What is the cause of menstruational cycle?

The menstrual cycle is primarily regulated by hormonal changes in the body, particularly involving estrogen and progesterone. It begins with the release of follicle-stimulating hormone (FSH) from the pituitary gland, stimulating the ovaries to produce follicles and release an egg. If fertilization does not occur, hormone levels drop, leading to the shedding of the uterine lining, which is experienced as menstruation. This cycle typically lasts about 28 days but can vary among individuals.