Which hormone stimulates contraction of the uterus and milk ejection?

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

Answer: (C)

Oxytocin is the hormone that drives both uterine contractions and milk ejection. It’s released from the posterior pituitary in response to signals like cervical stretching during labor and suckling at the breast. When it acts on the uterus, it stimulates smooth muscle to contract, helping with labor and delivery. In the mammary glands, oxytocin stimulates the myoepithelial cells surrounding the milk-containing alveoli, causing milk to be pushed into the ducts so it can be ejected when the baby nurses. Prolactin, by contrast, mainly drives milk production rather than movement of milk. Estrogen helps prepare and maintain the uterus but doesn’t trigger the immediate milk-ejection reflex. Adrenaline can actually dampen uterine contractions and isn’t involved in milk ejection.