Corpus Luteum

What is the corpus luteum?

The corpus luteum is a temporary collection of cells that forms on your ovary each menstrual cycle if you’re still getting a menstrual period. It appears right after an egg leaves your ovary (ovulation).

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, the corpus luteum dissolves and goes away until the next menstrual cycle.

What is the role of the corpus luteum?

The main job of the corpus luteum is to make hormones that support pregnancy — if a pregnancy were to occur that menstrual cycle.

The 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

The follicular phase lasts about 14 days. Small sacs inside your ovaries called follicles create eggs. Eventually, a dominant follicle forms (it’s bigger than the other follicles) and a mature egg develops inside it. All the other follicles shrink and eventually disappear.

Ovulation Phase

Luteinizing hormone causes the dominant follicle to release the mature egg. It takes anywhere from one to two days for the egg to leave the follicle. It’s the shortest phase of your cycle.

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 cells 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 your uterus into a healthy environment for a fetus to develop and grow.

What happens to the corpus luteum if you’re not pregnant?

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

• If sperm fertilizes the egg and a pregnancy occurs (conception), your corpus luteum will release progesterone for about 12 weeks. Around week 12 in your first trimester of pregnancy, the 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 until it goes away completely.
• If sperm doesn’t fertilize the egg, your corpus luteum will start to break down around 10 days after ovulation. Without the progesterone, your uterine lining won’t go through the changes that support pregnancy. Instead, you’ll shed the lining during your period.

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 more sac-like.

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, the 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.

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

The corpus luteum is a mass of cells that any person who menstruates develops each menstrual cycle. The two most common conditions that affect the corpus luteum are a corpus luteum cyst and a corpus luteum defect, also called a luteal phase defect.

Corpus luteum cysts

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 cyst.

Corpus luteum cysts:

• Are usually painless and harmless.
• Are most often discovered by your provider during a routine gynecological 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 if you’re not pregnant.

Luteal phase defect

A luteal phase defect happens when the corpus luteum doesn’t produce enough progesterone to thicken your uterine lining. Or your body may not use the progesterone as it should. A luteal phase defect may make it difficult for you to get pregnant. There isn’t one clear cause of a luteal phase defect, but risk factors for it are:

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

What are symptoms of conditions involving the corpus luteum?

If a problem with 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 by your next menstrual cycle. But sometimes, they can be uncomfortable and cause pain.

Symptoms of a cyst include:

• Pain in your pelvis.
• Fullness in your abdomen.
• Pain when you poop or pee.
• Aching in your low back.
• Pain during intercourse (dyspareunia).
• Bloody discharge when you’re not having your period.

Contact a healthcare provider if you have severe pain or if the pain doesn’t get better within a few weeks.

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

What are some common tests to check the health of the 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 the 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 does a corpus luteum on ultrasound mean?

It’s normal to see a corpus luteum on an ultrasound. Seeing one doesn’t mean there’s a problem.

Does a corpus luteum cyst mean I was pregnant?

No, it doesn’t mean you were pregnant. Any person who menstruates develops a corpus luteum during the first part of their menstrual cycle. A cyst can sometimes develop when the corpus luteum fills with fluid. Most of the time, the cyst goes away without treatment.

What are common treatments for conditions involving the corpus luteum?

Your healthcare provider 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 the corpus luteum isn’t making enough progesterone, your provider may recommend that you take human chorionic gonadotrophic (HCG) hormone or clomiphene 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.

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, such as:

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