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Corpus Luteum


The corpus luteum is an endocrine structure that is present in women on a temporary basis (according to the menstrual cycle). As you will have the opportunity to read below, the corpus luteum is responsible for the production of progesterone, estradiol and inhibin A. In simple terms, the corpus luteum is what remains of the follicle after the ovulation period has ended.

The menstrual cycle has two main phases, meaning the follicular and the luteal one. In the follicular phase, the FSH (follicle stimulating hormone) works to stimulate the production of follicles. Each of the follicles that have been produced contains an egg. With each menstrual cycle, there is one egg that has reached maturity and can now be used for ovulation and fertilization. During the ovulation process, the egg will practically come out of the follicle. The corpus luteum is what is left of the follicle, as soon as the bursting process has occurred.

After that, the menstrual cycle enters into the luteal phase. This is named after the corpus luteum and it is the second part of the menstrual cycle. As you might have figured by now, the luteal phase starts once with the ovulation process and continues until the appearance of the actual menstruation.

Where is corpus luteum located?

The corpus luteum is located at the level of the ovarian follicle, being composed of lutein cells. It is practically like a sac that holds the matured egg, releasing it when it’s the time for ovulation.

Function of corpus luteum

One of the main functions of corpus luteum is related to the production of progesterone. This hormone is essential – it actually makes the lining of the uterus thick, guaranteeing the implantation of the embryo and sustaining what is a normal and healthy pregnancy. Even if after the pregnancy has occurred, the corpus luteum is going to continue to produce progesterone. This usually happens until the 10th week of the pregnancy, when the progesterone production will start to be handled by the placenta.

In case the released egg does not become fertilized, the corpus luteum will stop the production of progesterone and degenerate in approximately ten days. Instead of the corpus luteum, there will be the corpus albicans, which is actually a mass of fibrous scar tissue.

In case the egg has been fertilized and the implantation was a success, the body will be stimulated to secrete hCG or the human chorionic gonadotropin hormone. This is the hormone that stimulates the corpus luteum to continue the production of progesterone, contributing the maintenance of the pregnancy. After the 10th weeks of pregnancy, the placenta will take over the production of the progesterone hormone; during that period, the corpus luteum will degenerate as well, being transformed into fibrous scar tissue (this does not affect the embryo or the already growing fetus in any way). Sometimes, the function of the corpus luteum requires a little bit of support – this is known as luteal support and it refers to the administration of progestins, with the purpose of increasing the success of the implantation.

What is a corpus luteum cyst?

The corpus luteum cyst is actually an ovarian cyst, which can become ruptured during the menstrual and takes several months to disappear completely. It is important that this corpus luteum cyst usually appears in women who are in their fertile years – after menopause, such cysts are extremely rare, as the ovaries no longer release eggs for fertilization. The corpus luteum cyst contains a wide range of fluids, including blood and it may contribute to the enlargement of the respective ovary.

According to the specialists in the field, the corpus luteum cyst appears after the egg has been released from the follicle. In the majority of the cases, if the egg doesn’t get fertilized, it will shrivel and transform into fibrous tissue. However, there are certain women, in which the corpus luteum does not degenerate but rather fills up with fluids, being transformed into a cyst. The corpus luteum cyst is usually located on one side of the ovary and it does not cause any obvious symptoms, being discovered accidentally.

It is possible that the corpus luteum cyst becomes symptomatic, especially if it grows larger in size. The cysts that are over 10 cm in diameter can lead to worrying symptoms, including bleeding or severe pelvic/abdominal pain. In the majority of the cases, the pain will subside at several days after the rupture has occurred. In rare situations, the corpus luteum cyst might cause the ovary to twist, cutting the blood flow. The pain caused by ovarian torsion is genuinely intense and immediate medical intervention is necessary.

There are certain drugs that can increase the risk for the appearance of the corpus luteum cyst, especially the fertility drugs that are commonly used for the induction of ovulation. Contraceptives are known to reduce to zero the risk of developing such a cyst; on the other hand, if the contraceptive contains only progesterone, the frequency of the corpus luteum cysts is going to become increased. It is important to talk to your doctor about the types of contraceptive pills you are taking and their content.

Corpus luteum cyst during pregnancy

The corpus luteum cyst can appear during pregnancy, causing pain or tenderness to the touch. The pain might be more intense in case the corpus luteum cyst has ruptured. On the other hand, it is important to understand and remember that the corpus luteum cyst is not going to affect the growing baby in any way. In the majority of the cases, it disappears on its own, without any additional complications or problems. The only situation in which one requires surgical intervention is if the cyst causes the torsion of the ovary, cutting its blood flow. Even though it is not usually dangerous, it might be for the best to talk to your doctor about your symptoms. Based on the physical examination and imaging studies, the doctor will be able to decide whether the surgical intervention is an option for you or not.

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