Prolactin (PRL) Blood Test

A prolactin (PRL) test measures how much of a hormone called prolactin you have in your blood. The hormone is made in your pituitary gland, which is located just below your brain. Its hormones help regulate important functions such as growth, metabolism, blood pressure and reproduction. When women are pregnant or have just given birth, their prolactin levels increase so they can make breast milk. Doctors may order prolactin tests to help diagnose, or monitor treatment of, prolactinoma.

The normal values for prolactin are:

Men: less than 20 ng/mL (20 µg/L or 425 mIU/L) Nonpregnant women: less than 25 ng/mL (25 µg/L or 530 mIU/L) Pregnant women: 80 to 400 ng/mL (1700 to 8510 mIU/L)

The natural levels of prolactin in the body change throughout the day. Levels gradually rise overnight and are at their highest in the morning. Doctors usually ask to take a blood sample 3 to 4 hours after a person has woken up.

High prolactin levels. High prolactin levels interfere with the normal production of other hormones, such as estrogen and progesterone. This can change or stop ovulation (the release of an egg from the ovary). So, prolactin levels over 100 ng/mL (2100 mIU/L) can alter the normal function of a woman's reproductive system, causing symptoms of menopause (absence of menstrual periods, hot flashes, vaginal dryness) and infertility. It can also lead to irregular or missed periods. Some women have high prolactin levels without any symptoms. Prolactin levels associated with stress or dopamine antagonists are usually below 100 μg/dl. However, small pituitary tumors will cause hyperprolactinemia as well, with no other abnormalities.

A prolactin level of over 150-200 ng/mL (3190 mIU/L) is almost always due to a prolactin secreting pituitary adenoma. In all patients with suspected pituitary tumors, a complete pituitary hormone evaluation should be performed. Other possible causes of prolactin overproduction include medications, other types of pituitary tumors, an underactive thyroid gland, ongoing irritation to the chest, pregnancy and breast-feeding.

Treatment for high prolactin levels.

The treatment depends on the cause. If no cause is found, the usual treatment may be:

• changing your diet and keeping your stress levels down. Foods that lower prolactin levels are generally high in zinc; think shellfish, beef, turkey and beans. It's also important to get plenty of B6, so foods like potatoes, bananas, wild salmon, chicken and spinach can help boost those vitamin levels.
• avoiding clothing that makes your chest uncomfortable.
• taking vitamin B-6 and vitamin E supplements.