Fempower Health

Progesterone vs. Estrogen | Dr. Jerilynn Prior

October 25, 2021 Georgie Kovacs / Dr. Jerilynn Prior Season 2 Episode 32
Fempower Health
Progesterone vs. Estrogen | Dr. Jerilynn Prior
Show Notes Transcript Chapter Markers

Until recently, all we ever heard about was the power of estrogen (good or bad).  We now know both are incredibly critical.  Dr. Jerilynn Prior, of the Centre for Menstrual Cycle and Ovulation Research (CeMCOR), is a Professor of Endocrinology and Metabolism at the University of British Columbia, with 40 years experience in women’s health.  

In this episode, Dr. Prior covers:

  • The role of estrogen and progesterone in bone health, breast and endometrial cancer risk, fertility, weight, and heart health
  • Why hormone balance is important regardless of whether you want to get pregnant
  • The confusion over whether and how stress impacts our reproductive health
  • Why it is hard for women to be aware of some of this research

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About Dr. Jerilynn Prior

Jerilynn C. Prior BA, MD, FRCPC investigates women’s menstrual cycles, ovulatory disturbances within regular cycles with osteoporosis, cardiovascular disease and breast cancer and endometrial cancer risks. She also studies the hormonal and experience changes in perimenopause and treatment of perimenopausal and menopausal hot flushes with progesterone. 

She is the 2019 recipient of the Michael Smith Foundation for Health Research Aubrey J. Tingle Prize awarded to a “BC clinician scientist whose work in health research is internationally recognized”. She is Scientific Director of the Centre for Menstrual Cycle and Ovulation Research (CeMCOR, since 2002) with its website (www.cemcor.ca) providing practical evidence-based information through a mean of 3,000 page-views/day.  She has led the British Columbia Centre of the population-based Canadian Multicentre Osteoporosis Study (CaMos) since 1994. In addition to authoring over 200 peer-reviewed papers (H Index 65), Dr. Prior is the author of the award-winning book, Estrogen’s Storm Season: Stories of Perimenopause (2005, 2nd ed. 2018), a novel written to inform/empower women with perimenopause information.

Georgie Kovacs  00:00

Are you struggling to find answers to that nagging symptom or a specific condition that you have? Welcome to the Fempower Health podcast, helping you become the CEO of your health. I'm Georgie Kovacs, your host, interviewing experts on all things women's health. We discuss periods, fertility, menopause diet, your pelvic floor, and general women's health. We discussed the condition, why it can be hard to find answers. And we always offer solutions. So if you're ready to get empowered, listen and learn. 


Georgie Kovacs  00:40

Welcome to Fempower Health, Georgie here. I interviewed Dr. Jerilynn Prior where we talk about the importance of estrogen and progesterone. Dr. Prior has been studying and advocating for women's health since the 1970s. Talk about knowing your stuff. And what I like about this episode is in addition to the important facts about estrogen and progesterone, Dr. Prior adds a bit of color around the challenges that researchers may face when it comes to getting important information to the public. And it might help answer some of your questions around why you're struggling to get your own answers. So take a listen. As Dr. Prior begins with how she got so passionate about this topic.


Dr Jerilynn Prior  01:29

I began to study women's reproduction when the sort of aerobics bad was happening in the 70s. And I was incensed that immediately, they were doing bad studies sort of cross sectional, not taking into account. For example, the one I remember was university athletes who went to a different town, and we're training so they're dislocated their students already. So those two things also increase their risk for ovulatory disturbances. But when they had funny periods, it was all blamed on exercise without taking either their prior cycle characteristics into account or these other sociocultural things that can alter the cycle. In other words, exercise was... was being forbidden to women. And when we started demanding it, then there was this phony science happening. So I I said, "Okay, we have to figure out how to track women's cycles in a way that's easy." So I said, "Let's, let's teach women to use the basal temperature." But then in those early studies with volunteer women who were increasing their training, I quickly realized that there was shortening of the luteal phase as they ramped up their training. Then I was trying to understand bone and I was working with the nephrologist, who was the bone expert in the area and learned about the two phases of bone remodeling, estrogen decreased bone decreases bone loss, or resorption. So I said, what, what is it that increases bone formation for women, there's got to be something. And I said, maybe it's progesterone.


