Hyperprolactinemia is the most common endocrine disorder of the 
hypothalamic-pituitary axis. While it can occur in men, it occurs more commonly 
in women. The prevalence of hyperprolactinemia ranges from 0.4% in an unselected 
normal adult population to as high as 9-17% in women with reproductive 
disorders. There are many possible causes of hyperprolactinemia, falling into 
three general categories: physiologic, pharmacologic and pathologic. When 
specific treatable underlying causes have been eliminated and in cases of severe 
hyperprolactinemia, the most likely cause is a prolactin (PRL)-secreting 
pituitary adenoma. Microadenomas should be treated medically, with a dopamine 
agonist, if there is an indication for therapy (such as amenorrhea, infertility 
or bothersome galactorrhea). If there is no indication for therapy, 
microadenomas may be followed conservatively, as growth is uncommon. 
Macroadenomas may grow larger; medical therapy is recommended initially, with 
neurosurgical evaluation reserved for specific clinical situations, such as 
failure of medical therapy and evidence of mass effect despite medical therapy. 
In the United States, the dopamine agonists indicated for treatment of 
hyperprolactinemia are bromocriptine and cabergoline. Bromocriptine is usually 
given once or twice daily, while cabergoline has a long duration of action and 
is given once or twice weekly. Results of comparative studies indicate that 
cabergoline is clearly superior to bromocriptine in efficacy (PRL suppression, 
restoration of gonadal function) and tolerability.