Overview

corpus luteum during menstrual cycle — The ovarian cycle and formation of the corpus luteum.

What is your corpus luteum?

Your corpus luteum is a completely normal cyst that forms on the ovary every single month in women of childbearing age. This cyst is actually a group of cells inside your ovaries that forms during each menstrual cycle. It appears right after an egg leaves your ovary (ovulation). Although it’s inside your ovaries, the corpus luteum’s job is to make your uterus a healthy place for a fetus to grow. It releases a hormone called progesterone that prepares your uterus for pregnancy. Once it’s no longer needed to make progesterone, your corpus luteum goes away.

Function

What does your corpus luteum do?

Your corpus luteum forms after your ovaries release an egg and lasts just long enough to help your uterus support a developing fetus. To understand what your corpus luteum does, it helps to understand the phases of your menstrual cycle. Your corpus luteum becomes especially important in the third phase (luteal phase).

Follicular phase

Small sacs inside your ovaries called follicles can create eggs (ova or oocytes). During the first 14 days of your menstrual cycle, a dominant follicle forms that’s bigger than the other follicles. An egg develops inside it. All the other follicles shrink and eventually disappear.

Ovulation Phase

Luteinizing hormones cause the dominant follicle to release that egg. It takes anywhere from 1 to 2 days for the egg to leave the follicle.

Luteal Phase

The luteal phase lasts for about 14 days. After the egg has left the follicle, your corpus luteum starts to form from the materials that made up that follicle. Your corpus luteum produces the hormones estrogen and progesterone. Making progesterone is the corpus luteum’s most important job, though. Progesterone changes the uterus into a healthy environment for a fetus to develop and grow. Progesterone:

Makes your uterus bigger.
Thickens the lining of your uterus (endometrium) so that a fertilized egg can embed there (implantation).
Keeps your uterus supplied with enough oxygen and blood so that an egg can develop into a healthy fetus.

After it forms, your corpus luteum does one of two things:

If the egg gets fertilized, your corpus luteum will release progesterone for about 12 weeks. Around week 12 in your first trimester of pregnancy, the organ that holds the developing fetus (placenta) will start to produce enough progesterone for the fetus so that the corpus luteum doesn’t need to anymore. The corpus luteum will get smaller and start to break down.
If the egg doesn’t get fertilized, your corpus luteum will start to break down around 10 days after the egg leaves the dominant follicle. Without the progesterone, your uterus lining won’t go through the changes that support pregnancy. Instead, you’ll shed the lining during your period.

Anatomy

What does the corpus luteum look like?

Your corpus luteum is inside your ovaries, where the dominant follicle used to be. Most people imagine a follicle as tunnel-shaped, like a hair follicle, but the follicles inside your ovaries are different. Imagine each follicle as a tiny sac that can hold a developing egg. When the egg escapes your dominant follicle during ovulation, that sac breaks. A saffron-yellow mass of cells forms where the follicle once was, sealing the break and taking shape as a new structure. This new structure, your corpus luteum, can range anywhere from a little under 2 centimeters to 5 centimeters as it grows.

What is the corpus luteum made of?

There are two main types of cells in your corpus luteum: follicular theca cells and follicular granulosa cells. Both kinds of cells can be found in the follicles in the ovaries. A hormone called human chorionic gonadotrophic (HCG) spurs these cells to make progesterone.

Conditions and Disorders

What are the common conditions and disorders that affect the corpus luteum?

Sometimes, your corpus luteum will keep growing instead of breaking down when it should. When this happens, your corpus luteum fills with fluid, creating a corpus luteum cyst. A corpus luteum defect, also called a luteal phase defect, happens when your corpus luteum doesn’t produce enough progesterone for the uterus lining to thicken. Or, your body may be producing progesterone, but the progesterone just isn’t making the uterus lining thicken like it should.

Corpus luteum cysts:

Are usually painless and harmless.
Are most often discovered by your provider during a routine pregnancy exam.
Can affect people who menstruate, whether they’re pregnant or not.
Usually go away on their own by the second trimester if you’re pregnant.
Usually go away within a few weeks up to three complete menstrual cycles if you’re not pregnant.

A corpus luteum defect may make it difficult for you to get pregnant or have a baby. It's been linked to certain conditions, characteristics, and behaviors, but there isn’t one clear-cut thing that causes it. These include:

Having a condition like anorexia nervosa, endometriosis, polycystic ovary syndrome.
Having a body mass index (BMI) that’s too high or too low.
Engaging in too much exercise.
Dealing with an unhealthy amount of stress.

What are common signs or symptoms of conditions involving the corpus luteum?

If your corpus luteum causes symptoms, a cyst is the most likely culprit. Corpus luteum cysts are usually harmless and painless. They usually go away on their own. But, sometimes they can be uncomfortable. Symptoms include:

Pain in your pelvis.
Fullness in your abdomen.
Pain when you poop or pee.
Pain on one side of your body.
Aching in your low back and low body.
Pain during intercourse (dyspareunia).
Bloody discharge when you’re not having your period.
Tenderness in your breasts or on one side of your body.

Having trouble getting pregnant or maintaining your pregnancy may be a sign that your corpus luteum isn’t producing the progesterone your uterus needs for an egg to implant in the lining.

What are some common tests to check the health of my corpus luteum?

Often, providers find corpus luteum cysts during pelvic exams or as part of routine imaging during pregnancy. If your provider thinks that issues with your corpus luteum are affecting your fertility, they may order:

A transvaginal ultrasound to measure the thickness of your uterus lining.
Tests to measure your hormone levels, especially follicle-stimulating hormones (FSH), luteinizing hormones (LH), and progesterone.

What are common treatments for conditions involving the corpus luteum?

Your doctor may remove a corpus luteum cyst if it’s painful or if it grows so big that it could pose risks. Usually, though, cysts go away on their own. If your corpus luteum isn’t making enough progesterone, your provider may recommend that you take chorionic gonadotrophic (HCG) hormone or clomphene citrate. Both hormones jumpstart processes in your body that encourage your corpus luteum to make progesterone. Or, your provider may recommend you take progesterone supplements. Talk with your provider about the best options available to you.

Care

What are some simple lifestyle tips to keep my corpus luteum healthy?

Don’t worry about keeping your corpus luteum healthy. After all, you’ll get a new one with each menstrual cycle. Instead, focus on doing things that keep your hormone levels balanced. The good news is that many of the behaviors that make for a healthy lifestyle also help keep your hormones in good shape.

Get plenty of high-quality sleep.
Exercise regularly, taking special care not to overexert yourself.
Eat healthy, balanced meals each day, including lots of protein and good fats.
Learn ways to manage stress so that it doesn’t throw your hormone levels out of balance.

A note from Cleveland Clinic

Your corpus luteum plays an important role in your pregnancy. The progesterone that it makes during the first trimester of pregnancy makes it possible for an egg to develop into a healthy fetus. This is just one reason why it’s so important to keep your hormone levels healthy, so that your corpus luteum can do this important work if the time comes.

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Corpus Luteum