Georgie Kovacs  03:28

Then let's talk about the importance of progesterone. So you've talked about the luteal phase, you've talked about bone density. Talk to us about, you know, the summary now of what you're finding the value of progesterone is.


Dr Jerilynn Prior  03:44

Let me, before we get to that point, let's talk about what estrogen and progesterone do at the cell or tissue level. Estrogen is powerful... it's a growth stimulator.  You can put it with any cells in any Petri dish, and they will multiply. However, if you think about it, perpetual growth can lead to, you know, genetic mistakes and lead to cancers. So progesterone's main job is to decrease the proliferation or the overgrowth or the growth caused by estrogen, decrease it within a normal parameter, and also to help the cell to become more specialized. So the two hormones complement and counterbalance each other.


Georgie Kovacs  04:41

Tell us more about how hormone balance is defined as we go through various stages of life.


Dr Jerilynn Prior  04:49

So first of all, there's a process of ramping up the coordination and learning to ovulate and stuff that happens to you in adolescence, and it takes several years. You can't understand it without understanding the whole person - nutrition, exercise, social support, discordance or not between goals and opportunities. It's normal to not have that balance for a transitional period in adolescence. And it's also normal not to have that balance during the perimenopausal years. The quicker the ovulatory cycles are established, the better it is in adolescence and the longer that ovulatory cycles are preserved in perimenopause, the better it is. Now in the middle, if you will, of the premenopausal years, the proportion of normally ovulatory cycles matters. And what we know now is that you can have perfectly regular cycles and either not release an egg and therefore make no increase in progesterone. Or you can have regular cycles and release an egg but make too short a period of time when progesterone is high. So those two things together anovulation and short luteal phase are ovulatory disturbances. They're not a disease, they're an adaptation.


Georgie Kovacs  06:27

How important is it for us to be aware of our reproductive health, even if we're not looking to get pregnant and have a child?


Dr Jerilynn Prior  06:37

It's important because it is such a key indicator of whether we're happy, healthy, you know, secure, well-nourished. It's an indicator of optimal health in the broadest WHO (World Health Organization) definition. The other reason is that if you want to have a child, you need to ovulate normally, having regular cycles is not sufficient. gynecologist notwithstanding. I mean, it's incredible that like 23% of all infertile couples have no obvious reason for their infertility. Part of that, I am absolutely sure, is because their regular cycles are not consistently normally ovulatory.  See, progesterone is a time-important hormone. It takes more than 10 days, 14 days ideally, for the lining of the uterus to have become secretory to overcome the proliferative effects of estrogen and to become optimal for implantation of a fertilized egg. That's why it's key that there'll be a sufficiently long luteal phase.


Georgie Kovacs  07:55

Over the course of the podcast, I've interviewed a couple of founders who focused on better understanding progesterone, so that we can better understand ovulation. And there's some really interesting data out there. I mean, 10 years ago, it was really all about your LH surge going to the drugstore peeing on that stick. And now there's just a lot more information around progesterone. And one of the founders had spoken about how, by looking at progesterone, were understanding LH surges in a completely different way, and how that relates to the timing of when you're ovulating relative to what we knew before we had this information. So talk to us about what you're finding in your research on this topic as well.


Dr Jerilynn Prior  08:38

So my... my perspective is based on what the data I've collected, of course, and that is using quantitative basal temperature. So it takes between two and three days from the LH peak before the temperature is statistically above that mean, for using the quantitative basal temperature, you need a 10 day... 10 is the minimum day. And remember, it takes two to three days from the LH peak until that temperature is significantly up. The progesterone is... is rising up up to a plateau at that point.


