A prolactin test measures the level of the hormone prolactin, which is made by the pituitary gland, in your blood. See a picture of thepituitary gland.Pregnant women have high levels of prolactin, which helps make breast milk. During pregnancy, prolactin levels increase by 10 to 20 times. After the baby is born, prolactin stays high if you are breast-feeding. In women who do not breast-feed, prolactin levels return to normal soon after they give birth. After months of breast-feeding, prolactin levels may also return to normal levels even if you still breast-feed.
The pituitary glands of men and nonpregnant women also make prolactin but it is not clear what it does in the body for these people.Prolactin levels are different throughout the day. The highest levels occur duringsleep and shortly after you wake up. Prolactin levels also get higher during times of physical or emotional stress.Many medicines can cause prolactin levels to go up. Tumors of the pituitary gland can sometimes cause prolactin to be made. A damaged pituitary gland may not be able to make normal amounts of prolactin so levels will be lower.
Prolactin is a hormone released by the pituitary gland. The prolactin test measures the amount of prolactin in the blood. Alternative Names:PRL
How the Test is Performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
Why It Is Done
A test for prolactin is done:
- To find the cause of abnormal nipple discharge, or if a woman is not having periods (amenorrhea) or if a woman is having a hard time becoming pregnant (infertile).
- In a man when a pituitary gland problem is suspected. Also, a prolactin test may be done to check levels if a man lacks sexual desire or if he has a hard time having an erection (erectile dysfunction). Prolactin levels may be checked when a man’s testosterone levels are really low.
- To see whether a tumor in the pituitary gland (called a prolactinoma) is making large amounts of prolactin.
How To Prepare
Do not eat or drink for a certain number of hours as instructed by your health professional before having a prolactin test.
A blood prolactin test is usually done about 3 hours after you wake up, sometime between 8 a.m. and 10 a.m.
Emotional stress or strenuous exercise just before the test can raise prolactin levels. You may be asked to rest quietly for up to 30 minutes before having your blood drawn.
Stimulation of the nipples can raise prolactin levels. Avoid nipple stimulation for 24 hours prior to prolactin testing. A woman having abnormal nipple discharge should not do anything to cause more discharge before the test.
How is it used?
Prolactin levels are used, along with other hormone tests, to help:
- Determine the cause of galactorrhea
- Determine the cause of headaches and visual disturbances
- Diagnose infertility and erectile dysfunction in males
- Diagnose infertility in females
- Diagnose prolactinomas
- Evaluate anterior pituitary function (along with other hormones)
- Monitor treatment of prolactinomas and detect recurrences
How It Is Done
The health professional drawing blood will:
- Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
- Clean the needle site with alcohol.
- Put the needle into the vein. More than one needle stick may be needed.
- Hook a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Put a gauze pad or cotton ball over the needle site as the needle is removed.
- Put pressure to the site and then a bandage.
Is there anything else I should know?
Stresses from illness, trauma, and even the fear of having the blood test done can cause moderate increases in prolactin.Prolactinomas are often small. Along with prolactin levels, a doctor may do an MRI (magnetic resonance imaging) of the brain to locate and determine the size of the tumor as well as the size of the pituitary gland.