North American Registry of Midwives (NARM) Practice Exam

What is the primary hormone responsible for milk ejection?

1. Prolactin

2. Oxytocin

3. Estrogen

4. Progesterone

The correct answer is: Oxytocin

The primary hormone responsible for milk ejection is oxytocin. During breastfeeding, when the infant suckles at the breast, nerve signals are sent to the brain, triggering the release of oxytocin from the posterior pituitary gland. Oxytocin acts on the myoepithelial cells surrounding the alveoli in the breast tissue, causing them to contract and squeeze the milk down the ducts toward the nipple, facilitating the milk ejection reflex. Prolactin plays a vital role in milk production, but it is not directly responsible for the ejection of milk. Estrogen and progesterone are also important hormones involved in the development of breast tissue and preparing the breasts for lactation but do not play a direct role in the ejection process. Thus, understanding the specific roles of these hormones highlights why oxytocin is identified as the key hormone for milk ejection during breastfeeding.