The Menstrual Cycle


The menstrual cycle is an automatic and self-regulating process during which the female body undergoes physiological and hormonal changes over the course of 24 to 42 days. This process plays an integral role in to the overall health and function of the female reproductive system and fosters the growth of fertilized ovum into developing fetuses.  The menstrual cycle is regulated by two hormones secreted from the pituitary gland, follicle stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH control the production of estrogen and progesterone, hormones are produced in the ovaries that determine the different stages of the menstrual cycle.

A peeled tangerine split in half.

The Menstrual Cycle

Phases of the Menstrual Cycle

Females begin their menstrual cycle during puberty at the onset of menarche, the first menstrual period, between the ages of 9 and 16. Females typically continue to have menstrual cycles throughout their lives until menopause occurs between the ages of 40 and 60; however, this cycle may be periodically interrupted over a female’s lifespan due to pregnancy, amenorrhea, the effects of hormonal birth control, of a combination of other factors.  The average menstrual cycle spans about 28 days, but in some females it can last anywhere from 24 to 42 days. There are three major phases of the menstrual cycle: the menstrual phase, the proliferative phase, and the secretory phase. A variety of menstrual products have been developed in order to ease the uncomfortable and sometimes painful side effects that may accompany the menstrual phase (also referred to as menstruation or a period).

The Menstrual Phase: The Start of the Cycle

The menstrual phase is the first phase of the menstrual cycle during which the lining of the uterus, called the endometrium, is shed as menstrual flow out of the cervix and vagina. Females experience this process during their menstrual periods, and the menstrual flow itself consists of a mixture of blood, mucus, and tissue from the outer walls of the uterus. The first day of menstrual flow marks the first day of a new menstrual cycle. Menstruation lasts for another 3 to 7 days on average, although some females do experience significantly shorter or longer periods. Menstruation is triggered by reduced levels of the hormones estrogen and progesterone in a female’s body at the end of the previous menstrual cycle. This decline in hormone levels is due to the absence of a fertilized egg implanting on the walls of the endometrium. The onset of a new menstrual period indicates that the female is not pregnant. However, this does not mean that a woman cannot become pregnant during her period; because a female is able to ovulate (release an egg to be fertilized) at any time during her menstrual cycle (even immediately after the end of their period), it is possible to become pregnant at any point in the menstrual cycle. During the menstrual phase, the pituitary gland begins to secrete follicle-stimulating hormone (FSH). Rising levels of FSH trigger the beginning of the next phase, called the proliferative phase.

The Proliferative Phase

Also referred to as the follicular phase, the proliferative phase is the part of the menstrual cycle during which follicles inside the ovaries develop and mature in preparation for ovulation. The levels of FSH increase in the bloodstream during the proliferative phase, stimulating the maturation of follicles. Each follicle contains an ovum, or egg, and although many follicles may grow and increase in size during this phase, only one will reach full growth and release an ovum at the time of ovulation. The name of this phase of the cycle stems from the proliferation of life-nourishing cells in the uterine lining during this time.

Another change that occurs during the proliferative phase involves the ovaries producing a substantial amount of estrogen. The rising levels of estrogen cause the lining of the uterus to thicken. Once the levels of estrogen are at their peak, the pituitary gland slows the secretion of FSH and instead begins to secrete luteinizing hormone (LH). As a result of the increase in LH, the mature follicle ruptures and releases the mature ovum into the fallopian tubes, where the egg begins its winding journey towards the uterus. This process of releasing a mature egg from a follicle is known as ovulation. While ovulation usually occurs 14 days before the beginning of the next menstrual period, individuals with a menstrual cycle shorter than 28 days may ovulate anywhere from 7 to 14 days after the start of their menstrual phase. These individuals may be at a risk of pregnancy right at the end of their period as ovulation is the most fertile time in a female’s menstrual cycle.1

The Secretory (Luteal) Phase

After ovulation occurs, LH causes the burst follicle to develop into a small yellow structure in the ovary called the corpus luteum, which secretes the hormones estrogen and progesterone. These hormones are at at their peak level during the secretory phase, and they prepare the endometrium to secrete the nutrients necessary to nourish a conceptus if a fertilized egg were to implant in it. If conception and implantation do not occur, the pituitary gland will reduce LH and FSH production. Without the presence of LH, the corpus luteum deteriorates and, subsequently, the estrogen and progesterone levels drop rapidly. The drop in estrogen and progesterone levels then triggers the endometrium to shed, causing menstruation to begin and allowing the cycle to start over again at the menstrual phase.

