Prolactin and oxytocin are the two main hormones that directly impact milk production.
Both already exist in your body, and both are secreted from the pituitary gland, deep inside your brain. They each have different pathways, which means they are triggered in different ways.
Let’s start with prolactin, which is the one that makes the milk.
As we mentioned before, prolactin already exists in your body. After birth, you’ll see a big increase, with some people increasing faster and higher than others.
You don’t need to be a breastfeeding mother to make it. Here’s a case of a woman, who had already been through menopause, who established breastfeeding.
Prolactin and your nervous system
To understand how prolactin works, you need to understand a little bit about your nervous system. One of the functions of your nervous system is to take information that you sense around your body, process it, and trigger reactions.
Too vague? Fair enough. Let’s imagine that you touch a hot stovetop. The heat creates pain signals that travel back to your central nervous system (your spinal cord and brain) that cause you to pull your hand away.
In the case of feeding, your baby sucks at your nipple, which sends a message through the nerve (called T4) that runs from your nipple to your spinal cord up to your brain. Your brain secretes prolactin to your blood, which runs all the way back through your body and to your breast to create milk (pro - lactin = pro - milk!).
Stimulating your nipple (and your breast) to increase prolactin
Now, it doesn’t have to be a baby that sucks at your nipple for this message to be sent and responded to. Theoretically, it could be a pump or your hands. It’s just that a baby is very good at stimulating the nipple by latching, and also at stimulating your breast with their body.
There are two other nerves (called T3 and T5) that run from your breast above and below the nipple that also send the signal to release prolactin when stimulated. Have you ever seen a breastfeeding baby massage or play with their mother’s breast?
[insert gif of baby playing with breast]
So if you’re trying to increase your prolactin, you would spend time early on stimulating your nipple (T4) AND your breast (T3, T5), although the nipple is most important. Check out this study, that shows the highest level of prolactin release occurs when you stimulate nipple and breast, as opposed to just breast.
Timing of stimulation to increase prolactin
Now as with all things in the human body, it’s never that simple. Your prolactin response and levels aren’t the same every time you stimulate your nipple. One study showed prolactin levels rising at about 25 - 30 minutes into a feed, and dropping off between feedings. The longer the period your baby is away from your breast, the less prolactin you have.
This is supported by other studies that show that more frequent nursing (10x per day) resulted in more weight gain for babies at Day 15, than less frequent nursing (7x per day), even though the total time nursing was the same (137-138 minutes).
Unfortunately,again, we couldn’t find any studies looking at the effect on prolactin from pumping (as opposed to nursing).
Creating receptor sites for prolactin
In the first few hours after your placenta is no longer in your body, your hormones have a big change.
Happens early - first two hours after birth - get more receptors
Prolactin increases during pregnancy, which helps increase the mammary glands to prepare for milk production. Suckling at the nipple stimulates milk production by increasing prolactin blood levels.
There is a balance of prolactin and oxytocin necessary for producing the milk and keeping it in the breast. Oxytocin makes the cells in the breast tissue (alveoli) contract, which allows the milk to be collected in lobules. When oxycontin is produced more quickly than prolactin, the milk is released from the alveoli and travels through the ducts. Skin-to-skin contact also promotes oxytocin release. Both prolactin and oxytocin levels are stimulated by suckling at the nipples.