Which hormone is primarily responsible for stimulating milk production?

Prolactin is the hormone primarily responsible for stimulating milk production in the mammary glands. This hormone is produced by the anterior pituitary gland and its secretion is critical in the early stages of lactation. When a baby suckles at the breast, it triggers nerve impulses that signal the pituitary gland to release prolactin. Increased levels of prolactin lead to the production of milk, making it essential for breastfeeding and establishing a successful breastfeeding relationship.

While oxytocin plays a significant role in milk ejection (let-down) by causing the smooth muscles around the alveoli to contract and release milk, it does not stimulate milk production itself. Estrogen and progesterone are hormones involved in breast development and preparing the mammary glands for lactation during pregnancy, but they do not directly stimulate the production of milk after childbirth. Thus, prolactin is the key hormone responsible for initiating and maintaining milk production post-delivery.