Is Progesterone Testing Always Accurate? (Episode 648)

Full Transcript: Episode 648

Lisa Hendrickson-Jack: This is the Fertility Friday Podcast, episode number 648. In today’s episode, we are going to dive into progesterone. We are going to talk about progesterone testing, what it can and can’t tell you. We’re also going to be talking about the menstrual cycle and the important role that it should be playing if you’re trying to test progesterone or understand what’s happening with progesterone throughout the menstrual cycle.

If you’re new to the podcast, I’m Lisa Hendrickson-Jack, Certified Fertility Awareness Educator, and I’ve been teaching women to chart their menstrual cycles and use the menstrual cycle as a vital sign for over 20 years now. In fact, I literally wrote the book on it. I’m the author of The Fifth Vital Sign, co-author of Real Food for Fertility, and founder of the Fertility Awareness Institute, where we teach women’s health professionals to use the menstrual cycle as a vital sign in their practices.

What’s remained the same over the past two plus decades is the message that we really should be paying closer attention to the menstrual cycle, because there’s so much we can learn about our bodies, about our fertility, about our health by tracking our fifth vital sign.

In today’s episode, I’ll be looking at two separate studies that looked at progesterone levels as they fluctuate throughout the menstrual cycle in different ways. And the insights are really interesting and really powerful because they do show us some of the limitations that can come with lab testing alone.

In order to study the variation of progesterone production over the course of a given day, the researchers took 15 women — in the study they are identified as paid volunteers — and they actually admitted them into a hospital for 24 hours and did blood draws every 10 minutes. They did this in the luteal phase as a way to test progesterone levels, but more specifically to test the fluctuation of progesterone levels over the course of that 24-hour period.

What they found was that earlier in the luteal phase, progesterone levels tended to stay fairly steady. But as they got later on into the mid and late luteal phase, the progesterone levels that they measured varied widely, swinging from as low as 2.3 to as high as 40.1, often within a few minutes.

I think this is something that we should take into consideration with luteal phase testing, especially when we’re looking to get a spot check of progesterone levels with a single blood draw. I think the implication here is pretty obvious. If your progesterone levels could swing so widely, especially in the mid to late luteal phase, a single blood draw on any given day could tell you something, you could base decisions on it, and it may not be an accurate reflection of what was actually going on overall.

Now, one of the reasons for this fluctuation is the way that progesterone is produced in the body. While it would be super convenient if we were just producing progesterone at a very steady level all the time, the researchers suggested that progesterone is produced in pulses. That pulsation is at least somewhat responsible for the increased variability, particularly in the mid to late luteal phase.

This brings me right to the second point that I wanted to share, which is that it is possible, of course, for women with normal luteal phases to have low progesterone in their lab work.

Now, when we look back at the same study, each woman had a confirmed normal cycle. They made sure that all of the participants had cycles within normal range, and they all reported a luteal phase longer than 13 days, and also a mid-luteal progesterone level above 9 nanograms per milliliter.

The parameters looked great, but when these women were then admitted and the blood draws were taken every 10 minutes, sometimes these mid-luteal levels dipped as low as 4.1 nanograms per milliliter. If these women had come in just for a random blood draw at that time, it could appear as though they have extremely low progesterone, even though overall their progesterone is in a healthy range.

Now, I want to share an interesting quote from the researchers on this point. They said, quote, single progesterone estimations in the mid and late luteal phase do not accurately reflect corpus luteum adequacy, end quote.

In particular, when they were looking at that second half of the luteal phase — that would be typically seven days after ovulation and beyond — testing around that time was less reliable because of the swings in progesterone levels over that time.

At this point, I want to share a little bit about why this is important. For practitioners who rely heavily on lab tests to really get any indication of what’s happening in the cycle, we may not always be taking into consideration some of these fluctuations. And conversely, when you are incorporating testing alongside a detailed and thorough analysis of the menstrual cycle via fertility awareness charting, for example, you can actually see the patterns a little bit more broadly.

When you have your clients charting their menstrual cycle, or when you yourself are charting your menstrual cycle and you’re tracking your cervical fluid, you’re tracking your basal body temperature, and you’re tracking throughout the whole cycle, then what you can actually see is more of a pattern of what’s happening.

What’s interesting is that when you track your cycle over several months, or if you’re a practitioner and you’re working with clients who are tracking their cycles and you’re seeing multiple charts, you will see certain fluctuations from day to day. Sometimes if you have clients tracking their temperature in the luteal phase particularly, you may see the temperatures go up and up and up, following a normal pattern. But on one random day, you may see that temperature completely drop down and have that outlier situation.

