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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-teenage 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. 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 of a pituitary tumor?
There are several different types of pituitary tumors, each with its own set of symptoms.
- Microadenomas and Macroadenomas
Microadenomas are less than 10mm on a scan, while those larger than 10mm are called macroadenomas.
- Prolactin-producing pituitary tumors
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 pituitary tumors
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-producing pituitary tumors, or ACTH-producing pituitary tumors
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 tumors
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 pituitary tumors
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.
How is a pituitary tumor diagnosed?
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, 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 best 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.
- Surgery. Removing the tumor surgically may be the only treatment necessary for small pituitary tumors. Neurosurgeons most often perform the
transsphenoidal surgical approach, using very small instruments and microscopes to remove the tumor through an incision under the upper lip or
through a nasal passage. Other times, a craniotomy (removal of a portion of the skull bone) may be necessary to gain access to the pituitary
gland. Additional treatment is then determined, based on the location, size and hormonal activity of the tumor.
- Image-guided neurosurgery
- Interventional MRI
- High-precision radiosurgery, including three-dimensional conformal radiotherapy and stereotactic radiosurgery
- Medical therapy. 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.
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