Britannica Sources used in this answer

How do estrogen and progesterone affect the female reproductive cycle?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram showing the locations of major human endocrine glands in male and female bodies, including pineal gland, hypothalamus, pituitary gland, parathyroid glands, thyroid gland, thymus, adrenal glands, pancreas, kidneys, testes, and ovaries. — Endocrine system The glands of the human endocrine system.

In the female reproductive cycle, estrogen and progesterone act as primary regulators of the ovaries and the uterus. Their levels fluctuate to prepare the body for potential pregnancy.123

Estrogen

During the follicular phase, maturing ovarian follicles secrete increasing amounts of estradiol, the most potent estrogen. This hormone stimulates the endometrium to thicken and become more vascular, preparing the uterine lining for a fertilized egg. Estrogen also plays a role in triggering the surge of luteinizing hormone (LH) that leads to ovulation.32

Progesterone

Following ovulation, the ruptured follicle transforms into the corpus luteum, which produces large quantities of progesterone. This hormone induces the secretory phase of the endometrium, making it receptive to embryo implantation. Progesterone also inhibits uterine contractions that might reject an egg and increases basal body temperature.4231

If fertilization does not occur, the corpus luteum degenerates, causing levels of both hormones to drop. This withdrawal triggers the shedding of the uterine lining, known as menstruation.423