Student Question

Outline how hormones regulate lactation.

Quick answer:

Several hormones regulate lactation. During pregnancy, estrogen and progesterone are responsible for inhibiting breastmilk production. After a mother gives birth, prolactin helps promote and regulate breastmilk production, and oxytocin causes the "milk let down" that occurs when a baby breastfeeds.

Expert Answers

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There are two main hormones involved in lactation and breastfeeding, prolactin and oxytocin. Prolactin is a hormone that is responsible for breastmilk production and the regulation of breastmilk. During pregnancy and breastfeeding, prolactin levels are elevated in order to increase insulin resistance, regulate lipid metabolism, and increase growth factor levels. Once a baby is born, oxytocin is responsible for the muscle contractions in the alveoli of the breasts in order to squeeze milk into the milk ducts of the breasts. Oxytocin also causes the "milk let down" that results when a baby sucks on the mother's nipple.

During pregnancy, a woman experiences elevated levels of hormones estrogen and progesterone. It is important that both of these hormone levels decrease after a woman gives birth because they result in a decrease in milk production for breastfeeding women. However, estrogen stimulates the milk duct system within the breast to grow and differentiate in preparation for breastfeeding. Following the few months after birth, estrogen levels decline significantly so that the mother can breastfeed. Progesterone levels are also elevated during pregnancy in order to promote the growth of the alveoli and lobes within the mother's breast. Elevated levels of progesterone inhibit milk production during pregnancy also. When a mother gives birth, progesterone levels decrease, allowing the mother to produce milk for her baby.

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