Pituitary tumors account for about 7 percent of all primary brain tumors. They can occur in every age group but are most common in very young adults. Most are benign and curable. Their exact cause is not understood.
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 in accordance with the body’s needs.
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, thereby causing the patient to experience 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-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 a patient has symptoms that may suggest a pituitary tumor, the patient’s 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 the brain, and x-rays of the skull. The patient may also be examined by an endocrinologist, a physician who specializes in hormone disorders. An ophthalmologist, or eye specialist, may be consulted if the patient is experiencing vision loss.
Working with the patient, family, nurses and other medical resources, this team will develop a treatment plan that is right for each individual patient.
What treatments are available?
A variety of treatment options exist for people with pituitary tumors. The treatment strategy for each individual patient will depend on the patient’s 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.
- High-precision radiosurgery, including three-dimensional conformal radiotherapy and stereotactic radiosurgery
- Image-guided neurosurgery
- Intraoperative MRI
- Medical therapy
- Minimally invasive surgery
- Surgery (craniotomy)
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. In some cases, however, a craniotomy (the 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.
Radiosurgery also is used to treat pituitary tumors in select patients. The goal of Radiosurgery is to destroy the tumor with a targeted beam of radiation while preserving surrounding structures
Medical therapy can be used 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.