In more extreme cases of these outlier situations, you may even see some spotting that correlates with this drop in temperature, which would indicate that there could be a drop in progesterone on that day.

Often if I’m working with a client, or our practitioners are sharing a chart of a client who’s experiencing something like this, the next step is really to investigate: what was going on on that day, and was anything happening at that time? Do you remember what was going on that week? What we often see is a correlation between these random changes and something that was going on.

Interestingly, even if you see a fluctuation like that at one point in the cycle, it’s also very possible that that’s a one-off and the following days after that could be completely fine.

But if we go back to the progesterone testing, if you have a client and they’ve been sent for a blood draw to test their progesterone mid-luteal and it happens to be on a day where you had this intense fluctuation, it could appear based on that one lab test that she has low progesterone levels, even if her luteal phase is in normal range and even if overall her cycle is not showing much disruption.

But of course, that doesn’t mean that we should throw out progesterone testing. Of course, progesterone testing is extremely helpful. I think the point that I’m making is that it’s often even more helpful in the context of the menstrual cycle when you can actually see what’s going on. When you combine the testing alongside the daily tracking, then you get a more complete picture.

Interestingly, the researchers confirmed that progesterone testing is extremely helpful to confirm ovulation. After all, if we think about the hormone cycle that happens in the menstrual cycle, from the first day of your period until the last day before your next period begins, what we find is that you don’t produce significant progesterone until after ovulation. Naturally, that’s because before ovulation, the follicle is primarily producing estrogen. It’s not until the follicle releases the egg and turns into the corpus luteum that we start to produce significant progesterone in the luteal phase.

Doing a progesterone test post-ovulation is extremely helpful as a way to confirm ovulation. But what it can’t do is tell you exactly when you ovulated. Although we’re able to confirm if ovulation happened with the progesterone testing, even with those fluctuations, we’re not able to say, okay, this is the exact day that ovulation occurred on.

And of course, this is one of the reasons why cycle charting and actually tracking basal body temperature allows you to confirm ovulation with a retrospective measure. Tracking cervical fluid allows you to identify the mucus changes that occur as you lead up to ovulation and the shift in mucus after ovulation occurs.

Now, the second study that I wanted to share with you measured this phenomenon a little bit differently. These researchers actually used fertility awareness techniques to time when they would do ultrasounds. They did an ultrasound every other day from when the participants started to show signs of cervical mucus, indicating that they were moving into their fertile window. They were doing a series of ultrasounds to really determine the date of ovulation.

Through their testing, they were able to determine that it was possible to confidently confirm ovulation with a blood draw, as long as it was done at the right time of the cycle. Interestingly, they did identify that depending on when these tests are done, it is possible that a false positive could result.

If you remember, in the first study they talked about the swings, the shift in progesterone. Especially between the mid to late luteal phase, there could be very high measurements and very low measurements. The researchers did conclude that it is also possible that you could have a client who did ovulate — a woman who did ovulate — but depending on when that test is done, it could appear that she hadn’t yet, especially if it just happened to fall on one of the days where she has quite a low reading.

The interesting thing about this study is that they did pair the hormone testing data with the ovulation data. That’s certainly not something you see all the time. They were able to know and confirm if these participants ovulated independent of the blood test.

What they did find was that of the 251 blood draws that were taken after ovulation — so after they confirmed ovulation with ultrasound — 26 did not show a positive. There was a small percentage of women, just over 10%, who actually did not show a positive when they did the blood draw.

They had set the standard at 5 nanograms per milliliter as the level of progesterone that they were looking at to confirm ovulation. Even though they knew that these women had ovulated because of the ultrasound data, they still found that about 10% of these women did not read positive on the blood test.

Again, this doesn’t mean that progesterone testing is not helpful. It’s extremely helpful. But it does mean that there are limitations. And it does mean that there are literal cases when a woman has actually ovulated, but if that blood draw is done at the typical time when it’s done — it’s typically recommended to do it mid-luteal. It is typically a recommendation for women to do this test in the middle of that luteal phase, and that’s around the same time that the researchers identified that there are more likely to be these fluctuations.

