What hormone is primarily responsible for lactation?

Prolactin is the primary hormone responsible for lactation. It is produced by the anterior pituitary gland and plays a crucial role in stimulating breast tissue development and milk production in response to childbirth. After delivery, the levels of progesterone and estrogen, which help prepare the breasts for lactation during pregnancy, drop significantly. This hormonal shift allows prolactin to take effect, leading to the initiation of milk synthesis.

While oxytocin is important for the milk ejection reflex, allowing milk to be released from the alveoli into the ducts when the baby suckles, it does not initiate milk production itself. Estrogen and progesterone also have roles in mammary gland development during pregnancy but are not directly involved in the stimulation of milk production postpartum. Thus, prolactin is the key hormone when it comes to the actual production of milk necessary for breastfeeding.