Estrogen and Progesterone: Understanding the Role of Each when TTC

We often refer to hormones as a group because they work together, and their balance is essential to good health. 

However, when it comes to two of the most important hormones for women — estrogen and progesterone — it can be helpful to look at them individually. 

In this article, we’ll cover the basics of what estrogen and progesterone do, how they influence reproductive health, and what to do if your estrogen and progesterone levels are out of balance. 

What Are Estrogen and Progesterone?

Estrogen and progesterone belong to a class of hormones called sex hormones — a group of hormones responsible for sexual development and reproductive health. 

In women, estrogen and progesterone are primarily produced by the ovaries, and they influence everything from puberty and breast development to the menstrual cycle, fertility, and pregnancy.

Although these hormones work together, they also support the body in their own unique ways. 

It’s important to note that estrogen and progesterone are not exclusive to women or people who menstruate. However, because other people may not have ovaries or ovulate, their hormone supply is produced in other areas of the body (such as fat tissue or the adrenal glands).

The Purpose of Estrogen and Progesterone

What Does Estrogen Do?

During puberty, estrogen is responsible for female sexual development, triggering the growth of breasts, pubic hair, and other sex characteristics.

After puberty, estrogen plays a key role in supporting the following: 

• In the ovaries, it helps stimulate the growth of the egg follicle. 

• In the vagina, it helps maintain the thickness of the vaginal wall and supports lubrication. 

• In the uterus, it helps control the growth of the uterine lining at the beginning of your menstrual cycle and during pregnancy.

• In the breasts, it helps stop the flow of milk after weaning from breastfeeding. 

In addition to regulating the menstrual cycle, estrogen is also crucial for overall health and helps regulate: 

• Bone metabolism

• Cholesterol metabolism

• Body weight

• Glucose metabolism

• Insulin sensitivity 

• Mood regulation

• Brain functioning

• Skin and hair growth

It’s important to note that there are four different types of estrogen found in the female body: estradiol, estrone, estriol, and estetrol. 

• Estradiol is the most potent form of estrogen, mostly produced by the ovaries during your reproductive years. 

• Estrone is a weaker form of estrogen, produced in the ovaries, adrenal glands, and fat tissue after menopause. 

• Estriol is the weakest form of estrogen, produced by the placenta during pregnancy to support fetal development. 

• Estetrol is a potent form of estrogen, produced by the human fetal liver during pregnancy.

Please note: when we refer to ‘estrogen levels’ in this article, we are referring to estradiol and its role in menstruation, fertility, and overall reproductive health. 

What Does Progesterone Do?

Progesterone is the major hormone in a class of hormones called progestogens, which primarily impact sexual development and reproduction. 

Progesterone is made by the ovaries, placenta (if pregnant), and adrenal glands. 

During your reproductive years, the rise and fall of progesterone helps signal the body to shed the uterine lining, which triggers your period.

During pregnancy, progesterone also helps to:

• Prepare the uterine lining to welcome a fertilized egg. 

• Concentrate cervical mucus to keep harmful bacteria out. 

• Maintain the uterine lining and prevent uterine contractions during pregnancy.

• Priming the mammary glands and milk ducts for breastfeeding. 

Progesterone is the building block of a healthy pregnancy, and in its synthetic or natural-like form, is commonly used as a fertility treatment. It’s also widely used to treat certain health concerns, such as luteal phase deficiency, abnormal uterine bleeding, and easing menopause symptoms. 

The Production of Estrogen and Progesterone

How Is Estrogen Produced?

Estradiol is primarily produced in the ovaries, with small amounts also produced by the adrenal glands and fat tissue. 

During pregnancy, the main type of estrogen produced is estriol, which is primarily made and secreted by the emerging placenta approximately five weeks after implantation. The developing fetus also produces estetrol, which is secreted by the liver. 

During menopause, estrone is the dominant form of estrogen. Estrone is produced by the ovaries, adrenal glands, and fat tissue. 

