Menstrual Cycle Phases and Hormones
Most women who have entered their reproductive years experience a menstrual cycle. The menstrual cycle is the body’s way of preparing for pregnancy. The only times a woman won’t have a regular menstrual cycle (referred to as amenorrhea) is during pregnancy, breastfeeding, or after menopause.
The menstrual cycle consists of four main stages and each stage is caused by the release of certain hormones. Hormones are chemical messengers found in the body and are responsible for the transition from one menstrual phase to the next.
Depending on which hormones are present is directly related to how you feel mentally, emotionally, and physically at any given time of the month.
How Hormones Affect You During Your Menstrual Cycle
Your monthly menstrual cycle can be divided into four important phases, each governed by a different cocktail of hormones. If your menstrual cycle was a 4 part symphony, your hormones would be the musicians; they control the mood and tone at any given time of the month.
Main Hormone(s) Involved
Estrogen and progesterone
Follicle Stimulating Hormone (FSH), estrogen, and progesterone
Luteinizing Hormone (LH)
Progesterone and Human Chorionic Gonadotropin (if fertilization occurs)
The average menstrual cycle is 28 days, and the first day of menstruation (or the menstrual phase) signifies Day 1 of your cycle. Having said that, many women experience cycles as short as 21 days or as long as 35 days. Moreover, many women experience irregular menstrual cycles, which can be caused by many factors. Do not be alarmed if your body doesn’t run like steady clockwork month to month.
Let’s dive deeper into each of the 4 main phases of the menses cycle, the role of hormones, and how they might make you feel during each particular phase.
During menstruation, your female sex hormone levels (estrogen and progesterone) take a nosedive. This radical drop in hormone levels causes the collapse of your uterine lining. During menstruation, your uterus then sheds its lining (endometrium) alone with the unfertilized egg through the vagina.
The first day of menstruation represents Day 1 of your cycle and typically lasts about 5-7 days. It’s more commonly referred to as your period.
Signs & Symptoms of the Menstrual Phase
As a result of the sudden drop in female sex hormones, the menstrual phase is often the phase when you’ll experience the most dramatic symptoms. During your menstrual phase, you may experience all or none of the following.
- Abdominal cramps
- Breast tenderness
- Bloating or fluid retention
- Lower back pain
- Diarrhea or constipation
- Low energy, fatigue
- Cravings for specific foods
- Mood swings
- Trouble sleeping
The follicular phase of your cycle includes menstruation and extends to the ovulation phase, at around Day 14.
During this phase, your pituitary gland releases Follicle Stimulating Hormone (FSH). FSH does exactly as its name implies—stimulates follicle growth on the ovaries. About 5-20 tiny follicles collect on the ovary’s surface, each containing an egg. Only one of those eggs will mature into an oocyte that is released when you ovulate.
The follicles trigger a surge of estrogen and progesterone that stimulates the uterine lining to thicken in preparation for a possible pregnancy.
How You Might Feel During the Follicular Phase
You’re in luck! Aside from the menstrual phase (Day 1-7), the changes occurring in your body during the rest of the follicular phase (Day 8-13) are typically not observed.
Ovulation is the phase of the menstrual cycle when you’re most fertile—and you have Luteinizing Hormone (LH) to thank for that!
LH is released by the brain’s pituitary gland in the days leading up to ovulation. The surge of LH causes an ovarian follicle to burst from the ovary, travel down the fallopian tube, and become an ovum (or egg). The egg stays there for about 24 hours waiting for a single sperm to fertilize it. At that point, the egg either gets fertilized by a sperm or it doesn’t.
If the egg is not fertilized, pregnancy won’t occur and the corpus luteum withers and dies as the body prepares to shed its uterine lining and start the menstrual cycle over again. This typically occurs around Day 22 of a 28-day menstrual cycle.
