Overview
Pituitary tumors account for about 15 percent of all primary brain tumors. They can occur in every age group, but are more common in post-pubescent adults. Although the exact cause is not understood, most pituitary tumors are benign and often curable.
What is a pituitary tumor?
A pituitary tumor, or pituitary adenoma, is a growth that most often appears in the front portion of the pituitary gland. The pituitary gland is a small, bean-shaped organ that sits at the base of the brain, behind the bridge of the nose (Fig. 1). The pituitary gland is connected to the hypothalamus of the brain by a stem, or stalk. This gland secretes hormones such as prolactin, growth hormones, and adrenocorticotropic hormones that control or regulate certain functions of the body, including sexual development, bone growth, muscle growth, and the ability to control stress and fight disease. A healthy pituitary gland will release the secretions into the bloodstream and provide feedback to the hypothalamus, which regulates pituitary hormone responses depending on the needs of the body.
Tumors of the pituitary gland interfere with this normal hormonal regulation process. They may ignore the signal from the hypothalamus and secrete excessive amounts of one or more of the hormones listed above. Sometimes, a pituitary tumor doesn't secrete any active hormones, presenting instead with fatigue, headache, and progressive loss of vision.
What are the symptoms?
There are several different types of pituitary tumors, each with its own set of symptoms. Pituitary tumors are generally classified according to their size or secretory function. Microadenomas are less than 10mm in diameter, while those larger than 10mm are called macroadenomas. Of hormonally active adenomas, about 50% secrete prolactin, 20% secrete growth hormone, another 20% secrete adrenocorticotropic hormone, and 10% secrete multiple hormones.
Prolactin-Producing
The most common pituitary tumor is the prolactin-producing adenoma, or prolactinoma, which involves the secretion of prolactin, a hormone that helps control sexual function. Most commonly occurring in women of childbearing age, the tumor can cause the overproduction of prolactin, which in turn may cause menstruation to stop or inappropriate production of milk by the breasts. In men, prolactin-producing tumors may cause headaches, vision loss, impotence or a decreased sex drive.
Growth Hormone-Producing
Most commonly found in men, these tumors are larger and may extend toward the third ventricle of the brain and/or the cavernous sinus. These tumors may cause gigantism in children or adolescents. Fully-grown adults may experience acromegaly, or the enlargement of hands, feet or lower jaw. Other medical conditions, such as hypertension, heart disease, and diabetes mellitus, may also be aggravated by excessive growth hormone secretion.
Adrenocorticotropic (ACTH)-Producing
Adrenocorticotropic-producing adenomas, or ACTH-producing adenomas, are more common in women. The ACTH hormone stimulates the adrenal gland, which secretes glucocorticoids, or natural steroids. Excess glucocorticoids cause Cushing's disease, with such symptoms as weight gain, diabetes, menstrual irregularities, excessive hair growth, bruising, and hypertension.
Non-secreting
Non-functioning pituitary tumors have few symptoms and are difficult to recognize until they grow to be quite large. This excessive growth can press against nearby optic nerves, causing headaches or vision loss. It can also cause the pituitary gland to decrease secretion of hormones, which can cause apathy, weakness, fatigue, and pale skin color.
Other Hypersecreting
Other pituitary adenomas that cause hypersecretion of hormones represent less than 1 percent of all pituitary tumors and can affect the thyroid gland, ovaries and testes.
What are the causes?
The cause of pituitary tumors is unknown, although some neuroscientists believe they occur when a cell in the pituitary gland becomes abnormal, or mutates. The cell then reproduces additional mutations until a tumor is formed.
How is a diagnosis made?
If you have symptoms that may suggest a pituitary tumor, your physician will work with a team of specialists to confirm the diagnosis. This team may include a neurosurgeon, endocrinologist, ophthalmologist, pathologist, and radiologist. Diagnostic tests may include blood tests to determine hormone levels, a neurological examination, Magnetic Resonance Imaging (MRI) scans to obtain images of your brain, and skull x-rays. You may also be examined by an endocrinologist who specializes in hormone disorders, and an ophthalmologist, or eye specialist, may be consulted if you have vision loss.
Working with the patient, family, nurses and other medical resources, this team will develop a treatment plan that is right for you.
What treatments are available?
There are a variety of treatment options for people with pituitary tumors. The treatment that is right for you will depend on your age, general health status, and the location and size of the tumor. Each treatment has benefits, risks and side effects that should be discussed and understood before a decision is made.
Medication
The goal of medical therapy is to block the tumor from making abnormal quantities of hormones. Specific drugs are used to control specific types of hormone secretion. The production of prolactin is controlled by use of the drug bromocriptine, which reduces the size of the tumor while maintaining normal prolactin levels. Bromocriptine may also be used with other treatments as well. Somatostatin analogues, such as Sandostatin, are used in conjunction with surgical removal for growth hormone-secreting tumors. These drugs are also used on recurrent tumors. Mitotane (Lysodren) and ketoconazole (Nozoral) are drugs used for ACTH-secreting tumors. New drug therapies are also in clinical trials around the world.
