Which hormone primarily causes milk letdown during lactation?

Which hormone primarily causes milk letdown during lactation?

• A. Prolactin
• B. Estrogen
• C. Oxytocin
• D. Progesterone

Answer: (C)

Milk letdown is driven by oxytocin. When the infant nurses, nerve signals reach the hypothalamus and trigger the posterior pituitary to release oxytocin. Oxytocin then acts on the myoepithelial cells surrounding the milk-producing alveoli and ducts, causing them to contract and push milk into the ducts for ejection. Prolactin, on the other hand, handles milk production itself by stimulating milk synthesis in the gland. Estrogen and progesterone support gland development during pregnancy and modulate lactation, but they do not cause the milk to be ejected.

Milk letdown is driven by oxytocin. When the infant nurses, nerve signals reach the hypothalamus and trigger the posterior pituitary to release oxytocin. Oxytocin then acts on the myoepithelial cells surrounding the milk-producing alveoli and ducts, causing them to contract and push milk into the ducts for ejection. Prolactin, on the other hand, handles milk production itself by stimulating milk synthesis in the gland. Estrogen and progesterone support gland development during pregnancy and modulate lactation, but they do not cause the milk to be ejected.