American Medical Association Family Medical Guide - American Medical Association [600]
Hormone-Producing Tumors
Some cancerous tumors may secrete hormones or chemicals that imitate hormones, causing symptoms similar to those that result from overactive endocrine glands. For example, lung cancers may secrete hormones that are similar to corticotropin (the pituitary hormone that stimulates the adrenal glands), parathyroid hormone, or arginine vasopressin (antidiuretic hormone). Carcinoid tumors of the intestine (see page 761) also may secrete these hormones. Tumors of the islet cells in the pancreas (which produce insulin) also often secrete abnormal hormones. Because a wide range of tumors may secrete similar hormones, it can be difficult to identify the tumor that is causing the problem. However, a doctor will make a thorough evaluation of any suspected hormone-producing tumor. Surgery or radiation therapy to remove or destroy the tumor may help relieve the symptoms.
Treatment
Prolactinomas often can be treated successfully with dopamine agonists (such as bromocriptine), which control the growth of the tumor. Taking a long-acting dopamine agonist such as cabergoline twice a week can shrink the tumor, often making surgery unnecessary or easier to perform. Dopamine agonists are drugs that imitate the actions of the chemical messenger dopamine and suppress the secretion of growth hormone by the pituitary gland. However, the most effective treatment for some prolactinomas and all other types of pituitary tumors is surgery or radiation therapy or, in some cases, a combination of both.
Surgery to remove a pituitary tumor is a delicate procedure that is performed as the surgeon looks through a powerful microscope (microsurgery). The tumor is reached either through a nostril or through a small hole that the surgeon creates in the bridge of the nose. If the tumor is large and is pressing on the optic nerves, open-brain surgery may be required. There is a risk that the pituitary gland will be damaged during surgery, which can lead to hypopituitarism or diabetes insipidus, or both. These disorders are treated with lifelong hormone replacement therapy.
In some cases, the surgeon may destroy the tumor with extreme cold (cryosurgery; see page 22) or by inserting tiny radioactive implants (called radioactive pellets or seeds) into the tumor. If the tumor is large or if it is difficult to pinpoint, the doctor may use radiation therapy on the entire gland. Like surgery, radiation therapy can damage the pituitary gland. Although the long-term outlook depends largely on the size of the tumor, in many cases a complete cure is possible.
Acromegaly
Acromegaly is a rare condition in which a noncancerous pituitary tumor (see previous page) causes the pituitary gland to produce too much growth hormone. Excess growth hormone causes bone deformities and enlargement of internal structures and organs, including the heart, kidneys, liver, spleen, pancreas, thyroid gland, and parathyroid glands. The condition usually occurs in adults between ages 30 and 50.
Symptoms
Symptoms of acromegaly include enlargement of the hands and feet, lengthening of the face, broadening of the head and neck, and enlargement of the lower jaw, brow, nose, and ears. The skin may thicken and darken, and coarse hair may appear on the arms, legs, and body. The tongue may enlarge and, in some cases, the voice may deepen or become hoarse. These changes develop gradually and may go undetected for many years.
Other symptoms of acromegaly can include tingling in the hands, increased sweating, fatigue, severe headaches, joint stiffness, and dull, persistent pain throughout the body. Enlarging tissues