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The goal of treatment for prolactinoma is to return prolactin secretion to normal, reduce tumor size, correct any visual abnormalities, and restore normal pituitary function. In the case of very large tumors, only partial achievement of this goal may be possible. Because dopamine is the chemical that normally inhibits prolactin secretion, doctors may treat prolactinoma with bromocriptine or cabergoline, drugs that act like dopamine. This type of drug is called a dopamine agonist. These drugs shrink the tumor and return prolactin levels to normal in approximately 80 percent of patients. Both have been approved by the Food and Drug Administration for the treatment of hyperprolactinemia. Bromocriptine is the only dopamine agonist approved for the treatment of infertility. Another dopamine agonist, pergolide, is available in the U.S., but is not approved for treating conditions that cause high blood levels of prolactin.
Bromocriptine is associated with side effects such as nausea and dizziness. To avoid these side effects, it is important for bromocriptine treatment to start slowly. An example of a typical approach used by an experienced endocrinologist follows:
Begin by taking a quarter of a 2.5 milligram tablet of bromocriptine with a snack at bedtime. After 3 days, increase the dose to a quarter of a tablet with breakfast and a quarter at bedtime. After 3 more days, take half a tablet twice a day, and 3 days later, one tablet at night and half with breakfast. Finally, the dose is increased to one tablet twice a day. If prolactin is still high, add half a tablet with lunch. If the medication is well tolerated, increase the dose to a full tablet. If side effects develop with a higher dose, return to the previous dosage. With time, side effects disappear while the drug continues to lower prolactin.
Bromocriptine treatment should not be interrupted without consulting a qualified endocrinologist. Prolactin levels often rise again in most people when the drug is discontinued. In some, however, prolactin levels remain normal, so the doctor may suggest reducing or discontinuing treatment every two years on a trial basis.
Cabergoline is also associated with side effects such as nausea and dizziness, but these may be less common and less severe than with bromocriptine. As with bromocriptine therapy, side effects may be avoided if treatment is started slowly. An example of a typical approach used by an experienced endocrinologist follows:
Begin by taking .25 milligrams (or 1/2 tablet) twice a week. After four weeks, increase the dose by .25 milligrams to .50 milligrams (or 1 tablet) twice a week. After four more weeks, increase the dose by .25 milligrams to .75 milligrams (or 1 1/2 tablets) twice a week. Finally, after four additional weeks, the dose can be increased to 1 milligram (or 2 tablets) twice a week. If side effects develop with a higher dose, the doctor may return to the previous dosage. If a patient's prolactin level remains normal for 6 months, a doctor may consider stopping treatment.
Cabergoline should not be interrupted without consulting a qualified endocrinologist.
Surgery should be considered if medical therapy cannot be tolerated or if it fails to reduce prolactin levels, restore normal reproduction and pituitary function, and reduce tumor size. If medical therapy is only partially successful, this therapy should continue, possibly combined with surgery or radiation.
The results of surgery depend a great deal on tumor size and prolactin level as well as the skill and experience of the neurosurgeon. The higher the prolactin level, the lower the chance of normalizing serum prolactin. In the best medical centers, surgery corrects prolactin levels in 80 percent of patients with a serum prolactin less than 250 ng/ml. Even in patients with large tumors that cannot be completely removed, drug therapy may be able to return serum prolactin to the normal range after surgery. Depending on the size of the tumor and how much of it is removed, studies show that 20 to 50 percent will recur, usually within five years.