What are pituitary tumors?

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 only 7 percent of brain tumors. However, because of the location of the pituitary gland, at the base of the skull, a pituitary tumor grows upward. Eventually, most pituitary tumors will press against the optic nerves, causing vision problems.

What causes pituitary tumors?

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, thyroid tumors, and pancreatic tumors. Multiple endocrine neoplasia, type I (MEN 1) has been shown to be responsible for about all inherited (those that run in families) pituitary tumors, but only 3 percent of all pituitary tumors.

What are the types of pituitary tumors?

Most pituitary tumors are not cancerous. About 1,300 pituitary tumors are diagnosed each year. However, because many of these tumors do not cause symptoms or affect health, many are not diagnosed or are found incidentally during routine brain imaging studies. Almost 25 percent of persons with small pituitary tumors will not have any symptoms.

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

    • tremor

    • increased appetite

    • feelings of being warm or hot, or not tolerating cold

    • trouble falling asleep

    • feeling anxious

    • frequent bowel movements

    • a lump in the front of the neck, due to an enlarged thyroid gland

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