Which hormone is primarily responsible for regulating female reproductive functions?

Progesterone plays a crucial role in the female reproductive system, primarily in regulating the menstrual cycle and maintaining pregnancy. This hormone is produced by the ovaries following ovulation, specifically by the corpus luteum, and is essential for preparing the endometrium for potential implantation of a fertilized egg. If pregnancy occurs, progesterone helps sustain the uterine lining, making it suitable for fetal development. Furthermore, it inhibits further ovulation during pregnancy, ensuring that only one embryo has the chance to develop at a time.

In contrast, testosterone is primarily associated with male reproductive functions and development, while prolactin, although important for milk production in females, does not directly regulate the overall reproductive cycle or processes like ovulation. Adrenaline, known for its role in the fight-or-flight response, is not involved in the regulation of reproductive functions. Therefore, progesterone's essential role in supporting and regulating female reproductive health makes it the correct choice.