Calendar of a month with red tacks every seven days, with a circle around the last day of the month.

Menstrual Difficulties

Menstruation can be uncomfortable and painful so it can be confusing and frustrating when things seem to go wrong The human body is not without its flaws, and the female reproductive system is a very fragile system susceptible to many problems that could hamper its functioning. In addition to the effects that STI’s can have on the health of the reproductive system and menstruation, there are several problems that females might eventually struggle with during their periods.

Premenstrual Syndrome (PMS)

Premenstrual syndrome (PMS) is a relatively controversial, diagnosable disorder; even though around 75% of females from North America and Europe report experiencing the symptoms of PMS at least once in their lives, researchers cannot determine the root cause of the syndrome. Some studies even suggest that PMS may be a cultural creation rather than a syndrome with a distinct biological explanation.2,3 Even if the exact nature of PMS is still unknown, and even if it might be a cultural syndrome felt strongest by highly feminine females, the symptoms of PMS, which millions of people experience every year, are very real and treatable.3

Even though there is ongoing debate as to whether PMS is due to psychological, sociological, or physiological causes of the menstrual cycle (or some combination of the three), approximately 75% of females report suffering from mild PMS symptoms during their menstrual cycle.4  In addition to the uncertain cause of PMS, the list of reported symptoms is expansive, and sometimes even contradictory. Some of the most common symptoms on the PMS checklist include the following:

  • Lethargy
  • Sadness or mood swings
  • Headaches
  • Lack of interest in sex (or a heightened interest in sex)
  • Bloating
  • Constipation or diarrhea
  • Clumsiness or loss of balance
  • Irritability
  • Anxiety

Some attribute PMS to the female “complaining” and argue that their symptoms are “all in their head.” This mentality is sometimes used to disregard a female’s views, opinions, or complaints by claiming that whenever a female gets moody, they must be premenstrual. These kinds of attitudes discredit the real physiological symptoms that many females actually experience before their period. Even if some cross cultural research suggests that the majority of PMS symptoms are bound to cultural and societal expectations, these symptoms are not fabricated and can be very debilitating for those experiencing them.3

PMS is perhaps the most common menstrual problem. It is estimated that 30 to 90% of females experience mild discomfort during the premenstrual portion of their cycle, while only 5% of females experience no symptoms of PMS. Individuals who have experienced emotional, physical, or sexual abuse early in life are nearly three times as likely to suffer from moderate-to-severe PMS than individuals without a history of abuse, suggesting that the risk of suffering from PMS is modified by or associated with early trauma.5 Even cross-culturally, menstruation is associated with serious emotional and psychological distress. The culprit for these ailments is thought to stem from a malfunction in the production of progesterone, which disrupts the menstrual cycle. This theory is only speculatory as research has failed to prove causation.

Premenstrual Dysphoric Disorder (PMDD)

PMDD is much less common than PMS and is a recognized disorder that can be diagnosed. Approximately 5% of females have severe enough symptoms that qualify as PMDD. A female is not diagnosed unless their daily functioning is impaired. Just like PMS, the exact cause of PMDD is unknown. The disorder PMDD, while it has physical symptoms, is considered a distinct type of depressive disorder and is applied to a female only when they consistently have five or more of the following symptoms during the week before their period:

  • Sad or hopeless feelings
  • Tense or anxious feelings
  • Marked mood changes
  • Frequent irritability or anger and increased interpersonal conflicts
  • Decreased interest in usual activities
  • Lack of concentration
  • Lack of energy
  • Lack of appetite
  • Insomnia or sleepiness
  • Feelings of being overwhelmed or out of control
  • Swollen breasts
  • Headaches
  • Muscles pain
  • A “bloated” sensation
  • Weight gain

While the causes of PMDD are still unknown, there are a number of treatment options that relieve the symptoms and interrupt the disorder from manifesting during the menstrual cycle. One of these treatments relies on the use of antidepressant medications to modulate the levels of serotonin in the brain as PMDD seems to be linked to an absence of this neurotransmitter during the premenstrual phase of the cycle. Another possible treatment involves the use of hormonal birth control to suppress ovulation and interrupt the menstrual cycle, stopping PMDD and its symptoms from appearing. However, this treatment method might not work for some females that are trying to become pregnant or are opposed to the use of contraceptives. These predilections should be brought up to a doctor when discussing possible treatments for PMDD.


