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A photo of Dr. Virginia J. Vitzthum

Photo by Herb Ascherman

Reading time: 11 min

Hormones and your environment: a conversation with Dr. Virginia J. Vitzthum

When it comes to hormones, there is more than one “normal.”

Here at Clue, we’re nerds about menstrual and reproductive health. Which is why we were so excited when Dr. Virginia J. Vitzthum joined our team in 2017 as Director of Scientific Research—she is a big deal.

Virginia is an evolutionary biologist who explores how reproductive hormones are different (or similar) across continents and cultures. She has studied women across the world, from Bolivia to Germany to Central Asia to Iceland. Her trailblazing work has changed how scientists understand women’s bodies. Currently, Virginia is studying light exposure in northern environments and how this affects reproduction. We can’t wait until this research is published.

Virginia is also a professor in the Department of Anthropology at Indiana University, where she also serves as a Senior Scientist at the Kinsey Institute and Director of the Evolutionary Anthropology Laboratory.

We are honored to have Virginia as our colleague, and when she shared a summary of research with the team over the summer, everyone clamored to learn more.

We thought Clue users would also want to know more about Virginia’s research, so we invited her to talk about her work.

It’s difficult to condense your research career, but let’s try. Can you tell us about your early work?

The reason I do what I do is because I'm passionate about women's health, and committed to the absolute right of every woman, everywhere in the world, to have access to all the information and resources that she needs to achieve physical and emotional wellness. Anything less is unacceptable.

What initially brought me to this field was a growing concern in the mid-1980s that women in resource-rich industrialized countries were losing their capacity to reproduce because of too much exercise. There was a new push then for women to take up exercise, especially running. But a great many of these newly exercising women stopped menstruating. Why?

Some physicians thought this failure might be a permanent pathology somehow caused by the exercise. Others said not menstruating is a normal temporary response to a new stress, specifically, suddenly increased energy demands or inadequate energy intake. And a third group of specialists (demographers) who calculated fertility rates for whole countries, pointed to the high fertility in poor countries and said energy intake and demands had almost nothing to do with human reproduction.

There was a lot of debate about these contradictions, much of it focused on which statistics or which data were wrong or right. The prevailing assumption was that only one answer could be right (either energy did or did not influence human reproduction) and that this one answer applied to all women everywhere.

I proposed a novel approach to these questions. As an anthropologist, I’ve a keen appreciation of the enormous range of human biological variation and the power of evolutionary and developmental processes to create that variation. I argued that these processes could explain what seemed like an unresolvable paradox:

How is it that women in industrialized wealthy countries, with lots of resources, were experiencing suppression in menstrual cycling when they were exerting energy through exercise? And yet women in poor countries who worked everyday, in the fields in hard labor, and had limited food resources, and very difficult lives, had lots of babies? Why wasn’t their menstrual cycling suppressed during all those arduous efforts?

So I looked at the available data from an evolutionary perspective, and in terms of the specific environments in which individuals grow up. Genes and environments interact from the moment of conception and throughout our lives to make it possible for us to survive and reproduce in the conditions into which which are born and grow.

The women in these wealthy countries had, for the most part, always experienced well-resourced conditions as they grew up. If they start strenuous exercise for the first time as adults, their bodies are metaphorically saying, “Whoa, this is really different from what I'm used to. I'm going to shut down the ovaries for a bit and adjust to these new conditions because I suspect these conditions will change.”

But in poorer countries where women grow up experiencing demanding conditions, these conditions are normal for them. These conditions have always existed and can be expected to exist for the rest of their lives. So their ovaries don't shut down temporarily in the face of these demands, because these conditions are normal. And so they have children under those conditions. From an evolutionary perspective, if you don't have a reproductive system that is satisfied with the conditions in which you will live the rest of your life, then you contribute no genes to the next generation. So if you're waiting around for conditions that look like some lady in Toronto, or Berlin they're just never going to happen. You're not going to contribute your genes to the next generation.

Our bodies are highly responsive to specific conditions. I called this the flexible response model. Our bodies have mechanisms that calibrate your appropriate responses. If you grow up under good conditions, you'll respond appropriately to those good conditions. If you grow up under tough conditions, then those tough conditions just aren't that tough, they're normal for you.

So I went to the Highlands of Bolivia for almost two years [to test my model] where I collected data from 316 women for up to eight cycles. Every other day we went to a woman's house and we collected a small sample of saliva. And that saliva was used to measure progesterone, which is a hormone in an ovulatory menstrual cycle. By collecting this saliva throughout a menstrual cycle, I could ascertain whether or not they were ovulating.

