Why do women have anovulatory functional uterine bleeding?

In a normal menstrual cycle, the hypothalamus produces gonadotropin-releasing hormone (Gn-RH), which stimulates the anterior pituitary gland to secrete follicle-stimulating hormone and luteinizing hormone. Follicle-stimulating hormone causes the follicles to begin to develop, and under the action of a small amount of luteinizing hormone, the follicles secrete estrogen. Estrogen acts on the endometrium and causes proliferative changes.

When the follicle matures, it secretes a large amount of estrogen, causing the pituitary gland to release a large amount of luteinizing hormone, forming a luteinizing hormone peak, which can cause the mature follicle to rupture and ovulate. Under the action of luteinizing hormone and follicle-stimulating hormone, the ruptured follicle forms a corpus luteum. The corpus luteum secretes progesterone and estrogen, and progesterone can transform the proliferative endometrium into the secretory phase.

Because the corpus luteum secretes a large amount of progesterone and estrogen, it in turn inhibits the hypothalamus, causing a decrease in luteinizing hormone and follicle-stimulating hormone, atrophy of the corpus luteum, and a decrease in the secretion of progesterone and estrogen. The endometrium cannot get the support of estrogen and progesterone, resulting in necrosis, shedding, and the onset of menstruation.

If the follicles only develop to a certain extent but are immature, they can secrete a certain amount of estrogen, but they cannot reach the peak of estrogen secretion, resulting in the ovary failing to ovulate. Without ovulation, there is no corpus luteum formation, and no progesterone secretion. In this way, the endometrium remains in the proliferation phase and cannot change to the secretory phase. Although the uterus bleeds on time, it is not true menstruation, but anovulatory menstruation. Because there is no ovulation, it will inevitably lead to infertility.