Breast hormones of development and lactation
Hormones and lactation (Lactation hormones)
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.
This hormone causes the breast tissue to multiply, but inhibits milk production. After birth, progesterone levels drop, this triggers milk production.
Prolactin and cortisol:
Prolactin 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 produced after exposure to cortisol.
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 mom 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 increase prolactin levels.
- High prolactin levels are inclined to delay ovulation.
Functions of the lactation hormone Oxytocin:
- 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 ones.
Tracy Ann Behr, CBC, CLD (CBI)
Courses on hormones of lactation through Child birth international
Other pages on breastfeeding problems in connection with this page on lactation hormones
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hormones releesed during breast feeding