Which hormones are involved in lactation and let-down, respectively?

• A. Oxytocin stimulates milk production; prolactin triggers let-down
• B. Prolactin stimulates milk production; oxytocin triggers let-down
• C. Estrogen stimulates milk production; progesterone triggers let-down
• D. Progesterone stimulates milk production; estrogen triggers let-down

Answer: (B)

Milk production is stimulated by prolactin from the anterior pituitary, while let-down (milk ejection) is driven by oxytocin released from the posterior pituitary in response to nipple stimulation and infant suckling. Estrogen and progesterone support breast development during pregnancy but suppress milk production; after birth, their levels fall, allowing prolactin to act. So the correct pairing is prolactin for milk production and oxytocin for let-down.