in low energy, we would expect to see those numbers really decrease in as little as five days or so. And we did have fat mass loss, which may indicate some energy deficit, but we did have total body mass increase, which may indicate the opposite. But overall, it's kind of interesting. And the reason I mentioned this, 'cause most people will see this number or this, they'll say, oh, so basic training. Yeah, they go to basic training and they lose weight, they have no energy availability. That's why their periods go down. This isn't necessarily pointing toward that. We're not having a loss in body weight. We're actually having an increase in body mass. Our hormones aren't that disrupted, but we're still seeing a change in our ovulation. So it may not be specifically tied to that, which is kind of an interesting take on point. And why did this actually happen? Well, it's most likely multifactorial. So there's gonna be metabolic and psychosocial stresses going on here. You take people away from their social support. You probably do have some sort of nutritious deficiencies here, the diet's not the best, especially if they're in the field, they're eating things like MREs, which is these super processed things, which are always very fun to have. And obviously we've disturbed sleep here. It's a lots of disturbed sleep. We do see higher cortisol seen in the non-luteal group phase. So typically a sign of some sort of stressor. And so once again, this is probably multifactorial. This is not just one specific thing, but I think that the big take home from this article is that people were having menstrual disruption without potentially an energy availability issue, which a lot of people think, hey, it has to be because of that. It could be because of multiple different things, right? Is it sleep? Is it energy? Is it who knows what else? Could be lots of different things. And so why is this important? Well, it's important that, and shows that self-reported menstruation may not be completely accurate. So those undergoing hard training or in stressful environments, they may actually have a suppressed HBO access without us even knowing it. I think that's the biggest take home point here is that people may think they're having their regular periods and they think everything's fine, but this shows that that may not be the whole story. So that's just something to think about and which is kind of interesting. And then for me, limitations perspective, there's always limitations, right? Every paper, first was sample size. This was a super small group, not big at all, but hey, you take what you got. These were short-term results. We have no idea how long this could have affected the women. Also don't know the long-term implications or when they regain their normal cycle. And on top of that, we're unsure if the baseline was already suppressed. Like were these females already training? And so they already had a suppressed baseline. Not sure that may throw things off. And then collection issues, we've missed a lot of tests. So kind of scattered data. And then energy availability, we talked about that could be a problem, but we don't necessarily know. We don't know if they had negative energy balance. That could definitely affect things. And then the sleep was another thing. They reported sleep, but could sleep be actually different? You could have a substantially different amount of sleep based off of self-report and then actually validated measurements of that. So all those things to say, hey, there are limitations, right? Smaller study. It's not the biggest thing in the world, but I thought it was a very interesting thing. And the reason I wanna talk about this is my takeaway is I thought this was a super interesting study 'cause we all know that female athletes should have periods when they're working out, right? Like that is non-negotiable. We should know that. But that may not be enough to know the whole story. And another reason why we should really take this seriously and we should take menstruation seriously in athletes is 'cause it's so critical for long-term bone health, reproductive health and cardiovascular health, right? So if we're disrupting those without even knowing it, that's something we don't wanna be harming them later on. So that's something we have to think about. And we may really need to focus on nutrition to make sure energy availability is adequate, right? So if we're seeing decreases here in situations where energy availability isn't everything, then nutrition is one thing you have to lock in 'cause if you're very stressed and you're having poor sleep, then maybe energy is one dial we can turn. But as you can see, it's multifactorial. And on top of that, people need to work on life stressors. So probably not practical for the tactical athlete or warrior athlete at basic training. You can't say, "Hey, I'm not gonna do this. "I need to not be stressed." But for regular athletes, this is very, very doable. And the reason for me, the takeaway here is that people who are athletes and are training really hard, right? We're training for something that's great, but we really gotta lock in all those lifestyle factors, right, so nutrition, obviously, you have to make sure we have enough energy. That's important. Sleep, sleep is critically important. And then stress as well. And so all three of those things are kind of the big things play a big picture inside. Even if just one of those things is off, that may be disruptive. And that's the thing here is what was very interesting is even when we have normal cycles, saying, "Hey, everything looks good. "I'm having normal cycles, everything's fine." On top of that, we're showing that we may have some issues still. And so that's the biggest thing we have to take home from this is like, "Hey, I'm not saying we have to go crazy "and check our morning progesterone and estrogen by urine. "I'm not saying that at all, "but I'm just saying it's something to consider that, "hey, our body may show like early signs of things "without us even knowing." And so it's just really important to have everything locked in so that we can try to do it. What's the general takeaway? How does this affect your training? Well, I don't think you need to go and get urine studies on this, but understand that, hey, what I really take this as is, hey, we need to control our stress, our sleep, and our diet and our activity all together. Have those things to try to give females the best possible chance of recovery and then making sure that we're not having any long-term consequences in terms of bone health or cardiovascular health or things like that. Overall, I think it was cool. It's not incredibly practice changing, but I think it's just really interesting to look at. But this does conclude the podcast. Thanks so much for stopping by, really appreciate it. If you did find this helpful, it'd mean the world to me if you either left a five-star review in your podcast, platform of choice, or if you shared it with a friend who you think might enjoy it. And if you ever wanna get more information from me, consider signing up for my mailing list. I'll put a link in the description below. I'll just send out things that I think are interesting, whether they're links or research reviews, from time to time, and I promise I'll never spam you 'cause I hate spam so much. But that's it for today. Now get off your phone, go be active, have a great rest of the day. We'll see you next time. Disclaimer, this podcast is for entertainment, education, and informational purposes only. The topics discussed should not solely be used to diagnose, treat, or prevent any condition. The information presented here was created with an evidence-based approach, but please keep in mind that science is always changing, and at the time of listing this, there may be some new data that makes this information incomplete or inaccurate. Always seek the advice of your personal physician or qualified healthcare provider for questions regarding any medical condition.
