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 cabergoline and bromocriptine (Parlodel®), can often both stop prolactinomas from making too much prolactin and shrink these tumors. Both drugs work well, although cabergoline seems to work better and lasts longer than bromocriptine, so it doesn’t need to be taken as often.
Most people with prolactinomas can control their prolactin levels with these medicines. The drugs also shrink most prolactin-secreting macroadenomas. In fact, these drugs work so well that surgery usually isn’t needed for prolactinomas. Only about 1 out of 5 of these tumors doesn’t 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. For women whose high prolactin levels had been causing infertility, these drugs may restore fertility. Cabergoline may cause fewer side effects than bromocriptine, but it might also increase the risk of heart valve problems. However, this is rare when taking this drug for prolactinomas.
Drugs for growth hormone-secreting tumors
These tumors can cause acromegaly in adults and gigantism in children (discussed in Signs and Symptoms of Pituitary Tumors). Medicines are often not as effective for these tumors as they are for prolactinomas, so they’re not usually the first treatment used.
Somatostatin analogs: Drugs such as octreotide (Sandostatin®), lanreotide (Somatuline® Depot), and pasireotide (Signifor® LAR) are man-made forms 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.
Octreotide 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. Lanreotide and pasireotide are 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.
These drugs can have side effects, such as a slowed heart rate, 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 cause diabetes or worsen it if a person already has it.
Growth hormone antagonists: 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 can lower blood sugar levels and cause mild liver damage in some people. It is given by daily injection under the skin.
Dopamine agonists: Drugs such as cabergoline or bromocriptine can 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.
Drugs for corticotropin (ACTH)-secreting tumors
These tumors cause the adrenal glands to make excess steroid hormones such as cortisol, which leads to Cushing’s disease (discussed in Signs and Symptoms of Pituitary 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).
Several different kinds of drugs can be used, although medicines aren’t always as effective in ACTH-secreting tumors as they are in some other types of pituitary tumors.
- Pasireotide (Signifor®) is a newer somatostatin analog. This drug can help some people who have Cushing’s disease from ACTH-secreting tumors when surgery is not an option or has not been effective. Along with side effects such as nausea, vomiting, and diarrhea, this drug can cause high blood sugar levels and gallstones.
- Cyproheptadine (Periactin®) is an antihistamine drug that can suppress ACTH production in some of these tumors.
- Drugs called steroidogenesis inhibitors can be used to keep the adrenal gland from making cortisol, although they don’t affect the pituitary tumor itself. These include ketoconazole, aminoglutethimide, etomidate, metyrapone, and mitotane. These drugs can sometimes be helpful after surgery or radiation (or if surgery is not an option), but they can be hard to take because of side effects.
- Mifepristone (Korlym®) is a type of drug called a cortisol receptor blocker. It limits the effects of cortisol on other tissues in the body. This drug can help treat high blood sugar levels in people with Cushing’s disease, although it doesn’t affect the pituitary tumor itself. It can have serious side effects and requires close monitoring.
- Dopamine agonists such as cabergoline or bromocriptine can also be tried if other drugs are not effective.
Drugs to treat thyrotropin (TSH)-secreting tumors
For these tumors, somatostatin analogs such as octreotide and lanreotide can usually reduce the amount of TSH that is produced. Dopamine agonists such as cabergoline or bromocriptine can also be used. These drugs are discussed in more detail above.
Last Medical Review: May 8, 2014 Last Revised: December 17, 2014