Which hormone primarily regulates the menstrual cycle?

The hormone that primarily regulates the menstrual cycle is estrogen. Estrogen plays a crucial role in the development and regulation of the female reproductive system and secondary sexual characteristics. During the first half of the menstrual cycle, known as the follicular phase, estrogen levels rise in preparation for ovulation. This hormone is responsible for the thickening of the uterine lining, which is essential for a potential implantation of a fertilized egg.

While progesterone, luteinizing hormone, and oxytocin also have roles in the menstrual cycle and reproductive processes, estrogen is key to initiating and maintaining the cycle. Progesterone, for instance, primarily functions after ovulation, preparing the uterine lining for pregnancy, while luteinizing hormone plays a role in triggering ovulation itself. Oxytocin, although important in childbirth and lactation, does not regulate the menstrual cycle directly. Understanding estrogen’s pivotal role provides insight into the biological processes that sustain reproductive health in women.