Amenorrhea is the unexpected absence of menstruation, and it is a fairly common problem for females. There are two types of amenorrhea: primary, when a female fails to menstruate at puberty, and secondary, when there is a disruption of an established menstrual cycle with the lack of menstruation for three or more months. Primary amenorrhea is caused by a variety of factors such as a hormonal imbalance, poor health, or a problem with the reproductive organs. Secondary amenorrhea is a condition that can manifest during and after pregnancy (postpartum amenorrhea) and during breastfeeding (lactational amenorrhea). Secondary amenorrhea is also quite common for females who just started menstruating or are nearing menopause. Another kind of secondary amenorrhea is referred to as pathological amenorrhea because it manifests as a pathological absence of menstruation that is unrelated to any known physical causes.

There are many factors associated with the absence of menstruation. Age plays a substantial role in the regularity of a female’s cycle; the greatest variation in menstrual cycles have been found in groups younger than 19 years of age and between 40 and 50 years of age. Another important factor to a female’s reproductive health is nutrition. Extreme malnutrition, either self inflicted by eating disorders or as a result of environment such as famine, can produce temporary amenorrhea. Once malnutrition ends, the female body demonstrates a remarkable potential to recover from damages as menstruation usually resumes shortly after. There is a possibility of later repercussions, such as spontaneous abortions, difficulty birthings, longer postpartum amenorrhea, and reduced fertility.

A female’s psychological state also greatly affects her menstruation cycle. Both prolonged stress and fear can cause amenorrhea. Varying levels of psychological disturbance can lead to a disturbance in the menstrual cycle. These disturbances can include trauma caused by rape, chronic stress, and minor stressors from exams. Some research shows that amenorrhea could be caused by a conscious or unconscious desire to avoid the responsibility and consequences of having a role in reproduction. The last important factor related to secondary amenorrhea is physical activity. The female body has an adaptive mechanism which turns off menstruation in response to strenuous physical conditions, and this is a common occurrence for female athletes. Athletic amenorrhea is connected to rigorous activity, emotional stress of competition, weight loss, and low estrogen levels.

Usually, a female’s main concern with amenorrhea is their fear of being unable to conceive. Amenorrhea does not directly correlate with sterility. It does, however, still have an affect on fertility, but research has yet to fully explain this relationship.


Many people assume that females have a higher tolerance for pain than males as they possess the capacity to undergo the pain and distress of childbirth. Even with a greater tolerance for pain, many females find their periods to be an agonizing ordeal, referring to particularly painful and recurring menstruation as dysmenorrhea. There are two basic types of dysmenorrhea: primary and secondary. The main difference between the two is their underlying cause. Primary dysmenorrhea is caused by the overproduction of prostaglandins, a hormone that causes the muscles of the uterus to contract.6 Symptoms of primary dysmenorrhea are listed below:

  • Abdominal cramping
  • Nausea
  • Vomiting
  • Diarrhea
  • Headache
  • Dizziness
  • Fatigue
  • Irritability

Secondary dysmenorrhea is caused by a variety of factors, such as the presence of an IUD, PID, uterine tumors, obstruction of the cervical opening, or endometriosis (a condition where uterine tissue grows on various parts of the abdominal cavity).6 Secondary dysmenorrhea has a wide range of symptoms:

  • Constant (almost spastic) lower abdominal pain
  • Pain in the back and thighs
  • Painful intercourse
  • Abdominal cramping

There are many ways to treat the symptoms of dysmenorrhea including taking pain relieving medications, using a heating pad on the lower back or abdomen, avoiding caffeine and alcohol, getting a massage against the lower back or abdomen, and getting more rest during menstruation. For most females, the symptoms of dysmenorrhea eventually subside as they become older and after they experience the labor of childbirth.


Spotting occurs when the uterus sheds blood intermittently between periods. Alternative names for spotting include abnormal uterine bleeding, bleeding between periods, intermenstrual bleeding, and metrorrhagia. Spotting can cause anyone a great deal of concern and anxiety, but it is a common that females experience it sometime during their otherwise healthy and regular menstrual cycle.

If an individual experiences spotting, they should first make sure that the bleeding is coming from the vagina and not from the rectum or urethra so that they may properly understand the situation and relay accurate information to a doctor if necessary. To check if the bleeding is coming from the uterus, insert a clean tampon inside the vagina, remove it, and inspect it for any traces of blood. Do not douche as it can cause additional pain and discomfort. Spotting is a natural process and should be left to run its course; however, if the pain or discomfort becomes too much to handle, contact a physician to seek treatment options.

