What Is the Prolactin Hormone?

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Question: What is Prolactin?


Prolactin is a hormone secreted by the pituitary gland, a small structure in the brain which secretes other hormones. Prolactin's primary function is to enhance breast development and initiate lactation (breastfeeding). Prolactin levels are normally elevated in pregnant and nursing women.

If you are having irregular menstrual periods, infertility, or breast milk leakage (especially if you aren't nursing a baby), your physician may order a blood test to see if your prolactin levels are elevated.



Symptoms of hyperprolactinemia (or high prolactin levels) may be nonexistent, or women may notice the following:

  • infertility
  • White milk leaking from nipples
  • Absent, infrequent or irregular periods
  • Loss of libido
  • Painful or uncomfortable intercourse
  • Vaginal dryness
  • Acne
  • Excessive body and facial hair growth (hirsutism)
  • Hot flashes

Causes Of High Prolactin Levels

Hyperprolactinemia, or high prolactin levels, can be caused by numerous factors such as:

  • Pituitary tumor or disease
  • Disease of the hypothalamus
  • Hypothyroidism
  • Kidney disease
  • Cushing's disease
  • Medications can also cause high prolactin levels including tricyclic antidepressants (specifically clomipramine and desipramine), certain antipsychotics (i.e., Haldol, Zyprexa, and Risperdal), verapamil (for blood pressure), Reglan (metoclopramide; an antinausea medication) and acid blockers (H2 blockers).

How Is Prolactin Measured?

Prolactin can be easily measured through a routine blood test.

Because a number of factors can affect the blood values, women should avoid breast stimulation and intercourse the night before the test.

What Does High Prolactin Levels Mean?

If the blood test comes back elevated, the doctor may wish to repeat the test, this time after fasting for at least 8 hours. A magnetic resonance imaging (MRI) may be ordered to look for evidence of a pituitary growth or for damage to surrounding tissues.

Blood tests to assess the production of other pituitary hormones may be done and can be helpful to rule out other conditions causing similar symptoms. 

The treatment for high prolactin levels is to return levels to normal ranges. This can usually be done with medications such as dopamine agonists, or in more serious conditions, surgery to reduce or remove the tumor. Going forward, once prolactin levels are in normal ranges, your doctor may recommend you undergo regular monitoring of prolactin levels by doing blood tests. Occasionally, an MRI may also be needed to check the size of the tumor and look for growth. 

Updated by PCOS Expert Angela Grassi, MS, RDN, LDN

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