To determine whether your prolactin levels are higher (or occasionally, lower) than normal. Prolactin is a hormone released by the pituitary gland that stimulates breast development and milk production in women. When you have symptoms of elevated prolactin, such as galactorrhea, a condition that occurs when a woman's breast makes milk (or a milky discharge) even though she is not breast feeding a baby, and/or visual disturbances and headaches; as part of a workup for female and male infertility; for follow-up of low testosterone in men.