Prolactin is a polypeptide hormone essential for lactation. Its production in 
the lactotroph cells of the anterior pituitary is regulated primarily by the 
inhibitory action of hypothalamic dopamine. Hyperprolactinemia is the most 
common endocrine disorder of the hypothalamic-pituitary axis, occurring mostly 
in women and presenting most commonly with amenorrhea and galactorrhea. Causes 
of hyperprolactinemia include physiologic, pharmacologic and pathologic factors; 
pituitary adenoma is a common pathologic cause. Women may present with decreased 
libido, infertility, oligomenorrhea/amenorrhea and galactorrhea. Men may present 
with decreased libido, infertility, gynecomastia or impotence. In the absence of 
an identifiable and treatable underlying cause, hyperprolactinemia is generally 
treated with dopamine agonist medications.