Prolactin: Function, Levels, Symptoms and Testing
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What does prolactin do?
Prolactin helps develop mammary-gland tissue and supports lactation and breastfeeding. It rises during pregnancy and breastfeeding, is made mainly by the pituitary gland, and is regulated by dopamine and estrogen. It is a hormone, a chemical messenger involved in many body processes. [1]
Core idea | Plain-language meaning |
Hormone | A chemical messenger involved in many body processes. |
Main roles | Mammary-gland development and lactation. |
Main source | The pituitary gland makes and releases most prolactin. |
Natural high points | Pregnancy and breastfeeding. |
Persistently high levels | Called hyperprolactinemia. |
Main test | A prolactin or PRL blood test. |
What the research says
About 1 in 5 high prolactin results may be macroprolactin. A systematic review and meta-analysis of 67 studies from 27 countries found a global prevalence of macroprolactinemia of 18.9% (95% CI 15.8–22.1%) among patients with hyperprolactinemia, with considerable variation between studies (I² = 95.7%). The authors concluded that screening for macroprolactin should be routine before other causes of high prolactin are investigated (Che Soh et al., Int J Environ Res Public Health, 2020). [2]
Quinagolide, a dopamine-agonist drug, normalized prolactin in most patients studied. A systematic review and meta-analysis of 33 studies including 827 patients treated with quinagolide, a dopamine agonist used for hyperprolactinemia, found prolactin normalization in a pooled 69% (95% CI 61–76%) and tumor reduction of more than 50% in 20% (95% CI 15–28%). The pooled proportion with adverse effects was 13% (95% CI 11–16%) (Zeng et al., Front Endocrinol, 2023). [3]
What is prolactin?
Prolactin is a hormone, also known as lactotropin or PRL. It is responsible for lactation, supports certain breast-tissue development and contributes to hundreds of other bodily processes. Prolactin levels are naturally elevated during pregnancy and breastfeeding. [1]
What is the function of prolactin?
Prolactin has two main functions: triggering mammary-gland development within breast tissue and supporting lactation and breastfeeding. [1]
During pregnancy, prolactin, estrogen and progesterone stimulate breast-tissue development and milk production. They help develop mammary alveoli, which are pockets in mammary glands that make and store milk. [1]
After delivery, the number of prolactin receptors on mammary alveolar cells increases. This allows milk to flow out of the nipple during lactation. [1]
How does the prolactin feedback loop work?
Prolactin is one of the hormones that has a positive feedback loop. In this case, a baby's suckling sends nerve signals that prompt the pituitary gland to release more prolactin, and more feeding leads to more release. Nipple stimulation through a baby's suckling triggers more prolactin release. The biology of lactation is complex, so prolactin is one part of a larger process. [1]
Where does prolactin come from?
Most prolactin comes from the pituitary gland, which makes and releases it. Dopamine, a neurotransmitter, and estrogen, a hormone, control prolactin production. [1]
Structure or signal | Role |
Pituitary gland | Makes and releases most prolactin. |
Dopamine | Helps control prolactin production. |
Estrogen | Helps control prolactin production and works with prolactin in breast development. |
Mammary alveoli | Make and store milk; prolactin receptors help milk flow after delivery. |
Why do prolactin levels change?
Prolactin levels naturally rise during pregnancy and breastfeeding. They may also rise slightly and temporarily after physical stress, exercise, eating a meal, sexual intercourse, nipple stimulation unrelated to breastfeeding, chest injury or seizures. A temporary increase is different from persistently high prolactin, so the context and timing of a test matter. [1]
What is hyperprolactinemia?
Hyperprolactinemia means that prolactin levels are too high for a long time. Certain conditions and medications can cause it. Common causes include certain medicines (such as some antipsychotic and anti-nausea drugs), an underactive thyroid and prolactinoma, a pituitary adenoma or tumor. A high result does not by itself identify the cause, so a healthcare professional must interpret it with symptoms, medicines and other relevant information.
Symptoms of high prolactin
Symptoms of hyperprolactinemia can include infertility, loss of interest in sex, milky nipple discharge called galactorrhea, irregular periods and erectile dysfunction. These symptoms can have other causes and do not prove that prolactin is high. [1]
What causes temporary prolactin increases?
Situation | Effect on prolactin |
Physical stress or pain | May temporarily increase prolactin. |
Exercise | May temporarily increase prolactin. |
Eating a meal | May temporarily increase prolactin. |
Sexual intercourse | May temporarily increase prolactin. |
Nipple stimulation | May temporarily increase prolactin. |
Chest injury | May temporarily increase prolactin. |
Seizures | May temporarily increase prolactin. |
What does low prolactin mean?
Outside pregnancy and breastfeeding, prolactin levels are normally low. The only sign of abnormally low prolactin is a lack of breast-milk production after giving birth. Hypopituitarism, a rare condition in which the pituitary gland does not make one or more of the hormones it normally makes, may be a cause. [1]
Lactation is complex, and low milk supply can have several possible causes. A low milk supply does not automatically mean prolactin is low.
What test measures prolactin?
A prolactin or PRL test measures prolactin in the blood. A healthcare professional may recommend it when signs of elevated prolactin are present. The test can also help assess pituitary-gland function. [1]
What are normal prolactin levels?
Normal prolactin levels follow general reference values, but ranges vary slightly among laboratories, so use the range printed on your report.
Group | General value |
Males | Less than 20 ng/mL |
Females who are not pregnant or breastfeeding | Less than 25 ng/mL |
Pregnant or breastfeeding people | 80 to 400 ng/mL |
Normal ranges can vary slightly among laboratories. Use the reference range printed on your laboratory report and ask a healthcare professional about questions or unexpected results. Individual interpretation may also depend on pregnancy or breastfeeding status, medicines, symptoms and the laboratory method.
