Hormone-Secreting Tumors

Hormone-secreting tumors are benign * or malignant * abnormal cell masses that produce and release one or more hormones in an uncontrolled manner. The high levels of the hormone in the bloodstream can cause various symptoms, depending on the hormone's effects on the body.

What Are Hormone-Secreting Tumors?

Hormones are chemical messengers that control many body functions. They are produced and released into the bloodstream by specialized glands * of the endocrine * system, including the pituitary, adrenal glands, thyroid gland, and pancreas. Hormones stimulate responses in their target cells, which are cells that contain receptors for that specific hormone. In line with this process, the word hormone derives from the Greek word hormon, which means to “set in motion” or “excite.”

Most endocrine glands continuously secrete small amounts of their particular hormones, so that at any given time there may be minute quantities of more than 50 different hormones circulating in the blood. The human body has elaborate mechanisms for ensuring that enough—but not too much—of each hormone is released by each gland. Most hormones are regulated by negative-feedback mechanisms. Information about the amount of hormone or an affected substance is relayed from the target tissue to the secreting gland, which then adjusts the production or secretion of the hormone accordingly. Hormones can also be regulated by counter-regulatory hormones, which counteract or interfere with the hormone's effects.

Pituitary tumors

The pituitary gland is located inside the brain above the nasal * passages. The size of a pea, it is the master hormone control gland, regulating hormone production of most other glands in the body. The pituitary itself is regulated by the hypothalamus * of the brain, which releases chemicals that stimulate or inhibit pituitary-hormone production and release. The anterior, or front part, of the pituitary is the area in which five different types of cells each produce one or two specific hormones. Most hormone-secreting tumors occur in this area.

About 10,000 pituitary tumors are diagnosed in the United States each year. It is estimated that 10 to 20 percent of all people eventually develop tumors in the anterior pituitary. Of the diagnosed pituitary tumors, almost all are benign glandular tumors called adenomas. These tumors do not usually grow beyond the pituitary, but their effects can be profound. About 75 percent of pituitary adenomas are functional, meaning that they produce hormones and may not respond to normal feedback signals from the hypothalamus and other glands. Instead, they release an excess amount of a specific hormone:

WHAT CAUSES HORMONE-SECRETING TUMORS?

Most hormone-secreting tumors probably result from acquired mutations * in an endocrine cell's DNA that lead to the loss of a regulatory mechanism that prevents the cells from growing and producing hormones. The only known risk factor for hormone-secreting tumors is an inherited condition called multiple endocrine neoplasia type 1 (MEN1). People with MEN1 are at very high risk of developing pituitary, parathyroid, and pancreatic tumors. MEN1 accounts for about 25 percent of pituitary tumors.

Pancreatic tumors

The amount of glucose (sugar) in the blood is one of the most delicate balances maintained by the body. Too much blood glucose, or hyperglycemia, can irreversibly damage organs. Too little glucose, or hypoglycemia, can cause convulsions * , unconsciousness, and even death. When the blood-glucose level rises, beta cells in the group of endocrine cells called the islets of Langerhans in the pancreas are stimulated to increase insulin * secretion, which lowers blood glucose by allowing glucose to enter body cells, which use it for energy. As blood-glucose levels drop, alpha cells in the islets of Langerhans are stimulated to increase glucagon * secretion, which raises the level of glucose in the blood. Insulin and glucagon secretion by the pancreas are both directly regulated by the concentration of glucose in the blood. Insulin secretion is also controlled by counter-regulatory hormones, including glucagon, growth hormone, adrenaline, and cortisol, which counteract the effects of insulin by raising blood-sugar levels.

There are three main types of hormone-secreting pancreatic tumors:

What Are the Symptoms of Hormone-Secreting Tumors?

The symptoms of hormone-secreting tumors—as well as their diagnosis and treatment—depend on the physiological effects of the hormones that they secrete.

Pituitary-gland tumors

Most pituitary adenomas are harmless and cause no symptoms. They are sometimes detected during MRI * brain scans for an unrelated problem. Some pituitary-hormone-secreting tumors cause symptoms of hormone overproduction. Others may continue growing until they impinge on normal pituitary cells, nerves, or neighboring parts of the brain, causing neurological * symptoms, including headaches and vision problems.

