What hormone is primarily responsible for stimulating milk secretion in the breast?

Prolactin plays a crucial role in stimulating milk secretion in the breast after childbirth. It is produced by the anterior pituitary gland and is essential for lactation. During pregnancy, elevated levels of prolactin help prepare the mammary glands for milk production. After delivery, the drop in estrogen and progesterone levels allows prolactin to act effectively, leading to the synthesis and secretion of milk.

Oxytocin is important for milk ejection, allowing milk to be released from the alveoli to the ducts and nipple, but it does not stimulate the production of milk itself. Estrogen and progesterone support breast development during pregnancy but do not directly trigger the secretion of milk. Thus, prolactin is recognized as the primary hormone responsible for this vital function in breastfeeding.