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How Hormones Rise and Fall Throughout the Menstrual Cycle

Published on October 31, 2023

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Fertility Awareness Method For Contraception

Back in 2012, I was really sick and while we were trying to figure out what was going on, my doctor recommended I discontinue hormonal birth control for a while. For about 6 months, I used conductivity monitoring to avoid pregnancy. Each morning, I’d record the conductivity of my salivary and vaginal secretions looking for a change to indicate I was approaching ovulation and another change to indicate ovulation had occurred.

Back then, it felt confusing to me and a little black box”ish”, so when I was cleared to go back on hormonal birth control, I went back on it and didn’t give another thought to Fertility Awareness Methods (FAMs), until I decided to ditch hormonal birth control again.

This time, I did a deep dive and discovered new methods alongside familiar methods of FAM, and I went head-over-heels into the science of it.

In the decade since I relied on FAMs last, at-home urinary monitors are now available, and being a data driven girl, this is the method I opted for. Qualitative devices such as the ClearBlue Fertility Monitor (CBFM) didn’t quite offer the numbers I craved, so I went with the Mira Fertility Monitor even though, to date, no FAM endorses the use of this monitor for contraception (though Marquette University is actively testing the Mira against the CBFM with its protocols).

This ability to monitor your hormones at home also revolutionizes maintaining healthy hormonal balance and body literacy. Indeed, body literacy and the natural rise and fall of hormones throughout a healthy cycle is the topic of this post.

Hormones of the Menstrual Cycle

In this article, we will discuss:

follicular phase and ovulation
- follicular development, how follicles are recruited and begin maturing throughout a woman’s reproductive life span
- how testosterone and estradiol are produced in the developing follicles
- the role of the hypothalamus and pituitary glands in follicular development and ovulation
- the role of progesterone in ovulation
luteal phase
- key changes in hormone production during the luteal phase (second half of the cycle)
finally, the entire menstrual cycle will be summarized in a single graph showing the rise and fall of hormones throughout the cycle

Why does all of this matter? When you understand how the menstrual cycle works, it becomes much easier to determine hormonal imbalances and much easier to navigate fertility. Women are only fertile for around a maximum of 5 days during any given menstrual cycle and when you have a condition like PCOS (polycystic ovarian syndrome) or experience delayed ovulation (or anovulation) for any reason during a cycle, menstrual cycle literacy makes it possible to pinpoint your fertile days when trying to conceive and naturally improve your chances of conception in each cycle.

For women who are not trying to conceive, cycle awareness is profoundly beneficial to overall health because you are better able to determine which part of your cycle is unhealthy and better able to address the underlying imbalance simply by knowing how your cycle works. Maintaining a healthy cycle throughout your reproductive years is of utmost importance even when your intention is to avoid pregnancy because the reproductive hormones impact every system within your body and are critical for everything from maintaining a healthy weight to a healthy heart.

This particular article (while containing lots of information) is an overview of the topics bulleted above. You will find a more in-depth discussion of these topics in this post.

An Overview of Follicular Development

Non-cyclical follicular development: Early follicular development of pre-antral follicles (follicles that don’t respond to follicular stimulating hormone) happens in a way that is not well understood by modern science and this part of follicular development is not governed by the menstrual cycle but instead occurs throughout a woman’s reproductive years beginning at the onset of puberty and ending with menopause.

Cyclical follicular development: A follicle is a structure within the ovary and it contains an ovum (immature egg). Each ovary houses several hundred thousand follicles at birth and throughout a woman’s reproductive life, these follicles mature and are responsible for releasing the reproductive hormones, estradiol and progesterone, which control release of these hormones:

GnRH (gonadotropin releasing hormone) released by the hypothalamus in a pulsed pattern
FSH (follicular stimulating hormone) released by the pituitary gland
LH (luteinizing hormone) released by the pituitary gland

The brain’s role in follicular development and ovulation: The tempo at which GnRH releases from the hypothalamus controls the secretions of FSH and LH by the pituitary, and these two hormones influence ovarian hormone patterns and those ovarian hormones affect the tempo of GnRH pulses by the hypothalamus. This feedback loop is what the term, hypothalamic-pituitary-ovary (HPO) axis refers to. It is important to know about the brain’s involvement in follicular development and ovulation because when there is a problem with the menstrual cycle, practitioners generally look at where in this axis the misfire is occurring. Conditions like hypothalamic amenorrhea (HA) arise due to an issue with the release of GnRH from the hypothalamus and we will revisit this condition along with others caused by a dysregulation of hormonal release in the brain rather than the ovaries in future articles.

