Breast growth hormones Estrogen and Human Placental Lactogen work on the growth of the breast before pregnancy. Progesterone, Prolactin, and Oxytocin are all involved during pregnancy and lactation.
During pregnancy the levels of Estrogen are higher, these levels cause the growth of the breast tissue.
Human Placental Lactogen:
Also higher during pregnancy and stimulates the growth of the breast tissue, the nipples, and areola.
hormone causes the breast tissue to multiply but inhibits milk
production. After birth, progesterone levels drop, this triggers milk
Prolactin and cortisol:
makes the cells differentiate to perform their own specific role. After
birth, the alveoli produce milk because of Prolactin (this hormone is
sent via the hypothalamus) Prolactin can only be created after exposure
Prolactin levels vary according to:
Levels of Prolactin are higher at night.
Prolactin levels are at their highest until two months postpartum.
They are also higher in women who breastfeed after this period. Once the mother weans, the levels drop again.
Prolactin levels increase if more milk is removed from the breast.
Women who smoke have lower Prolactin levels.
Stress and anxiety may decrease Prolactin levels.
High Prolactin levels are inclined to delay ovulation.
It causes muscle contractions, which cause the muscles of the uterus
to contract in labor. Oxytocin also helps the uterus return to its
normal size after pregnancy.
Oxytocin is released when the
nipples are stimulated, it causes the alveoli to contract, which squeezes
the milk out into the duct system. This is called a let-down. A let-down
happens a few times while breastfeeding.
Oxytocin has a calming effect. Women who breastfeed, have lower levels of stress hormone than non-breastfeeding women.