Prolactinomas are most common in women but also occur in men. Most prolactinomas affect people under age 40, but most of the larger tumors occur in older men. In women they can cause abnormal breast-milk production and the cessation of menstruation. In men they can cause a loss of sexual interest or impotence.

Growth-hormone-secreting tumors can cause children to grow very tall—sometimes over seven feet—in a very short time. Although the arm and leg bones of adults cannot grow, overproduction of growth hormone can cause the bones of the hands, feet, skull, jaws, and face to grow and become distorted. Other symptoms of acromegaly may include:

Both gigantism and acromegaly can cause increased sweating and joint pain. Acromegaly can also lead to kidney stones * , diabetes * mellitus, and heart disease.

When a pituitary adenoma involves the overproduction of ACTH, this is known as Cushing's disease. The resulting symptoms are referred to as Cushing's syndrome, which can also be caused by the excessive production of cortisol for other reasons. Symptoms of Cushing's disease may include:

*
  • Moodiness or depression *
  • Osteoporosis *
  • Symptoms of hyperthyroidism caused by TSH-secreting tumors include the following:

    Pancreatic tumors

    Symptoms of hypoglycemia from insulinomas may be as mild as anxiety or hunger or as severe as convulsions, coma * , or death. Other symptoms may include:

    Symptoms of glucagonoma include:

    Symptoms of gastrinomas include:

    Who Was Harvey Cushing?

    The American neurosurgeon Harvey Williams Cushing (1869–1939) developed many of the basic techniques for operating on the human brain. Known widely as the father of neurosurgery, he first reported on “polyglandular syndrome,” which became known as Cushing's syndrome, in 1912. In 1932 he published a landmark work on pituitary adenomas. Cushing also won a Pulitzer Prize in 1926 for his biography of Sir William Osler, a father of modern medicine.

    HOW ARE HORMONE LEVELS MEASURED?

    Most hormones are tiny molecules that are present in very low concentrations in human blood and urine. Until the 1960s no effective method for determining hormone levels existed. But in 1959 biophysicist Rosalyn Yalow (1921–2011) and physician Solomon A. Berson (1918–1972) at the Bronx Veterans Administration Hospital in New York announced the results of experiments in which they proved that radioactive isotopes * could be used to measure hormone levels in blood. They called their technique the radioimmunoassay (RAY-dee-oh-imYOU-no-AAH-say) (RIA). RIAs are so sensitive that they can measure one-trillionth of a gram of a substance in a milliliter of blood.

    An RIA mixes a known amount of radioactively labeled hormone with an antibody * that specifically binds to that hormone. When human plasma (the liquid part of blood) containing the hormone is added to the mixture, the hormone in the plasma also binds to the antibody, displacing some of the radioactive hormone. By measuring the amount of radioactive hormone that remains bound to the antibody, laboratory technicians can determine the amount of hormone in the blood.

    Yalow and Berson's 1959 study proved that their RIA could measure the amount of insulin in diabetic patients' plasma. They later showed that RIAs could accurately measure other hormones, including ACTH and growth hormone. Soon RIAs were measuring hundreds of substances, revolutionizing diagnostic medicine. But despite its commercial potential, Yalow and Berson refused to patent their method because they wanted it to remain freely available to doctors. In 1977, five years after Berson's death, Yalow received the Nobel Prize in Physiology or Medicine. Eventually, enzyme * -linked immunosorbent (im-YOU-no-SORE-bent) assays (ELISAs), which use enzymes and colored dyes rather than radioactive isotopes, became the primary hormone-measurement tool.

    How Are Hormone-Secreting Tumors Diagnosed and Treated?

    Diagnosis

    Hormone-secreting tumors are diagnosed by measuring specific hormone levels or levels of chemicals associated with these hormones in the blood or urine. A low blood-glucose level after fasting may indicate an insulinoma, whereas a high glucose level may indicate a glucagonoma. High blood levels of insulin or C-peptide, a by-product of insulin production, may also indicate insulinoma. High glucagon levels in the blood may suggest a glucagonoma. A high level of gastrin may indicate a gastrinoma.

    If a doctor suspects that a patient has a hormone-secreting tumor, he or she may then use imaging tests such as CT scans * , MRI, or ultrasound * to visualize the tumor. A biopsy * can then confirm the diagnosis. For some types of pituitary adenomas, hormone tests are accurate enough that a biopsy is not necessary.

