Which hormone is responsible for regulating breast milk production?

Prolactin is the hormone primarily responsible for regulating breast milk production. Secreted by the anterior pituitary gland, prolactin stimulates the mammary glands to produce milk following childbirth. Its levels increase during pregnancy, preparing the breasts for lactation. After delivery, the stimulation of the nipples during nursing triggers further release of prolactin, promoting continued milk production to meet the infant's demands.

While estrogen, oxytocin, and progesterone play roles in the overall process of breastfeeding, especially during pregnancy, they do not directly regulate the production of milk in the way that prolactin does. Estrogen helps develop the milk ducts and glandular tissue of the breast, oxytocin is crucial for milk ejection or letdown during breastfeeding, and progesterone supports the pregnancy and prepares the breasts for lactation but does not directly facilitate the synthesis of milk.