Georgie Kovacs  09:23

Do we chalk this up to - this is evolution - and, you know, this is how certain women's bodies are and it is what it is? Or do we... is it more complex than that or maybe simple where it's - this is happening and something's causing it.


Dr Jerilynn Prior  09:43

Okay. So I think the key thing is to not view it as a disease, but view it as an adaptation, the way the body is trying to protect us from pregnancy. If we're overstressed, underfed under threat from, you know, an abusive partner, you know, those kinds of things. It's an adaptive process that is life preserving basically, understanding it any other way just doesn't make sense.


Georgie Kovacs  10:16

But you know, here's a question for you is, you know, so many people in the fertility world say that the data doesn't show that stress impacts us. And I'm, I'm so confused about that, because it's not empirically what I've been seeing.


Dr Jerilynn Prior  10:30

That is just not true. If you cover your eyes, you're not gonna see anything. And I think that there's been a lot of eye covering happening. For example, there are two randomized, double blind, placebo controlled trials of cognitive behavioral therapy that show 80% improvement in women with hypothalamic or stress-related amenorrhea. How can there not be an interaction between the world as we experienced it and how our reproductive system works? Because they're so tightly tied together.


Georgie Kovacs  11:11

So I guess this leads to then why is our understanding of progesterone so behind that of estrogen and by the way, I did want to note, I don't know if it was the same study from Australia, you were referring to earlier, where they incorrectly revert to... refer to progesterone as progestin, which is the ingredient in birth control.


Dr Jerilynn Prior  11:31

They've happened that I had a very early review of progesterone as a bone-trophic hormone in the same issue of that journal. It...


Georgie Kovacs  11:43

That's fun. 


Dr Jerilynn Prior  11:44

Yeah, it was meant to be that I was going to learn that from her work.


Georgie Kovacs  11:48

So why do you think that we understand so little relative to estrogen? I mean, where... where do you think this stemmed from?


Dr Jerilynn Prior  11:58

Basically, estrogen - it was actually estrone - was characterized first, when it was characterized. At that point, the scientists were using women's urine that the gynecologist brought to them. So they were already working together. And as soon as they had a purified chemical, then they tried it out as therapy. In other words, this was a time of great excitement in 1929. And... and estrogen immediately was viewed as the woman's hormone. 


Dr Jerilynn Prior  12:39

Progesterone was characterized just a few years later, progesterone was characterized before estradiol, which is the biological hormone of premenopausal years. However, by that time, the estrogen mythologies were already huge. And the focus was already on estrogen. 


Dr Jerilynn Prior  13:03

Another part of the story is that when they tried to use progesterone as a therapy, they probably didn't use a large enough dose. Because that misunderstanding of how much progesterone we make is still alive and well today. They didn't use a big enough dose and they gave it by mouth and it was ineffective. It didn't cause anything they could measure. And so then the.. the... all the scientists and the gynecologists got together and said, "We have to make something that acts like progesterone on the lining of the ute..., you know, uterine lining and in pregnancy, so that we can use it for therapy." 


Dr Jerilynn Prior  13:47

That's the definition of a progestin - is something that can change the lining of the uterus from proliferative to secretory. And secondly, that will preserve a pregnancy. It doesn't have to do anything else that progesterone does in the body. So that's one of the reasons that there's this progesterone - progestin confusion. 


Dr Jerilynn Prior  14:13

The other is the very wrong term progestogen. Progestogen is defined by the gynecologists as progesterone and all the progestins. But it's just wrong to put progesterone in the same bin, if you will, as progestins. It's its own chemical, its own hormone and its own unique biological hormone. And so I think we should never use that term. But because there is one term that includes both progestins and progesterone, it's commonly confused.


Georgie Kovacs  14:56

Let's take a moment to hear from our sponsor. 


Georgie Kovacs  14:59

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Georgie Kovacs  15:41

And now let's get back to the episode. 


Georgie Kovacs  15:44

So where do you think we are today then with what we know about progesterone and what we don't?


