Hot Stuff: Body Temperature And Ovulatory Cycles

My name is Azure and for nearly a year now I’ve been tracking my ovulatory cycles by taking my body temperature every minute. And for about the past six months, I’ve been expanding to do this with friends and family.

But today I’m super super excited to show you guys a peek at this data. To show you some of the interesting things we’ve been finding, phase transitions, when you’re going to start your period, but also really interesting within and across individual variability in cycles.

So the first question is what can high temporal body resolution body temperature actually tell me about my cycle? This project was inspired by work that was done in the lab I worked in, Berkeley in undergraduate. And a lot of it was done in mice, but I was excited to transfer it to humans.

So in mice it was found that you can actually tell what day they’re going to ovulate based only on their body temperature. They only have a four day cycle, so what you’re looking at is their ovulation day which has a different shape compared to the other days of temperature data.

There were other projects that could do amazing things, like show you within hours if a mouse is going to get pregnant from when it could have had a conception. So this inspired me to do a sort of and where I asked what is the physiological underpinning of why temperature can tell us so much about our internal systems like a reproductive system?

And I think the best way to sort of answer that question a little vaguely is through music analogy. So if you think of your body as a symphony, and you think of your different organ systems like your reproductive system as the players in that symphony, you can think of your body temperature as the din that would echo out through the concert hall walls. So by listening into it you can get an idea of what’s going on inside.

And today, women are taking advantage of this at a slightly lower resolution, so you can take your temperature every day and learn something about your fertile window. But I want to propose that it’s even more exciting to rather than just say listen to the symphony and when you think you’re at the crescendo piece to actually not miss any of the show and look at as much as possible.

So this is actually not a new idea at all, and I wanted to bring up this quote from Boethius, who was a thinker about music mainly in 520 AD, who said “whoever looks within his own self perceives human music. What unites reason with the body if not a certain harmony; a careful tuning of high and low pitches as though producing on consonance?”

So it’s sort of flowery language, but I think it really helps drive home the point. If you’re thinking about your body as the symphony that’s producing music because of coordinated activity across systems, it produces some sort of consonance metric like body temperature, that you can listen to to get an idea about what’s going on in an individual system.

So with all that said, what did I actually do?

If you’ve seen me walking around you might have noticed that I have a weird blue square on my arm. So I and my group are wearing Distil but also Axial and core body temperature monitors. They’re called iButtons, we do about one minute resolution, sometimes longer if we need to. And they’re precise to 0.6 of a degree, which is really important because your body entire temperature range is only about two degrees when you’re healthy.

I can sync the data with my laptop and then export it to Matlab, Python, Excel to do some basic time series analyses.

I’m going to show you three cycles today, that’s all we have time for but I think it’ll illustrate some important points. It’s my friend, myself, and my mom. And I want you to pay attention to what we have in common and also what’s different between us.

This is Kate. She’s 25, she’s naturally cycling not on birth control and she has a 28 day cycle. You’re looking at a heat map with days stacked vertically and each one of these horizontal bars is a day. It sort of goes from one day time, cool nighttime into the early morning, and so the first thing that you might notice is that not all of these days cycle look the same.

In fact you might even see that it looks like there’s a sort of a state change that happens in the middle. When it’s dark blue of the nighttime up here, sort of becomes a lighter green. And in the daytime these yellow spots become a sort of a huge mass of yellow.

If you look in the literature both in mice, other rodents, and in humans albeit it’s only been done in lower resolution in time, it’s actually true that when there’s a switch from the follicular to luteal phase of your cycle you get this warming up. So I think that’s what we’re seeing here and I’ll come back to that later.

And then these spots at the bottom, those represent when she started spotting and when she started menstruating. And those are actually corresponding to the warmest days of that entire 28 day cycle.

This is a foil, this is me aged 21 a couple of months ago, when I was having really irregular cycles post birth control. So I’m like Kate, this is again 28 days but I don’t have any sort of stable phase change from follicular to luteal. I do however have two periods within this 28 day continuum and they did correspond to the highest temperature days on that whole 28 day phase.

Next, I want to show you my mom because I think she’s really the most interesting of the three of us. She’s 49 now and she’s on hormone replacement therapy. Meaning before she started taking doses of estrogen, E, I show the curves here, and progesterone at the bottom, that solid curve she had very low levels of hormones in her blood.

So we’re sort of thinking of this as a kind of natural experiment, where we have almost a time series of daily doses of hormones in her blood to compare with her temperature. And my question was do we see that phase change like we saw in Kate, that you would expect to come at a certain time of her cycle.

And if you look closely I think you can see that it does seem to get warmer about half way down. You see that yellow splotch and you see that dark blue kind of transition into a warmer green color. I’m really excited and I think that is actually corresponding with her follicular to luteal phase change. And just like I saw in myself, and in my friend Kate, the warmest day of the cycle corresponded to her starting her period.

So and sort of the end of this talk I would like to take you through things that we can generalize from at least this small peek of the dataset and what I’d like to come next. So fine, we can see when you’re going to get your period, we can maybe even see when you’re switch phase from follicular to luteal. That’s really interesting, but I think what’s more interesting is that there is a ton of unseen things in this data so far.

It’s incredibly rich structurally, which I think you can see visually without any fancy analyses at all that there is much left to be discovered here. And I want to take you through a couple of things that I want to do next and then if any of you have ideas for me later or want to talk to me, please come do that.

So my first idea is, I’ve been jet lagging myself for the past month or so travelling around Europe. I know that jet lag affects the female reproductive system quiet severely so I’m really interested to see if that had an impact on my cycle this month.

Also ovulation detection like we did in the mice is something that I’m interested in bringing into my human work for. We’ve tried it once sort of over the counter with LH strips and it seemed to give a pattern similar to what we saw in the mice but I want to do that more.

And then finally, I want to look more carefully at my transition from birth control, no birth control to stable cycling. So if you guys have any insights into that or want to talk to me later I would love to hear from you.

Thank you very much.