How Estrogen and Progesterone Impact Your Cycle

Written by:, PhD, Founder and Inventor of the Proov test — the first and only FDA-cleared test to confirm successful ovulation at home.

Hormones are chemical substances circulating in the bloodstream, telling the different body organs what to do and when to do it.  They regulate bodily functions, including growth and development, sexual function, reproduction, metabolism, sleep, mood, and menstruation. 

Estrogen and progesterone are two main sex hormones that control the menstrual cycle. 

Here’s what you need to know about these hormones, how they impact your cycle, and why having optimal levels of these hormones at every phase of your cycle matters.  

How estrogen and progesterone impact your cycle

Here's what you need to know about estrogen and progesterone!

What is estrogen? 

Estrogen is a hormone that plays a vital role in sexual and reproductive health, mainly in women. Although this hormone can be found in all sexes, it’s known as a female sex hormone.

Before you reach menopause, the ovaries are the organs that produce most of the estrogens in your bloodstream. The adrenal gland (small glands that stay on your kidneys) and body fat make estrogen. And when you’re pregnant, the placenta (a temporary organ in the uterus formed during pregnancy) will secrete estrogen too. 

Although estrogen is a sex hormone, it plays a part in overall health and bodily function. This hormone supports bone health, hair growth, heart health, immune function, fertility, brain function, and skeletal growth. 

How does estrogen impact your menstrual cycle?

Hormones coordinate different activities in the body — the estrogen hormone is responsible for regulating the menstrual cycle. 

Estrogen levels vary by person and rise at different times during the menstrual cycle. So it's normal for these levels to fluctuate during the menstrual cycle.

The menstrual cycle exists in three phases: the follicular phase (before the release of the egg), the ovulatory phase (egg release), and the luteal phase (after the release of the egg).

Estrogen levels peak in the later part of the follicular phase and go up again in the luteal stage. 

At the beginning of the menstrual cycle, during the follicular phase, estrogen levels are low. Here’s why: estrogen thickens the uterus to the possibility that a fertilized egg will attach and grow in the uterus. When implantation doesn’t occur, estrogen levels decline, causing the top layers of the uterine lining to break down and shed, leading to period.

During the follicular phase, follicle-stimulating hormone rises, causing follicles (fluid-filled sacs that house eggs) in the ovaries to grow. The follicle growing faster than the others, also called the dominant follicle, starts secreting estrogen which leads to a steady rise in estrogen levels. 

As estrogen levels increase, follicle-stimulating hormones decline, causing all except the dominant follicle to die. This rise in estrogen levels nurtures the uterus for implantation and stimulates the sudden surge in the luteinizing hormone. 

The cycle then goes into the ovulatory phase, marked by a surge in luteinizing hormones. This surge in the luteinizing hormones causes the dominant follicle to rupture and release an egg.

Enter the luteal phase. During this phase, the ruptured follicle grows into a temporary hormone-secreting organ called the corpus luteum. This gland produces more estrogen. 

High estrogen levels in this phase cause:

  • The uterine lining to thicken so that if the released egg gets fertilized, it can attach to the uterus. 
  • The milk ducts to become larger. The breasts may become swollen and sore as a result.  
  • The cervical mucus to thin so that sperm can travel easily to meet and fertilize an egg. 

If no pregnancy occurs, the corpus luteum breaks down after about 14 days. Estrogen levels decline and a new cycle starts. 

But, what about progesterone? Let's dive in!

How estrogen and progesterone impact your cycle

Estrogen is produced throughout the cycle, but is more dominant during the first half. 

What is progesterone? 

Progesterone is another female sex hormone that regulates the menstrual cycle. The corpus luteum makes most of this hormone. The adrenal glands and placenta during pregnancy are the other organs that produce progesterone. 

In addition to regulating the menstrual cycle, progesterone prepares the body for pregnancy and helps it carry the pregnancy to term. Some even call it the pregnancy hormone

Asides from coordinating menstruation and reproduction, progesterone impacts other functions in the body. This hormone supports bone health, heart function, immune health, metabolism, and the central nervous system.  

How does progesterone impact the menstrual cycle? 

Like estrogen, progesterone levels fluctuate throughout the menstrual cycle, peaking in the luteal phase and dropping in late-luteal and early follicular stages.

During the luteal phase, the corpus luteum produces large amounts of progesterone. This hormone gets to work immediately to ready the body for pregnancy. Here’s what it does:

  • It creates a healthy uterine environment so the uterus can host and nourish a fertilized egg.
  • It thickens the cervical mucus so that sperm or bacteria won’t enter the uterus.
  • It causes a slight rise in basal body temperature (body temperature when resting). This temperature stays high until you have your period. 

If pregnancy occurs, the corpus luteum continues to produce progesterone till the 7th to 9th week of pregnancy, when the placenta takes over. 

If pregnancy doesn’t occur, the corpus luteum dies off, and progesterone levels drop. This decrease in progesterone causes the uterine lining to shed, leading to menstruation and a new menstrual cycle.  

How estrogen and progesterone impact your cycle

A decrease in progesterone causes the uterine lining to shed, leading to menstruation and a new menstrual cycle. 

Why having the right balance of estrogen and progesterone is important

When your body produces too much or too little estrogen and progesterone during the menstrual cycle, your hormone levels become imbalanced. Imbalanced hormone levels can cause menstruation-related problems like irregular or no periods and heavy periods.

Low estrogen levels may cause a person to experience symptoms like:

  • Hot flashes and night sweats
  • Sore breasts
  • Weak bones
  • Poor mood
  • Vaginal dryness
  • Irritability
  • Headaches before or during period
  • Trouble sleeping
  • Low sex drive
  • Painful sex

High estrogen, on the other hand, may cause irregular periods. It may also worsen symptoms of conditions like:

  • Ovarian cancer
  • Endometriosis 
  • Insulin resistance
  • Polycystic ovarian syndrome (PCOS)

Low progesterone may also affect a person’s health. It may lead to problems with getting pregnant or carrying a healthy pregnancy. Miscarriage, early labor, and ectopic pregnancies (pregnancy where the fertilized egg attaches outside the uterus) are issues tied to having too little progesterone hormone. 

A person with low progesterone levels may also experience symptoms like:

Estrogen and progesterone are two female sex hormones that regulate the menstrual cycle. They work in sync to ensure that you have your periods at regular times. If you’re trying for a baby, they make it more likely that you’ll have one sooner than later. Having them in the right balance promotes reproductive health and overall wellbeing. 

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