What hormone levels drop at the end of the menstrual cycle, triggering menstruation?

At the end of the menstrual cycle, the decrease in progesterone levels is critical for triggering menstruation. After ovulation, the corpus luteum forms and secretes progesterone, which plays a vital role in preparing the uterine lining for a potential pregnancy by thickening it. If fertilization does not occur, the corpus luteum degenerates, leading to a drop in progesterone levels. This decline in progesterone is what ultimately causes the breakdown of the uterine lining, resulting in menstruation.

Other hormones such as estrogen, follicle-stimulating hormone, and luteinizing hormone have roles in the menstrual cycle but are not directly responsible for initiating menstruation through their decline in levels. Estrogen typically fluctuates in tandem with progesterone during the cycle, contributing to the development of the uterine lining. Follicle-stimulating hormone and luteinizing hormone are involved in the earlier phases of the menstrual cycle related to follicle development and ovulation, rather than the process that triggers menstruation itself.