What is prolactin?
Prolactin (also known as lactotropin and PRL) is a hormone that’s responsible for lactation, certain breast tissue development and contributes to hundreds of other bodily processes. Prolactin levels are normally low in people assigned male at birth (AMAB) and non-lactating and non-pregnant people. They’re normally elevated in people who are pregnant or breastfeeding (chestfeeding).
Most of your prolactin comes from your pituitary gland. It makes and releases (secretes) the hormone.
Your pituitary gland is a small, pea-sized gland located at the base of your brain below your hypothalamus. It’s a part of your endocrine system and is in charge of making many different important hormones, including prolactin. Dopamine (a brain chemical) and estrogen (a hormone) control prolactin production and release from your pituitary gland.
- Nipple stimulation.
How does prolactin affect my body?
Prolactin contributes to hundreds of bodily functions, but its two main functions include:
- The development of mammary glands within breast tissues and milk production.
- Lactation and breastfeeding (chestfeeding).
Prolactin’s role in mammary gland development and milk production
During pregnancy, the hormones prolactin, estrogen and progesterone stimulate breast tissue development and milk production.
Prolactin promotes the growth of a certain type of breast tissue called mammary alveoli, which are the components of the mammary gland where the production of milk occurs. Prolactin also stimulates the breast alveolar cells to create milk components, including:
- Lactose (the carbohydrate component of milk).
- Casein (the protein component of milk).
- Lipids (components that provide energy, essential fatty acids and cholesterol).
Prolactin’s role in lactation and breastfeeding (chestfeeding)
After delivery of your baby, progesterone levels drop, which increases the number of prolactin receptors on the mammary alveolar cells. This allows for milk secretion through your nipple, commonly known as lactation.
After delivery, prolactin levels don’t remain constantly elevated. Prolactin levels will only spike during periods of nipple stimulation through suckling by your baby. As long as your baby maintains suckling, prolactin levels stay elevated. During periods when you’re not breastfeeding, your prolactin levels decrease, and milk production reduces. If a person doesn't breastfeed their baby, prolactin levels fall to non-pregnant levels after one to two weeks.
What causes prolactin to increase?
Prolactin levels normally rise during pregnancy and breastfeeding (chestfeeding). They may also rise slightly due to the following situations:
- Physical stress, such as experiencing pain.
- Eating a meal.
- Sexual intercourse.
- Nipple stimulation unrelated to chestfeeding.
- Injury to your chest area.
- Epileptic seizures.
These increases in prolactin are usually slight and temporary. Certain conditions and medications can cause long-term (persistent) elevated prolactin levels.
What test measures prolactin levels?
A prolactin (PRL) test measures the level of prolactin in your blood. Your healthcare provider may order a prolactin blood test for you if you experience signs and symptoms of elevated prolactin levels and/or to evaluate the function of your pituitary gland.
What are normal prolactin levels?
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 or ask your healthcare provider if you have questions about your results.
In general, the normal values for prolactin include:
- For people assigned male at birth: Less than 20 ng/mL (nanograms per milliliter).
- For people assigned female at birth who are not pregnant or chestfeeding: less than 25 ng/mL.
- For people who are pregnant or chestfeeding: 80 to 400 ng/mL.
What are the signs and symptoms of high prolactin levels?
For anyone, higher-than-normal prolactin levels in your blood can cause the following symptoms:
- Loss of interest in sex.
- Milky discharge from your nipples when not pregnant or chestfeeding (galactorrhea).
For people assigned female at birth (AFAB), symptoms of excess prolactin include:
- Changes in menstruation not related to menopause, such as irregular periods (menstruation) or no periods (amenorrhea).
- Pain or discomfort during penetrative sex due to vaginal dryness.
For people assigned male at birth (AMAB), common symptoms of a prolactinoma include:
What causes abnormally high levels of prolactin?
Several factors and conditions can cause higher-than-normal levels of prolactin in your blood (hyperprolactinemia), including:
- Prolactinoma, a pituitary gland tumor (most common cause).
- Certain medications.
- Certain health conditions.
- Other pituitary gland tumors.
Prolactinomas can cause elevated prolactin levels
A prolactinoma is the most common cause of higher-than-normal prolactin levels in your blood. A prolactinoma is a benign (non-cancerous) tumor that forms in your pituitary gland and causes excess production of prolactin. It’s a type of pituitary adenoma.
Prolactinomas occur most commonly in people under the age of 40. They’re more common in people assigned female at birth (AFAB) than in people assigned male at birth (AMAB). They rarely occur in children and adolescents.
Healthcare providers usually treat prolactinomas with medication, but they can also be treated with surgery and radiation therapy.
Medications that can cause elevated prolactin levels
The brain chemical dopamine helps suppress the production of prolactin in your body. Any medication that affects the production or use of dopamine in your body can make your prolactin levels rise.
Medications that can increase prolactin levels include:
- Certain antipsychotic medications, such as risperidone.
- Certain high blood pressure medications.
- Medications that treat nausea and vomiting.
- Pain relievers that contain opioids.
If you have high prolactin levels due to a medication, your levels will usually return to normal three to four days after you stop taking the medication. Never stop taking a prescribed medication unless your healthcare provider has told you to do so.
Health conditions that can cause elevated prolactin levels
Health conditions other than a prolactinoma that may cause hyperprolactinemia include:
- Kidney disease.
- Hypothyroidism (underactive thyroid).
- Shingles, especially if the rash or blisters are on your chest.
Other pituitary gland tumors that can cause elevated prolactin levels
Large tumors (other than prolactinomas) located in or near your pituitary gland can cause hyperprolactinemia by reducing the effect of dopamine. Prolactin release is suppressed by dopamine, but if the tumor blocks the flow of dopamine to the prolactin-producing cells, then hyperprolactinemia will develop.
What causes abnormally low levels of prolactin?
Your prolactin levels are usually low unless you’re pregnant or breastfeeding (chestfeeding), so the only sign of having lower-than-normal levels of prolactin is a lack of breastmilk production after giving birth.
In these cases, hypopituitarism is often the cause. Hypopituitarism is a rare condition in which there’s a lack (deficiency) of one, multiple or all of the hormones your pituitary gland makes. It’s usually caused by abnormal pressure on your pituitary gland or damage to your pituitary gland.
When should I see my doctor about my prolactin levels?
If you experience symptoms of excess prolactin levels (hyperprolactinemia), such as irregular periods and/or loss of interest in sex, contact your healthcare provider. They can order a simple blood test to check your prolactin levels.
A note from Cleveland Clinic
Prolactin is an important hormone for pregnancy and chestfeeding. While having higher-than-normal prolactin levels if you’re not pregnant or chestfeeding isn’t life-threatening, it can cause certain issues, such as infertility, and lower your quality of life. Be sure to contact your healthcare provider if you’re experiencing signs or symptoms of hyperprolactinemia. They’re available to help you.
- Al-Chalabi M, Bass AN, Alsalman I. Physiology, Prolactin. StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2021. Accessed 2/14/2022.
- MedlinePlus. Prolactin Blood Test. Accessed 2/14/2022.
- MedlinePlus. Prolactin Levels. Accessed 2/14/2022.
- National Institute of Diabetes and Digestive and Kidney Diseases. Prolactinoma. Accessed 2/14/2022.
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