Prolactin:Ahormonesecreted by thepituitary glandthat stimulateslactation(milk production). It also has many other functions, includingessentialrolesinthe maintenance of theimmune system. Abnormally high prolactin can delaypuberty, interfere withovulationin women, decreaselibidoin men, and decreasefertility. Elevated prolactin (hyperprolactinemia) may be due to abenigntumorin thepituitaryglandcalled aprolactinoma.
