How Will My Breasts Know How Much Milk To Make?
There are 4 different hormones that contribute to the making of milk. Each comes into play at a different stage, and understanding their roles will help you understand the milk-making process.
The Four Key Hormones
Estrogen
Estrogen stimulates the growth of breast duct tissue and is essential for breast development during puberty and pregnancy. During pregnancy, high estrogen levels contribute to the growth of milk-producing structures.
Progesterone
Progesterone works alongside estrogen to prepare the breasts for lactation. It promotes the growth of lobules (milk-producing glands). High progesterone levels during pregnancy actually inhibit milk secretion — it's the sudden drop in progesterone after birth (or stopping it in an induction protocol) that triggers milk production.
Prolactin
Prolactin is the primary hormone responsible for milk production. It is released by the pituitary gland in response to nipple stimulation (suckling or pumping). The more stimulation, the more prolactin is released, and the more milk is produced. This is the foundation of the supply-and-demand principle of lactation.
Oxytocin
Oxytocin is responsible for the "let-down" reflex — the release of milk from the alveoli into the milk ducts. It is also released in response to nipple stimulation, but can also be triggered by emotional cues such as hearing a baby cry, thinking about nursing, or physical closeness with a partner.
Supply and Demand
Your breasts regulate milk production through a simple but effective feedback loop. When milk is removed frequently and thoroughly, the body produces more. When milk remains in the breast, production slows. This is why consistent stimulation and emptying on a regular schedule is critical — especially during the early stages of inducing lactation.
