What is a Corpus Luteum?

Human corpus luteum seen under microscope at x 100 magnification
Human corpus luteum seen under microscope at x 100 magnification. De Agostini Picture Library/Getty Images

The corpus luteum is a small scar or structure that remains at the site of the ovarian follicle that released an egg during ovulation. This structure produces progesterone and estrogen, the hormones necessary to maintain a pregnancy.

If pregnancy does occur, the corpus luteum will continue to function for a few months, providing the necessary hormonal support. If pregnancy does not occur, the corpus luteum simply reabsorbs and stops producing estrogen and progesterone.

Corpus Luteum and PCOS

Research suggests hormonal irregularities in women with PCOS who ovulate may impact corpus luteum development. When this occurs it is known as luteal phase deficiency.

The luteal phase of the menstrual cycle occurs after ovulation, and typically lasts 13 to 14 days. At this time, the corpus luteum is churning out estrogen and progesterone in case ​of a pregnancy.

When pregnancy occurs, the implanting embryo releases hCG, prompting the corpus luteum to continue releasing progesterone for the first few months of pregnancy. If there is no fertilized embryo, the corpus luteum stops producing progesterone and estrogen after 12 or 13 days, prompting the start of menstruation a day or two later.  

In luteal phase deficiency, or LPD, the corpus luteum does not produce enough progesterone to maintain a pregnancy.  As a result, the luteal phase is shortened by 3 or 4 days.

For women who are actively trying to get pregnant, LPD can be determined by tracking your cycles and ovulation, using basal body temperature.

Your doctor will follow this with a blood test to check hormone levels through out your cycle. If LPD is uncovered, there are several medications that can help to address the problem.

Corpus Luteum Cysts

Sometimes after the egg is released, the corpus luteum seals off and fills with fluid, causing it to swell and get trapped in the ovary.

This is known as a corpus luteum cyst, one of several kinds of ovarian cysts. 

Women with PCOS who are trying to get pregnant often take fertility drugs to induce ovulation, such as Clomid, which can increase the risk of corpus luteum cysts.

This type of cyst typically does not produce any symptoms. Sometimes, however, it can grow as large as 4 inches, and twist itself causing pelvic or abdominal pain.

The cyst may fill with blood and rupture, causing sharp pains and internal bleeding, but often just goes away on its own.

Women with PCOS who do not ovulate will not develop corpus luteum cysts but may develop follicular cysts. These form when an egg doesn't get released as expected, so the follicle keeps growing.


Mayo Clinic website. Diseases and conditions: Ovarian Cysts. http://www.mayoclinic.org/diseases-conditions/ovarian-cysts/basics/causes/con-20019937

NIH website. Menstruation and Menstrual Problems: Condition Information. https://www.nichd.nih.gov/health/topics/menstruation/conditioninfo/Pages/default.aspx.

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