Selection of one follicle for ovulation: Once follicles have matured into antral follicles, further development is governed by FSH and the follicles need FSH to not only continue growing but also to prevent atresia (follicular death). More than one follicle matures during each menstrual cycle and because of the well-designed negative feedback between estradiol concentrations and FSH, the fastest growing follicle generally outcompetes all other follicles by releasing more estradiol, which then suppresses FSH production and starves out the remaining developing follicles. The dominant follicle survives this period of FSH famine because it has more FSH receptors. The additional FSH receptors make it better able to sequester the small amounts of FSH released at this time. It is also larger and has more energy reserves than smaller and slower growing follicles. This is why women typically release only one egg (mature ovum) at ovulation.

Testosterone and estradiol in follicular development: During follicular development, follicles produce both testosterone (and several other androgens [male hormones]) and estradiol (plus small amounts of estrone). The androgens are produced in the theca cell layers. The theca cell layers are not able to convert these androgens into estradiol or estrone because they lack the necessary enzymes. Instead, through diffusion, these androgens enter the granulosa cell layer of the follicle where the necessary enzymes are found (aromatase) to convert testosterone to estradiol and androstenedione to estrone. A separate enzyme converts the estrone into estradiol within the granulosa cells. In conditions like polycystic ovarian syndrome (PCOS), there is an imbalance in the androgen and estradiol ratio with higher levels of androgens suggesting a problem with conversion of these hormones in that condition. We will revisit this in future articles on PCOS.

Ovulation

Progesterone prompts ovulation. Historically, it was thought that the LH surge caused the follicle to release the mature ovum (egg) in a reversal of the negative feedback loop between estradiol and the pulse of GnRH which suppresses release of both FSH and LH from the pituitary. New research suggests that the adrenals release a small surge of progesterone that stimulates ovulation and prompts a rise in LH. This pathway explains why women who are under stress experience delayed ovulation.

Based on my own at-home hormone monitoring of urinary metabolites of estradiol and progesterone plus LH and FSH, I can confirm this pre-ovulatory temporal rise in progesterone. In fact, if this new theory proves correct, it may help explain the sudden shift in the electrolyte composition of vaginal secretions at ovulation.

Progesterone concentrations just prior to ovulation are much lower than concentrations mid-luteal phase, and so it is likely that the adrenal cortex, rather than the developing follicles, are producing the progesterone necessary to prompt the surge in luteinizing hormone (LH). It is also of note that high concentrations of progesterone (like those produced during the luteal phase and during pregnancy) inhibit ovulation. In in-vitro fertilization, when progesterone is given at doses to simulate the blood concentration seen during the luteal phase, this prompts the “vanishing follicle” phenomenon suggesting that a low progesterone concentration is vitally important to successful ovulation.

This theory may also explain why women under stress do not ovulate. It is common for women who develop a cold or illness during the peri-ovulatory phase to have either delayed ovulation or an anovulatory cycle. Other forms of stress (mental, over-exercise, disturbances to the circadian rhythm) are also known to delay ovulation. Considering that pregnenolone is the precursor to both cortisol and progesterone, this progesterone rise theory as the key event leading to ovulation evolutionarily fits the concept of conserving eggs or preventing reproduction when conditions aren’t favorable to pregnancy. Elevated demands for cortisol during times of high stress would deplete the body’s ability to create progesterone.

Role of LH: LH (luteinizing hormone) transforms the follicle into the corpus luteum. While the follicle primarily generated the hormones testosterone and estradiol throughout follicular development and leading up to ovulation, the corpus luteum releases progesterone and estradiol to maintain the uterine lining after ovulation.

Key Takeaways From the Luteal Phase and Menstruation

Progesterone released by the corpus luteum throughout the luteal phase is vitally important for pregnancy because it sustains the uterine lining providing nourishment to the developing embryo until the placenta fully forms around 12 weeks gestational age. It is especially important that concentrations of progesterone be maintained until implantation of the fertilized egg occurs. Luteal phase deficiencies, which we will talk about more in future posts, is one of the common causes of implantation failure.

In the absence of pregnancy, the corpus luteum atrophies between 10 and 16 days after ovulation. As the corpus luteum atrophies, levels of progesterone and estradiol both fall, resulting in atrophy of the uterine lining resulting in onset of menses.

An Overview of a Healthy Menstrual Cycle

In summary, a slowdown in the rate of release of GnRH from the hypothalamus prompts an increase in FSH secretion from the pituitary and this awakens further development in antral follicles within the ovaries. As these follicles mature, both testosterone and estradiol are made by the developing follicles increasing the amount of both these hormones within the body. Estradiol quickens the release rate of GnRH by the hypothalamus which reduces FSH secretions by the pituitary gland.

