lactation

Lactation is the body's whole milk-making operation: building the “factory,” switching it on, and then matching its output to demand. It is one of the clearest examples of how several hormones cooperate over time, from pregnancy through breastfeeding.

It depends on a two-hormone teamwork. Prolactin, from the anterior pituitary, drives the actual synthesis of milk in the breast's glandular tissue. Oxytocin, from the posterior pituitary, causes the milk to be ejected toward the nipple when the baby suckles. During pregnancy, high estrogen and progesterone prepare the breast but also block milk secretion; only after birth, when those placental hormones fall sharply, does abundant milk production begin.

Lactation is regulated by demand. Suckling stimulates nerves in the nipple, which both releases oxytocin for let-down and sustains prolactin to keep making milk. The more a baby feeds, the more milk is produced, a feedforward arrangement of supply meeting demand.

A caveat: lactation is robust but not unconditional. Severe maternal illness, certain medications, retained placenta, or major postpartum hemorrhage damaging the pituitary can all impair milk production, so difficulties with breastfeeding are not simply a matter of effort or willpower.