Signs & Symptoms of the Ovulation Phase
The symptoms of ovulation are primarily physical, rather than emotional. Women often use devices to detect these changes such as a sensitive thermometer or Ovulation Predictor Kit that measures your levels of LH. Other changes include:
- Drop in basal body temperature falls just before ovulation
- Rise in basal body temperature 24 hours after egg’s release
- Cervical mucus changes indicating when ovulation might occur
- Creamy: Ovulation may be coming
- Wet or watery: Ovulation may start soon
- Wet and stretchy (egg white texture): You may be ovulating
- Your cervix softens and opens up (sometimes known as having a short, high, open and wet cervix or SHOW)
- Slight twinge or cramping (aka “Mittelschmerz”)
- Light spotting (caused by the tiny follicle ruptures when the egg is released)
The luteal phase begins approximately 17 days into your menstrual cycle and lasts around 11 days. After the egg bursts from its follicle during ovulation, the ruptured follicle stays on the surface of the ovary and slowly transforms into a structure called the corpus luteum.
The corpus luteum releases progesterone (along with small amounts of estrogen). These hormones maintain the thickened lining of your uterus, in preparation for the implantation of a fertilized egg. There are two main things that can happen during this phase which determine the hormones that are present:
- The egg is fertilized and implants: If fertilization occurs, the fertilized egg produces a hormone called human chorionic gonadotropin (HCG) hormone. This is the hormone detected during a pregnancy test. The corpus luteum also keeps producing progesterone to maintain the thickened lining of the uterus (endometrium).
- The egg is not fertilized: If the egg isn’t fertilized, the corpus luteum dies. Since the corpus luteum is responsible for releasing progesterone, levels of progesterone drop toward the end of this phase causing the uterine lining to fall away.
Signs & Symptoms of the Luteal Phase
Signs and symptoms of the luteal phase vary depending on whether or not you get pregnant.
The hormones released during this phase are responsible for the symptoms of premenstrual syndrome (PMS). You will notice that a lot of these symptoms are also symptoms of menstruation, such as:
- Bloating and fluid retention
- Breast tenderness
- Mood changes
- Trouble sleeping
Causes of Hormone Imbalances in the Menstrual Cycle
While hormone fluctuations are necessary for the 4 phases of the menstrual cycle to occur, there are circumstances that can lead to hormone imbalances that disrupt your cycle. Factors that can lead to hormone imbalances include medical conditions, emotional factors, and lifestyle choices.
Under normal circumstances, hormone levels change as a woman gets older, ultimately leading to menopause. Menopause typically occurs after the age of 45 and causes periods to stop.
Some of the factors that can disrupt your hormone balance can be easily managed and others may require more extreme treatments. Either way, no need to panic as hormone imbalances are a common occurrence and can be easy to get under control. Here are some of the main reasons for hormone imbalances in women:
- Autoimmune conditions: Conditions that affect your immune system, like rheumatoid arthritis, can have a knock-on effect for the menstrual cycle because they alter your levels of estrogen.
- Polycystic ovary syndrome (PCOS): PCOS prevents an egg from developing normally and leads to a hormone imbalance. Women with PCOS may have infrequent or prolonged menstrual periods or excess male hormone (androgen) levels.
- Birth control & other medications: Hormonal birth control deliberately sets out to interrupt your natural menstrual cycle in order to prevent pregnancy.
- Perimenopause: This is the final stage before menopause (when periods cease completely) and is usually characterized by an irregular menstrual cycle as periods gradually stop. Menopause is diagnosed when you go 12 months without a period.
- Tumors, cysts, or cancers: Anything that affects the natural functioning of the endocrine glands will to hormone imbalances that impact your reproductive cycle.
- Diet: For example, phytoestrogens are naturally-occurring plant estrogens found in soy products. Consuming extremely high levels can affect your cycle.
- Primary ovarian insufficiency (POI): POI is also known as premature ovarian failure. It occurs when a woman stops producing eggs naturally before the age of 40 and is different from menopause.
Signs and Symptoms of Hormone Imbalances In Women
Some reasons for hormone imbalance, such as menopause or pregnancy, are completely natural and no need for concern. Unless you’re on the birth control pill, it’s also completely normal if your cycle doesn’t work like clockwork month-to-month.
However, if you notice any of the following unusual symptoms on a regular basis, it’s advised to consult with your doctor:
- Heavy periods with a lot of clotting (especially clots larger than a quarter)
- Irregular or exceptionally light periods
- Spotting between periods accompanied by abdominal pain or cramping
- Pain or a burning sensation when peeing
- Unusual vaginal discharge and/or redness and itchiness
- Hair loss
- vaginal dryness or pain when you have sex
- Unexplained weight gain
- Hot flashes or night sweats
- Growth of facial hair
- Skin tag formation