A Prolactin Serum Test measures the prolactin level in the blood. The prolactin test is typically ordered to diagnose galactorrhea, or abnormal lactation, but can also be useful in the diagnosis of headaches and visual disturbances.
Fasting is not required for this blood test, and results will be delivered within 1-2 days. The Prolactin Serum Test may also be referred to as PRL. This test is available with or without a doctor’s order; insurance is not necessary to order this test.
What is prolactin?
The primary role of prolactin, a hormone produced in the pituitary gland, is to promote lactation (breast milk production). Both men and women produce prolactin in small amounts, although levels are much higher in pregnant women. Prolactin levels remain high in women who breastfeed, but soon return to pre-pregnancy levels in those who do not.
Besides pregnancy, prolactin levels can increase as a result of a prolactinoma, a prolactin-producing tumor of the pituitary gland, potentially causing milk production in non-pregnant women and sometimes men. Depending on its size and location, a prolactinoma can cause headaches and visual disturbances (a result of the tumor impacting the optic nerve) and also interfere with the other hormones produced by the pituitary gland. A prolactinoma may cause infertility and irregular menstruation in women, and loss of sexual function and libido in men. An abnormally high level of prolactin (hyperprolactinemia) may cause progressive pattern hair loss.
Prolactin levels change throughout the day. Levels are highest during sleep and shortly after waking. Prolactin levels are also higher when experiencing physical or emotional stress.