What physiological change primarily occurs during the luteal phase?

During the luteal phase of the menstrual cycle, one of the most significant physiological changes is the increase in progesterone production. This occurs after ovulation when the ovarian follicles transform into a structure called the corpus luteum. The corpus luteum is responsible for secreting progesterone, a hormone that plays a crucial role in preparing the endometrium for potential implantation of a fertilized egg.

The rise in progesterone levels leads to several physiological effects, including thickening of the uterine lining and suppression of further ovulation during this phase. This hormonal environment is essential for maintaining a healthy uterine condition for early pregnancy if fertilization occurs. If fertilization does not happen, progesterone levels will eventually decline, leading to menstruation.

While estrogen does also increase during the luteal phase, it is the rise in progesterone that is notably higher and more significant for the changes that occur in the uterus and overall cycle regulation.