Dr Jerilynn Prior  15:53

Okay, so what do we know for sure about progesterone... First of all, it's essential for fertility. Second of all, it's essential for optimal health. And it's essential to counterbalance that estrogen, proliferative growth stimulating effect. For example, we... we learned the hard way after giving estrogen alone to menopausal women that it caused endometrial cancer. So we know for sure that progesterone is necessary to prevent endometrial cancer. We know that in a population of about 4,000 women with regular normal length menstrual cycles between 21 and 35 days long, that in a given cycle, 31% of them did not have the expected increase in progesterone levels, between cycle day 14 and three days before their expected flow. 


Dr Jerilynn Prior  16:58

That study that we did in Norway, it was rejected by all the major medical journals without review. Finally, I finally got it published in PLOS ONE. 


Dr Jerilynn Prior  17:11

We know that progesterone raises the core temperature in a stepped dose response. In other words, you need enough of it before the temperature goes up. An interesting thing that women need to know is that, if you're ovulatory, you are burning about 300 kilocalories more every day, during that luteal phase, which means that if you don't eat those extra calories, you.. it's a way of preventing weight gain.


Georgie Kovacs  17:44

Well, I was actually just about to chuckle and say, Alright, I know how I'm going to get people to listen to this episode. I'm just gonna title it - if you want to lose weight, listen to this episode. I'm kidding. But before we jump into that, I did want to ask you a couple questions there. You did mention that progesterone is essential for optimal health. And you said we'd get more into what that means. Is there something you wanted to add there?


Dr Jerilynn Prior  18:08

Yes. The study that I told you about from Norway was a single random cycle. What we need is prospective data. In other words, the same woman followed over a year, say, to know what happens whether your cycle and what happens to the luteal phase and how variable it is over a full year. And we need that from a large number of randomly selected women in the population. We need to know what proportion of cycles are normally ovulatory in... in premenopausal and perimenopausal women, and how that relates to their risk for fracture later in life.


Georgie Kovacs  18:54

Some might respond and say, well, the peer reviewed journals are hard to get into. And there's a reason why because of A,B,C of your study design or whatever, that it was turned down. Now you did say it wasn't even reviewed. So talk a little bit about that. But I also try to do in this podcast is help people understand the dynamics of what's happening, because a lot of women feel dismissed and they're frustrated. And so I'm very curious if there's some interesting tidbit of information that's important for us to know about why that study wasn't published.


Dr Jerilynn Prior  19:27

Okay, let me just say that.. that characteristic is that that occurrence with that single study has happened over and over and over again. Right now. It has been since the spring of 2018 that I've known the results of a randomized double blind placebo controlled trial of progesterone for perimenopausal hot flashes and night sweats and I have not been able to get that in any general medical or several obstetrics and gynecology or endocrine journals, so far, the majority of them out of the 10 submissions that we have results from eight of them were without peer review.


Georgie Kovacs  20:18

How do you know if they're without peer review? I would assume if you're submitting....


Dr Jerilynn Prior  20:22

The editor said.... we talked about this at the editorial committee, and decided it wasn't of sufficient interest to send out to reviewers.


Georgie Kovacs  20:33

Wow. Okay, then. 


Dr Jerilynn Prior  20:36

So I, you know, you said women don't feel heard? Well, as a scientist, I don't feel heard. And, and what's ironic about this rejection at the editorial level, is that usually the letter from the editor's desk is signed by a junior woman.


Georgie Kovacs  20:59

I'm just gonna leave that at that, because I like to be solution-oriented, and I'm not sure I have a solution. So we're creating awareness. So let's call this an awareness campaign. 


Dr Jerilynn Prior  21:08



Georgie Kovacs  21:09

I'm not sure what else to say.


Dr Jerilynn Prior  21:11

I have to tell you what I did. I was really, really getting aggravated about the... the repeated rejections of the, the data from Norway showing that so many women didn't have a normal progesterone level when we expected them to.  The British Medical Journal online information for authors says, "If you think we made a wrong decision, get in touch." So I wrote a letter and sent it by courier and sent it by fax and sent it by email, and basically said, you were you reported that this wasn't very interesting. But I believe that if a third of men at any one month were infertile, that that would be major news. And I said, so perhaps we should rename British Medical Journal to British Medical Men's Journal. Anyway, just to let you know, I never heard back from any 


Georgie Kovacs  22:20

Of course.  Of course. 


