Hyperprolactinemia (HPRL) unrelated to pregnancy is a disorder characterized by excess production of prolactin (PRL) and may result in infertility, hypogonadism, and galactorrhea. Such nonphysiological hyperprolactinemia is caused mainly by drugs or by tumors in the anterior pituitary gland, which are usually identifiable by means of magnetic resonance imaging (MRI). Some cases are due to prolactinomas and lesions in the pituitary stalk. A human germline PRLR mutation has been found in familial isolated hyperprolactinemia.