Now, what’s interesting is, again, when you are able to incorporate the use of menstrual cycle charting into your practice — whether it’s your own personal daily practice of tracking your cycle, or whether you’re a women’s health professional and you’re actually teaching your clients to track their cycles and having them share their charts with you so you can actually see what’s going on — when you’re able to pair the lab testing data with what we’re seeing in the chart, it can increase your confidence significantly. I tend to like having more data, not less.

But in a situation like was described in the paper, where you had confirmation via ultrasound that these women had ovulated but the blood draw was showing low, if they were also tracking their cycles, we would not only be able to see if that’s consistent with what we’re seeing, but we’d also be able to see a little bit more information. You’d be able to see if that blood draw was taken potentially on a day where there had been a drop in her temperature. You would also be able to see if there were any patterns that would indicate that her progesterone was generally low or if this was a one-off. And ultimately, you’d be able to be a lot more confident.

As someone who has worked primarily in the field of fertility awareness cycle charting, and whose practice has been primarily focused on reading menstrual cycle charts, it’s astounding to me that practitioners can be working with women and supporting them with their hormones without having that additional cycle data to support what’s happening.

I would say one of the key differences when you have the mindset of cycle tracking versus hormone testing, depending on how you’re doing it, is that with cycle tracking, you’re getting daily information, you’re getting daily data. Whereas when you’re doing hormone testing, there are times when you may be able to do continuous testing or daily testing, but a lot of the time women are going to the lab and getting their blood drawn on a certain day, or doing spot urine tests or spot saliva tests.

While you’re getting a spot test, what you’re not necessarily getting is the overall picture. And you’re certainly not getting the context, especially if you have clients that you work with over several months and you’re able to actually see trends in their cycle charts, meaning you have cycle one and you know what was going on there. You can see the patterns. You have cycle two, you have cycle three. This gives you a lot more context, a lot more data, and you’re able to assess whether this particular cycle was a one-off related to stress or something going on, or whether you’re actually seeing a pattern over several cycles that would indicate low progesterone or something more concerning.

Now, the last point that I want to make, especially as it pertains to the second study that I was sharing with you today, is that the cycle data really helped the researchers to gather the data more accurately. Certainly, this is one of the huge benefits of learning about cycle charting. If you are a practitioner, yes, it is really helpful to be able to track your own cycles, but tracking your own cycles is not sufficient to be able to broadly bring that to your clients and have them charting in a way that’s going to be clinically useful when you’re supporting them, especially with hormonal issues.

In this study, having the cycle data — having the clients track their mucus data — was a way of allowing the researchers to know when their fertile window was starting so they could time the ultrasounds alongside that. And the fact that they were using ultrasounds to confirm ovulation, and letting that guide when they were doing the blood draws, allowed them to be a lot more precise in their approach. I would say it helped the study immensely, so that the data is a lot more meaningful.

Often when you’re looking at the study design, especially when we’re looking at how they’re testing for hormones throughout the menstrual cycle, I tend to be highly critical. But I’m also very thankful that these studies are there. I recognize how challenging it must be to gather dozens of women and try to get these tests done at a certain time, especially because everyone’s cycle is not happening on the same rotation and everyone’s cycle isn’t the same. Most women are not having exactly 28-day cycles with day 14 ovulation.

I do recognize why there may be certain trends when they’re doing testing throughout the cycle with hormones, to try to make it easier on them. But one of the benefits of being so particular is that we can actually gain more data.

I would say one of the biggest issues that I haven’t even touched on today would be the cycle day 21 progesterone test phenomenon. Most of our conventional approaches to understanding what’s happening hormonally with women are based on the 28-day cycle conception. While the average cycle does run about 29 days or so — there’s a lot of cycle data, there’s a lot of studies that we can draw from — the average woman is not ovulating on cycle day 14, cycle after cycle, month after month, year after year.

But what is happening is that when women have concerns about their hormones and they’re going to their practitioners, they are very, very typically advised to go and get that progesterone blood draw on day 21 of their cycle. The rationale behind that is that if she did ovulate on day 14, then seven days after day 14 would be day 21, and that would fall within that luteal phase — again, of this mythical woman who only ever ovulates on day 14 all the time, and it’s always the same.

But what we see in the real world is that when women are sent to do blood testing on day 21, the vast majority of the time, it’s not necessarily meaningful or significant. If it comes back negative, you can’t say, oh, well, she’s not ovulating, because you don’t have any cycle data. It could be that she ovulated on day 20 and the progesterone hasn’t risen yet.

