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Harvard Medical School's Dr. Kathryn Rexrode on Hormones & Health [VIDEO]

By Erin Sharoni, June 29, 2016

When it comes to the subject of hormones, there's plenty to discuss. For most of us, hormones are as confusing and complex a topic as they are fascinating. How do they work, exactly? What roles do they play in our bodies at different points in our lives? Why are men and women affected so differently by the same ones? Thankfully, we have an expert on hand to help us sort through it all! Dr Kathryn Rexrode is a rockstar in the world of women's health, and an expert on hormones and metabolic health.

Dr. Rexrode is an associate professor at Harvard Medical School and a physician at Brigham and Women’s Hospital. She’s the Principal Investigator of several NIH studies and is a member of our Scientific Advisory board here at InsideTracker, where she has been invaluable to us when it comes to understanding the role hormones like testosterone play in our bodies. In this video, Dr. Rexrode breaks down the science behind how hormones work, why both women and men need testosterone, and how lifestyle factors like diet, weight and exercise affect things like metabolism and disease risk.

"Hormones are really our body's way of connecting and communicating between different organ systems...sort of these networks of messengers. And then the hormones themselves really interact with cells across our whole body," Dr. Rexrode explains. Check out the video for more.

Read video transcript

Video outline:

01:35 - Dr. Rexrode's recent work examining hormones and their impact on health  

04:46 - Hormones, their role in our body, and how they affect different processes in our body 

07:58 - The differing effects of testosterone on men and women 

08:33 - Testosterone and the athletic world 

10:56 - How different lifestyle factors can affect your hormones 

12:44 - Dr. Rexrode's upcoming study evaluating women and their metabolic profiles 


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Full video transcript:

Erin: All right everyone, I am incredibly excited Dr. Kathryn Rexrode joining us today. She is – to put it lightly – an absolute rock star expert in the world of women's health so I'm obviously really excited to talk to her for personal reasons. But first a little bit of background on her so you can see what I mean about the rock star status.

Dr. Rexrode is an associate professor at Harvard Medical School at physician at Brigham and Women's Hospital. She also has a private practice. She has particular interest in the world of metabolic and hormonal factors so she's studied the effects of sex hormones like estrogen and testosterone, related generic variance and risk of cardiovascular disease. She's also the principal investigator of several NIH grants examining risk factors for stroke and coronary heart disease in women and she's actively involved in several large studies on women's health.

And if that wasn't enough she's also one of our wonderful scientific advisory board members here at Inside Tracker and she's really just been invaluable to us when it comes to understanding the role of hormones in the body and of course as a physician we want to know what she thinks about using Inside Tracker with her patients. So it sounds like you are a very busy woman, Dr. Rexrode.

Kathryn: Hi, I think I stay busy.

Erin: Well, thank you for making the time for us. I appreciate it.

Kathryn: It's really a pleasure.

Erin: So first things first, obviously I gave an overview there but I would love for you to tell everyone about some of maybe the more interesting things that you're working on in the field of hormonal health whether in your private practice, your studies, Harvard, one of the many things that you do.

Kathryn: Sure, so I've really been interested throughout most in my career on how lifestyle factors such as diet, physical activity and weight impact health, in particular cardiovascular heart disease and stroke and how hormones may be part of that connection. So my earliest work looked at how body mass index and waist-hip ratio were related to heart disease and stroke and when we found that sort of an apple shape, a male pattern of weight gain as it were for women significantly increased the risk of heart disease; I was really intrigued by how that related to sex hormone differences in women.

So women who have that “male pattern” obesity tend to also have higher androgen levels, higher DHEAS, higher testosterone levels, free androgen index and I was interested in whether that would translate through into seeing those levels predict risk. That's really sort of what shaped the course of my career. We've not yet been able to find that magic ratio for women and I know we've talked previously about how it can be hard, women's hormone levels change throughout their cycle, through pregnancy, through the perimenopause and it can be hard to really catch an accurate snapshot of women's hormonal status but I'm still very much involved in trying to tease a part that understanding how hormone therapy, how oral contraceptives might health long term and whether we can get a better handle on what kind of a profile would predict the risk.

Recently I've been studying something called metabolomics which is profiling a small molecule metabolites and how that relates to coronary heart disease in women, I'll be doing some other studies for stroke coming up. So a lot of my research does touch on biomarkers, both hormonal and otherwise and that's definitely how it connects to what Inside Tracker does as well.

Erin: So I really have you to thank for instead of complaining about how every piece of cake I eat goes to my hips and I would say “Well, given my waist-hip ratio I'm actually at lower risk for heart disease so thanks mom.”

Kathryn: It is. It's better if it goes to your hips than your tummy. So you can be glad for estrogen for that.

Erin: Yep. I can thank my mom for those genetics finally. But all kidding aside, though you mentioned a couple of obviously hormonal markers there and I think hormones are obviously a popular topic of conversations these days in the media and scientific literature, yet relatively few people in the general public and probably even some academics understand how and why sex hormones, well, all hormones really work in the body. So if you had to explain it to a new student, not a Harvard Medical school student but let's say, I don't know... an entry level science class in an undergraduate university or something, how would you explain that?

Kathryn: So hormones are really our body's way of connecting and communicating between different organ systems. So for instance the pituitary is one of the controlling spots for producing hormone regulators and it sends out messages to the thyroid to produce more or less thyroid hormone and sends messages to the ovaries or the testis to produce more or less estrogen or testosterone. And so that's sort of these networks of messengers. And then the hormones themselves really interact with cells across our whole body. So for instance estrogen receptors are present throughout most of our organ systems: the skin, the brain, the blood vessels the heart. And I think one of the fascinating things we're still trying to unpack is exactly what are all those messages doing? You know, that is sometimes less clear than the fact that there's a lot of messaging going on.

