What is a period?
A period is the shedding of the uterine lining.
Menstruation (or period) is the routine discharge of the uterine lining. It is the first stage of the menstrual cycle.
The first period (or menarche) happens at around 12 years old (early adolescence) but can start as early as 8 years old (late childhood). The last period typically happens at around the late 40s to early 50s, after which it will be considered menopause.
What actually causes periods?
When there is no fertilization in the uterus, the nutrient-rich tissue that was built up to support an embryo is sloughed off.
Periods happen because the nutrient-rich tissue in the uterus that was prepared to support a fertilized egg did not receive one.
The uterus grows a thick inner lining during ovulation, which is when an egg gets released from the ovaries. This lining contains the necessary materials to cultivate an embryo (a fertilized egg). The uterus continues to grow this lining for a certain time, which is the fertile window. When this window passes and it's clear that the body won't need the facilities to sustain a child, the uterus stops growing its lining. The lining, cut off from its supply of nutrients, collapses and exits through the vagina.
In short, it’s the uterus’ natural way of clearing itself to lay the groundwork for a potential pregnancy.
What is a menstrual cycle?
The menstrual cycle is a routine hormone-induced sequence of processes that prepares a body for a pregnancy.
It is the repeating hormone-induced sequence of processes the body undergoes to prepare itself for a pregnancy. It happens over the course of around 28 days, starts on the first day of the period, and ends before the first day of the next period.
Phases of the Menstrual Cycle
The menstrual cycle has two phases, pre-ovulation and post-ovulation, separated by ovulation, which is the moment an egg is released from the ovaries.
Remember that the whole cycle prepares the body to bear a child. If you think of ovulation as the “main event,” pre-ovulation sets the stage for it, and post-ovulation is in anticipation of fertilization. The tail end of post-ovulation involves clearing out the unused fertilization facilities if no conception occurs. Afterward, the cycle repeats itself and starts with pre-ovulation.
The menstrual cycle can be looked at from two points of view: the ovarian cycle and the uterine cycle. Here’s a summary of the two cycles before we go in depth:
| THE MENSTRUAL CYCLE | |||||
|---|---|---|---|---|---|
| Cycle | Pre-ovulation | Ovulation (right after ~2nd week) The egg is released from the ovaries |
Post-ovulation | ||
| OVARIAN CYCLE | Follicular phase | Luteal phase (after ovulation to ~4th week) |
|||
| Early follicular phase (~1st week) Start of period |
Late follicular phase (~2nd week) Preparation for ovulation: Dominant follicle appears |
Early luteal phase (after ovulation to ~3rd week) Preparation for possible pregnancy |
Late luteal phase (~4th week) Preparation for next cycle if no fertilization occurs |
||
| UTERINE CYCLE | Menstruation (aka Period) (~1st week) |
Proliferative phase (~2nd week) Preparation for ovulation: Endometrium (the inner lining of the uterus) thickens |
Secretory phase (after ovulation to ~4th week) Preparation for possible pregnancy: Endometrium continues to develop
Preparation for next cycle |
||
We also mention some hormones in this article that are key to the menstrual cycle. They are chemicals manufactured by glands or organs that instruct organs to function. If there's an overproduction or lack of them, certain bodily functions would be excessive or halt respectively. For example, you may experience an irregular cycle if you have an imbalanced level of estrogen (E2).
Here's a quick guide to your cycle's hormones.
Menstrual Cycle Hormone Cheat Sheet
Four key hormones, the follicle stimulating hormone, estrogen, luteinizing hormone, and progresterone send signals to various parts of the body during menstruation.
| Menstrual Cycle Hormone Cheat Sheet | |||||
|---|---|---|---|---|---|
| Hormone | From | To | Message | What it does to you physically | What it does to you mentally |
| Follicle stimulating hormone (FSH) | Pituitary gland (located in the brain) |
Ovaries | Stimulate the follicles | N/A | N/A |
| Estrogen (E2) | Ovaries *The adrenal glands and fat cells also produce small amounts of it (via hopkinsmedicine.org) |
Brain and Uterus *And a great number of places |
We’re ready for ovulation, release LH | Increases energy, thickens uterine lining | Increases libido |
| Luteinizing hormone (LH) | Pituitary gland | The whole system | Release the egg (ovulate) and prepare for pregnancy | Increases energy | Same as E2 |
| Progesterone (PG) | Corpus luteum (previously the ruptured dominant follicle where the egg came from) |
Uterus | Prepare yourself for a fertilized egg | Prepares uterine lining for implantation | Relaxes |
THE OVARIAN CYCLE
The uterine cycle tracks the changes in the ovaries during menstruation.
The ovarian cycle tracks changes in the ovaries. It includes two phases: the follicular phase and the luteal phase, which are separated by ovulation.
1. a. Pre-ovulation: Early follicular phase/Period
You aren’t pregnant. Your body has settled from a decline in E2 and PG and are at their lowest concentration. These two were present in your body at a levelsuitable for pregnancy. Because your egg wasn’t fertilized, your uterine lining is shed. This is also when your hormone levels are at their lowest.
1. b . Pre-ovulation: Late follicular phase
Your body prepares itself to ovulate again. E2, FSH, and LH get produced and processed by their respective organs. Once there is a high enough concentration of these hormones, they set off physiological changes to make ovulation happen. The largest follicle (dominant follicle) gets closer to releasing the egg.
The spike in E2 and FSH levels also comes with a spike in energy. It’s during this period that you may feel like you want to be out and about and engage in activities that will lead up to the fertilization of your egg. In other words, you’ll be in a mate-seeking mood. Your temperature also increases around the time right before ovulation. This is why you can track your ovulation by basal body temperature.