Surgery
Removing the tumor surgically may be the only treatment necessary for small pituitary tumors. Neurosurgeons most often perform the transsphenoidal approach, using a microscope and very small instruments to remove the tumor through an incision under the upper lip or through a nasal passage (Fig. 2). When pituitary tumors enlarge they can compress and invade surrounding structures making them inaccessable from a transsphenoidal approach. In these cases, a transcranial, skull base approach for pituitary tumors may be better suited to ensure effective tumor removal. Additional treatment is then determined, based on the location, size, and hormonal activity of the tumor.
Image-guided surgery (IGS) uses stereotactic techniques to help the neurosurgeon pinpoint the exact location of a tumor within normal tissue. Stereotactic means to locate a structure by use of three-dimensional coordinates.
During surgery, skin markers and infrared cameras correlate the “real patient” to a 3D computer model of the patient created from their MRI or CT scans. Image-guided surgery allows very precise planning of the approach by pinpointing the tumor location and allowing precise skin and bone openings. This leads to shorter operating time, improved surgical visibility, and shorter length of stay.
Interventional MRI or CT is a specially designed operating room in which the patient can undergo an MRI or CT scan before, during, and after surgery. This enables the surgeon to have real-time images of the patient’s brain and to know exactly how much tumor has been removed prior to ending the procedure. This technology improves the ability for total tumor removal and reduces the possibilty of a second operation.
Radiotherapy
Radiation therapy uses controlled high-energy rays to treat pituitary tumors. The radiation dose is delivered over many visits and uses a mask to precisely locate the tumor and accurately reposition the patient for each treatment session. With this therapy, radiation beams are manipulated by the computer to precisely conform to the shape of the tumor. Three-dimensional conformal radiation treatments significantly spare normal brain tissue and allow much higher doses to be delivered to the tumor. For patients with tumors that are usually successfully treated with radiation (e.g., pituitary tumors, meningiomas, craniopharyngiomas) three-dimensional conformal radiation should result in fewer early and late side effects.
Stereotactic Radiosurgery
Stereotactic radiosurgery uses a highly concentrated and precisely directed beam of radiation to treat a pituitary tumor during a single session. Because a single radiosurgery dose is more damaging than multiple fractionated doses, the target area must be precisely located and completely immobilized with a stereotactic head frame. Although it is called surgery, no incision is made. Patients spend most of the day at the center while the tumor is precisely located, a treatment plan is developed, and a radiation dose is delivered. The effects of treatment occur over a period of time so the tumor will not show immediate results. Gradually, the lesion will stop growing, shrink, and in some cases, completely disappear. Treatment with stereotactic radiosurgery has proved to be very successful for patients with pituitary adenomas. It is often effective in treating tumors that have not responded to surgery.
Sources & links
If you have more questions, please contact the Mayfield Clinic at 800-325-7787 or 513-221-1100. The Neuroscience Institute and the Mayfield Clinic include some of the most internationally recognized neuro-oncology specialists in the world, several of whom specialize in the treatment of pituitary tumors. Call 1-888-797-4TNI.
Pituitary Network Association (PNA) www.pituitary.com
National Brain Tumor Foundation (NBTF) at 1-800-394-CURE
American Brain Tumor Association (ABTA) at 1-847-827-9910 or www.abta.org
For support groups in Cincinnati, Ohio, and Northern Kentucky, contact The Wellness Community at 513-791-4060.
Glossary
acromegaly: enlargement of the hands, feet or lower jaw due to overproduction of growth hormone.
adenoma: medical term for a tumor located in a gland.
Cushing's disease: an endocrine disease caused by increased production of cortisol or by excessive use of cortisol or other steroid hormones; most often adrenocorticotropic hormone (ACTH) by the pituitary gland.
endocrinologist: doctor who is a specialist in hormonal disturbances.
hypertension: high blood pressure.
hypothalamus: a part of the brain that regulates pituitary hormone responses by secreting releasing factors or inhibiting factors, depending on the needs of the body.
neuroscientist: a physician or scientist dedicated to research, education, and clinical care of neurological diseases and disorders.
ophthalmologist: doctor who is a specialist in vision problems.
prolactin: a hormone that helps regulate sexual function.
Questions to ask your doctor
1. Are my symptoms caused by a pituitary tumor?
2. Do I need any special diagnostic tests?
3. What are the risks and benefits of all treatments for pituitary tumors?
4. Which treatment is best for my specific situation?
5. Will this pituitary tumor grow back?
6. Are there any local resources or support groups?
updated > 6.2004
reviewed by > John Tew, MD |