Historically, it was believed that once estradiol achieved a critical threshold, this negative feedback loop reverses, and FSH spikes along with an LH surge to cause ovulation. New research shows a transient rise in progesterone ahead of the LH surge. This rise in progesterone is about one-tenth the maximum rise in progesterone seen during the luteal phase of the cycle and is presumably produced by the adrenal cortex. If this theory (that a transient concentration-dependent rise in progesterone) prompts ovulation, then this better connects the dots between why stress and undereating cause anovulatory cycles.

Luteinizing hormone, which spikes around the time of ovulation, elicits key changes within the follicle allowing for rupture of the mature egg from the follicle and conversion of the follicle into the corpus luteum. The corpus luteum produces both progesterone and estradiol and in the absence of pregnancy naturally atrophies resulting in falling levels of progesterone and estradiol. As circulating blood concentrations of these two hormones, which are necessary for maintaining the uterine lining fall when the corpus luteum atrophies, the uterine lining itself also atrophies and sloughs off the walls of the uterus leading to the onset of menses between 10 and 18 days after ovulation in a healthy cycle.

hormones across menstrual cycle — Figure 1. Hormone concentration throughout the menstrual cycle.

In Summary

This very quick overview of the menstrual cycle (aka ovulation cycle) forms the basis of every single fertility awareness method (FAM) today. Whether the method involves monitoring changes in cervical mucus, cervical position, basal body temperature, electrolyte composition of salivary/vaginal secretions, and/or at-home urinary hormone monitoring, these methods are highly reliable for predicting ovulation and are so reliable that their efficacy for avoiding unplanned pregnancy vies that of hormonal birth control.

These methods are also invaluable for shining light on a woman’s reproductive health and elucidating where hormonal imbalance lies within her cycle when things are a bit off. FAMs also provide real time data for women who are tracking their cycles so that you are able to adjust diet and lifestyle to support hormonal balance.

I will refer back to this article often in future posts on FAMs and hormonal health.

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Intense Exercise, PCOS, and Hypothalamic Amenorrhea

by Laura Vegh, PhD

Published on August 4, 2022

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Understanding PCOS and Hypothalamic Amenorrhea

Polycystic ovarian syndrome (PCOS) is an endocrine disorder characterized by various signs: irregular periods, anovulation, high androgens, and insulin resistance. Because it is a syndrome, it presents differently in every person. Two women might have PCOS and have completely different symptoms. The signs through which it is often diagnosed will also vary. For instance, insulin resistance is very common, along with excess weight, but someone with no insulin resistance and at a perfectly normal weight could have it as well.

Hypothalamic amenorrhea (HA) is characterized by anovulation and absent periods. With PCOS there is usually one or more hormones that are high, such as luteinizing hormone (LH), or testosterone, in most cases of HA, hormones are low. Hypothalamic amenorrhea is usually present in athletes and women who under eat and/or are underweight. It can also appear in times of acute stress, after a strong emotional shock, but also, due to chronic stress.

Something that not many people talk about is that the two conditions can co-exist. For instance, it is very possible for someone with PCOS to go on an extremely restrictive diet and lose their period as a result. In the same way, someone with PCOS can over-exercise and lose their period, because these women usually have irregular periods, pinpointing the diet or the exercise regime as the cause for the new hormonal imbalance isn’t always easy. Features of one condition can be present in the other, which further proves why looking at the lifestyle of a woman is imperative before setting a diagnosis.

My Battle With PCOS, HA, and Exercise Intensity

I was diagnosed with PCOS a couple of years ago when I got off the pill. In my teens, the condition had been suggested based on ultrasound and symptoms, but I was never told to do any further testing.

At almost 32, I was through with the side effects of the pill: anxiety, depression, low libido, and more. I had been on it without a break for over 12 years and a few more years on and off before that. My cycles were never regular, but the doctor’s only solution was birth control. So far, I’m sure this is nothing out of the ordinary and is in fact something that most women with PCOS experience. My story is slightly different though.

At 8 years old, I was diagnosed with scoliosis, a condition in which your spine curves into an S shape. Due to my young age, there was a huge risk it would progress rapidly, and I would end up needing surgery.

My family wanted to avoid that at all costs. The surgery is not without risks, and the prognosis, at least at that time, over 20 years ago, was not good. The chances of living a normal life post-surgery were small. So, they decided to take a different approach: managing the condition through sports, specifically swimming.

