What is the primary hormone responsible for the regulation of the menstrual cycle?

The primary hormone responsible for the regulation of the menstrual cycle is estrogen. Estrogen plays a crucial role in the development of the ovarian follicles and the growth of the uterine lining, which is essential for preparing the body for a potential pregnancy. During the menstrual cycle, fluctuating levels of estrogen influence various stages, including the proliferation of the endometrium following menstruation and triggering the surge of luteinizing hormone (LH) necessary for ovulation.

While progesterone also plays a significant role, especially after ovulation by maintaining the uterine lining for a possible implantation, it is estrogen's rise and fall that governs the timing of the menstrual cycle phases. This hormone's fluctuations dictate the cycle's phases, including the follicular phase, ovulation, and luteal phase. The balance and interplay between estrogen and progesterone are critical, but estrogen is predominantly considered the main regulator when looking at the entire menstrual cycle as a whole.

Insulin is involved in metabolic processes and does not directly impact the menstrual cycle, while testosterone, primarily known as a male hormone, is present in smaller amounts in females and does not play a significant role in regulating the menstrual cycle.