Definition - What does Luteinization mean?

Luteinization is the process where the follicular cells of an ovarian follicle transform into a structure called the corpus luteum after the egg is released from the ovary. The corpus luteum is a yellow colored body that temporarily remains in the ovary, where it produces progesterone and to a lesser amount estrogen, preparing the uterus for implantation of the fertilized egg. Defects in luteinization, also known as luteal insufficiency, can cause infertility by hindering the implantation of the embryo in the uterine lining.

FertilitySmarts explains Luteinization

A surge of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) that occurs mid-menstrual cycle acts as a trigger for ovulation and luteinization. Immediately after the egg is released, the follicle becomes a blood-filled structure referred to as the corpus hemorrhagicum, and within a few hours the blood clots and dissolves and it becomes the corpus luteum.

The LH surge plays a crucial role in luteinization. It stimulates the follicular cells to produce progesterone, the primary hormone driving the process of luteinization and subsequent luteal phase of the menstrual cycle.

The product of luteinization, the corpus luteum, mainly produces progesterone that prepares the endometrium, the inner lining of the uterine cavity, to receive the fertilized egg. It makes the endometrium thick and raises the body temperature to provide the optimum environment for implantation to occur.

Estrogen that is produced in moderate amounts by the corpus luteum inhibits the release of gonadotropin-releasing hormone (GnRH) which in turn reduces FSH and LH levels, thus inhibiting further follicular maturation and luteinization. In the first few days after the release of the egg estrogen also facilitates production of thin cervical mucus that aids the passage of sperm towards the egg.

The corpus luteum remains in the ovary for about 14 days, the period known as the luteal phase of the menstrual cycle. In the absence of fertilization and implantation, the hormone secretion from the corpus luteum diminishes and it degenerates to become non-functioning fibrous tissue known as the corpus albicans.

Defects in luteinization can interfere with the development of the corpus luteum and lead to infertility.

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