By the age of 9, I had a pretty good swimming schedule. Most of the school year, I would swim 3-4 times per week, an hour a day, and do some gymnastics at home on the other days. Then, 3 months per year I would train intensely, swimming 2-3 hours per day, usually 6 days a week. I loved it, I would have spent all day every day in the water, so I was far from complaining!

Somewhere around the age of 11, I got my period. Right from the start, it was irregular, happening anywhere between 35-60 days. That wasn’t ideal, but I wasn’t having any other symptoms that something was off.

Then, I experienced the first “odd” thing. My swimming season started, and everything proceeded as normal with my many hours spent at the pool. Halfway through, I realized I hadn’t gotten my period in quite some time, way longer than usual. The season ended, and a few more weeks went by, and still no period in sight. Finally, after about 2 or 3 months after the swimming season had ended, I got my period back.

For the rest of the time, I continued with my irregular pattern of 35-60 days. The year went on and the swimming season got back. Guess what? My period vanished again, only to return about 2-3 months after the season had ended.

The pattern repeated each year. Finally, when I was around 15 my mom decided to take me to see a doctor. Again, it was well beyond 3 months since I had had a period. The doctor did an ultrasound and didn’t see anything abnormal, so he decided to put me on the pill. I stayed on it for a few months, then quit, and the cycle of irregular periods, that would completely stop when I was exercising intensely, continued.

I had a few more ultrasounds in the years that followed, at different times in my cycle. During a few of them I had polycystic ovaries, so PCOS was suggested, though an official diagnosis was not made at the time. Also, nobody ever considered requiring blood work for me. Just like nobody ever suggested that the workouts could be the root cause of my missing periods for half of the year.

It was only many years later, while I studied to become a health coach and a fitness trainer that I became more interested in the relationship between hormones and workouts and learned about hypothalamic amenorrhea in female athletes.

Covering Up PCOS and HA with the Pill

When I left for university at age 20, I decided I would stay on the pill. The on-and-off pattern was making me feel less than well. I would always get mood swings coming off it, and I wasn’t having any of that in a new environment.

For the first few years, I was ok, or at least I thought I was. I continued working out, but because I had developed a slight allergy to chlorine, I had to start looking at different sports. I discovered fitness, and later yoga. During many of these years, I continued training intensely. I loved doing it and I decided to become a trainer. Being on the pill, I had no way of knowing if my reproductive system was reacting or not.

It was during those years that I was introduced to the concept of hypothalamic amenorrhea. I remember feeling pretty mind blown that neither my OBGYN nor my GP had ever mentioned it. Nobody had ever even mentioned the risks of HA or taking birth control pills to “cover up” HA.

Coming Off of the Pill and Listening to My Body

A couple of months before my 32nd birthday, I decided enough was enough and I quit the pill. Thanks to all the years of training, plus studying to be a trainer and a coach, I learned to listen to my body. I could feel how it was rebelling more and more against the pill. On top of the health issues, I developed anxiety, panic attacks, and depression that were getting worse and worse out of the blue.

I started doing a lot of research about hormonal health, PCOS, and HA – and I do mean A LOT. I have a PhD. It is in computer engineering, mind you, but the point is I’m a bookworm and research is my middle name. With each new book, or new research article that I read, my mind was blown, but I’m getting ahead of myself.

Coming off the pill, I experienced something very common: my body didn’t know how to restart itself. I went 5 months without a period. My doctor’s answer was more birth control, a different brand maybe. “I only experienced side effects to one brand, they’re not all the same”, she said. Thanks, but no thanks. I’m not going down that road again.

Again, I was faced with the same issue: nobody questioned me about my lifestyle. Someone suggested I go on a low-calorie, no-sugar diet since I have PCOS. They didn’t bother to ask me how much I exercise or even what I currently eat. In case you’re wondering I’m right in the middle of the perfect weight for my height, I have absolutely no reason to go on a low-calorie diet or to lose even one pound.

The Most Dangerous Advice for PCOS: Just Lose Weight

While the low-calorie advice was ridiculous for obvious reasons in my case, and it made me turn my back to that doctor without any remorse, it did shed light on the most common (and most dangerous) advice, women with PCOS receive: just lose weight.

Lose weight, and all your hormonal troubles will go away.

Look, I’m not saying losing weight won’t help some people. What I am saying is that the way this problem is perceived is dangerous and unhealthy. Just look at all the people who saw me, who knew about my lifestyle, who had all the evidence right there in front of their eyes and they didn’t even consider the over-exercise (and subsequent weight loss) that happened when I was training could be to blame.

