The Menstrual Cycle

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Today we're going to be talking all about the menstrual cycle and the reason I think it's so important to talk about the menstrual cycle is because if you clearly understand the menstrual cycle, you understand about 90 percent of what I do. So looking at the menstrual cycle, we're going to start at the very beginning and get more advanced and more complex as we build on it.

So initially most menstrual cycles start with the period. The period or the menstrual bleed is the shedding of the lining of the uterus. If that's happening regularly once a month, then it's more than likely that the patient is ovulating. So what happens in a normal menstrual cycle to arrive at ovulation and then to arrive at the next menstrual period?

Initially what happens is that the brain releases a hormone that is known as FSH or follicle stimulating hormone and some of you may know FSH because it's one of the hormones we check when we're doing part of our fertility evaluation. FSH is released by the brain and it's a signal to the ovaries ‘Hey guys, it's time to go to work.’ So the ovaries then recognize that signal and from the group of recruits that is sitting there in the ovaries waiting to be recruited (remember the antral follicle count or ovarian reserve is that group of recruits that is waiting to respond to that signal). Of that group, one follicle is selected out to be the dominant follicle. The others undergo a process of atresia, which just means that they die off and are reabsorbed into the body. The dominant follicle then begins to grow and grow. As it grows it makes estrogen, so estrogen is building building building in that follicular phase or in that first half of the menstrual cycle.

Now initially estrogen is turning off the brain so its it's going back up to the brain saying ‘Hey brain, we're good. We have everything that we need. You can stop releasing those signals now’. So it produces what we call negative feedback. But after a certain threshold, it actually converts to a positive feedback trigger, and it provokes the LH surge of ovulation.

So let's talk about the LH surge. LH is the Luteinizing hormone, it is the main hormone of ovulation and it is released by the brain in response to a certain level of circulating estrogen.

The LH surge occurs and provokes three primary things. The first one that we all know is follicle rupture. The egg that was housed inside of that follicle is now released into the pelvis and hopefully picked up by the Fallopian tube fertilized by a sperm and an embryo implanted into the uterus. So follicle rupture is the first big action that is a result of that LH surge. The second one is the formation of the corpus luteum. The corpus luteum is the cyst left from where the egg was released. It becomes a corpus luteum and it makes estrogen and progesterone in the second half of the cycle and we'll talk about that in just a second. And then the third big thing is the resumption of meiosis. I'm going to take you back to Cell Biology 101 for just a minute here.

The egg at baseline is arrested in prophase one of Meiosis one, but in that stage it's not capable of receiving sperm, so what the LH surge does is it triggers a reinitiation of that process. A reactivation; gets it going again, and turns it into a metaphase two oocyte. My embryology friends might say M2s, you may have heard that term kicked around. A metaphase 2 oocyte has released half of its DNA and is now capable of being fertilized by a sperm.

So again those 3 big things are: follicle rupture; formation of the corpus luteum, which is responsible for estrogen and progesterone in the second half of the cycle and then reactivation of the meiosis process producing a metaphase 2 oocyte, which is capable of fertilization.

Once those three things have occurred, the LH surge goes away. Remember it's a defined time in the cycle, it's a window or a peak. After that time, estrogen and progesterone are the two main hormones of the cycle being produced by that corpus luteum.

The corpus luteum has a fixed half-life of about two weeks. At the end of those two weeks, if there's no pregnancy hormone around to continue that stimulation of the corpus luteum, the corpus luteum involutes and reabsorbs. Because of that involution and reabsorption, estrogen and progesterone fall. And now there's no hormone to support the lining of our uterus, and we get a period.

The reason that those 14 days are important and let's give or take a day or two. I don't want you to be super fixed on 14, but the idea is that it's a relatively fixed half-life and that is important because that's going to help us track ovulation. So if month to month, our cycle length is 28 days and the corpus luteum is around for 14 days. We know ovulation is going to happen around cycle day 14.

When we have a 21-day cycle, ovulation is going to occur much sooner. So if we start testing around day 14, we will have already missed our ovulation. Why? Because if the corpus luteum has a fixed half-life of 14 days and our cycle length is 21 days 21 minus 14, you're really ovulating probably around closer to day 7. Vice versa. Let's say we have a 32 or 33-day cycle. Those cycles are going to be longer, and if the patient starts testing on day 14, she may get false negatives. And why is that? Because again, if the corpus luteum has a fixed half-life of 14 days 32/33 minus 14 is going to give us an ovulation more like around cycle day 18 or 19. So if she's testing on day 14, she won't get a positive.

