Prolactin - Pregnancy

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Prolactin (PRL), also known as the luteotropic hormone (LTH), is the milk hormone which plays an important role in preparing your body for breastfeeding. Prolactin is mainly produced in your pituitary gland and in response to increased estrogen levels, its levels increase between 10 and 20 times during pregnancy.

Prolactin’s first and foremost function during pregnancy is to stimulate the growth of your mammary glands, so that you will be able to breastfeed when your baby finally arrives. If you have low levels of prolactin in your body it can make breastfeeding difficult and even impossible. During pregnancy, increased estrogen and progesterone levels prevent you from lactating, but as soon as your baby is born, the levels of these hormones drop drastically and you begin to lactate. Soon after, your prolactin levels begin to drop as well, but the sucking action of your babystimulates the nerves in your breasts causing your body to produce more prolactin.

Woman holding breasts

You will probably go up a cup size or due during your pregnancy, you have prolactin to thank for that.
Free image courtesy of

During your pregnancy, prolactin is also important for your baby’s brain development, the formation of surfactant on your baby’s lungs and your baby’s immune tolerance. In some cases, your baby (whether it is a girl or boy) may secrete witch’s milk, a milk-like substance, from their nipples. This is NOT lactation and is a normal response to prolactin in their bodies.

Prolactin is also a fertility hormone and too much of it can make conception difficult. This is why when you breastfeed it is almost impossible to become pregnant. High levels of prolactin prevent you from ovulating, because they inhibit the release of the ovulation hormone FSH.

What does prolactin do to your body?

  • Your wonderful new cleavage is partly due to increased prolactin levels, which increase the size of your mammary glands.

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