Dr Jerilynn Prior  22:22

We sent it by email every two weeks all summer, just to be sure they got it.


Georgie Kovacs  22:27

Wait, wait till I tell Dr. Alyson McGregor because she wrote a book about Sex Matters. And she also did a TED talk. And one of the things that she made a call for is more women researchers. Sounds like we need more women medical journal publishers. 


Georgie Kovacs  22:41

Let's take a moment to hear from our sponsor. 


Georgie Kovacs  22:44

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Georgie Kovacs  23:24

And now let's get back to the episode. 


Georgie Kovacs  23:27

A question about endometrial cancer, too. So we know that it's the estrogen, and we know women who are older get it, but we also talked about the natural cycle of estrogen being higher later in life. So where's the nuance if there's that natural cycle of who gets endometrial cancer? Like what's that line? And again, I don't know if there's a study on this. And you know, maybe it's more just using logic to understand how the hormones work. I don't know what sort of data there is, but I'm very curious.


Dr Jerilynn Prior  23:59

It's clear that younger women can get endometrial cancer. For example, in polycystic ovary syndrome, there's almost a four-fold increased risk for endometrial cancer, because they have, even if their periods are far apart, they still have rather tonically normal or high estrogen levels with very rare or absent progesterone levels.


Georgie Kovacs  24:30

This is now another so we've gotten diet as a motivation, fertility as a motivation and cancer as a motivation for making this important, right?


Dr Jerilynn Prior  24:40

Yes, you're correct. Very correct. And let me give you two more reasons. So I told you that I began this whole, you know, investigation of women's normal menstrual cycles. And my original design... my original study was to take women who were normal weight, non-smokers having regular cycles, and in whom two cycles in a row were normal length and normally on regulatory and study them over a full year. Now, I wanted to see what happened to their cycles, because the variable here that was different among women, these women was that some of them were training for a marathon. Some of them were running for fitness and health. And some of them were just playing a little tennis on the weekend, or maybe swimming with their kids or whatever. But I couldn't get funding just to see whether or not they're different exercise choices influence their cycle over the year. So I said, "Okay, I'm gonna link it to change at home. And I did, and then we got funding. 


Dr Jerilynn Prior  25:52

So in that cycle, in that study, what we learned with 66 women who finished it was that one, their amount of exercise did not make a difference in their menstrual cycles, or in their change in bone as a first thing. So basically, we showed that this group of healthy women were losing bone. And that was in spite of the fact that they continue to have normal regular length cycles all year. So then the question was, "Why are they losing bone?" And what we discovered and this was published in the New England Journal in 1990. And I was lucky, I'll tell you that story in a minute, was that those women who had more than one short luteal phase in that year, or any anovulatory cycles, were losing significant amounts of canceletservecular bone in their spines. So that was the first observation, saying that progesterone was important for bone.


Georgie Kovacs  27:00

I'd like to get your perspective on female athletes and more and more research that's being done around how they should be adjusting that type of exercise that they do based on where they are in their menstrual cycle.


Dr Jerilynn Prior  27:15

I can't say I've seen very good research. What did you notice?


Georgie Kovacs  27:19

I do notice that I prefer when I have my period, more gentle like yoga, and I have more energy right around ovulation. Honestly, now I'm in perimenopause. So it's a bit all over the place. And so what I... I joke, I think Dr. Briden, somewhat referred to it as perimenopause is the time where your body screams really, really loudly, whereas you could get away with stuff when you were younger. And so my body is very loudly like no, this is a yoga day. 


Dr Jerilynn Prior  27:47

I think that most of the changes that may occur related to this cycle, occur in premenopausal women in which the cycle is adapted to the exercise. So if we go back to the reasons why it's important to ovulate, normally have enough progesterone, are obviously to prevent endometrial cancer, which doesn't show itself usually until you're well beyond your last menstrual flow. 