There are a lot of issues with the way that we conceive of the menstrual cycle and the very rigid idea that we have that it’s always a certain number of days and all of that. Cycle charting would really help with that. It would really help us, because then we could actually see what’s going on with this person. Instead of randomly sending her to get a blood draw and wasting everybody’s time when it could have absolutely nothing to do with what’s going on in her cycle, we could have her track her cycle. We could have her track her mucus and track her temperature and actually use that data — wait for the temperature rise, identify ovulation by looking at the cervical fluid and the temperature and seeing how they come together — and then send her for testing on the right day so we can actually get a more useful progesterone measure.

But even if we have the perfect circumstance — we have her tracking, we have her going and getting this test done at the right time — the research that we went through today shows us that there are still limitations. Even when we set up the ideal situation and we’re actually testing at the right time, it is still possible that the test could come back and it’s not necessarily optimal.

Again, I’m all for testing. I love data, and I’m all for having more data, not less. But ultimately, the point that I’m making is that when it comes to testing, I think it tends to work best when we’re able to put that data in line with what’s happening in a woman’s cycle in real time, so that we can put it all in context and have a much greater understanding of what’s happening.

Now, one data point that I want to share from the study I was mentioning with ultrasound testing: the women in the study were chosen because they had regular cycles. According to the researchers, when they entered into the study, these women typically had cycles that ranged from 24 to 34 days, which does fall right within the normal range. But when they actually tested these women over the course of the study, they actually ovulated anywhere from day 9 to day 33. The range of ovulation in these women was significant.

What I’ll say is that this is not abnormal. When you look at cycle data, when you look at studies that measure real ovulations, real cycle length, real luteal phase length in the real world, you do find fluctuation. This further supports what I was saying about this whole day 21 progesterone testing thing. That’s just not the way to go.

Now, of course, today’s episode was focused on progesterone testing, and I wanted to share what the research had to say and talk a little bit about some of the limitations, and obviously make my case for cycle tracking and having that be part of this process so that we can really put everything into context.

There is a lot more that we could say about this. Being able to identify when ovulation is happening in the cycle is crucial, especially for women who are trying to conceive, because of the many misconceptions that we have due to the fact that we have very little to no education about our bodies as women. Many, many women are trying to time sex on day 14, thinking that that is the right strategy and way to go.

Ultimately, when it comes to conception, when you have an awareness of what’s happening in your cycle, the best strategy for conception is to actually learn about cervical fluid and learn how to track it. For anyone who’s not familiar, cervical fluid during the fertile window, or as you approach ovulation, tends to look either like creamy white hand lotion or like clear, stretchy, raw egg whites.

If you take one piece of information away from today’s episode as it pertains to conception, it would be that day 14 is not what you should be focusing on when it comes to timing sex correctly or advising your clients or your patients. It really should be based on the observation: learning about cervical fluid, identifying the fertile window, and timing sex when you actually see it leading up to ovulation. That would be the best strategy.

The days that you have cervical fluid that is clear and stretchy in the most abundant quantities would be the days that you’d want to try to have sex, even if it falls on day nine, even if it falls on day 20. Because again, in the study, they actually found the range of ovulation dates to be between 9 and 33 days, even in women with so-called regular cycles.

Of course, this is merely the tip of the iceberg. There is so much more to learn about using the menstrual cycle as a vital sign, teaching your clients to track their cycles so that they can confidently identify when they’re ovulating and identify any potential issues — luteal phase issues, progesterone issues, even estrogen issues.

Whether you have already started working with your clients, sharing information about menstrual charting, or if you’ve already started to review your clients’ charts in practice and advise them about timing or cervical fluid, we’ve created an incredible resource for women’s health practitioners: how to interpret virtually any chart your client throws at you. This is our guide to advanced chart interpretation. You can head over to fertilityfriday.com/chart to grab your copy today.

Whether you have been a longtime listener to the show or you’ve just recently found the podcast, I would invite you to leave a rating or review on Apple Podcasts. That has really been the primary driver for new people finding the show. It’s really just been the community that has come together and shared this episode. If you can think of someone who would really benefit from today’s episode, then please do share it. You’ll find the share link and information for today’s podcast over at fertilityfriday.com.

I try to read all of the reviews that you leave on Apple Podcasts, and I so much appreciate it, because if you think about it, that is how we figure out if this is something that we want to do. I thank all of you who have left a review. It makes such a huge difference.

With that said, I hope you have a wonderful week, weekend, whenever you’re tuning into the show. And of course, as always, until next time, be well and happy charting.