The corpus luteum is a short-lived but vital organ that appears in one of your ovaries during every menstrual cycle. Its job is to produce hormones (progesterone and relaxin) that support pregnancy and childbirth. If the egg your ovary produces is fertilized, the corpus luteum progesterone production continues for several weeks. Without fertilization, the corpus luteum stops working in a few days and withers away. You'll have a corpus luteum hundreds of times during your reproductive years. The corpus luteum sometimes functions abnormally, causing troublesome symptoms or serious conditions.
What Is the Corpus Luteum?
The corpus luteum is a hormone-producing body that appears in one of your ovaries approximately once a month through your childbearing years. It is a yellow body, 3/4 to 2 inches (2 to 5 centimeters) in size. The corpus luteum is made up of two types of cells -- follicular granulosa cells and follicular theca cells.
During the early part of the menstrual cycle, several follicles appear in the ovaries, each containing an egg (ovum). One of the follicles grows bigger and releases its egg halfway through your menstrual cycle. This follicle then converts to the corpus luteum. Its cells convert cholesterol to progesterone. This hormone is essential for pregnancy.
Where Is the Corpus Luteum Located?
There are two ovaries inside your abdomen, one on each side. The corpus luteum forms in one of them after the follicle releases the ovum.
Corpus Luteum Function
The corpus luteum stops working if the ovum is not fertilized. Without the progesterone, the uterus sheds its lining, resulting in a period.
If the ovum is fertilized, the corpus luteum performs several crucial functions for maintaining pregnancy:
- Prepares your uterus to receive and nourish a baby by producing progesterone
- Suppresses the brain and pituitary to alter hormonal production
- Produces the hormone relaxin. This softens the joints of your pelvis, which is necessary for delivering vaginally
The corpus luteum fulfills these needs for the first 12 weeks of pregnancy. The placenta then takes over the production of progesterone and other hormones. The corpus luteum gets smaller and stops functioning.
The corpus luteum has a role in the control of blood pressure during pregnancy. The hormone relaxin is a potent vasodilator and prevents blood pressure elevations. If the corpus luteum is not present, there is a higher risk of pre-eclampsia, a dangerous condition of raised blood pressure.
Corpus Luteum Progesterone
Progesterone is the chief product of the corpus luteum. It affects the uterus in several ways:
- The uterus lining (the endometrium) changes to allow the fertilized ovum to settle and grow.
- The blood supply of the uterus increases to supply oxygen and nutrients to the growing baby.
- The uterus itself gets larger.
All these changes are aimed at creating a pleasant place for a fertilized ovum to settle and grow into a baby.
Progesterone helps the pregnancy in many ways. It stimulates the glands and changes the pattern of proteins in the endometrial cells. These proteins support the growth of the embryo in early pregnancy. Progesterone also calms the muscles of the uterus (the myometrium), protecting the pregnancy from being ousted early.
The hypothalamus in the brain and the pituitary gland produce and release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones operate the menstrual cycle and stimulate the ovaries to produce estrogen and release an egg during each menstrual cycle. Progesterone acts on the brain and the pituitary gland to suppress the production and release of these hormones.
Conditions Affecting the Corpus Luteum
Corpus luteum defect. This happens when this organ fails to produce progesterone. Without this vital hormone in sufficient amounts, the lining of the uterus won't thicken and support a pregnancy. You may find it difficult to get pregnant and have a baby. Corpus luteum defect is sometimes associated with obesity, malnutrition, stress, too much exercise, or medical conditions like endometriosis and polycystic ovary syndrome (PCOS).
Luteal phase defect. Sometimes, the corpus luteum produces progesterone, but your uterus doesn't respond to it. This is called luteal phase defect and is a common cause of the inability to conceive. If you are unable to have a baby despite trying, you should consult your doctor.
If your doctor feels your corpus luteum may be causing infertility, they will ask for laboratory tests to measure your hormone levels — progesterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH). They may also order an ultrasound examination to measure the corpus luteum and the thickness of your uterus lining.
Signs Something Is Wrong With the Corpus Luteum
The corpus luteum should stop working and shrink once its function is over. But it may keep growing instead and fill with fluid or blood, forming a cyst. Such a corpus luteum cyst is usually harmless and causes no pain. It can happen with or without pregnancy.
Sometimes, a corpus luteum cyst does cause symptoms:
- Pain or fullness in the lower abdomen
- Pain when you pass urine or stools
- Pain on one side of your body
- Pain during sexual intercourse (dyspareunia)
- Blood stained vaginal discharge when you don't have your period
Corpus luteum cysts are often discovered during pregnancy examinations. They go away on their own by the second trimester. If you're not pregnant, a corpus luteum cyst may last a few weeks or months.
A corpus luteum cyst can continue producing progesterone. This can last for up to three months when the cyst vanishes. Sometimes, these cysts can burst, causing bleeding into the abdominal cavity (hemoperitoneum). This is more likely and more dangerous in people on blood-thinner drugs. If you think you may have a burst cyst, you should seek medical care immediately.
Corpus Luteum Treatment
Your doctor will treat a corpus luteum cyst only if it is necessary. Most cysts reduce in size and disappear on their own. If a cyst is large enough to create problems or is very painful, your doctor may remove it surgically.
Lack of the hormone progesterone from the corpus luteum may be preventing pregnancy. If your doctor detects this, they may prescribe clomiphene citrate or human chorionic gonadotropin (HCG) to stimulate your corpus luteum to produce the hormone. Another option is to take progesterone itself.
Keeping Your Corpus Luteum Healthy
A new one forms in each menstrual cycle, so you don't need to do anything special for corpus luteum health. A balanced, nutritious diet; enough sleep and rest; and freedom from stress benefit your overall health and your reproductive health.