Dr Jerilynn Prior  28:21

But the more important ones, I think, are that we've clearly shown that you need both estrogen and progesterone in order to maintain final bone density. So we did a meta-analysis of all the studies that are available of changing bone related to the proportion of the cycles that have ovulatory disturbances. So these were all regular cycles. So the proportion that had ovulatory distur...., most ovulatory disturbances, or losing almost 1% of their spinal bone a year, compared to the other portion of the same cohort that had better ovulatory characteristics. 


Georgie Kovacs  29:06

But back to the endometrial cancer, so women get it later in life. But you know, if our estrogen levels are higher, why do some get it and others don't?


Dr Jerilynn Prior  29:16

Well, it's integrated with a whole bunch of other stuff. I mean, there are, in fact, rare kinds of endometrial cancer that aren't, as far as we know, driven by estrogen excess or lack of progesterone. So... so there's other variables, genetics, etc, that play a role here. Okay. Clearly, obesity, and diabetes, increase the risks for endometrial cancer, other variables being the same.


Georgie Kovacs  29:47

But before I dive into the last question I ask every guest, I wanted to.... because we could probably talk about progesterone for a really long time, but I did want to leave with - what would be the main takeaway you want women to understand about progesterone?


Dr Jerilynn Prior  30:02

I want women to know that their normal menstrual cycles are crafted to provide them with appropriate balanced estrogen and progesterone levels through 30 to 50 years of our menstruating lives. And that imbalance, which is usually too much estrogen, and not enough progesterone, are risks for osteoporosis, early heart attack, breast cancer and endometrial cancer later in life.


Georgie Kovacs  30:40

I think that is a perfect summary. So then what is your greatest hope for women's health?


Dr Jerilynn Prior  30:45

My greatest hope is that women will learn about their own cycles, learn the things that are stressful for them, and that shorten their own luteal phase length. And that... that knowledge that self-knowledge will empower them to demand equal treatment, the opportunity to experience their full potential in life, and to be treated with respect and honor.


Georgie Kovacs  31:18

Very well said. Thank you so much, Dr. Prior.  It has been an absolute pleasure to connect with you and an honor. And thank you for the work that you have stuck by for women and will continue to do in the future.


Dr Jerilynn Prior  31:31

Thank you, Georgie.


Georgie Kovacs  31:33

Thank you for tuning in to today's episode with Dr. Jerilynn Prior about estrogen and progesterone.  And if you'd like to check out her work, please feel free to visit her website, which is the Centre for Menstrual Cycle and Ovulation Research, which you will also find in my show notes. And if you liked the episode, I greatly appreciate you rating and writing a review. And as I had alluded to before, all the information that we discussed in the podcast, as well as links to discounts and other helpful information is in the show notes. So be sure to check that out. 


Georgie Kovacs  32:07

Now for next week. The holidays are approaching. Yes, if you can believe it. The end of year is almost here. But before we get to those holidays, I wanted to educate you about how you can prevent burnout because let's face it, we need after everything that's been going on in the planet to enjoy and celebrate these holidays with our friends and loved ones. So stay tuned next week as I speak with Dr. Renee Wellenstein about burnout and how you can prevent it. And as a reminder, the information shared in the Fempower Health podcast is not to be substituted as medical advice. Thank you for tuning in and see you next week.

Dr Prior Background
Estrogen and Progesterone at the Cellular Level
How Hormone Balance Changes Over Your Lifetime
Why Reproductive Health is More Than Just About Getting Pregnant
Progesterone & LH
Fertility & Stress
Why Are We Only Now Talking about Progesterone? And how that now impacts our view of Estrogen
What do we know for sure about Progesterone to date?
The Facts about Getting Trial Results Published
Endometrial Cancer
Bone Loss
Adapting your Workout to you Cycle
Her Main Takeaway on Progesterone