So understanding ovulation and when it's occurring is important to be able to time intercourse. The menstrual apps, that have now recently been called into question because of privacy data concerns, are helpful in tracking cycle length. But that's also easily done on a calendar or on a calendar notebook. And the idea is to try to identify your first cycle day 1 of your period, to your next cycle day 1 of your period, and your next cycle day 1 of your period, over three to six months, this is going to give us a sense of what is your cycle length 28 days, 30 days, 32 days, etc.

So what is normal?

The textbooks talk about 28 day cycles but normal has been documented as anywhere from 21 days to 35 days. So really there's a broad range of what we providers define as normal for menstrual cycle length. And the reason that knowing your menstrual cycle length is important is because that will help you know when you're going most likely to be ovulating and that will help you test with the ovulation predictor kits at a more defined time.

The ovulation predictor kits are urine kits. You typically will pee on a stick, sometimes in the morning, sometimes in the afternoon. If you're working with a provider, they may have a specific time that they want you to do it. If not, typically you'll test in the morning with that first urine. If you get a positive, that means that your LH hormone (the hormone of ovulation) is surging. So we know that ovulation is imminent. With that, we want to do intercourse that day of the positive and the next day.

The reason that I like focusing on timed intercourse is because intercourse can become a chore. Some providers will talk about every other day for two weeks or every other day in the first half of your cycle, or every other day for the whole month, God forbid. And it becomes mechanical. It becomes medicalized. You take away any spontaneity or intimacy with it. So if you can identify when you're ovulating and you can reserve that intercourse for baby-making or specifically for conception, that then frees you up for the rest of the time to be able to reconnect with your partner and to be able to allow intercourse to remain a part of your emotional and sexual intimacy versus completely defining it around conception and baby-making.

Now what happens if you don't get a positive with the ovulation predictor kit or what happens if you're trying to time your cycle and your cycle lengths are 2-3 months apart, maybe 6 months apart? Maybe you don't get a period at all. That is definitely not normal. It's probably very convenient because you don't have to worry about a menstrual bleed, but it's definitely not normal. A reproductive-age female who is otherwise healthy with no significant medical problems should be getting a regular monthly menstruation. If she's not, then she definitely needs to talk to her OBGYN provider. And if the OBGYN provider is not giving answers, then maybe it's time to seek out the help of a fertility specialist. So skipping periods is not normal and something you want to be talking to your healthcare provider about.

But what happens if you are getting regular monthly periods and you're just not getting a positive with the Ovulation Predictor kit, so that's making it difficult to time intercourse? There is a small percentage of women about 15 to 20% who will get either a false positive or a false negative with the Ovulation Predictor Kit. Unfortunately, it makes it a little bit harder. If you know your cycle length, then you can subtract 14 days and you can estimate that probably you're ovulating around that time. But if you're anxious about it, if it's affecting intimacy with your partner, or if you're just not sure, then it's definitely something to discuss with your healthcare provider.

There are ways that we can actually check for ovulation, so for example, if we're not doing an ovulation predictor kit at home, we can do serial ultrasound monitoring, checking for that follicle growth and estimating when we think that follicle is going to rupture. We could do serial blood levels although I don't recommend that. But we could do blood draws checking for that LH hormone looking for that LH surge.

We could do an endometrial biopsy. That biopsy, while uncomfortable, can show us if there have been ovulatory changes, and the important thing is that all of these things are trying to assess what is happening in the body. We won't be able to tell you exactly when you're ovulating, but we'll be able to give you an estimate of the window of ovulation either by serial ultrasound, by biopsy, by blood draw. There are many different ways to do it, and I encourage you to speak with your provider.

Hopefully this has been helpful. The idea is to know what is normal, what is regular and when should you seek out the help of a provider. It's really important if you're not understanding if the ovulation predictor kits are not working, or your cycle length is irregular and doesn't allow you to properly time intercourse, or periods are very painful, intercourse is very painful, cycles are irregular, you're skipping to 3 months, 4 months, etc. It's definitely time to talk to a healthcare provider, whether that's your OBGYN that hopefully you're seeing every year for your annuals or whether that's a fertility specialist. Now, remember, you don't necessarily need a referral to see a fertility specialist. So if you would like to see one, call the clinic and see if they're accepting new patients at the time.

I hope this video has been helpful. This is my short snippet on the menstrual cycle. More to come on progesterone, more to come on irregular cycles, so be on the lookout for that.

*This content is intended solely for educational purposes and is not to be construed as medical advice. For personalized recommendations concerning your specific healthcare needs, kindly consult with your healthcare provider.