2. Ovulation
E2, FSH, and LH reach their peaks and set off a series of processes that end with releasing the egg. The dominant follicle ruptures and out from it comes the egg.
Immediately after the egg gets released, E2, FSH, and LH levels rapidly decline. From having increased energy levels and feeling on top of the world from the high level of hormones, you experience a very dramatic comedown. It’s no wonder that you usually would feel horrible now.
3. Luteal phase
This phase starts when the egg makes its way from the ovaries to the fallopian tube, and ends right before the period.
The corpus luteum forms from the ruptured dominant follicle. The hormone PG (along with some E2) is produced here and cues the uterus to prepare itself for a fertilized egg (or zygote). The uterus responds to this signal by making itself thicker with blood and tissue, which help a fertilized egg implant itself and survive. This inner lining (or endometrium) gets shed off during the period if no fertilization takes place.
PG reaches its highest point at around the third week of the cycle. It's from the start of the luteal phase to this point when you are most fertile. You can think of this hormone as having the opposite effect on your mood as E2. You may start to feel more focused internally and more likely want to stay in. You’ll be more inclined to engage in behaviors that would be conducive to safeguarding the development of a fertilized egg. In other words, your body will be in (potential) baby nurturing mode.
If the uterus doesn’t receive a fertilized egg, the corpus luteum stops the production of PG and breaks down.
Speaking of breaking down, along with the sharp decline in PG (and E2) may come an equally sharp decline in your mood. You may know this point in the menstrual cycle as premenstrual syndrome. The ovaries stop sending signals (the hormones PG and E2) to the uterus to prepare itself for a baby.
THE UTERINE CYCLE
The uterine cycle tracks the changes in the uterus during menstruation.
The uterine cycle tracks changes in the uterus. It includes three phases: menstruation, the proliferative phase, and secretory stage. Ovulation comes after the first two phases. A lot of the uterine cycle was covered in the ovarian cycle, so this may look abridged. Just remember, the uterine cycle happens in parallel with the ovarian cycle.
1. Pre-ovulation: Menstruation/Period
The endometrium that was built up for a potential egg fertilization sheds its top layers through the cervix and vagina. After it sheds, it is at its thinnest.
2. Proliferative phase
E2 tells the uterus to prepare itself for pregnancy, so it thickens. Without a thick inner uterine lining, it would be difficult for an egg to embed itself into it.
3. Ovulation
The egg is released from the ruptured dominant follicle and enters the fallopian tube.
4. Secretory Phase
The uterus readies itself for a potential pregnancy or menstruation. If no zygote implants itself into the uterus during the fertile window, prostaglandins from the uterus trigger the uterine muscles to contract. These contractions help shed the endometrium during the period. When the uterus stops receiving cues from the ovaries to support a pregnancy, it's cut off from its heightened blood flow. The thick inner lining that was built up over the last week or so is shed off because it stopped receiving the nutrients it needed to maintain itself.
How Does a “Normal” Cycle Look Like?
Each person has a unique cycle and some uncommon features are no cause for alarm.
Menstrual cycles usually last 28 days, but they can vary from person to person. Things like one’s age, diet, frequency and intensity of exercise, stress levels, presence of birth control, and sickness can affect a cycle’s duration. Having a regular cycle (i.e., consistently an x amount of days over several months) can be an indicator of good health. You can view it as a sign that your body is in working order, that you’re receiving the appropriate nutrition, and that your stress levels are balanced.
Fluctuating hormones during your cycle is normal. It’s how your organs communicate with each other to turn your body into an environment that can support life. With the rise and fall of those hormones comes the rise and fall of your mood. Each of the chemical messengers involved in the cycle has its corresponding effect on your physical and mental state. Your highest points are right before ovulation (when FSH, E2, and LH are at their peaks) and the days before your period (when PG is at its peak). The times when you feel like your mind and body are taking a toll on you coincide with the sudden decline in the aforementioned hormones.
Other symptoms, which might catch you off guard but are also quite common, are:
- Diarrhea on the first 1 or 2 days of the period
- Missing a period or two (possibly because of stress and not pregnancy)
- Bleeding shorter than seven days
- Gaining weight on or before your period (PMS bloat)
All these are totally normal and should be no reason for concern.
How Does a “Not Normal” Cycle Look Like?
Certain extreme symptoms should be addressed by a medical professional.
These are some instances when your cycle is considered “not normal” and should be brought up with a medical professional:
- Absence of the period for more than 90 days – and you’re not pregnant
- Irregular periods after having been regular
- Cycles lasting less than 21 days or more than 35 days
- Bleeding between periods
- Experiencing severe pain during your period
| Is My Cycle Normal? | |
|---|---|
| Normal Cycle | Not Normal Cycle |
| Diarrhea on the first 1 or 2 days of the period Missing a period or two (possibly because of stress and not pregnancy) Bleeding shorter than seven days Gaining weight on or before your period (PMS bloat) |
Absence of the period for more than 90 days – and you’re not pregnant Irregular periods after having been regular Cycles lasting less than 21 days or more than 35 days Bleeding between periods Experiencing severe pain during your period |
Consult an OB-GYN
Book an appointment with an OB-GYN with Dima to get expert advice about sexual health.
If you want to know more about your menstrual cycle, birth control methods, or get an accurate diagnosis of possible symptoms, consult a medical professional. You can book an online OB-GYN consultation with us here. No topic is off-limits for an OB-GYN. They will gladly answer your questions about pregnancy and prevention, sexually transmitted diseases (STDs), hormones, and anything reproductive health-related. Dima Health wants to provide everyone with easy access to expert advice.