What I showed was, [these Bolivian women] are ovulating, and yes, their hormone levels are lower than American women’s hormone profiles, and they conceive at those low hormone levels. And those babies are born full term and normal weight at those hormone levels. So they don't have impaired reproduction—their reproduction is functioning very normally in those conditions because they're adapted to those conditions.

How does your work impact women's health?

One of the things that I think is really important is contraceptive technology. Women have for too long been told to tolerate formulations of hormonal contraceptives that are not suitable for them. In industrialized countries, women are typically offered a buffet table of different formulations and they can experiment with them and figure out which ones are right for them.

But in much of the world, women are offered one or two formulations and they are told that they should just grin and bear it when they experience high levels of side effects from these hormonal contraceptive formulations. And I would argue that this is because these formulations have been designed with western European and [North] American women in mind because that's still the biggest market for hormonal contraception.

But women in the rest of the world [have] endogenous hormone levels that are likely to be quite different from women in these other places in Europe or North America because their lifestyles are different. So these women have been told repeatedly to just tolerate the side effects. “You'll get over it.” Or even worse, they've been told those side effects don't really exist because we don't see them in Europeans or North Americans, so those side effects must be all in your head.

The fact that there's so much variation in endogenous levels [of hormones] argues for more appropriate formulations [of contraceptives] and a greater variety of formulations available to women, so that they can pick the most appropriate one for them.

And this means listening to women and what they're experiencing instead of forcing women to fit the contraceptive—that we in fact change the contraceptive to fit the woman.

So what are you working on now?

We are gathering information about the dynamic interactions between the immune system and the reproductive system. I'm looking at changes in [inflammation markers] across the menstrual cycle that are related to sexual activity and that are related to ovulation.

We're not just machines. You don't just turn on the ignition and we click clock, click clock, click clock through the rest of our lives from menarche onward. We are responsive organisms to environmental conditions.

Those environmental conditions include things like time of year, availability of resources, having a partner, and having sex.

*The data we have suggests that you are more likely to ovulate if you are having intercourse than if you are not. *

So, if there’s a woman who's not having penis-vagina intercourse, and she is worried about her ovulation rates, it may not be that she has “a condition”; it may simply be that this is a normal response of her body.

And this is not bad. This is really an amazing mechanism to protect the woman because ovulation carries a risk. Ovulation means shifts in the immune function that put the woman at risk of infection and other diseases. It's a delicate balance between what's being traded off, the possibility of conception or the possibility of infection.

So if she's not got a sexual partner and she doesn't have any chance of getting pregnant, then why risk ovulation and the shifts that occur in immune function? This is a very intriguing mechanism for protecting a woman when there's no chance of getting pregnant.

What about masturbation, does this also cause a shift in the immune system? Is it the trauma of sex? The action? The presence of semen?

I would argue that it is probably due to a protein components in male semen. For example, in women undergoing assisted reproductive procedures of one kind or another, if they have intercourse with their husband or their partner, they are more likely to have successful conception under those assisted technologies.

Other models say that it's simply physical irritation of the vaginal walls as might happen during intercourse. But I don't think that's enough. Otherwise masturbation might do it for you.

And I also don't think it's romance or arousal. I don't think arousal is specific enough. Human beings can be aroused by a really good chocolate cake. It lacks the specificity of a good signal.

It's a very cool set of ideas and to the best of my knowledge my data from Bolivia is the first from a non-industrialized population to support this facultative ovulation model.

Some studies suggest that in fact women have more sex around the ovulation and it's been argued that ovulation and the hormonal changes make you want to have sex. What I think is more likely going on is that when you have sex you're metaphorically priming the pump and thus increasing the chance of ovulating.

How do you think working with Clue can help you with your research?

I think that Clue offered the first opportunity to really look at these questions globally, instead of having to go to each place to look at long tracked data from large numbers of individuals. Consider that I was in Bolivia for two years and I collected data from the cycles of 300 women. In two years at Clue, you are collecting [data about] literally millions of cycles.

So the ability to test ideas and to see patterns that we never even thought of, the ability to look at seasonality—we have a young researcher at Stanford who's going to be looking at seasonality. I think that it's a fantastic opportunity for science to forge forward. One of the things I really like about Clue is the respect for our users. We see them as fellow citizen scientists, as opposed to just subjects.

To learn more about Dr. Virginia J. Vitzthum’s work, check out some of her publications.

Interpopulational differences in progesterone levels during conception and implantation in humans.

Links among inflammation, sexual activity and ovulation: Evolutionary trade-offs and clinical implications.

Hormonal Contraception and Physiology: A Research‐based Theory of Discontinuation Due to Side Effects

Download Clue and track your cycle to help Virginia’s work and become a fellow citizen scientist.

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