Which hormone is secreted primarily by the pituitary gland and stimulates milk production?

Prolactin is the hormone that is primarily secreted by the anterior pituitary gland and plays a key role in stimulating milk production in the mammary glands after childbirth. It is essential for lactation, as it facilitates the synthesis and secretion of milk in response to the hormonal changes that occur during pregnancy and after delivery. Elevated levels of prolactin during pregnancy prepare the mammary glands for lactation, and after childbirth, suckling by the infant stimulates further prolactin release, reinforcing the milk production process.

While oxytocin also plays a significant role in lactation, it mainly acts to trigger milk ejection (let-down), rather than stimulating milk production itself. Follicle-stimulating hormone is involved in the growth and maturation of ovarian follicles and has no direct role in lactation. Estrogen, while important for breast development during pregnancy, does not directly stimulate milk production in the same way that prolactin does. Thus, prolactin is the key hormone to associate with milk production.