Treatment of prolactin-secreting adenomas (prolactinomas)
Unlike most other pituitary tumors, surgery is usually not the first treatment for these tumors. Instead, medicines that block the production of prolactin (bromocriptine or cabergoline) are used (see "Medicines to treat pituitary tumors"). These drugs also stop the adenomas from growing. They work so well that surgery is usually not needed. Although both of these drugs are effective in treating prolactin-secreting tumors, cabergoline may have fewer side effects. It also lasts longer, so it does not need to be taken as often as bromocriptine.
Most patients are able to control their prolactin levels with medicine. The drugs are also very effective in reducing the size of prolactin-secreting macroadenomas. Most of these tumors shrink to less than half of their original size after medical treatment. Only about 15% to 20% of the tumors show no decrease in size after treatment. Even when the tumors don't shrink, these drugs usually prevent them from growing larger.
Within 3 months of starting treatment, the blood prolactin level is measured again and an MRI scan of the pituitary is done to check whether the medicine has been effective. If it has worked, the drug treatment may be continued for the rest of the patient's life. If after 6 months of treatment the response has not been good, or if serious side effects occur, then surgery should be considered.
Some doctors recommend surgery in special situations such as in men because their tumors are usually found when they are in an advanced stage, or in women who want to become pregnant (the drugs must be stopped during pregnancy, and pregnancy may cause the tumor to grow fast). Surgery may also be used to treat very large tumors after first shrinking them with drug treatment.
Radiation may be used if drug treatment and surgery are not successful.
Treatment of growth hormone-secreting adenomas
Adults with these tumors often have acromegaly, while children have gigantism.
Surgery is usually considered the best treatment for these tumors. If it isn't successful, radiation therapy or treatment with medicine may be tried. Many experts recommend medical treatment first if the surgery doesn't work. Radiation is used most often when drug treatment doesn't work. This is because radiation is very slow to act and over time it can lead to lowered levels of other pituitary hormones.
Octreotide (Sandostatin®) and lanreotide (Somatuline®) are modified forms of the natural hormone somatostatin that return insulin-like growth factor-I (IGF-I) to normal levels in about two thirds of patients. They are taken as injections, usually about once a month. The dose of either of these drugs may need to be adjusted based on blood IGF-1 levels.
Because these drugs work well and only need to be given monthly, doctors have started to question whether surgery should always be the first treatment for people with growth hormone-secreting adenomas. In those who might have problems with surgery, such as frail elderly people, drug treatment might be a good choice as the first treatment. Sometimes, drug treatment may be given for a short time before surgery. This may help in certain cases by causing the tumor to shrink, and improve the chance that the surgery will be successful.
Another drug, pegvisomant, works by blocking the action of growth hormone. It may be used if octreotide (or lanreotide) isn't doing enough to block growth hormone production.
Drugs such as bromocriptine or cabergoline (see "Medicines to treat pituitary tumors") may be helpful in reducing growth hormone levels in about 1 out of 5 patients. Unfortunately, some patients have trouble tolerating the high doses often needed to be effective. The main advantage of these drugs is that they are in pill form.
If surgery and drug treatments fail, then radiation therapy may be used.
Treatment of corticotropin (ACTH)-secreting adenomas
These tumors cause Cushing's disease. Surgery is usually the main treatment. If the surgery doesn't work completely or the tumor is growing back, the 2 main options are a second surgery and radiation therapy. If surgery and radiation have not controlled the cortisol production, treatment options may include removing both of the adrenal glands (see below) or using medicines to try to control cortisol levels.
Cyproheptadine lowers ACTH production in about half of these tumors. If the ACTH level is still high while the patient is taking cyproheptadine, other drugs can be used to stop the adrenal glands from making too much cortisol. These include ketoconazole, aminoglutethimide, etomidate, metyrapone, and mitotane. These drugs are often hard to take for long periods because of side effects.
If medicines cannot control the cortisol level, or if the patient can't take the drugs because of side effects, the next option is to remove both adrenal glands with an operation called a bilateral adrenalectomy. It can usually be done with laparoscopic surgery, which uses several small incisions in the abdomen instead of one large one. The surgeon works through these small incisions with special long, thin instruments, including one with a tiny camera lens on the end (called a laparoscope) for looking into the abdomen. Adrenalectomy stops all cortisol production, so high cortisol levels will no longer be a problem. But after the surgery the patient will require lifetime adrenal steroid hormone replacement. This can be taken by mouth.
Before a patient has their adrenal glands removed, the pituitary gland needs to be treated with radiation. If this is not given, removing the adrenals can cause the pituitary tumor to grow larger and even start growing into the structures near the pituitary. This is known as Nelson syndrome. When the adenoma gets large, it can damage the function of the normal parts of the pituitary gland, causing problems from hormone deficiency. It can also lead to high levels of ACTH. Because ACTH is similar to the hormone that causes tanning of the skin, the high ACTH levels will make the skin darker.
Treatment of thyrotropin (TSH)-secreting adenomas
The treatment of choice for these tumors is usually surgery. If that doesn't work, radiation therapy may be used as well. Often, radiation is not very helpful, and medicines may be needed to control the tumor's hormone production. Some of the drugs that can be helpful include bromocriptine, cabergoline, octreotide, and lanreotide. These should be used only after other treatments have failed to control the tumor.
It is important to treat the pituitary tumor to prevent the damage it may do to nearby structures. Drugs that stop the thyroid gland from making thyroid hormone can actually make things worse because reducing thyroid hormone production may cause the pituitary tumor to grow.
Treatment of gonadotropin (FSH/LH)-secreting adenomas
The hormones produced by these tumors rarely cause major symptoms. This is why these tumors are often not found until they are large and threaten vital structures. Surgery is often the best option because it works right away. Follow up with frequent MRI scans will tell if the tumor is growing back. If it does, radiation may be used.
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