The Corpus Luteum

What the Corpus Luteum Does + Corpus Luteum Cysts and Deficiency

Illustration of the female repructive system, including the corpus luteum
The corpus luteum forms from the follice the egg released from.. ttsz / iStock Photo

Quick Definition:  After an egg has matured and been ovulated from the follicle, the empty follicle becomes a corpus luteum. The corpus luteum secretes the hormones estrogen and progesterone, preparing the body for the possibility of conception.

If conception does not take place, the corpus luteum diminishes, leading to a drop in progesterone and estrogen. This drop leads to menstruation, and the reproductive cycle starts over again.

How Does the Corpus Luteum Work

To understand how the corpus luteum works, you need to understand what happens during ovulation.

There are two primary phases of the menstrual cycle...

  • The follicular phase: this is when a select number of follicles in the ovary mature, until one releases an egg.
  • The luteal phase: this is post-ovulation, when the body prepares the womb to accept a fertilized egg, or embryo.

(Learn much more about these phases in this explanation of the female reproductive system, this article on follicles, and this article on egg development.)

Just before ovulation, there is a surge in the hormone LH, or luteinizing hormone. This hormone is vital both for ovulation and what happens just after ovulation.

Before ovulation, LH triggers the follicle and the developing egg inside to speed up growth and development. LH also triggers enzymes to begin breaking down the outer walls of the follicle.

 

Eventually, finally, the egg reaches full maturity, and the follicle wall breaks open. This releases the mature egg in a process known as ovulation.

Once the egg is released, LH continues to impact cellular structure of the former follicle.

Before ovulation, granulosa and theca cells in the follicle produce estrogen.

 

However, after ovulation, LH triggers these cells to transform. They begin to release the hormone progesterone.

Progesterone plays an important role in the luteal phase.

Firstly, progesterone signals the pituitary and hypothalamus glands in the brain to slow down production of the hormones FSH, LH, and GnRH.

This prevents additional follicles in the ovaries from developing and ovulating.

Secondly, progesterone prepares the endometrium, or the uterine lining.

Progesterone triggers the endometrium to secrete proteins. These proteins maintain the endometrium and create a nourishing environment for a fertilized egg (or embryo.)

Something else progesterone does is signal your breast tissue to prepare to produce milk. This is why your breasts can be tender after ovulation and before menstruation.

What Happens to the Corpus Luteum If You Get Pregnant? Or If You Don’t?

If you get pregnant, and an embryo implants itself into the uterine lining, a very early placenta is formed.

This early placenta releases the pregnancy hormone hCG.

(That’s the hormone pregnancy tests detect.)

hCG signals the corpus luteum to continue secreting progesterone. The progesterone prevents the endometrium from being expelled and continues to prevent further ovulation.

However, if pregnancy doesn’t occur, the corpus luteum slowly disintegrates. This happens about 10 to 12 days after ovulation, or two to three days before your period starts.

As the corpus luteum breaks down, the cells in the corpus luteum stop producing as much progesterone.

Eventually, the drop in progesterone leads the endometrium to break down. Menstruation begins.

Also, the drop in progesterone signals the pituitary and hypothalamus glands to increase production of FSH, LH, and GnRH.

This restarts your menstrual cycle, and the follicular phase starts anew.

What Is the Corpus Albicans?

When the corpus luteum breaks down, scar tissue is left behind. This scar tissue is known as the corpus albicans. It remains on the ovary for a few months post-ovulation of that follicle.

While the corpus luteum is yellow in color (corpus luteum means yellow body in Latin), the corpus albicans is white.

Corpus albicans means white body in Latin.

What Is a Corpus Luteum Cyst?

You may remember from above that the corpus luteum is formed from the broken open follicle that released an egg during ovulation.

Sometimes, the opening of the corpus luteum seals back up. Fluid fills the cavity and forms a cyst.

This kind of cyst is known as a functional cyst. They are usually benign (not cancerous) and go away on their own.

If you’re going through fertility treatments, an ultrasound conducted at the beginning of your cycle may spot a corpus luteum cyst.

Depending on the size of the cyst, your doctor may delay your treatment cycle or drain the cyst.

If you tend to develop corpus luteum cysts, your fertility doctor may put you on birth control the cycle before treatment. This would prevent ovulation, which in turn would prevent the formation of a cyst.

Usually, corpus luteum cysts are painless and harmless.

Some women find out they have one during an early pregnancy ultrasound. In these cases, the cyst will usually resolve on its own by the second trimester of pregnancy.

If your doctor sees the cyst is unusually large or growing, or it’s especially painful, your doctor may surgically drain or remove it.

In rare cases, a corpus luteum cyst can cause severe pain. In very rare cases, if the cyst grows especially large, it can cause the ovary to twist. This may lead to ovarian torsion. Surgical intervention would be required.

As always, if you’re experiencing severe pain or unusual bleeding, go to the nearest emergency room, or contact your doctor immediately. Ovarian torsion can be very serious.

What Is a Corpus Luteum Deficiency or Defect?

As you read above, the corpus luteum is responsible for producing the hormone progesterone.

In some cases, the corpus luteum doesn’t produce enough progesterone. This can lead to abnormal spotting.

Low levels of progesterone may lead to a “light period,” making you think you’re not pregnant when you really are.

When the progesterone levels are low after ovulation, this may be called a corpus luteum defect. More commonly, it’s referred to as a luteal phase defect.

A corpus luteum deficiency may increase your risk of early miscarriage.

Treatment may include progesterone supplementation or the use of fertility drugs like Clomid or hCG injections.

The theory is that boosting the hormones leading up to ovulation (with fertility drugs) will help produce a stronger corpus luteum.

The topic of luteal phase defect is controversial. Not all doctors believe treatment with progesterone supplementation can really prevent an early miscarriage. Also, proper diagnosis of a corpus luteum defect is controversial and unclear.

More on the reproductive system:

Sources:

27.2 Anatomy and Physiology of the Female Reproductive System. OpenStax College. Rice University. Accessed February 9, 2016. http://cnx.org/contents/FPtK1zmh@6.27:nMy6SWSQ@5/Anatomy-and-Physiology-of-the-

Current clinical irrelevance of luteal phase deficiency: a committee opinion. American Society for Reproductive Medicine. Accessed on February 9, 2016. https://www.asrm.org/uploadedFiles/ASRM_Content/News_and_Publications/Practice_Guidelines/Committee_Opinions/Luteal%20phase%20deficiency2012members.pdf

Ovarian Cysts: Disease and Conditions. MayoClinic.org. Accessed on February 9, 2016. http://www.mayoclinic.org/diseases-conditions/ovarian-cysts/basics/causes/con-20019937

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