What is a prolactin levels test?

A prolactin (PRL) test measures the level of prolactin in the blood. Prolactin is a hormonemade by the pituitary gland, a small gland at the base of the brain. Prolactin causes the breasts to grow and make milk during pregnancy and after birth. Prolactin levels are normally high for pregnant women and new mothers. Levels are normally low for nonpregnant women and for men.

If prolactin levels are higher than normal, it often means there is a type of tumor of the pituitary gland, known as a prolactinoma. This tumor makes the gland produce too much prolactin. Excess prolactin can cause the production of breast milk in men and in women who are not pregnant or breastfeeding. In women, too much prolactin can also cause menstrual problems and infertility (the inability to get pregnant). In men, it can lead to lower sex drive and erectile dysfunction (ED). Also known as impotence, ED is the inability to get or maintain an erection.

Prolactinomas are usually benign (noncancerous). But left untreated, these tumors can damage surrounding tissues.

Other names: PRL test, prolactin blood test

What is it used for?

A prolactin levels test is most often used to:

  • Diagnose a prolactinoma (a type of tumor of the pituitary gland)
  • Help find the cause of a woman’s menstrual irregularities and/or infertility
  • Help find the cause of a man’s low sex drive and/or erectile dysfunction

Why do I need a prolactin levels test?

You may need this test if you have symptoms of a prolactinoma. Symptoms may include:

  • Production of breast milk if you are not pregnant or breastfeeding
  • Nipple discharge
  • Headaches
  • Changes in vision

Other symptoms are different depending on whether you are a man or woman. If you are a woman, symptoms also depend on whether you have gone through menopause. Menopause is the time in a woman’s life when her menstrual periods have stopped and she can’t become pregnant anymore. It usually starts when a woman is around 50 years old.

Symptoms of excess prolactin in women who have not gone through menopause include:

  • Irregular periods
  • Periods that have stopped completely before the age of 40. This is known as premature menopause.
  • Infertility
  • Breast tenderness

Women who have gone through menopause may not have symptoms until the condition worsens. Excess prolactin after menopause often causes hypothyroidism. In this condition, the body does not make enough thyroid hormone. Symptoms of hypothyroidism include:

  • Fatigue
  • Weight gain
  • Muscle pain
  • Constipation
  • Trouble tolerating cold temperatures

Symptoms of excess prolactin in men include:

  • Nipple discharge
  • Breast enlargement
  • Low sex drive
  • Erectile dysfunction
  • Decrease in body hair

What happens during a prolactin levels test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You will need to take your test about three to four hours after waking up. Prolactin levels change throughout the day, but are usually the highest in early morning.

Be sure to tell your health care provider about any medicines you are taking. Certain medicines can raise prolactin levels. These include birth control pills, high blood pressure medicine, and antidepressants.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

If your results show higher than normal prolactin levels, it may mean you have one of the following conditions:

  • Prolactinoma (a type of tumor of the pituitary gland)
  • Hypothyroidism
  • A disease of the hypothalamus. The hypothalamus is an area of the brain that controls the pituitary gland and other body functions.
  • Liver disease

If your results show high prolactin levels, your health care provider may order an MRI(magnetic resonance imaging) test to get a closer look at your pituitary gland.

High prolactin levels may be treated with medicine or surgery. If you have questions about your results, talk to your health care provider.