Estrogen is the hormone that helps control breast cell proliferation and division. Breast development during puberty begins after the ovaries start to secrete estrogen.
Progesterone is a steroid hormone that works together with estrogen to regulate breast development.
Prolactin causes the alveoli to take nutrients (proteins, sugars) from the blood supply and turn them into breast milk.
Oxytocin causes the cells around the alveoli to contract and eject milk down the milk ducts. This passing of the milk down the ducts is called the “let-down” (milk ejection) reflex.
