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Prolactin Blood Test

Last updated May 26, 2019

Approved by: Maulik P. Purohit MD, MPH

The Prolactin Test is a blood test that measures the levels of circulating prolactin.

What are the other Names for this Test? (Equivalent Terms)

  • HPRL Blood Test
  • Human Prolactin (HPRL) Blood Test
  • PRL Test

What is Prolactin Blood Test? (Background Information)

  • Prolactin (PRL) is a hormone central to breast-feeding. It stimulates both the growth of breast tissue and lactation (“pro-” before, “lact-” milk)
  • The pituitary gland produces PRL, along with several other hormones. This pea-sized gland is situated in the center of the skull, behind the bridge of nose. Due to its positioning, an enlargement in its size can cause noticeable abnormalities
  • During pregnancy, the placenta makes PRL; while, after delivery, PRL hormone is stimulated by the suckling of an infant and its level increases. This is known as hormonal positive feedback
  • Normally, PRL levels are low in men and women. It is held in check by other hormones, such as dopamine; also, the positive feedback stimulation is absent
  • PRL levels also fluctuate throughout the day in accordance with the circadian rhythm; levels peak during nights and are lower during the day
  • Certain disorders (like tumors) and behaviors, such as drug use and anorexia, may cause a disruption of the hormonal system, which can manifest as abnormal PRL levels
  • Prolactin Test is a blood test that measures the levels of circulating prolactin

What are the Clinical Indications for performing the Prolactin Blood Test?

The following are clinical indicators for performing the Prolactin Blood Test in women:

  • Lactation without pregnancy (galactorrhea)
  • Infertility
  • Abnormal menstrual cycle with indications like:
    • Infrequent periods (oligomenorrhea)
    • Lack of ovulation (anovulation)
    • Lack of menstruation entirely in non-menopausal women (amenorrhea)
  • Headaches and visual disturbances from pituitary gland enlargement
  • Excessive hair (hirsutism) 

The following are clinical indicators for performing the Prolactin Blood Test in men:

  • Erectile dysfunction
  • Infertility
  • Low testosterone levels
  • Headaches and visual disturbances from pituitary gland enlargement
  • Abnormal breast growth (gynecomastia)

The following are gender-neutral clinical indicators for performing the Prolactin Test:

  • Monitor recurrence of prolactin-producing tumor (prolactinoma)
  • Monitor health of the pituitary gland, or for progress of a disorder
  • Monitor effects of a medication

How is the Specimen Collected for Prolactin Blood Test?

Sample required: Blood

Process: Insertion of a needle into an arm vein.

Preparation required: Wakefulness for 3-4 hours (please consult your healthcare provider)

What is the Significance of the Prolactin Blood Test Result?

High prolactin levels (hyperprolactinemia) may indicate the following:

  • Normal pregnancy/nursing
  • Hypothyroidism
  • Kidney disease or kidney failure
  • Hypothalamic disease
  • Acromegaly
  • Stress
  • Anorexia
  • Use of recreational and hormonal drugs, such as estrogen
  • Addison’s disease
  • Polycystic ovary syndrome
  • Prolactinoma

Low prolactin levels (hypoprolactinemia) are generally less challenging (medically); nevertheless, they may indicate the following:

  • Pituitary disease or tissue death (necrosis), possibly due to blood supply obstruction (infarction)
  • Osteoporosis
  • Decreased sex hormones - estrogen in females and testosterone in males

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Prolactin, which stimulates milk production, should not be confused with oxytocin, which stimulates milk excretion and uterine contractions
  • PRL levels typically remain constant with age, all other factors remaining constant/stable
  • Prolactin Testing is often combined with imaging techniques, such as MRI scans. This enables better diagnosis of pituitary gland enlargement, which may possibly be indicative of a tumor
  • Up to 25% of increased prolactin levels are actually due to the test picking up macroprolactin, an inactive form of prolactin

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: March 27, 2014
Last updated: May 26, 2019