Stress, many people define it as a state of mental, emotional strain, or tension resulting from adverse or demanding circumstances. This is the common definition that most people are familiar with; not necessarily termed in those fancy words, but it has the same meaning in the minds of most people.
However, from a medical point of view the definition varies slightly. And for the sake of this topic, you’re going to have to think of the term “stress” from a biological perspective. Here’s the definition:
In a medical or biological context: stress is a physical, mental, or an emotional factor that causes bodily or mental tension. Stress can be external (from the environment, psychological, or social situations) or internal (illness, or from a medical procedure).
So, as you can see, stress is not solely defined as the mental unease you feel before an exam or a job interview. Working out in the gym is considered a stress to your body from the medical scope, even though it’s good for your health.
Your internal alarm system:
You’re walking around in the savanna of Africa minding your own business with no care in the world. Suddenly, a lion appears out of nowhere and starts chasing you. Your body is in a physiological crisis, it has to get you to run away as fast as it can. Your neuroendocrine system activity is getting off the charts, your glands are secreting stress hormones: epinephrine, norepinephrine, cortisol, etc. And these hormones will activate your sympathetic nervous system (SNS), which is the Fight or Flight response. It’s a natural response to dangerous situations, like an alarm system, only much more sophisticated.
The hormones secreted will activate the SNS, then what? Well, your fight or flight system will increase your heart rate and vasodilate (increase the vessels’ diameter) the muscles’ vessels, especially your thighs and legs. Remember, you’re trying to run away from a lion, you need blood to reach your muscles so you can use them for running. The SNS will also increase the size of your pupils (mydriasis) to get as much light as possible to the retina in order to get a better view of the field that you’re running on.
To be able to refer the blood to your muscles, your body also has to do something else, it has to defer the blood from your other organs which their usage is not critical at the moment, we have no need for your digestive system right now, this also applies to the female reproductive system. The thickening of your uterine wall is not a priority at the moment.
Chronic stress:
All of what is mentioned above is your body’s normal response to stress; this is only for a temporary period of time when the body homeostasis is out of whack. This is all physiological and harmless for your body, unless the lion catches you, of course.
On the other side, when dealing with a long term problem, chronic stress develops. If the nature of the stressor is physical, your body will turn on the chronic stress response that will be adaptive to that situation. However, if the stressor is psychological and/or psychosocial (e.g. stage fright) in nature which we, humans, specialize in. It makes no sense for your body to switch to chronic stress mode. You’ll be basically running away from a lion every hour of everyday and there is a price to pay in doing so.
Stress and reproduction:
To emphasize how much impact all of this stress has on the female reproductive system, we’ll need to look at some estimates on how much reproduction costs from an energy point of view:
-50,000 calories consumed over the course of a pregnancy.
-1,000 calories consumed daily on nursing.
This shows that reproduction is really expensive, and it is simply something hard to afford when you’re running away for your life.
To get a firm understanding of stress’s effect on the female reproductive system, we’ll have to first tackle down one of the endocrine axis, the hypothalamic-pituitary-ovarian axis. Don’t go panicking just yet; this will be essential to better grasp the cause and effect.
Let’s start by breaking down the names of the axis:
1-Hypothalamic: the hypothalamus is a gland located in your brain with many functions, including the regulation of your metabolism, core temperature, the autonomic nervous system, and the endocrine system. The latter is the function that is relevant to our topic. It modulates endocrine secretions by stimulating or inhibiting another gland, which is called the pituitary gland.
2-Pituatary: it is another gland that is also located in your brain, responsible for the secretion of all kind of hormones; some of which will generate a response directly. Others will need to stimulate other hormones to get that response
3-Ovarian: as you probably guessed, we are talking about the ovaries which you’re all familiar with, they are responsible for maturing eggs and preparing the uterus for a potential pregnancy.
The axis mechanism of action:
Now that we are done with the nomenclature, let’s see how it all works together.
The hypothalamus releases a hormone bizarrely named: “Luteinizing hormone Releasing Hormone” (LHRL), this hormone will stimulate the pituitary gland to secrete two other hormones:
- Luteinizing Hormone (LH)
- Follicule-Stimulating Hormone (FSH)
These two hormones will go to the ovaries via blood circulation, and then stimulate the ovaries to do two things:
First, mature the egg and prepare it for gestation.
Second, release estrogen which will also help in the egg maturation.
All of the above happens in the first half of the menstrual cycle. In the second half, another hormone will be the orchestra chef, progesterone. The name itself gives us an idea of what it does, it’s the Pro-Gestational hormone, and it will thicken the wall of the uterus to prepare it for a potential pregnancy. By the way, period happens when your body realizes that no fertilization has happened. Thus, there is no need for this wall and it is degraded. This typically happens around day 5-10 of the first half of the menstrual cycle.
