why estrogen and progestrone inhibits secretion of milk from breast but prolactin stimulates it

Answer 1

Estrogen and progesterone are hormones produced during the menstrual cycle and pregnancy. They play important roles in regulating the reproductive system. During pregnancy, high levels of estrogen and progesterone maintain the structure of the milk ducts in the breast and prepare them for milk production.

However, estrogen and progesterone also have inhibitory effects on lactation, or the process of milk production. They prevent the full expression of lactation by inhibiting the release of prolactin, a hormone necessary for milk synthesis. This inhibition serves to prevent milk production before childbirth.

After childbirth, the levels of estrogen and progesterone decrease significantly, while the level of prolactin increases. Prolactin is the primary hormone responsible for milk production and secretion in the breast. When the nipple is stimulated, prolactin is released, which signals the mammary glands to produce milk. This allows for the initiation and maintenance of lactation.

In summary, estrogen and progesterone inhibit milk secretion from the breast by suppressing prolactin release, while prolactin stimulates milk production after childbirth when estrogen and progesterone levels drop.