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The most important task of the pituitary hormone prolactin is to start lactation and maintain it after childbirth. It also affects the development of the mammary glands. Prolactin (PRL) is secreted from the anterior pituitary gland. The top layers of the brain prevent excess production.

Normally, the secretion of prolactin is increased, besides pregnancy and breastfeeding, by physical strain, touching the breasts, and stress.

When to measure prolactin levels?

Prolactin levels are usually measured in women when examining infertility, disturbances of the menstrual cycle, excess milk secretion from the breasts (galactorrhea), or suspected diseases of the pituitary gland.

Correspondingly, men’s prolactin levels are measured when examining infertility, impotence, loss of libido, overgrowth of breasts (gynaecomastia), excess milk secretion from the breasts (galactorrhea), or suspected diseases of the pituitary gland.

Prolactin is measured in connection with the following symptoms:

  • Disturbance of the menstrual cycle
  • Infertility
  • Milk discharge from the breasts
  • Loss of libido
  • Impotence in men
  • Headache
  • Vision disorders
What does a prolactin test measure?

The test can indicate the level of prolactin in the blood and find out whether there are disorders present in the pituitary gland, hypothalamus, thyroid, or brain.

Normally, the result is: 

  • Women ≥ 19y: 109-557 mIU/l
  • Men ≥ 19y: 73-407 mIU/l
  • Children under 1-18y: 88-480 mU/l

Please contact your physician or other healthcare professional if you suspect an illness or need help interpreting the results.

The reference values of this examination have changed 6.10.2022. You will find your own result's reference values from My LOUNA in touch with the graph. Read more about defining reference values.

Prolactin normally increases during pregnancy, and its level remains elevated after childbirth. Prolactin levels increase up to 10–20-fold during pregnancy. The prolactin level returns to normal within a few weeks of stopping breastfeeding.

Overproduction of prolactin occurs in the following contexts:

  • Prolactinoma, a benign tumour that produces prolactin in the pituitary gland
  • Certain drugs (especially psychoactive drugs and oestrogen)
  • Hypothyroidism (underactive thyroid)
  • Diseases and tumours of the kidneys
  • Diseases and tumours of the liver
  • Injuries or tumours in the brain and pituitary gland

Low prolactin levels are very rarely observed. Their meaning is uncertain.

  • LH
  • FSH
  • Testosterone

SYNLAB test list: Prolactin (S-PRL) https://www.yml.fi/tuotekuvaus_show.php?tuotenro=305

[Rivityskohta]Terveyskirjasto health library: Aivolisäkkeen sairauksia https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=dlk00003&p_hakusana=prolaktiini

Terveyskirjasto health library: Prolaktinooma (maitohormonia tuottava kasvain) https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=dlk00998&p_hakusana=prolaktiini

Suomen endokrinologiyhdistys: Prolaktinooma (Leena Moilanen) https://www.endo.fi/tietoa-endokrinologisista-sairau/potilasohjeet/prolaktinooma/


Fasting is not required

This examination does not require fasting