Spotting may occur for a variety of reasons, including stress, changes in hormone levels (which may be linked to hormonal birth control use), IUD use, poor diet, excessive exercise, or lack of proper lubrication during sex. Inadequate lubrication can cause small tears inside the vagina that may lead to bleeding. This problem can be easily remedied by using a lubricant, such as KY Jelly or Astroglide. It is common for females to experience spotting for a few days before or after their period. Spotting usually stops once the problem is identified and treated, but it may also stop naturally over time.

Spotting is common during the first month or two of starting hormonal birth control pills or when switching birth control methods. When an IUD is first inserted, cramping and spotting are common complications.

If spotting becomes incessant, painful, or problematic, consult a physician who can ascertain the cause of the bleeding through a careful exam. Doctors are able to give the best evaluation while the bleeding is occurring, so do not wait for the bleeding to stop before contacting a doctor. In order to keep track of how much bleeding is occurring, a female can count the number of pads and tampons used to control the bleeding. Share this information with the physician if the bleeding becomes heavy, painful, or problematic. See a doctor to find out whether or not your spotting is a sign of a larger problem.

Problematic occurrences for vaginal spotting are listed below:

  • Ectopic Pregnancy
  • Low Thyroid Function
  • Injury or disease to the vaginal opening caused by intercourse, infection, uterine fibroids/polyps, genital warts, ulcers, varicose veins, insertion of foreign objects, or malignancy
  • Cervical Conization or cauterization procedures
  • Drugs such as anticoagulants

The following individuals should contact their physician immediately if they notice any vaginal bleeding or spotting: pregnant individuals, postmenopausal females, or those that experience bleeding alongside other unusual or unexpected symptoms. Any vaginal bleeding among people in these categories may be an indication of a more serious problem that should be dealt with at soon as possible.

At a young age, and especially for the first few years after menarche, it is normal for menstruation to fluctuate. Sometimes the distinction between spotting and a “light period” may be unclear. A light period is not as heavy as a normal period but still requires a change of regular pads or tampons a few times during the day. Spotting would involve wearing light tampons or pantyliners and having to change them only a couple times during the day.

If a female is experiencing pain along with spotting, they should refrain from taking aspirin, because it acts as a blood thinner. Instead, they should contact their physician for immediate care.

Close-up of a person's abdomen with their hand over it, appearing to be rubbing it.

Concluding Remarks

While it may sometimes seem that the female reproductive system has a mind of its own, the menstrual cycle is a delicate, yet beneficial process that refreshes and prepares the body for reproduction. Many females experience some kind of menstrual problem at some point in their lives including amenorrhea, dysmenorrhea, and spotting, but there are many things that can be done to alleviate the unpleasantness of periods. Moderate and proper exercise can help both body and mind. Cutting back on salty foods helps reduce water retention and bloating, and many vitamins and minerals often alleviate cramping. It is a good practice to keep a written record of your past periods in order to track the symptoms, length of cycles, stresses, etc. There may be a pattern between menstrual difficulties and aspects of your own life. For example, you might find, as many people do, that exercise throughout the month helps mitigate period pain.

If your menstrual cycle is causing you great discomfort, it might be a good idea to see a doctor. Prescription drugs and over-the-counter medications are available to help alleviate menstrual pain and regulate cycles. Depending on the diagnosis your doctor gives you, there should be a variety of treatment options available. So although the topic may be embarrassing and somewhat uncomfortable to talk about, consult your doctor about any problems related to you or your partner’s menstrual cycle.


  1. “Can You Get Pregnant on Your Period?” American Pregnancy Association, 2 Sept. 2016.
  2. Steiner, M. (2000). Premenstrual syndrome and premenstrual dysphoric disorder: guidelines for management. Journal of Psychiatry and Neuroscience; 25(5): 459–468.
  3. Cosgrove, Lisa, and Bethany Riddle. “Constructions of Femininity and Experiences of Menstrual Distress.” Women & Health, vol. 38, no. 3, 2003, pp. 37–58.
  4. Casper, Robert F. “Patient Education: Premenstrual Syndrome (PMS) and Premenstrual Dysphoric Disorder (PMDD) (Beyond the Basics).” UpToDate, 6 Mar. 2017.
  5. Bertone-Johnson, Elizabeth R. et al. “Early Life Emotional, Physical, and Sexual Abuse and the Development of Premenstrual Syndrome: A Longitudinal Study.” Journal of Women’s Health 23.9 (2014): 729–739. PMC. Web. 30 Apr. 2018.
  6. “What Is Dysmenorrhea / Menstrual Cramps | Cleveland Clinic: Health Library.” Cleveland Clinic, 13 July. 2014.

Last Updated: 29 May 2018.