How does stress affect this system?
First thing that happens during stress is the decrease in the secretion of LHRH. This is mediated by the release of cortisol (the stress hormone), cortisol will go up to the hypothalamus and inhibit the secretion of this hormone. Another relevant hormone is Beta-endorphin which does the exact same thing as cortisol among other functions.
What happens next? Well, less LHRH means less LH and FSH and the cycle will be disrupted. But, that’s not enough. Your brain doesn’t trust that decreasing the release of LHRH would be enough, so it activates a couple of more mechanisms to be 100% certain that the system is at halt.
1-hormonal stress signals are sent to the pituitary to make it less responsive to stimulation by any LHRH that is coming out.
2-glucocorticoids will make the ovaries less sensitive to LH and FSH
3-the body secretes another hormone called prolactin which will thin the uterine walls.
Stress hormone consequences:
- Less LHRH
- Less LH and FSH
- Lower estrogen levels=lower chances of fertilization.
- Lower progesterone levels=uterine wall do not thicken.
- Higher levels of prolactin=lowering the chances of implanting the egg against already ridiculous odds.
This was some of the mechanisms your body uses to shut down the reproductive ovarian axis at every single level.
Physical stress effects on ovulation:
1. Male sex hormones in the female body
An additional, even more impressive mechanism has got to do with this very oddly thing that females do. Including human females which is, they secrete certain male sex hormones into the bloodstream, androgenic hormones like testosterone. They’re secreted from the adrenal glands (endocrine glands located on the top of each kidney). Note that the concentration of these hormones is very minimal, around 5% of what you’d see in a male. Nonetheless, you have to get rid of this stuff. Fortunately, fat cells have this enzyme that can do biochemistry 101, they can take this testosterone found in the blood and convert it into estrogen.
That’s great, everyone lives happily ever after. You’ve converted these bizarrely secreted androgens into female sex hormones and everyone is happy. But what if you’re stressed? What if you’re so stressed that you’re lacking on a 1000 calories a day and you’re entering the starvation phase? What happens is, your fat deposit begins to go down, and after a while you have very few active fat cells that can convert the androgens into estrogen.
Two consequences generate from this, you’re not putting that estrogen into the blood which is not a big deal, there’s plenty around. But, the biggeer deal is that you’re not converting that testosterone. Its levels build up and mess with the axis we’ve talked about.
2. Starvation and ovulation
Starvation is a major reason for the shut down of ovulation, including voluntary starvation. One of the early characteristics of the infamous condition “anorexia nervosa” in which ovulation is halted due to fat depletion.
That’s also the reason why some women who do tons and tons of exercise stop ovulating as well. This has been immensely studied, especially in kids, where there was a very significant delay with the onset of puberty in young female athletes that do intense exercise (e.g. gymnasts, ballet dancers).
A few years ago a study of gymnasts was done with the Romanian Olympic gymnastics team. These girls were like 15 years old weighing 60 pounds and winning gold medals. The average age of menstruation for these kids was approximately 19. For reference, the western average is 12.5 years.
3. Extreme exercise and Ovulation
Once you hit puberty, you’re not off the hook yet. Females who do intense exercise, for example women who run 50 miles a week, that’s typically when the fat deposits start to get depleted and you start to have those ovulatory problems. Males aren’t off the hook either, men who run an average of 45-50 miles a week will also have some testicular atrophy, sperm count going down. And I can hear your thoughts right now “wait a second, I thought exercise was good for me?” well, exercise is good for you. In fact, a lot of exercise is good for you, but that doesn’t mean that an insane amount of exercise is insanely good for you. At some point, you pass the point of optimal function and homeostatic balance, and too much of a good thing becomes be as bad as too little.
Extreme athleticism is not typical for humans. We are not built for that. To get a sense of this, sit down with some hunter gatherers from the Kalahari Desert and explain to them, “You know, back where I’m from. We have so much food, and so much free time that sometimes we just go run 26 miles for the sheer pleasure of it” and they’re going to say “ are you out of your mind?”
Look at it like this, throughout hominines history; if you’re running 26 miles in a day, you’re either very intent on eating somebody or somebody is very intent on eating you.
Prolactin, Nursing, and Ovulation
Prolactin is secreted during stress, and it turns out prolactin works by decreasing pituitary sensitivity to LHRH, and also helps block the release of progesterone among other functions in the stress response.
However, prolactin is not merely a stress hormone. It has many other roles, one of them stands out if you ever have a nipple stimulation; there is this neurological loop going up to the brain resulting in the release of prolactin.
