Hyperprolactinaemia (HP), or hyperprolactinemia in the United States (U.S.), is the presence of abnormally-high levels of prolactin in the blood. Normal levels are less than 580 mIU/L for women, and less than 450 mIU/L for men. Prolactin is a peptide hormone produced by the anterior pituitary gland primarily associated with lactation and plays a vital role in breast development during pregnancy. Hyperprolactinaemia may cause production and spontaneous flow of breast milk and disruptions in the… (More on Hyperprolactinemia)