International Board of Certified Lactation Consultant (IBCLC) Practice Exam

Which hormone is primarily responsible for milk ejection during breastfeeding?

1. Prolactin

2. Oxytocin

3. Estrogen

4. Progesterone

The correct answer is: Oxytocin

The hormone responsible for milk ejection during breastfeeding is oxytocin. This hormone plays a crucial role in the lactation process by facilitating the contraction of myoepithelial cells surrounding the alveoli in the breast. When a baby suckles at the breast, sensory nerves in the nipple send signals to the hypothalamus in the brain, prompting the release of oxytocin from the posterior pituitary gland. This release causes the milk to be ejected from the ducts toward the nipple, enabling the infant to receive milk effectively. In contrast, while prolactin is essential for milk production and stimulates the alveolar cells to produce milk, it does not directly induce milk ejection. Estrogen and progesterone are hormones that prepare the breast for lactation during pregnancy, but they do not have a direct role in the milk ejection reflex during breastfeeding. Understanding each hormone's specific function can clarify the physiological processes involved in lactation and breastfeeding.