The main conditions that cabergoline is used to treat are those related to hyperprolactinemia, a disorder marked by high blood levels of prolactin. The pituitary gland secretes the hormone prolactin, which is essential for controlling the menstrual cycle and preserving pregnancy. Prolactin, on the other hand, can cause irregular periods, amenorrhea (lack of menstruation), and even infertility when levels of the hormone rise unnaturally.