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.
You will need to take your test about three to four hours after waking up. Prolactin levels change throughout the day, but are usually the highest in early morning.