How Is Progesterone Produced?

Progesterone is primarily produced in the ovaries by the corpus luteum. The corpus luteum is a temporary gland that forms in the ovary after ovulation, and it is made from a follicle housing a maturing egg. 

A small amount of progesterone is also produced by the adrenal glands that sit on the kidneys. During pregnancy, progesterone production also takes place in the placenta.

Estrogen vs Progesterone Levels and Testing

In order to function properly, our bodies rely on our hormones working together in harmony. If estrogen and progesterone levels become out of balance, this not only impacts your reproductive health and fertility, but also your overall health and well-being. 

Common hormone imbalances include:

• Low progesterone, high estrogen — associated with estrogen dominance and polycystic ovary syndrome (PCOS)

• Low estrogen, high progesterone — associated with ovarian cysts and adrenal glands disorder

• Low estrogen and progesterone — associated with perimenopause and menopause. 

Read on for a more detailed look and progesterone and estrogen imbalance. 

Estrogen: What to Know About Estrogen Levels

What’s considered a ‘healthy’ estrogen level will change throughout your life cycle. 

For example, the two types of estrogen responsible for maintaining fertility (estrone and estradiol) change as your body evolves from puberty to the end of your reproductive years. Any irregular estrogen patterns during this time can affect growth, ovulation, fertility, and overall health.

How is estrogen tested?

Estrogen can be tested in blood, urine, or saliva. 

Blood testing is typically conducted by a doctor in order to investigate irregular menstrual cycles, heavy periods, and infertility. It’s also used to monitor high-risk pregnancies. 

Saliva and urine tests can be taken at home. Saliva tests tend to be used to check for estrogen deficiency or estrogen dominance. Urine testing (using a hormone monitor like Mira), tests for the metabolite of estradiol (E3G). This is helpful for monitoring fertility on a more regular basis in order to plan a pregnancy or anticipate menopause. 

What if my estrogen levels are high?

If you aren’t taking hormonal birth control, your estrogen levels will fluctuate dramatically throughout your cycle and can change every day. Even though these fluctuations are normal, as long as your hormones are in balance, you shouldn’t experience any symptoms associated with hormone imbalance. 

If your estrogen levels are too high, you may experience the following symptoms: 

• Irregular periods

• Difficulty getting pregnant

• Fatigue

• Heavier or lighter periods than usual

• Loss of sex drive

• Mood changes

• Unexplained weight gain

• Worsening premenstrual symptoms

High levels of estrogen can also indicate a condition called estrogen dominance, which is common among women with polycystic ovary syndrome (PCOS). Estrogen dominance can occur when either estrogen is too high or progesterone is too low. 

What if my estrogen levels are low?

Low estrogen levels are associated with infrequent or irregular ovulation, which can make it difficult to plan a pregnancy. 

If your estrogen levels are too low, you may experience the following symptoms: 

• Amenorrhea (lack of a period)

• Irregular periods

• Difficulty getting pregnant

• Fatigue

• Hot flashes and night sweats

• Irregular periods

• Loss of sex drive

• Mood changes

• Unexplained weight gain

Low levels of estrogen can also be a sign of certain underlying health concerns, such as ovarian failure, perimenopause, or a pituitary disorder. In some cases, low estrogen may be a sign of an eating disorder. 

What should I do if my estrogen levels are out of balance?

Progesterone: What to Know About Progesterone Levels

Similar to estrogen, progesterone levels change depending on your age, menstrual cycle phase, and pregnancy. 

How is progesterone tested?

Like estrogen, progesterone can be tested in blood, urine, or saliva.  

Doctors can use progesterone blood testing to confirm ovulation, assess fertility, and guide the timing of fertility treatments. In some cases, it’s used in high-risk pregnancies to monitor the health of the pregnancy in the first trimester. The downside to blood testing is that it only provides a snapshot rather than a ‘bigger picture’ of overall progesterone levels, which have even been shown to fluctuate hour by hour. 