    Treatment of pituitary tumors

    Medications known as dopamine agonists * , which shrink prolactinomas and reduce prolactin levels, can successfully treat 80 to 90 percent of prolactinomas so they are the most commonly-used treatments for these tumors. Most people with somatotropin-secreting tumors are treated with surgery, followed by treatment with medications that further reduce growth-hormone levels. When this combination is not entirely effective, radiation is often used. Concurrent treatment for the numerous other conditions that accompany acromegaly is also standard.

    Surgery often treats ACTH-, gonadotropin-, and TSH-secreting adenomas successfully, so it is usually the treatment of choice. If the tumor persists or returns, a second surgery or radiation therapy * is used. If possible, stereotactic radiosurgery or proton-beam radiation therapy is used instead of conventional radiation. These techniques deliver an intense radiation beam directly to the tumor and are less likely to damage surrounding tissue. However, the benefits from radiation therapy may not become evident for months or even years. In such cases, medications that control an adenoma's production of certain hormones may be used in the meantime. In severe cases involving an ACTH-secreting adenoma, doctors may have to remove both adrenal glands to control cortisol levels after pituitary radiation.

    Treatment of pancreatic tumors

    Insulinomas are usually cured by surgery. Multiple or malignant tumors may require partial or complete removal of the pancreas. If surgery is not possible or is ineffective, sometimes medication can be used to lower or suppress insulin secretion, or radiation or certain chemicals can be used to destroy the tumor. Since most glucagonomas are malignant, surgery is only effective in treating about 20 percent. Chemotherapy * is very rarely effective either.

    ZES is usually treated with medications called proton-pump inhibitors, which reduce stomach-acid production, promote ulcer healing, and relieve some symptoms. Surgery may remove a single tumor if the cancer has not spread to other organs. Although the cure rate for ZES is relatively low, these tumors usually grow slowly, so patients may live for many years following diagnosis, with effective symptom relief from acid-reducing medications.

    See also Cancer: Overview • Cushing's Syndrome • Tumor

    Resources

    Books and Articles

    Cook, Louis J., and Jeri Freedman. Brain Tumors. New York: Rosen, 2012.

    Parks, Peggy. Brain Tumors. San Diego: ReferencePoint Press, 2011.

    Wilson, Michael R. The Endocrine System: Hormones, Growth, and Development. New York: Rosen, 2009.

    Websites

    National Cancer Institute. “Pituitary Tumors Treatment.” http://www.cancer.gov/types/pituitary/patient/pituitary-treatment-pdq (accessed March 29, 2016).

    http://www.ninds.nih.gov/disorders/pituitary_tumors/pituitary_tumors.htm (accessed March 29, 2016).

    Organizations

    American Brain Tumor Association. 8550 W. Bryn Mawr Ave., Suite 550, Chicago, IL 60631. Telephone: 773-577-8750. Website: http://www.abta.org (accessed March 29, 2016).

    National Institute of Diabetes and Digestive and Kidney Diseases. 9000 Rockville Pike, Bethesda, MD 20892-2560. Telephone: 301-496-3583. Website: http://www.niddk.nih.gov (accessed March 29, 2016).

    Pituitary Network Association. PO Box 1958, Thousand Oaks, CA 91358. Telephone: 805-499-9973. Website: http://pituitary.org/ (accessed June 13, 2016).

    * benign (beh-NINE) refers to a condition that is not cancerous or serious and will probably improve, go away, or not get worse.

    * malignant (ma-LIG-nant) refers to a condition that is very serious and likely to worsen. The term is usually used to refer to a tumor or cells that are cancerous.

    * glands are cells, groups of cells, or organs that produce, store, and release substances such as hormones and chemicals that regulate body functions.

    * endocrine (EN-duh-krin) refers to a body system composed of a group of glands, such as the thyroid, adrenal, and pituitary glands, and the hormones they produce. The endocrine glands secrete the hormones they produce directly into the bloodstream. These hormones travel to cells that have receptors for them. Hormones regulate many functions, including metabolism, growth, and mood.

    * nasal (NA-zal) means of or relating to the nose.

    * hypothalamus (hy-po-THALuh-mus) is an almond-shaped structure located above the brain stem. One of its important functions is linking the nervous system and endocrine system by controlling the release of hormones by the pituitary gland. It also regulates hunger, thirst, sleep, body temperature, and other body functions.

