Prolactin Levels

A prolactin (PRL) test measures the level of prolactin in a sample of your blood. Prolactin is a hormone produced by the pituitary gland, a small gland at the base of the brain. Hormones are chemical messengers in your bloodstream that control the actions of certain cells or organs.

Prolactin affects many body processes. But its main role is to signal breast tissue to grow during pregnancy and make milk for breastfeeding after birth. So, prolactin levels in pregnant women and new mothers are normally high.

In nonpregnant women and men, prolactin levels are normally low. Having higher-than-normal prolactin levels (hyperprolactinemia) can affect the body in different ways: In women, it can affect how the ovaries work and can cause menstrual problems and infertility.; In men, it can affect how the testicles work and can cause a lower sex drive and erectile dysfunction (ED). Also known as impotence, ED is the inability to get or maintain an erection.; In men and women who are not pregnant or breastfeeding, it can signal your body to start making breastmilk.; Higher-than-normal prolactin levels can have different causes: Prolactinoma, a benign (noncancerous) tumor growing on the pituitary gland.

This is the most common cause. This type of tumor makes prolactin, which leads to higher-than-normal levels of prolactin in the blood.; Certain medicines.; Certain health conditions, such as hypothyroidism (underactive thyroid), kidney disease, and chest injuries; Other pituitary gland tumors.; A prolactin test can't show the cause of higher-than-normal prolactin levels. But finding out what your levels are can help your health care provider decide which other tests you need to diagnose the cause of your symptoms.

Why this test is done

You may need a prolactin levels test if you are having symptoms that could be caused by higher-than-normal prolactin levels. The symptoms are different for women and men.

In women, symptoms may include:

• Changes in menstruation (irregular periods or absence of periods)
• Production of breast milk when not pregnant or breastfeeding
• Nipple discharge
• Infertility

Symptoms also depend on whether you have gone through menopause, which is when your periods stop, normally around age 50.

In men, symptoms may include:

• Nipple discharge
• Erectile dysfunction/impotence
• Enlarged breasts (gynecomastia)
• Decreased facial and body hair
• Low sex drive

If you have higher-than-normal levels of prolactin because of a prolactinoma, you may also have other symptoms. A prolactinoma that is not treated can grow large enough that it presses against nearby parts of the pituitary gland and the brain. This can cause:

• Headaches
• Changes in vision, if the tumor is pressing on the optic nerve (the nerve at the back of the eye)
• Low levels of other pituitary hormones, such as thyroid hormones and cortisol

If you've already been diagnosed with high prolactin levels from a prolactinoma, you may need prolactin testing to check whether your treatment is working. After treatment, you may be retested to see if the tumor has come back.

How to prepare

Your provider will let you know if you need to do anything to prepare for your test. You may be asked to fast (not eat or drink) for several hours before your test.

Prolactin levels change throughout the day. For accuracy, your blood sample will usually be scheduled for three to four hours after you wake up.

Certain medicines and vitamins can affect prolactin levels. So, be sure to tell your provider about anything you are taking. But never stop taking any medicine without talking with your provider first.

Sample type

Blood

Other names for this test

PRL test, prolactin blood test