Final answer:
Prolactin stimulates the mammary glands to produce milk, which is essential for breastfeeding. During pregnancy, prolactin levels increase to prepare the breasts for milk production but are inhibited by other hormones until after childbirth. Postpartum, prolactin levels are maintained by frequent breastfeeding or pumping to ensure ongoing milk supply.
Step-by-step explanation:
The hormone prolactin plays a crucial role in the reproductive system, particularly in relation to the breasts. Prolac_tin's primary function is to stimulate the mammary glands to produce milk after childbirth, which is essential for nursing infants. During pregnancy, starting around the fifth week, the levels of circulating prolactin begin to increase significantly, and this rise continues until late pregnancy, when the levels of prolactin are high enough to initiate milk production. However, the presence of estrogen, progesterone, and other placental hormones during pregnancy inhibits milk synthesis. Once the placenta is expelled after childbirth, this inhibition is lifted, allowing prolactin to promote the production of milk in the mammary glands.
Additionally, prolactin is involved in several changes to the breast tissue during pregnancy, including the development and enlargement of the breasts, readying them for the task of feeding the newborn. After childbirth, frequent breastfeeding or pumping is necessary to maintain high levels of prolactin and sustain milk production. Over time, even with continued breastfeeding, baseline levels of prolactin will eventually return to pre-pregnancy levels. Other hormones such as oxytocin, growth hormone, cortisol, parathyroid hormone, and insulin also contribute to lactation by aiding in the transport of nutrients to breast milk.