Which hormone is primarily responsible for the luteal phase of the menstrual cycle?

The hormone that is primarily responsible for the luteal phase of the menstrual cycle is progesterone. After ovulation, the corpus luteum forms from the ruptured follicle and produces progesterone. This hormone plays a crucial role in preparing the uterine lining for a potential implantation of a fertilized egg. During the luteal phase, progesterone helps to maintain the endometrium by thickening it, creating a supportive environment for a pregnancy to sustain itself. If pregnancy does not occur, progesterone levels will decline, leading to the shedding of the uterine lining and the start of menstruation.

While estrogen and follicle-stimulating hormone (FSH) are also involved in the menstrual cycle, they play different roles. Estrogen is important for the follicular phase and helps to regulate the growth of the uterine lining, while FSH is involved in the growth and maturation of ovarian follicles. Testosterone has a different role entirely and is not directly involved in the menstrual cycle. Understanding these hormonal interactions helps clarify why progesterone is central to the luteal phase and its crucial supportive function for potential pregnancy.