The pituitary gland is a small, pea-sized organ in the brain behind the back of the nose. The pituitary gland produces hormones that affect many other glands in the body. Although rare, most pituitary tumors are noncancerous (benign), comprising 10-25 percent of brain tumors. However, because of the location of the pituitary gland, at the base of the skull, many pituitary tumors will press against the optic nerves, causing vision problems.
Researchers do not know at this time what causes pituitary tumors. However, research studies show that having a hereditary condition, multiple endocrine neoplasia, type I (MEN 1), increases the risk of developing pituitary tumors, parathyroid tumors, and pancreatic tumors. Multiple endocrine neoplasia, type I (MEN 1) has been shown to be responsible only a small percentage of all pituitary tumors.
Most pituitary tumors are not cancerous. About 7,000 pituitary tumors are diagnosed each year. However, because many pituitary tumors do not cause symptoms or affect health, they are either not diagnosed, or are found incidentally during routine brain imaging studies. Studies have shown that up to 25 percent of people may have small pituitary tumors without even knowing it.
Pituitary tumors are classified in several ways. One method is classification is by whether the tumor produces a pituitary hormone and the type of hormone produced. Based on this type of classification, types of pituitary tumors include, but are not limited to, the following:
- Non-functional adenomas (null cell adenomas)
These tumors are the most common type of pituitary tumor. They do not secrete an extra amount of hormone and until they become a certain size, the person does not have any symptoms. When the tumor is large enough, they may cause headaches and vision problems.
- Prolactin-producing tumors (prolactinomas)
These benign tumors are also common. In this type of pituitary tumor, prolactin is overproduced. High prolactin levels can cause menstrual periods in women to be irregular or stop, and can cause galactorrhea (abnormal breast milk production). Men may experience impotence (erectile dysfunction, or ED) or a lack of interest in sex. Men may also have enlarged breasts, infertility, or a decrease in body hair. If these symptoms go unrecognized and progress, headaches and vision problems may occur next.
- Adrenocorticotropic hormone (ACTH)-producing tumors
ACTH stimulates the adrenal gland to make glucocorticoids (or steroids, which influence metabolism and act as anti-inflammatory and immunosuppressive agents). An oversupply of ACTH, such as that produced by this type of tumor, can cause Cushing's disease. Cushing's disease is characterized by a buildup of fat in the face, back, and chest. In addition, the arms and legs tend to become thin. ACTH-producing tumors can also cause weakened bones.
- Growth hormone-producing tumors
Growth hormone-producing tumors secrete too much growth hormone. In children, too much growth hormone stimulates the growth of almost all the bones in the body. When this occurs, the result is termed gigantism. Gigantism can include features such as increased height (over seven feet), very quick growth, joint pains, and profuse sweating.
In adults, an overproduction of growth hormone results in a condition called acromegaly. Acromegaly may include the following symptoms:
- Extra growth in the skull, hands, feet (may necessitate an increase in hat, shoe, glove, and ring size)
- Deepened voice
- A change in the facial appearance due to extra growth in the facial bones
- A wide spacing of teeth because of the growth of facial bones
- Pain in the joints
- Thyroid hormone-producing tumors
Thyroid-stimulating hormone is produced by these tumors. They can become large and spread. Symptoms of hyperthyroidism may include:
- Fast heart rate
- Unintended weight loss
- Increased appetite
- Feelings of being warm or hot, or not tolerating heat
- Trouble falling asleep
- Feeling anxious
- Frequent bowel movements
- A lump in the front of the neck, due to an enlarged thyroid gland
Cancerous pituitary tumors, or pituitary carcinomas, are rare. They are generally found in older persons, although they can occur at any age. Pituitary carcinomas often make hormones, just as many benign pituitary tumors do. In most cases, the only definitive way to differentiate a cancerous pituitary tumor from a benign one is when the tumor metastasizes (spreads) to another part of the body several years later.
Symptoms vary depending upon what type of tumor is growing and what area of the pituitary gland is affected. Pituitary tumors can lead to symptoms that are caused by an excess or a reduced production of pituitary hormones. Each individual also experiences symptoms differently, and the symptoms many resemble other conditions or medical problems. Always consult your physician for a diagnosis.
In addition to a complete medical history and medical examination, diagnostic procedures for pituitary tumors may include:
- Blood and urine tests (to measure hormone levels)
- Computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
- Magnetic resonance imaging (MRI) - a diagnostic imaging procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
- Biopsy - a procedure in which tissue samples are removed (with a needle or during surgery) from the body for examination under a microscope; to determine if cancer or other abnormal cells are present.
Specific treatment for pituitary tumors will be determined by your physician based on:
- Your age, overall health, and medical history
- Extent of the disease
- Your tolerance for specific medications, procedures, or therapies
- Expectations for the course of the disease
- Your opinion or preference
Treatment may include:
- Surgical removal of the tumor
- External radiation (external beam therapy) - a treatment that precisely sends high levels of radiation directly to the cancer cells. The machine is controlled by the radiation therapist. Since radiation is used to kill cancer cells and to shrink tumors, special shields may be used to protect the tissue surrounding the treatment area. Radiation treatments are painless and usually last a few minutes.
- Radiosurgery (stereotactic radiosurgery) - a type of radiation therapy that uses a single high dose of radiation sent directly into the cancerous tissue with very narrow beams of radiation. This is a precise technique that targets the cancer tumor, causing less damage to the surrounding tissues. Radiosurgery is called "surgery" because it is a one-session radiation therapy treatment that creates a similar result as an actual surgical procedure. An example of radiosurgery is called "gamma knife."
- Medications - to control the growth-hormone production by the tumor (i.e., bromocriptine and cabergoline - medications which act on hormone-producing tumors to suppress its hormone-producing function).