The corpus luteum forms from the follicle immediately after ovulation and consists of the egg and luteinized theca and granulosa cells. These cells are responsible for the cycle-appropriate production of progesterone and estrogen. When the corpus luteum is insufficient, the cells produce too little hormone, which can complicate pregnancies or lead to early abortion.
What is the corpus luteum?
The female cycle is subject to the control of hormones. For example, the egg is detached from the female ovary by certain hormones and travels to the fallopian tube. The fallopian tube receives the detached egg. This movement corresponds to ovulation. Ovulation occurs around the middle of the female menstrual cycle and is often noticeable as a pulling pain in the area of the lower abdomen. Also under hormonal control, the corpus luteum develops after ovulation. This substance corresponds to the corpus luteum, which develops from the follicle. This is a hormone-producing cluster of cells that exists either as corpus luteum menstruationis or as corpus luteum graviditatis. The former form arises in unfertilized oocytes. The second form refers to fertilized follicles. For the development of the corpus luteum, the influence of the luteinizing hormone (LH) is decisive. From its formation, the corpus luteum controls the female cycle via internal hormone production.
Anatomy and structure
The corpus luteum is formed from the follicle after ovulation. To do this, the female egg changes shape immediately after ovulation. The basement membrane of the follicle dissolves. Under the influence of LH, the theca and granulosa cells it contains transform into so-called granulosalutein cells and thecalutein cells. This process corresponds to luteinization. Shortly before this process, a preliminary stage of the corpus luteum, the corpus haemorrhagicum, is first formed. This preliminary stage is formed by spontaneous hemorrhage into empty ovarian follicles. The blood is reabsorbed shortly after the hemorrhage and luteinization of the granulosa and theca cells begins. Once luteinization is complete, the corpus haemorrhagicum has changed to the corpus luteum. If the egg is not fertilized in a menstrual cycle, the corpus luteum regresses. Around nine days after ovulation, the corpus luteum reaches its maximum size and from then on continuously decreases in size due to connective tissue degeneration. If, on the other hand, the egg is fertilized, the hormones secreted from then on cause the corpus luteum to increase in size rapidly. The cells involved in the tissue begin to proliferate.
Function and tasks
The corpus luteum serves to produce hormones. The granulosalutein cells it contains are hormone-producing cells that can produce progesterone. Gynecologists also know progesterone as the corpus luteum hormone. After ovulation, progesterone is produced in daily amounts of about 20 to 50 milligrams. The progesterone level in the blood thus increases bit by bit. Within a few days, the blood level reaches 50- to 100-fold and is around 10 ng per milliliter. The thecalutein cells located in the corpus luteum are also responsible for the production of hormones. These cells produce the female estrogens instead of progesterone. The high level of progesterone keeps the gonadotropin level low during the luteal phase. This follows a negative feedback principle to the pituitary gland and prevents further oocytes from maturing during this period. If fertilization of the matured egg does not occur, the theca and granulosa cells in the corpus luteum produce less estrogen and progesterone. The resulting drop in blood levels initiates the breakdown of the endometrium. Menstruation begins. Unless the egg remains unfertilized, human chorionic gonadotropin (HCG) prevents gel body degeneration. Nothing more stands in the way of the growth of the corpus luteum. After fertilization, the corpus luteum produces pregnancy-maintaining hormones. In about the ninth week of pregnancy, the cells produce estrogens and progesterone. From the tenth week, a luteoplacental shift occurs. Hormone production now takes place in the fetoplacental unit, or placenta, rather than in the corpus luteum.
Diseases
The corpus luteum can develop cancer. Susceptible to this are the theca and granulosa cells, which can give rise to malignant tumors as well as benign ones.Tumors based on theca and granulosa cells are hormone-producing tumors that upset hormone levels through their profiling. Hormone-related complaints such as unscheduled bleeding can be the first signs. Almost any age group can be affected by the tumors. Insufficiencies of the corpus luteum are even more common than tumors of the corpus gelum. Like all other insufficiencies, those of the corpus luteum also manifest themselves in a general functional weakness of the anatomical structure. The cells involved in corpus luteum insufficiency produce less progesterone and estrogen. The plasma concentration of the corpus luteum hormones drops. As a consequence, the luteal phase of the cycle shortens. Under these conditions, the endometrium cannot transform in a way that is appropriate for the cycle. This phenomenon complicates pregnancy in many cases. Some of the affected women find it difficult to get pregnant at all. Others become pregnant but are unable to sustain the pregnancy. Insufficiency of the corpus luteum is the most common cause of miscarriage in terms of early abortion. Many of the patients experience several premature abortions in their lifetime. In the meantime, hormonal substitution has become the accepted therapy for corpus luteum insufficiency. Because progesterone in particular is relevant as a pregnancy hormone, the affected women are administered the corpus luteum hormone including its derivatives intravenously.
