Luteolízis

Luteolízis refers to the regression or breakdown of the corpus luteum. The corpus luteum is a temporary endocrine structure that forms in the ovary of female mammals after ovulation. Its primary function is to produce progesterone, a hormone essential for establishing and maintaining pregnancy.

In the absence of fertilization, the corpus luteum undergoes a process of degeneration. This breakdown is triggered by hormonal signals. If pregnancy does not occur, the levels of luteinizing hormone (LH) decrease, which in turn leads to the decline of progesterone production by the corpus luteum. This hormonal shift initiates luteolysis.

The process involves cellular changes within the corpus luteum, including apoptosis (programmed cell death) of luteal cells. Macrophages also play a role in clearing away the degenerating tissue. As the corpus luteum breaks down, progesterone levels drop significantly. This decline in progesterone is a crucial signal that triggers the shedding of the uterine lining, leading to menstruation in species that exhibit a menstrual cycle.

In species with an estrous cycle, the drop in progesterone signifies the end of the receptive phase and the beginning of a new cycle. In pregnant animals, however, the corpus luteum is rescued from luteolysis by hormonal signals from the developing embryo, such as interferon-tau in ruminants or chorionic gonadotropin in primates, ensuring continued progesterone production to maintain the pregnancy. Luteolízis is therefore a critical event that regulates the reproductive cycle and is essential for both initiating and terminating pregnancy.