Which hormone stimulates milk expulsion and uterine contractions?

Oxytocin is the hormone responsible for stimulating milk expulsion and uterine contractions. During lactation, oxytocin is released in response to the baby's suckling, which triggers the milk ejection reflex, allowing milk to be delivered to the infant. Additionally, during childbirth, oxytocin plays a crucial role by stimulating uterine contractions, which help to facilitate labor and delivery.

This hormone's dual function in both lactation and childbirth highlights its importance in reproductive physiology, emphasizing its role in maternal and infant health. In contrast, other hormones listed, such as prolactin, primarily promote milk production rather than its expulsion, while human growth hormone and aldosterone have entirely different physiological roles, focusing on growth and fluid balance, respectively.