What hormone is responsible for stimulating milk production in the breasts post-pregnancy?

Prolactin is the hormone primarily responsible for stimulating milk production in the breasts after pregnancy. This hormone is secreted by the anterior pituitary gland and plays a crucial role in lactation. Prolactin levels rise during pregnancy, but it is after childbirth that the levels increase significantly in response to the drop in estrogen and progesterone, which initially inhibited milk production during pregnancy. The primary function of prolactin is to facilitate and maintain milk synthesis in the alveolar cells of the breast, ensuring that the mother can produce milk for breastfeeding.

While oxytocin plays an important role in the breastfeeding process by facilitating milk ejection or let-down reflex, it does not stimulate milk production itself. Luteinizing hormone is involved in the regulation of the menstrual cycle and ovulation but is not directly related to lactation. Estrogen also has roles in breast development and the reproductive cycle but, like luteinizing hormone, it does not directly promote milk production in the same way that prolactin does. Therefore, prolactin is the hormone that directly influences milk production following pregnancy.