PCOS Versus HA

Before writing about the changes that helped me, I want to go a bit more in-depth on the two conditions, why they are so easy to confuse with one another, and why having one, doesn’t necessarily exclude the other.

We already know both are conditions that affect the reproductive system. While PCOS is an endocrine disorder with unclear causes, HA is triggered by lifestyle. You can reduce (or worsen) your PCOS through your lifestyle, but that is not the ultimate cause.

Common misconceptions say with PCOS you’ll be overweight, whereas to have HA you need to be underweight. Both are false. Lean women can have PCOS, and normal to overweight women can have HA.

The latest research says you need to have 25+ follicles (commonly called cysts) on your ovaries to have PCOS. That’s because polycystic ovaries can be present in HA as well, though it is rarer.

The fact that restrictive diets, over-exercise, and acute or chronic stress can stop the communication between the hypothalamus and your ovaries, and eventually cause HA is known. Due to their similarities, a constant evaluation of symptoms alongside lifestyle is necessary. Especially when a woman with PCOS begins a new diet or a new workout routine, following her evolution closely for any symptoms that could show her new regime is causing more trouble, is crucial.

You don’t have to go into full hypothalamic amenorrhea (low hormones, no periods, no ovulation attempt) to be impacted negatively by over-exercise. It is, for the biggest part unclear whether I had true HA alongside PCOS, or I was just somewhere in the middle. However, it is undeniable that high-intensity exercise affected me each time. It is also undeniable that as soon as I would take it slow and even gain a bit of weight back, my body would be back to what was normal. I was lucky because I had an offseason that was longer than the training season. If I hadn’t had that, the outcome could have been a lot worse.

Healing PCOS and HA: Nutrition, Low Impact Exercise, and Relaxation

A few months after coming off the pill, I had blood work done and I began working with a naturopath, trying to understand what was going on. As much as I would have liked to be in one category or the other, I didn’t fit anywhere. I had a high LH:FSH ratio, common in PCOS (but not completely excluded in HA). My uterine lining was not building up, also very common in HA and very uncommon in PCOS. My testosterone and DHEA-S were normal, my androstenedione was on the high end of normal. Ultrasound revealed cysts, but not 25+, only about 15. My thyroid was normal, and so was my prolactin. All in all, my tests looked very close to normal, except I wasn’t ovulating.

To recover my health, I decided to take the middle ground. For my PCOS, I went ahead and eliminated foods that I was somewhat intolerant to such as cow’s dairy, gluten, and sugar. I’m not saying this is a cure for everyone, but I have always known I wasn’t digesting these well. I always had inflammation symptoms after eating them in excess including headaches, joint pain, and digestive issues. However, I took a lot of care to eat enough. I allowed myself the occasional treats. For instance, I discovered raw vegan cakes that make me feel amazing and are perfect for my sweet tooth. I didn’t run away from carbs and I made sure I included lots of healthy fats.

With PCOS as my main diagnosis, I was, of course, encouraged to continue my normal exercise routine. At this time, this consisted of HIIT 1-2 times per week, strength training 2-3 times a week, and Ashtanga yoga (a dynamic, strong style of yoga) the rest of the time. Technically it wasn’t much, and it was certainly a reduction considering my background.

I’d been feeling less and less well after HIIT, so I knew something had to change. I decided to go against every advice I’d heard for PCOS and cut back on everything except yoga, which I now do daily. My scoliosis is still very much with me, so doing no exercise at all, which is usually the recommendation in HA, is not an option. I changed the type of yoga and introduced yin and restorative yoga 2-3 times per week.

A few months after deciding to switch to yoga only, I found a medical study proving the benefits of yoga and mindfulness for PCOS. I take it as a sign that we might finally see a change in the constant recommendation to eat less and eat harder, which is mindlessly recommended to most women with this condition.

On top of nutrition and changing my workout routine, I’ve also created a non-negotiable relaxation time. Whether I read, paint, spend time with friends and family or go for a walk outside in nature, I make sure each week my schedule includes relaxation. It has taken quite a few months since implementing all these changes, but I can say my cycles are regular for the first time in my life.

Bottomline: You Can Recover Your Health

If there is one lesson that I’d like you to learn from this story is to listen to your body. Truly listen. Watch out for any changes, both positive and negative, and when you see something negative, take a step back. If you’ve just started exercising and are experiencing amenorrhea, for instance, you don’t have to stop exercising, just take a step back, exercise one day less, do something less intense, or use a lower weight. Like anything, health requires attention.