Body Changes During the Menstrual Cycle

Up to two weeks before a menstrual period, hormone-driven changes in the body trigger a collection of premenstrual symptoms (PMS). These changes can cause cramps, breast pain, fatigue, mood swings, and upset stomach. Individual symptoms may vary since everyone's menstrual cycle is unique.

Other body changes during the menstrual cycle are less obvious. The menstrual cycle is controlled by several hormones, including estrogen and progesterone, which are produced by follicles in the ovaries. Hormone shifts throughout the month may affect your mood and energy levels.

This article explains what happens to your body on your period. It breaks down the four phases of the menstrual cycle, explaining how key events that occur during each phase of the menstrual cycle may affect you.

What Happens to Your Body on Your Period?

Your period is just one part of the menstrual cycle. The menstrual cycle consists of four distinct phases:

• Menstrual phase
• Follicular phase
• Ovulation
• Luteal phase

Here's what changes happen in the body during each phase of the menstrual cycle:

Menstrual Phase

The first phase of the menstrual cycle is the menstrual phase, also known as your period. The menstrual phase starts on day one when you get your period, and ends when your period stops, usually around days five to seven.

During this phase, the lining of the uterus, the endometrium, thickens in preparation for pregnancy. If pregnancy does not occur, the endometrium needs to "reset" by shedding its excess lining.

Leading up to a period, increased levels of the hormone progesterone widen milk ducts in the breasts and prepare the uterus for pregnancy. When implantation doesn't occur, progesterone levels quickly withdraw, triggering the endometrium to shed and the period to begin.

While on your period, you may feel one or more of the following symptoms:

• Abdominal or pelvic cramps
• Lower back pain
• Bloating
• Sore breasts
• Food cravings
• Mood swings and irritability
• Headache
• Fatigue
  

Follicular Phase

The second phase of the menstrual cycle is the follicular phase. This phase overlaps with your menstrual phase, beginning on day one with your period and ending when you ovulate, around day 14.

An ovarian follicle is a small, fluid-filled sac in the ovary that contains an egg. The ovaries contain about 400,000 follicles by the time puberty begins.

During the start of the follicular phase, the anterior pituitary gland triggers rising levels of follicular stimulating hormone (FSH). FSH causes several ovarian follicles to undergo maturation. Between days 10 to 14 of the menstrual cycle, just one ovarian follicle will fully mature into an egg.

It's also during this phase that progesterone decreases and estrogen peaks, causing the endometrium to thicken in preparation for ovulation.

Decreased progesterone levels may have a positive effect on you. Research shows that lower progesterone levels are linked to greater strength, power, and energy in athletes during the follicular phase of their cycles.

Ovulation

The third phase of the menstrual cycle is ovulation, occurring around day 14 of a 28-day cycle. During this time, luteinizing hormone (LH) levels suddenly surge, triggering ovulation within about 24 to 48 hours. Estrogen levels decrease during the LH surge while progesterone begins to rise again.

Ovulation occurs when the dominant ovarian follicle, containing a fully-matured egg, bursts, releasing the egg into the fallopian tube where it can be fertilized by a sperm.

Sperm is viable for approximately three days, but the released egg is only viable for one—the day of ovulation. Therefore, conception is most likely to occur if you have intercourse in the three days leading up to ovulation.

Cervical mucus is a common symptom of ovulation. You may notice it in your underwear or when you use the restroom. The discharge is typically clear, stretchy, and slippery like a raw egg white.

Luteal Phase

The fourth stage, called the premenstrual or luteal phase, occurs around day 15 of the menstrual cycle. It lasts about 14 days and ends when you get your period.

During the luteal phase, the follicle that released an egg in ovulation changes into a structure called the corpus luteum. This structure produces progesterone and estrogen. The rising hormone levels help thicken the endometrium.

If the egg is not fertilized with sperm, the corpus luteum dissolves, hormone levels decline, and the endometrium gets ready to shed. A period then marks the end of the luteal phase and the start of a new menstrual cycle.

According to an article published by the Harvard Review of Psychiatry, anxiety, stress, and binge eating may occur more frequently during the luteal phase.

Hormones and Your Menstrual Cycle

The menstrual cycle starts with your endocrine glands because they produce the hormones that determine when you get your period, the amount of menstrual flow, and what happens to your reproductive organs.

The area of the brain called the hypothalamus connects your nervous and endocrine system by way of the pituitary gland, which also is in the brain, and controls the hormones necessary for reproductive health and your period.

Six hormones serve as chemical messengers to your reproductive system:

1. Gonadotropin-releasing hormone (GnRH)
2. Follicle-stimulating hormone (FSH)
3. Luteinizing hormone (LH)
4. Estrogen
5. Progesterone
6. Testosterone

During your menstrual cycle, the hypothalamus first releases GnRH. This causes a chemical reaction in the pituitary gland and stimulates the production of FSH and LH.

Your ovaries produce estrogen, progesterone, and testosterone (yes, the "male" hormone) in reaction to stimulation by FSH and LH. When these hormones work harmoniously, normal menstrual cycles occur.

Summary

The average menstrual cycle is 28 days long. Each menstrual cycle is comprised of four distinct phases: the menstrual and follicular phases, ovulation, and the luteal phase.

Shifts in estrogen, progesterone, and other reproductive hormones can cause various symptoms throughout the month. Premenstrual symptoms like cramps and fatigue as well as clear discharge during ovulation are common. You may also notice changes in your mood and energy levels, particularly during the follicular and luteal phases.

A Word From Verywell

It is normal to have some uncomfortable symptoms at various times in your menstrual cycle, but only to a certain degree. If you are doubled over in pain or your symptoms are interfering with your life, considering seeing your healthcare provider or a gynecologist to rule out the possibility of another underlying cause. Some conditions like endometriosis can cause severe pain that isn't normal and must be treated.