Hormone Deep Dive: Prolactin – The Milk Hormone

The human body works in weird and wonderful ways to keep us moving and grooving through life. With so many intricate systems working in tandem with each other, it’s a miracle how much they get done.  One of the ways the human body supports itself is through high-tech methods of communication. One of those high-tech methods is the endocrine system.  Hormones are the hardworking messengers that make up the endocrine system. Over fifty hormones have been identified in the human body, each with its own special jobs or jobs. You’ve probably heard of hormones like estrogen, testosterone, and oxytocin, but not all hormones get the same amount of attention. So let’s take a deep dive and get to know a vital hormone that many people haven’t even heard of – prolactin.

What is Prolactin?

If you have heard of prolactin, it’s most likely been in the context of lactation, as that’s what it’s best known for.  Prolactin plays a vital role in all parts of fertility, not just lactation. That being said, it’s often called ‘the milk hormone’, because it helps with milk production for people who are lactating. These are some of the vital jobs that prolactin takes part in besides helping with lactation:

• Regulating metabolism
• Regulating fluids in the body
• Behavioral functions
• Regulating the immune system
• Production of sex hormones
• Fertility

While estrogen regulates prolactin, other hormones like dopamine and oxytocin can cause an increase or decrease in the amount of prolactin in the body. 

Where is Prolactin Made in The Body?

This incredible hormone is made primarily by the pituitary gland. The pituitary gland is a pea-sized gland at the base of your brain that helps regulate all sorts of bodily functions like your mood, energy levels, heartbeat, reproductive organs, vision, and growth. It’s often called the “master gland” because it tells other glands to release hormones.  Now back to prolactin! Prolactin is also produced and stored in the uterus, breasts, brain, prostate, immune cells, and adipose tissue. Although it mainly hangs out around reproductive organs, it’s crucial in many parts of the body and development. 

Prolactin and Lactation

Between clogged milk ducts, mastitis, and low milk levels, lactation isn’t always as straightforward as it may seem on the outside.  After birth prolactin levels go up giving your mammary glands the signal that it’s time to get moving – they have a baby to feed! This rise in prolactin gets the milk moving, but to keep it flowing, people who are lactating need a regular breast and nipple stimulation through nursing, pumping, and sometimes breast massage.  Without this stimulation, milk levels go down, hence why people tend to “dry out” when they wean or partially wean their babies. 

High levels of prolactin while lactating can affect fertility and menstruation. That’s why you hear people talk about not being able to get pregnant again while they’re lactating. While you might have a lower chance of getting pregnant while lactating, it’s totally possible, so be sure to use precaution if you don’t want another baby right away! If low levels of prolactin are affecting your milk supply, you can help to increase them by pumping and doing breast stimulation and eating certain herbs and foods like fenugreek, stinging nettle, and dark green vegetables.

Can You Have a Prolactin Imbalance?

Prolactin levels vary at different times in people’s lives, especially if they’ve been pregnant or are lactating. Still, an imbalance in prolactin levels, whether low or high, can be a result of an underlying condition, no matter what your sex is. Here’s what a prolactin imbalance may look like:

High Levels of Prolactin

People with PCOS may have slightly higher prolactin levels, PCOS also can affect fertility.  High levels of prolactin can also result in the development of a condition called galactorrhea, which can cause a milky discharge from the nipples that isn’t chest or breast milk. People with excess prolactin who aren’t lactating may experience absent or irregular periods, breast tenderness, fatigue, and low sex drive. High prolactin levels can also be caused by hypothyroidism, a thyroid condition that causes low thyroid levels.

Low Prolactin Levels

It’s not as common, low prolactin levels can also cause health issues. While rare, low prolactin levels are usually due to an underactive pituitary gland. Remember – the master gland that regulates prolactin production? It can also be caused by breast surgery that may cause nerve damage to the nipple that sends the signal to the brain to produce prolactin.

Other causes of low prolactin levels, especially for people who are lactating include:

• Smoking
• Obesity
• Depression

If your provider suspects a prolactin imbalance, they may give you a test to check the levels of it in your bloodstream. This can help determine if any underlying conditions are present or if you need further testing.