When should you contact a healthcare professional?
Contact a healthcare professional if you have symptoms associated with excess prolactin, such as irregular periods, infertility, loss of interest in sex, milky nipple discharge or erectile dysfunction. If you are having problems with milk supply, contact a lactation consultant or breastfeeding-medicine specialist. New, persistent or concerning symptoms need professional evaluation rather than self-diagnosis.
How is high prolactin evaluated?
A healthcare professional may order a PRL blood test to check the prolactin level and assess pituitary-gland function. The next step depends on the result, symptoms, medications and suspected cause. Do not stop prescribed medication or begin hormone treatment based on a single online result. Discuss the report with the clinician who ordered it.
How does prolactin support breastfeeding?
Prolactin supports lactation, but milk supply is a complex process. A low supply has several possible causes and cannot be attributed to prolactin alone without evaluation. A lactation consultant or breastfeeding-medicine specialist can help assess milk-supply concerns.
Conclusion: Prolactin is a hormone of lactation and more
Prolactin is made mainly by the pituitary gland and supports mammary-gland development, lactation and breastfeeding. Levels rise naturally during pregnancy and breastfeeding and may shift temporarily with stress, exercise, meals, sexual intercourse, nipple stimulation, chest injury or seizures. [1]
Persistently high prolactin is called hyperprolactinemia and can be associated with infertility, irregular periods, galactorrhea, low sexual interest and erectile dysfunction. Low prolactin is uncommon outside pregnancy and breastfeeding, and low milk supply can have several causes. A PRL blood test can measure prolactin and help assess pituitary function, and interpretation should use the laboratory's range and the person's clinical context. Use this guide to prepare questions for a qualified healthcare professional. Clear hormone information is a starting point for better care, not a diagnosis. [1]
Frequently Asked Questions
What is prolactin?
Prolactin, also called lactotropin or PRL, is a hormone that supports lactation and certain breast-tissue development.
What does prolactin do?
Prolactin's two main roles are triggering mammary-gland development and supporting lactation and breastfeeding.
Where is prolactin produced?
Most prolactin comes from the pituitary gland, which makes and releases it.
What controls prolactin production?
Dopamine and estrogen help control prolactin production.
Why is prolactin higher during pregnancy?
During pregnancy, prolactin works with estrogen and progesterone to stimulate breast development and milk production.
Does breastfeeding affect prolactin?
Yes. Prolactin levels are naturally elevated during breastfeeding, and nipple stimulation through suckling triggers more prolactin release.
What is hyperprolactinemia?
Hyperprolactinemia means prolactin levels are too high for a long time. Common causes include certain medicines, an underactive thyroid and prolactinoma, a pituitary adenoma.
What are symptoms of high prolactin?
Symptoms can include infertility, loss of interest in sex, milky nipple discharge, irregular periods and erectile dysfunction.
What is galactorrhea?
Galactorrhea is milky discharge from the nipples. It is one of the symptoms that can occur with hyperprolactinemia.
What causes a temporary prolactin increase?
Physical stress or pain, exercise, eating, sexual intercourse, nipple stimulation, chest injury and seizures may temporarily raise prolactin.
What is low prolactin?
Outside pregnancy or breastfeeding, prolactin is normally low. A lack of breast-milk production after birth is the sign of abnormally low prolactin.
Can low milk supply have causes other than prolactin?
Yes. Lactation is complex and low milk supply can have several possible causes.
What is a PRL test?
A PRL test is a blood test that measures prolactin. It can also help assess pituitary-gland function.
What are general prolactin reference values?
Less than 20 ng/mL for males, less than 25 ng/mL for females who are not pregnant or breastfeeding, and 80 to 400 ng/mL for pregnant or breastfeeding people. Laboratory ranges can vary.
Can a normal range vary between laboratories?
Yes. Use the reference range printed on your laboratory report and ask a healthcare professional about your results.
When should I see a healthcare professional?
Contact one for symptoms associated with excess prolactin, concerns about prolactin levels or milk-supply problems. A lactation consultant or breastfeeding-medicine specialist may help with milk-supply concerns.
Related Reading
Understanding Hyperprolactinemia (High Prolactin) explains the causes, symptoms and treatment of high prolactin.
Prolactinoma: Complete Guide to the Most Common Pituitary Tumor, Symptoms, Causes, and Treatment covers the pituitary tumor that most often raises prolactin.
Pituitary Gland: Anatomy, Hormones, Function and Related Conditions describes the gland that makes prolactin and other hormones.
Amenorrhea: Symptoms, Causes, Treatment & Complete Guide explains missed periods, which high prolactin can cause.
References
Cleveland Clinic. Prolactin: What It Is, Function & Levels. Cleveland Clinic. Updated December 30, 2024. https://my.clevelandclinic.org/health/body/prolactin
Che Soh NAA, Yaacob NM, Omar J, et al. Global Prevalence of Macroprolactinemia among Patients with Hyperprolactinemia: A Systematic Review and Meta-Analysis. Int J Environ Res Public Health. 2020;17(21):8199. PMID 33171973. https://doi.org/10.3390/ijerph17218199
Zeng Y, Huang Q, Zou Y, et al. The efficacy and safety of quinagolide in hyperprolactinemia treatment: A systematic review and meta-analysis. Front Endocrinol (Lausanne). 2023;14:1027905. PMID 36761195. https://doi.org/10.3389/fendo.2023.1027905
Disclaimer
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.
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