    * growth hormone is a chemical substance produced by the pituitary gland that regulates growth, cell reproduction, and cell regeneration. It is also known as so matotropin (so-MAT-oh-TRO-pin).

    * cortisol (KOR-ti-sol) is a hormone that plays a part in regulating metabolism, blood pressure, and the immune system. As the body's primary stress hormone, it also plays a critical role in the stress response.

    * hyperthyroidism (hy-per-THYEroyd-ih-zum) is excessive activity of the thyroid gland, characterized by an enlarged thyroid gland, increased metabolic rate, rapid heartbeat, and high blood pressure.

    * mutations (mu-TAY-shuns) are changes in a chromosome or a gene.

    * insulin is a hormone produced by beta cells in the pancreas. It is crucial in controlling the level of glucose (sugar) in the blood and in helping body cells use glucose to produce energy. When the body cannot produce or use insulin properly, a person must inject insulin or take other medications.

    * convulsions (kon-VUL-shuns), also called seizures, are involuntary muscle contractions caused by electrical discharges within the brain and are usually accompanied by changes in consciousness.

    * glucagon is a hormone produced by alpha cells in the islets of Langerhans of the pancreas. Glucagon stimulates the release of glycogen from the liver, which stores glucose in the form of glycogen for use in raising blood sugar when needed.

    * lymph nodes (LIMF) are small, bean-shaped masses of tissue containing immune cells that fight harmful microorganisms. Lymph nodes may swell during infections.

    * lesion (LEE-zhun) is a general term referring to a sore or a damaged or irregular area of tissue.

    * MRI is short for magnetic resonance imaging, which produces computerized images of internal body tissues using magnets and radio waves.

    * neurological (nur-uh-LAH-je-kal) refers to the nervous system, which includes the brain, the spinal cord, and the nerves that control the senses, movement, and organ functions throughout the body.

    * kidney stones are hard structures that form in the urinary tract when chemicals in the urine become overly concentrated. These stones can obstruct the flow of urine and cause tissue damage and pain as the body attempts to pass the stones through the urinary tract.

    * diabetes (dye-uh-BEE-teez) is a condition in which the body's pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood.

    * osteoporosis (os-tee-o-por-Osis) is the loss of bone mass that makes the bones weak and brittle.

    * depression (dih-PRESH-un) is a mental disorder characterized by feelings of sadness, despair, and hopelessness.

    * high blood pressure also called hypertension, is a condition in which the blood traveling through the arteries as a result of the heart's pumping action exerts greater than normal force against the blood vessel walls. This can lead to heart, kidney, blood vessel, and other damage.

    * coma (KO-ma) is an unconscious state, like a very deep sleep. A person in a coma cannot be awakened, and is usually unresponsive to stimuli.

    * ulcers are open sores on the skin or in the lining of a body organ, such as the stomach or intestine. They may or may not be painful.

    * isotope (ICE-oh-tope) refers to a variety of a particular atom or chemical that contains an unstable combination of atomic particles.

    * antibody (AN-tih-bah-dee) is a protein produced by the body's immune system to attack a specific antigen, or foreign substance, that enters the body. Antigens often consist of microorganisms like bacteria.

    * enzyme (EN-zime) is a protein that helps start or speed up a chemical reaction in cells or organisms.

    * CT scan, or computed tomography, is a medical diagnostic tool that uses special x-rays to generate computerized images of internal body structures.

    * ultrasound, also called a sonogram, is a diagnostic test in which sound waves passing through the body create images on a computer screen.

    * biopsy (BI-op-see) is a test in which a small sample of body tissue is removed and examined for signs of disease.

    * radiation therapy is a treatment that uses a high-energy radiation beam consisting of x-rays or other forms of energy to shrink and stop either malignant or benign tumor-cell growth.

    * dopamine agonists (DO-puhmeen) (a-guh-nists) are medications that mimic the actions of the brain chemical dopamine in the body. One of dopamine's normal jobs is controlling prolactin production. But dopamine agonists are stronger and longerlasting than natural dopamine, so they can effectively treat prolactinomas.

    * chemotherapy (KEE-mo-THER-apee) is the treatment of cancer with powerful drugs that kill cancer cells.

    Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

    (MLA 8th Edition)