Which hormone is primarily responsible for milk synthesis?

• A. Prolactin
• B. Oxytocin
• C. Catecholamines
• D. Beta endorphins

Answer: (A)

Milk synthesis is driven primarily by prolactin, a hormone from the anterior pituitary. Prolactin acts on mammary alveolar cells to stimulate the production of milk components—proteins, lactose, and fats—so continuous milk production can occur after birth, especially with regular infant suckling that boosts prolactin release. Oxytocin, while essential for milk ejection (let-down) by contracting the myoepithelial cells around the milk-alveoli, does not create milk itself. The other substances listed don’t promote milk synthesis as the primary driver: catecholamines can hinder lactation through vasoconstrictive effects and interference with let-down, and beta-endorphins aren’t the main hormone responsible for producing milk.