So in a snapshot hormones are substances that communicate between different parts of our body and really do regulate significant functions. Taking something a little more narrow like thyroid hormone which is made by the thyroid gland and then circulates in the blood, there are again – there are receptors that that axon in it tells our body how fast our metabolism might be. It affects many different processes in our body.

So there are these sort of long-acting messages that go to many different organ systems. And one the things that a hormone almost always has is a feedback loop. So some method of regulating whether the level is too high or too low and communicating that message. And that also makes hard – sort of complicated to study because they're usually in some kind of flux, both up and down and constantly being regulated by a number of factors. So we can sometimes get a one time snapshot and for some hormones those levels change much more frequently and for others they might be more tightly regulated within a narrow range.

Erin: That was a very elegant explanation. You must be a teacher! Obviously as you mentioned they fluctuate widely and that is why estrogen is the bane of my existence. But kidding aside though obviously both men and women have estrogen, testosterone. They affect the sexes very differently and they're both necessary for different reasons. We test for testosterone here at Inside Tracker so maybe you could give your take on why that particular hormone and related hormones are so critical – that it's so critical that we maintain balance. Like you said, sometimes within a fairly narrow window depending on where in your life cycle or your fitness level you happen to be.

Kathryn: Yeah. So testosterone obviously has a lot of effects and both men and women have testosterone. Men have much more in an absolute loveful way because of the way that it's produced directly in men. Most testosterone in women actually is converted from estrogen or much of it is or other products, related to thyroids in the body so we don't directly make testosterone in our testis. We don't have them.

Erin:  Hopefully not.

Kathryn:  Good thing, huh. So in terms of its impact, testosterone has some very specific effects that are of interest in the athletic world and to many of us who want to be more physically active and healthy as well in that it tends towards promoting increase the muscle mass as well as bone density. And so it has an impact on training and evaluating training in sort of optimal levels which Inside Tracker obviously tries to help people get into that optimal range. But women also have testosterone, it's just that it is less direct. So there are a lot of different things that might influence testosterone levels in women. It is – as I said mostly converted from other hormones but [inaudible 09:27] more androgenic pattern, certain genetics can control sort of how – what's the ratio of estrogen to testosterone. So in women it's often the relative proportion of estrogen and testosterone that we have to take into account. And again, as I've mentioned earlier, measuring estrogen in women is pretty challenging because our levels fluctuate a lot. You know, within days of each other could have very different levels. So it makes a little bit more difficult to interpret those levels in women. 

Erin:  And so anyone who happens to be watching and is either an Inside Tracker user or a perspective Inside Tracker user wondering why estrogen is left out of our equation, that's actually the reason why. Because as Dr. Rexrode said it depends on a whole lot of factors which is a completely separate video in and of itself I think.

So I think it's going back to what you said at the beginning how your interest in this whole field began related to these influences of lifestyle and diet on our hormones and our metabolism. What would you recommend as a physician yourself if someone is looking to balance their hormone levels? Are there certain foods that are sort of stapled in your arsenal? Does it really depend on the person? Are there things that you happen to think are new and interesting that we maybe didn't know about before?

Kathryn:  So in my clinical practice I'm a primary care physician, I spend a lot of time talking about diet and lifestyle. And I tend to not focus on their direct impact on one substance like testosterone or any particular compound but think about them holistically as what is the healthiest pattern. So and my own research hasn't looked as specifically on diet and hormones in terms of testosterone or estrogen, estradiol. What I would say is that absolutely having a healthy diet can impact your overall hormonal health as well as how you feel. So I know that Inside Tracker offers some very specific advice targeted towards key biomarkers, key hormones and I don't think I can sort of duplicate that level of specificity for “If you want to increase X, eat more pumpkin seeds.” So I don't think I can go there but I do know that there is some impact for sure of exercise and nutrition on these markers. Again, some of them are more tightly regulated by other factors as well.

Erin:  What's the next frontier do you think in this sort of field of studying hormones? Both in women and in men. I mean is it looking at generic variance, is it – I don't know something else that you happen to be study in one of your many hats that you wear in your different jobs?

Kathryn:  Well, one of the things that I'm going to be studying coming up, the first study that I've recruited patient's to with the Women's Health Initiative which studied postmenopausal hormone therapy in older women. And I'm going to be studying these metabolic profiles, metabolomic profiles in women who were in the different treatment groups so that we understand in a direct way what's happening. I think those kinds of studies among women who are using oral contraceptives, among women through the perimenopausal transition and in pregnancy and these kinds of states, that's certainly very current frontier of interest of how hormones and these metabolites which are really the end products of where all of those hormones are going and what messages they're sending throughout the body, that's the piece that I'm currently really interested in. And I do think within the next few years we'll know a lot more about that so that it may help us understand both how the hormones affect so many different processes as well as how some of that might be modified.

So that's the next frontier for me. I think the data on how lifestyle and diet affect these metabolites as well as hormonal markers, all these different biomarkers is definitely another rich area of study and to think about how to help people optimize that.

Erin:  Well, I'm interested in all those things too so I have to have a follow-up with you next time you'll learn, you have some massive scientific breakthrough which I'm sure you will. Thank you so much.

Kathryn:  Oh, it's really been a pleasure. Thank you for your interest.

Erin:  Absolutely.


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