Traditional at-home progesterone strips and more advanced fertility monitors like Mira can test for the metabolite of progesterone, pregnanediol glucuronide (PdG). This is helpful for confirming ovulation when planning a pregnancy. 

Please note that urine PdG should only be used for confirming ovulation. Mira Confirm Wands are not designed or approved for monitoring early pregnancy status, miscarriage, fetal health tracking, or other diagnostic uses for which progesterone might be an indicator. 

What if my progesterone levels are high?

Higher than normal progesterone levels can impact fertility by causing low estrogen levels in comparison. The resulting hormone imbalance, called functional estrogen deficiency, may impact your menstrual cycle and ability to conceive. 

If your progesterone levels are too high, you may experience the following: 

• Bloating 

• Breast tenderness

• Difficulty getting pregnant

• Fatigue

• Heavy menstrual bleeding

• Irregular periods

• Low sex drive

• Mood changes

Elevated progesterone levels may also indicate a more serious underlying health concern, such as ovarian cysts, adrenal gland disorder, and certain types of cancer. Elevated progesterone levels may also indicate pregnancy. 

What if my progesterone levels are low?

When progesterone levels are too low, this can cause estrogen levels to become too high in comparison, resulting in estrogen dominance. 

Common symptoms of low progesterone include:

• Amenorrhea (lack of a period)

• Abnormal uterine bleeding

• Difficulty getting pregnant

• Fatigue

• Irregular periods

• Recurrent miscarriages

• Short luteal phase (sometimes referred to as luteal phase defect)

• Worsening premenstrual symptoms

Low progesterone levels can indicate certain underlying health conditions, such as thyroid disorders, perimenopause, and eating disorders. Like high estrogen, low progesterone can also be caused by PCOS.

What should I do if my progesterone levels are out of balance?

Final Thoughts

Understanding your hormones and how they work together is the key to maintaining a healthy hormone balance and navigating your reproductive health. 

If you’d like to learn more, you may find the following resources on our website helpful:

• Library of free blog articles, webinars, and ebooks

• Sex Hormones Awareness Week

• How Mira Works

Frequently Asked Questions

What is the difference between progesterone vs estrogen?

Both progesterone and estrogen support puberty and menstrual cycle regulation. 

Estrogen plays a more active role in egg follicle development ahead of ovulation. Estrogen also supports overall health and well-being, including bone, heart, metabolic, and brain health. 

Progesterone plays a more active role in preparing the uterine lining for pregnancy, maintaining the uterine lining during pregnancy, and preparing the body for breastfeeding. 

Does progesterone lower estrogen?

Progesterone does not directly lower estrogen. Instead, it counteracts or ‘balances’ the effect of estrogen on the body. This helps to regulate the menstrual cycle and prevent symptoms associated with estrogen dominance.

What should I do if I have low estradiol and progesterone levels?

Low estrogen (estradiol) and progesterone levels are associated with perimenopause, menopause, and premature ovarian failure. Common low estrogen and progesterone symptoms include:

• Difficulty sleeping

• Fatigue and brain fog

• Hot flashes

• Irregular periods

• Mood changes

• Night sweats

• Vaginal dryness

If you are over 40 and experiencing signs of menopause, it’s a good idea to speak with your doctor. They can provide guidance on medications, supplements, and lifestyle changes that can help you manage your symptoms. 

If you are under 40 and experiencing signs of menopause, speak with your doctor as this could be a sign of a more serious underlying condition, such as premature menopause or a pituitary, thyroid, or adrenal gland disorder. 

What are the most common high progesterone, low estrogen symptoms?

The most common symptoms of high progesterone and low estrogen include: 

• Bloating 

• Breast tenderness

• Difficulty getting pregnant

• Fatigue

• Heavy menstrual bleeding

• Irregular periods

• Low sex drive

• Mood changes