What happens to the corpus luteum if fertilization does not occur?

The corpus luteum plays a crucial role in the menstrual cycle and early pregnancy. If fertilization does not occur, the corpus luteum, which forms from the remnants of the ovarian follicle after ovulation, undergoes a process called luteolysis. This leads to its degradation and a decrease in hormone production, particularly progesterone and estrogen.

As the corpus luteum degrades, its hormonal support for the endometrial lining decreases, leading to the onset of menstruation. This is vital for the preparation of the uterus for a new cycle. Thus, the correct scenario is that the corpus luteum degrades and menstruation begins if fertilization does not take place.

The other options are not accurate in this context. The corpus luteum does not continue to produce hormones indefinitely without fertilization, nor does it transform into a new follicle or turn into an endometrioma. The natural course following the lack of fertilization is a decline in hormone levels and the initiation of menstruation.