Pituitary Tumors

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Treating Pituitary Tumors TOPICS

Medicines to treat pituitary tumors

Several medicines can be used to treat pituitary tumors that are making hormones.

Drugs for prolactin-secreting tumors (prolactinomas)

Drugs called dopamine agonists, such as bromocriptine (Parlodel®) and cabergoline, are very effective in both blocking prolactin production by prolactinomas and preventing growth of these tumors. Although both drugs are effective, cabergoline lasts longer than bromocriptine, so it does not need to be taken as often.

Most people with prolactinomas are able to control their prolactin levels with medicine. The drugs are also very effective in reducing the size of most prolactin-secreting macroadenomas. In fact, these drugs work so well that surgery is usually not needed for prolactinomas. Only about 1 out of 5 of these tumors does not shrink with treatment. Even if the tumor doesn’t shrink, these drugs often can keep prolactinomas from growing larger. If successful, the drug treatment may be continued for life.

Possible side effects of these drugs include drowsiness, dizziness, nausea, vomiting, diarrhea or constipation, confusion, and depression. Another “side effect” is that these drugs may restore fertility in women whose high prolactin levels had been causing infertility. Cabergoline may cause fewer side effects than bromocriptine, but it might also increase the risk of heart valve problems. However, this is rare in patients taking this drug for prolactinomas.

Drugs for growth hormone-secreting tumors

Octreotide (Sandostatin®) is a man-made form of the natural hormone somatostatin. Somatostatin, which is made in the pituitary and other glands, blocks growth hormone (somatotropin) production by adenomas and returns insulin-like growth factor-1 (IGF-1) to normal levels in about two thirds of patients. It is first given as an injection under the skin 3 times per day. A longer acting form is available, which can be given as a monthly injection. A newer, similar drug called lanreotide (Somatuline®) is given as an injection about once a month. Doctors measure how well these drugs are working by testing blood growth hormone and IGF-1 levels. Tumors tend to shrink very slowly with these drugs.

Both drugs can have minor side effects, such as nausea, vomiting, diarrhea, stomach pain, dizziness, headache, and pain at the site of injection. Many of these side effects improve or even go away with time. They can also cause gallstones and may worsen diabetes if a person has it.

Dopamine agonists such as bromocriptine or cabergoline may reduce growth hormone levels in about 1 out of 5 patients. Unfortunately, higher doses are needed for these tumors than for prolactinomas, and some patients have trouble with the side effects they can cause (discussed above). An advantage of these drugs is that they can be taken as a pill.

Pegvisomant (Somavert®) is a newer drug that works by blocking the action of growth hormone on other cells. It is very effective in lowering blood IGF-1 levels, but it doesn’t block growth hormone secretion by the pituitary gland or shrink pituitary tumors. It has few side effects, although it may lower blood sugar levels and cause mild liver damage in some people. It is given by daily injection under the skin.

Drugs for corticotropin (ACTH)-secreting tumors

Medicines are not usually part of the treatment of these tumors unless surgery and radiation therapy don’t work (or if the effects of radiation have not yet been felt). Cyproheptadine (Periactin®) suppresses ACTH production in about half of these tumors. For patients who do not respond to cyproheptadine, several drugs can be used to keep the adrenal gland from making cortisol. These include ketoconazole, aminoglutethimide, etomidate, metyrapone, mifepristone, and mitotane. These drugs can be hard to take because of side effects, but they can have a clear benefit when surgery is not an option.

Drugs to treat thyrotropin (TSH)-secreting tumors

For these tumors, drugs such as octreotide and lanreotide (somatostatin analogs) can usually reduce the amount of TSH that is produced. Bromocriptine or cabergoline (dopamine agonists) can also be used. These drugs are discussed in more detail above.

Last Medical Review: 01/11/2013
Last Revised: 01/11/2013