What is a prolactin levels test?A prolactin (PRL) test measures the level of prolactin in the blood. Prolactin is a hormone made 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
