Which hormones affect female reproduction?

The ovaries secrete estrogen and progesterone, which promote sexual development during adolescence, prepare the uterus for pregnancy, and maintain the uterus during pregnancy. The pituitary gland secretes follicle stimulating hormone and luteinizing hormone, which stimulate ovulation. It also secretes oxytocin, which causes contractions of the uterus and milk ducts during labor, and prolactin, which stimulates the production of breast milk. The hypothalamus secretes hormones that regulate the pituitary gland.

Three main structures control hormone production – the ovaries, the pituitary gland, and the hypothalamus. Functions of these structures are highly integrated. For example, the hypothalamus sends signals to the pituitary gland, which then releases a particular hormone. This hormone may induce ovarian activities such as preparation for ovulation or ovulation itself. The ovary then has both structural and chemical functions, as it prepares for egg release and also secretes hormones. In this manner the ovary acts as both an organ and a gland.

Located in the central part of the brain, the pituitary gland has an anterior lobe and a posterior lobe. Each lobe secretes different hormones.

The ovaries secrete two hormones involved in female development and reproduction. Estrogen, the best known of these hormones, initiates the development of female secondary sexual characteristics during adolescence. Estrogen also initiates uterus preparation for pregnancy, and leads to stimulation of egg release during the middle of the menstrual cycle.

Progesterone maintains female secondary sexual characteristics, and also helps to prepare the uterus for pregnancy.

The anterior lobe of the pituitary gland releases several hormones – follicle stimulating hormone, or FSH, luteinizing hormone, or LH, and prolactin. LH and FSH play important roles in the development and release of an egg from the ovaries. These anterior pituitary hormones also stimulate the release of estrogen and progesterone from the ovaries. Prolactin stimulates the production of milk in the mammary glands of the breasts after childbirth.

The posterior lobe of the pituitary gland releases oxytocin, which stimulates contraction of the uterus during labor and initiates the milk-ejection reflex that enables breast feeding.

The hypothalamus regulates the release of reproductive hormones from the pituitary gland. Gonadatrophin-releasing hormone stimulates the pituitary gland to release FSH and LH, while prolactin-inhibiting hormone prevents secretion of prolactin (thereby stopping milk production).