Prolactin

What is prolactin?

Prolactin (also known as lactotropin and PRL) is a hormone that’s responsible for lactation and certain breast tissue development and contributes to hundreds of other bodily processes.

Prolactin is present in normal levels in people assigned male at birth (AMAB) and non-lactating and non-pregnant people. They’re elevated in people who are pregnant or breastfeeding (chestfeeding).

Where does prolactin come from?

Most of your prolactin comes from your pituitary gland. It makes and releases prolactin. Dopamine (a neurotransmitter) and estrogen (a hormone) control prolactin production.

What is the function of prolactin?

Prolactin contributes to hundreds of bodily functions. But its two main functions include:

• Triggering the development of mammary glands within breast tissues
• Supporting lactation and breastfeeding (chestfeeding)

During pregnancy, prolactin, estrogen and progesterone stimulate breast tissue development and milk production. Specifically, they trigger the development of mammary alveoli (pockets in your mammary glands that make and store milk).

After the delivery of your baby, the number of prolactin receptors on your mammary alveolar cells increases. This allows for milk to flow out of your nipple (lactation).

Prolactin is one of a few hormones that has a positive feedback loop. This means that the release of prolactin stimulates your pituitary gland to release even more of it. Nipple stimulation through suckling by your baby triggers more prolactin release.

What causes prolactin levels to change?

Prolactin levels naturally rise during pregnancy and breastfeeding. They may also rise slightly — and temporarily — due to the following situations:

• Physical stress, like experiencing pain
• Exercise
• Eating a meal
• Sexual intercourse
• Nipple stimulation unrelated to chestfeeding
• Injury to your chest area
• Seizures

Certain conditions and medications can cause your prolactin levels to be too high for a long time. This is called hyperprolactinemia. The most common cause is prolactinoma, a pituitary adenoma (tumor).

Hyperprolactinemia typically causes symptoms, like:

• Infertility
• Loss of interest in sex
• Milky discharge from your nipples (galactorrhea)
• Irregular periods
• Erectile dysfunction

What causes abnormally low levels of prolactin?

Your prolactin levels are normal unless you’re pregnant or breastfeeding (chestfeeding). So, the only sign of having abnormally low prolactin is a lack of breast milk production after giving birth.

In these cases, hypopituitarism may be the cause. Hypopituitarism is a rare condition in which your pituitary gland doesn’t make one or more of the hormones it normally does.

It’s important to note that lactation is a complex process. There are several possible causes of low milk supply.

What test measures prolactin levels?

A prolactin (PRL) test measures the level of prolactin in your blood. Your healthcare provider may recommend a prolactin blood test if you have signs of elevated prolactin levels. A prolactin test can also help assess the function of your pituitary gland.

What are normal prolactin levels?

In general, the normal values for prolactin include:

• For people AMAB: Less than 20 ng/mL (nanograms per milliliter)
• For people AFAB who aren’t pregnant or chestfeeding: Less than 25 ng/mL
• For people who are pregnant or chestfeeding: 80 to 400 ng/mL

Normal value ranges for prolactin levels may vary slightly among different laboratories. Be sure to look at the range of normal values listed on your laboratory report. Ask your healthcare provider if you have questions about your results.

When should I see my healthcare provider about my prolactin levels?

If you have symptoms of excess prolactin levels, contact your healthcare provider. They can order a simple blood test to check your prolactin levels.

If you’re having issues with milk supply, see a lactation consultant or breastfeeding medicine specialist.