What Does the Corpus Luteum Do?
Read on to learn how the corpus luteum develops, its role in pregnancy, and related conditions.
The corpus luteum is a temporary, hormone producing structure inside the ovary. It forms as part of menstruation.
To understand corpus luteum structure, it is helpful to know a little about the menstrual cycle. The first day of bleeding is day 1.
- Follicular phase: The pituitary gland releases follicle stimulating hormone (FSH) and luteinizing hormone (LH). In response, immature eggs in fluid-filled sacs called follicles begin to grow and mature. One usually grows faster than the others. The follicular phase lasts 12–14 days.
- Ovulatory phase: LH stimulates the dominant follicle to release the mature egg to the fallopian tube. It also stimulates the corpus luteum to grow. The ovulatory phase is about 2 days.
- Luteal phase: The corpus luteum forms from the empty follicle and begins to produce progesterone. This phase lasts 12–14 days.
Follicular granulosa cells and theca lutein cells make up the corpus luteum. The theca cells produce progesterone.
If fertilization occurs and an embryo develops, cells surrounding the embryo secrete human chorionic gonadotropin (hCG). This hormone stimulates the corpus luteum to continue growing. It can grow large enough to occupy most of the ovary.
Also, because of the lutein, which is a yellow carotenoid pigment, the corpus luteum is yellowish in color.
The main function of the corpus luteum is to produce and secrete progesterone to support possible pregnancy. Progesterone is a hormone that prepares the uterus for implantation of the embryo. The corpus luteum also makes estrogen.
After the egg is fertilized, the corpus luteum continues making progesterone. This happens for about 12 weeks. As the placenta forms and takes over progesterone secretion, the corpus luteum breaks down.
Without fertilization, the corpus luteum stops functioning about 10 days following ovulation. It then regresses and forms a scar, the corpus albicans.
People with ovaries and a uterus who have regular monthly ovulatory menstrual cycles develop a corpus luteum each month as part of menstruation.
Corpus luteum cyst and luteal phase deficiency are two conditions involving the corpus luteum.
Corpus luteal cyst
Sometimes, when pregnancy does not happen, the corpus luteum does not regress, explains the Office on Women’s Health. The persistent cyst can fill with blood, rupture, and cause pain. A corpus luteal cyst usually goes away on its own, although it may take up to 3 months to do so.
Possible symptoms of corpus luteum problems include:
- pain in the pelvis or on one side of the body
- pain using the bathroom
- lower back or body aches
- fullness in the abdomen
- pain during sex
- bloody discharge not during your regular menstrual cycle
- breast tenderness
Sometimes the corpus luteal cyst ruptures, leading to sudden, severe pain and internal bleeding. Blood can gather between the organs and the inner lining of the abdominal wall. This may require surgery to remove the cyst and stop the bleeding.
Luteal phase deficiency
With this condition, the corpus luteum may not develop correctly or it may not produce enough progesterone to thicken the uterine lining. Alternately, the lining of the uterus may not respond as it should to progesterone. Either of these scenarios could interfere with getting pregnant or carrying a fetus to term.
The clinical definition of luteal phase deficiency is a luteal phase lasting 10 days or less, according to the American Society for Reproductive Medicine (ASRM). Typically, the phase is 12–14 days, with a range of 11–17 days.
However, as the ASRM explains, luteal phase deficiency is a clinical diagnosis. There is no definitive proof that it causes infertility or pregnancy loss.
Some factors that could play a role in luteal phase deficiency include:
- too much exercise
- a body mass index that is too low
- unhealthy levels of stress
- certain conditions, such as:
Blood tests to measure hormone levels may reveal a luteal phase deficiency. However, there is no clear consensus on how to diagnose it.
A healthcare professional may evaluate corpus luteum structure and function with the following procedures:
- pelvic exam and ultrasound, to detect signs of corpus luteal cyst
- transvaginal ultrasound, to measure the uterus lining
They may also order blood tests to measure:
Amanda Kallen, M.D., reviewed the following frequently asked questions.
What is the role of the corpus luteum in pregnancy?
During the first 12 weeks of pregnancy, the corpus luteum produces progesterone to prepare the uterus for pregnancy. Once the placenta forms, it takes over progesterone production, and the corpus luteum will break down.
What does the corpus luteum do if I am not pregnant?
If the egg is not fertilized, the corpus luteum stops secreting progesterone and breaks down.
Can you feel the corpus luteum?
How long does the corpus luteum last?
If you are not pregnant, the corpus luteum lasts about 10 days. If you are pregnant, it typically lasts 12 weeks.
The corpus luteum plays a vital role by producing progesterone that will prepare the uterus for pregnancy.
Around week 12 of pregnancy, the growing placenta takes over progesterone production and the corpus luteum disappears.
If there is no fertilization, the corpus luteum breaks down in about 10 days.