Nursing causes prolactin release, and based on the information above. Prolactin release should be working as a contraceptive. Thus, nursing is a contraception. You’re probably sitting there saying “oh, what does he know about contraception, he doesn’t even have ovaries. Everybody knows nursing doesn’t work very well.”
But as a matter of fact, nursing works wonderfully as a contraceptive. The World Health Organization (WHO) estimates that there are more pregnancies prevented each year by nursing than by all contraceptives combined. All you need to do is nurse the correct way. Which I’m going to show you right now. Aren’t you folks wishing this was a YouTube video?
Let’s look at the two main patterns of nursing:
| Western Pattern of Nursing |
| Give birth |
| Nurse the child every couple of hours for 20 minutes or so |
| Over time you nurse less |
| Average nursing for 6 months |
In this pattern, prolactin levels go up each time you nurse and then go back to normal after 2 hours or so. You get this scalping pattern of prolactin going up and down. Normally, that’s not what humans and other primates do with nursing. Thus, with their prolactin levels.
To get a sense of that, we’ll look at a study done on a bunch of hunter gatherers. The people living in the Kalahari desert. Turns out, they have a very interesting reproductive pattern which is: they have tons of sex and they don’t use contraceptives.
And despite all of that, women get pregnant about once every 4 years. The answer was very easy at the time, hunter gatherers lifestyle is short, nasty, and brutal. They’re all malnourished, and they’re all depleted in fats to ovulate.
However, when studied properly. It turned out hunter gatherers live very comfortably, folks working 3-4 hours a day to get their daily calories. They’re far away from being in starvation. So, what’s actually going on there?
Well, this was discovered a number of years ago by two anthropologists Melvin Konner and Carol Worthman, and what they did was that they’ve noted the levels of prolactin and studied the nursing patterns.
Here’s what they’ve found:
| Hunter-Gatherer Pattern of Nursing |
| Give birth |
| Nurse the child for 30 seconds or so. |
| 20 minutes later, nurse the child for 30 seconds |
| Repeat the pattern around the clock for the next 3 years |
Hunter-gatherers carry their children on a hip sling, they nurse throughout the night, the mothers hardly even wake up, and the child just crawls over and does some nursing. Of course Konnor and Worthman were up all night with their infra-red goggles, but everybody else is undisturbed.
When you have a nursing pattern like that, the first time you nurse your newborn baby, prolactin will go up and stay plateaued for the next 3 to 4 years. That’s the typical human and non-human primates of nursing. This way you’re not going to ovulate.
Think about this for a second, what is the life history for one of these women?
She hit puberty maybe when she was about 14 or so, a year later she was pregnant. And from what we just saw, four years later, she began to ovulate again with a couple of cycles, so on and so forth until menopause.
You suddenly realize, over the lifespan of these women, they’re having like over a dozen of periods whereas typical western women have 300-400 periods. The pattern of nursing in the west produces at least a 10 folds number of periods and there is a reason to believe, this may contribute to increasing cases of some diseases in women like endometriosis.
Stress and miscarriage:
The mere fact that stress can cause a miscarriage is seen to run through all that classic literature, and all sorts of novels, where key points of stress (e.g. betrayal, infidelity) causes grief and miscarriage.
I could cite the names of those books, if I have read any of them. But it is the general theme and it fits. If you look at non-human species, you’ll find that punctual stress can cause miscarriages. In some cases, even harassment will have a similar effect. So, what’s going on with humans regarding this?
Well, it can happen, but the evidence for it is not very good. It’s not good because it relies on what’s dreaded in this field of epidemiology. What is called: Retrospective data. Something bad happens to someone in terms of a disease.
This disease could be related to stress, so they sit you down, and they say “oh, have you been stressed recently?” and it is guaranteed that most of you will say “yes, I have been”. When people are in the middle of awful situations, they preferentially remember bad things in their past. Suddenly, you have sorts of myths about stress and its relation to that particular disease.
How to deal with all this?
Stress is one of the main culprits when it comes to diseases, either mental or physical ones . We as humans are not programmed to deal with this kind of situations. It goes without saying that the management of your stress will improve your overall health immensely.
Here’s a few tips on what you can do to reduce your stress:
- Try to solve the problem that is causing your trouble.
- Realize that sometimes you can’t control everything.
- Try talking to a professional for help.
- Attend meetings about stress management.
- Meditation and Yoga.
- Be grateful for everything you have and everything you achieved in life.
Conclusion:
Finally, I would like to end this with one of my favorite quotes from a Tom Hanks‘s movie, Bridge of Spies. Where he asks Rudolf Abel (Mark Rylance) over and over again throughout the movie during difficult situations, “Do you never worry?”, and Mark Rylance would then answer “WOULD IT HELP?”