Answer: Prolactin
Explanation: During breastfeeding the anterior pituitary gland in the brain releases hormone prolactin as part of positive feedback mechanism. A mothers alveoli will collect nutrients from the blood and convert them into milk. Another hormone oxytocin, causes the muscles around the breast to eject milk (a let-down reflex) whilst a baby is sucking.
A sucking baby is actually a positive feedback that causes the brain to release more prolactin, which in turn causes the alveoli to convert more sugars and nutrients into milk.
