A pituitary tumor is a tumor that forms in the pituitary, a small, pea-sized organ in the brain located behind the back of the nose that produces and regulates hormones affecting other glands in the body. Most pituitary tumors are slow-growing, noncancerous tumors called a pituitary adenomas. Even a benign adenoma, however, can still cause the pituitary gland to produces excess hormones that overstimulate other endocrine glands and cause symptoms related to the overproduced hormone.
Each year, about 7,000 pituitary tumors are diagnosed, but this is just the proverbial tip of the iceberg. Research indicates that because these tumors often do not affect health or cause symptoms, many go undiagnosed or are found incidentally during routine brain imaging tests. In fact, up to 25 percent of the population may have a small pituitary tumor without knowing it.
Tumors that create hormones are called functioning tumors, while those that don’t are considered nonfunctioning. While functioning hormones produce various symptoms associated with the hormones they create, nonfunctioning hormones produce symptoms related to their growth, including headaches, vision problems, nausea and vomiting. Hormonal abnormalities that functioning tumors can produce are associated with Cushing’s disease, a condition in which fat builds up in the face, back and chest, and the arms and legs become very thin; and acromegaly, a disorder in which the hands, feet and face are larger than normal. Hormones that affect sex hormones, such as estrogen and testosterone, can cause women to produce breast milk without being pregnant or nursing, and cause men to lose their sperm count or sex drive.
One method of classifying pituitary tumors is by the hormones these tumors produce. Using this system, some type of pituitary tumor include:
- Nonfunctional adenoma (null cells adenoma): The most common type of pituitary tumor, these are nonfunctional tumors that only produce symptoms when they grow large enough, at which point they can cause headaches and vision problems.
- Prolactin-producing tumor (prolactinoma): These common benign tumors cause an overproduction of prolactin, which can cause irregular menstrual cycles and abnormal breast milk production in women, and in men impotence and a lack of interest in sex, as well as infertility, enlarged breasts and a decrease in body hair.
- Adrenocorticotropic hormone-producing tumor: Adrenocorticotropic hormone (ACTH) stimulates the adrenal gland to produce glucocorticoids, steroids that influence the metabolism and function as anti-inflammatory and immunosuppressive agents. Too much ACTH, which can be created by this functioning tumor, can lead to Cushing’s disease and/or weakened bones.
- Growth hormone-producing tumor: These functioning tumors produce an excess of growth hormone. When this happens in children, it results in gigantism, which can cause increased height, quick growth, joint pain and sweating. In adults, it produces a condition called acromegaly, which can cause such symptoms as extra growth in the skull, hands and feet; a deepened voice; a change in facial appearance due to extra growth in the facial bones; and joint pain.
- Thyroid-producing tumor: These tumors, which can become large and spread, produce a thyroid-stimulating hormone, which can lead to hyperthyroidism. Symptoms of hyperthyroidism include a fast heart rate, unintended weight loss tremor, increased appetite, trouble falling asleep, feelings of being warm or hot or not tolerating heat, feeling anxious, frequent bowel movements and a lump in the front of the neck caused by an enlarged thyroid gland.
While they are rare, cancerous pituitary tumors, called pituitary carcinomas, do exist. They’re generally found in older people, though they can affect people of any age. They often make hormones just like their benign counterparts—in fact, the only way to differentiate a benign tumor from a cancerous one is when the tumor spreads to another part of the body, which can happen several years later.