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

progesterone luteal phase womans cycle

Progesterone is the leading hormone in the luteal phase, the second half of a woman’s cycle. 

If you’re familiar with Proov, you’ve probably heard us say a thing or two about progesterone. After all, it is our favorite hormone!

While progesterone may not be new to you, have you ever wondered exactly what progesterone does? In today’s blog, we’re describe what progesterone does and why it’s so important!

What is progesterone?

Progesterone is one of the key female reproductive hormones that is involved in your cycle, conception, and pregnancy. Progesterone is also the hormone that confirms ovulation.

Hormones in your menstrual cycle

During a woman’s cycle, there are two main hormones at play: estrogen and progesterone. In the follicular phase, that’s the first half of your cycle, estrogen is high and progesterone is low. 

Menstrual Cycle
Menstrual cycle diagram. Woman health concept. Menstruation phases. Ovum development. Pergnancy and ovulation medical poster for clinic. Flat vector illustration. Female reproductive system.

There are two main hormones at play during your cycle: estrogen and progesterone.

After ovulation occurs the corpus luteum produces progesterone during the second half of your cycle — the luteal phase. The rises and falls in progesterone levels help to regulate your cycle and your period.

If you successfully conceive, progesterone will remain high throughout the implantation window and during early pregnancy. But, if you don’t conceive, progesterone levels will drop, the uterine lining will begin to shed, and your period begins. 

But what exactly does progesterone do?

As we said earlier, estrogen rises during the follicular phase and progesterone rises during the luteal phase. After estrogen thickens the uterine lining (also known as the endometrium) in the first half of your cycle, progesterone stabilises and prepares the lining for implantation during the second half. Basically, progesterone makes the uterine lining “sticky” enough to allow an embryo to implant, if conception does occur.

Progesterone also creates a healthy uterine environment in which an embryo can thrive. After implantation has occurred, the corpus luteum keeps producing progesterone into early pregnancy. 

Progesterone creates a healthy uterine environment in which an embryo can thrive.

During early pregnancy, progesterone stimulates the blood vessels in the uterine lining to secrete special proteins to bring nutrients to a growing fetus. Progesterone also suppresses your immune system so that the embryo isn’t recognised as a foreign body and attacked by the immune system. 

Once the placenta develops, during around weeks 8-12 of pregnancy, it takes over the production of progesterone from the corpus luteum. This keeps the levels elevated throughout pregnancy. In the later stages of pregnancy, progesterone suppresses ovulation and encourages the growth of milk-producing glands in the breasts. But, progesterone also prevents lactation from occurring until the breast milk is needed. 

How much progesterone do I need?

The amount of progesterone needed changes through the different phases of your cycle and fertility journey. Understanding baseline progesterone levels can help you better understand your body — and show up potential problems sooner rather than later.  

During the follicular phase, progesterone levels are low at about 1.5 ng/mL. After ovulation occurs, progesterone levels should rise to about 10 ng/mL, which is the widely accepted progesterone level at which conception can occur. 

If you do successfully conceive, you’ll want progesterone levels to continue to rise. Some medical centers suggest that progesterone should get to about 44 ng/mL during the first trimester of pregnancy.

If you have questions or are concerned about your progesterone levels, we recommend consulting your doctor!

How can I measure my progesterone levels?

Understanding your progesterone levels is a critical component of trying to conceive! This is why testing progesterone is so important.

Progesterone is a critical hormone when it comes to trying to conceive and understanding your levels can help you get pregnant faster.

There are two ways to measure progesterone levels: quantitatively and qualitatively. Here’s a quick breakdown of each:

Quantitative progesterone testing

A way to measure progesterone qualitatively is through a serum progesterone in your blood. These tests are typically taken on cycle day 21, or about 7 days after ovulation, when progesterone should be high. Serum tests are most often ordered by a doctor and give a quantified progesterone level — i.e. 10 ng/mL.

But, serum progesterone tests do have their limitations. These tests only show progesterone levels at one point in time. Studies show that serum progesterone levels can fluctuate up to 8 times in one day, so a one-time blood test could give you an inaccurate assumption about your levels depending on what time of the day you have it done. 

Qualitative progesterone testing

PdG testing, on the other hand, is a qualitative way to measure progesterone. PdG is the urine metabolite of progesterone. After progesterone circulates through the bloodstream, it gets metabolised, or broken down, by the liver into urine. PdG levels in first morning urine directly correlate to the average progesterone levels of the day before.

PdG tests are qualitative, meaning they’ll only turn positive when enough PdG is present in urine. A positive PdG test confirms ovulation and because these tests measure levels in urine, you can test non-invasively over several days to see a more complete picture of your PdG (and therefore progesterone) levels. 

But what if my progesterone levels are low?

If you suspect your progesterone levels are low, we recommend consulting your doctor as low progesterone can make it more difficult to get pregnant. They may want to run additional hormone tests.

You can read about natural ways to increase your progesterone here. There are a few ways to increase progesterone:

Seed cycling: Seed cycling involves eating certain seeds during certain phases of your cycle to promote a hormone balance. Eating pumpkin and flax seeds during the follicular phase promotes estrogen production, while sunflower and sesame seeds promote progesterone during the luteal phase.

Diet changes: While foods don’t directly contain progesterone, some have been shown to boost progesterone production. Some foods to try include nuts, spinach, kale, beans, and broccoli.

Herbal supplements: Herbals such as vitex (chasteberry), maca, and red raspberry leaf have been shown to help raise progesterone levels. 

Prescription supplements and medications: If you are in need of stronger progesterone support, we recommend consulting your doctor, as he or she could provide you with prescription-strength medications. 

Progesterone is a vital hormone when trying to conceive and having a better understanding of what it does can help you get pregnant faster!

We have reposted this blog with permission and minor edits from Proov.

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