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Glossaries - G

We've defined thousands of terms related to health care. This page discusses glossary terms with the letter G.

Galactose (guh-LAK-tos)

A type of sugar found in milk products and sugar beets. It is also made by the body. It is considered a nutritive sweetener because it has calories.

Galactosemia (guh-LAK-toh-SEE-mee-uh)

Buildup of galactose in the blood. Caused by lack of one of the enzymes needed to break down galactose into glucose.

Gallbladder (GAWL-blah-dur)

The organ that stores the bile made in the liver. Connected to the liver by bile ducts. The gallbladder can store about 1 cup of bile. Eating signals the gallbladder to empty the bile through the bile ducts to help digest fats.


Gallstones (GAWL-stonz)

The solid masses or stones made of cholesterol or bilirubin that form in the gallbladder or bile ducts.

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Ganglion (GANG-glee-on)

pl. ganglia; any group of nerve cell bodies located in the peripheral nervous system.

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The death of body tissue. It is most often caused by a loss of blood flow, especially in the legs and feet.

Gardner's Syndrome (GARD-nurz sin-drohm)

A condition in which many polyps form throughout the digestive tract. Because these polyps are likely to cause cancer, the colon and rectum are often removed to prevent colorectal cancer.

Gastrectomy (gah-STREK-tuh-mee)

An operation to remove all or part of the stomach.

Gastric (GAH-strik)

Related to the stomach.

Gastric Juices (GAH-strik JOO-suz)

Liquids produced in the stomach to help break down food and kill bacteria.

Gastric Resection (GAH-strik ree-SEK-shun)

An operation to remove part or all of the stomach.

Gastric Ulcer (GAH-strik UL-sur)

Gastrin (GAH-strin)

A hormone released after eating. Gastrin causes the stomach to produce more acid.

Gastritis (gah-STRY-tis)

An inflammation of the stomach lining.

Gastrocolic Reflex (GAH-stroh-KAW-lick REE-fleks)

Increase of muscle movement in the gastrointestinal tract when food enters an empty stomach. May cause the urge to have a bowel movement right after eating.

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Gastroenteritis (GAH-stroh-en-tuh-RY-tis)

An infection or irritation of the stomach and intestines. May be caused by bacteria or parasites from spoiled food or unclean water. Other causes include eating food that irritates the stomach lining and emotional upsets such as anger, fear, or stress. Symptoms include diarrhea, nausea, vomiting, and abdominal cramping. See also Infectious Diarrhea and Travelers' Diarrhea.


Gastroenterologist (GAH-stroh-en-tuh-RAW-luh-jist)

A doctor who specializes in digestive diseases.

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Gastroenterology (GAH-stroh-en-tuh-RAW-luh-jee)

The field of medicine concerned with the function and disorders of the digestive system.

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Gastroesophageal Reflux Disease (GERD) (GAH-stroh-eh-SAW-fuh-JEE-ul REE-fluks duh-zeez)

Flow of the stomach's contents back up into the esophagus. Happens when the muscle between the esophagus and the stomach (the lower esophageal sphincter) is weak or relaxes when it shouldn't. May cause esophagitis. Also called esophageal reflux or reflux esophagitis.

Digestive System

Gastrointestinal (GI) Tract (GAH-stroh-in-TES-tuh-nul trakt)

The large, muscular tube that extends from the mouth to the anus, where the movement of muscles and release of hormones and enzymes digest food. Also called the alimentary canal or digestive tract.

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A form of nerve damage that affects the stomach. Food is not digested properly and does not move through the stomach in a normal way, resulting in vomiting, nausea, or bloating and interfering with diabetes management. See also: Autonomic neuropathy.

Gastrostomy (gah-STRAW-stuh-mee)

An artificial opening from the stomach to a hole (stoma) in the abdomen where a feeding tube is inserted. See also Enteral Nutrition.


A basic unit of heredity. Genes are made of DNA, a substance that tells cells what to do and when to do it. The information in the genes is passed from parent to child-for example, a gene might tell some cells to make the hair red or the eyes brown.

Generic Drug Name

The generic or common name of a drug is its more-or-less scientific name created by agreement among manufacturers and physicians. Naproxen sodium, for example, is the generic name for Aleve(tm). Several brand-name drugs may have the identical generic name because they contain the same active ingredient. Thus, naproxen sodium is also sold as Anaprox(tm).

Genetic engineering

the laboratory technique of recombining genes to produce proteins used for drugs and vaccines.


An infection with the parasite Giardia lamblia from spoiled food or unclean water. May cause diarrhea. See also Gastroenteritis.

Gilbert Syndrome (GIL-burt sin-drohm)

A buildup of bilirubin in the blood. Caused by lack of a liver enzyme needed to break down bilirubin. See also Bilirubin.


An eye disease associated with increased pressure within the eye. Glaucoma can damage the optic nerve and cause impaired vision and blindness.

Glomerular filtration rate

Measure of the kidneys' ability to filter and remove waste products.


Network of tiny blood vessels in the kidneys where the blood is filtered and waste products are removed.


A hormone that raises the level of glucose (sugar) in the blood. The alpha cells of the pancreas (in areas called the islets of Langerhans) make glucagon when the body needs to put more sugar into the blood.

An injectable form of glucagon, which can be bought in a drug store, is sometimes used to treat insulin shock. The glucagon is injected and quickly raises blood glucose levels. See also: Alpha cell.


A simple sugar found in the blood. It is the body's main source of energy; also known as dextrose. Fluctuating levels of glucose can affect mood states and fat metabolism, and act as key triggers in the development of diabetes. See also: Blood glucose.

Glucose Tolerance Test

A test to see if a person has diabetes. The test is given in a lab or doctor's office in the morning before the person has eaten. A first sample of blood is taken from the person. Then the person drinks a liquid that has glucose (sugar) in it. After one hour, a second blood sample is drawn, and, after another hour, a third sample is taken. The object is to see how well the body deals with the glucose in the blood over time.

Gluten (GLOO-ten)

A protein found in wheat, rye, barley, and oats. In people who can't digest it, gluten damages the lining of the small intestine or causes sores on the skin.

Gluten Intolerance (GLOO-ten in-TAH-luh-runs)


A substance made up of sugars. It is stored in the liver and muscles and releases glucose (sugar) into the blood when needed by cells. Glycogen is the chief source of stored fuel in the body.

Glycoprotein IIB/IIIA (GP IIB/IIIA) (gli-ko-PRO-teen)

the fibrinogen receptor on platelets. GP IIb/IIIa antagonists are currently in clinical trial as anticoagulants.

Glycosaminogl  Lycosaminoglycan (GLI-kohs-ah-me-no-GLI-kan)

Any of several high molecular weight linear polysaccharides having disaccharide repeating units containing an N- acetylhexosamine and a hexose or hexuronic acid; either or both residues may be sulfated. This class includes heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate, and hyaluronic acid. Formerly called mucopolysaccharide.

Glycosylated Hemoglobin Test

A blood test that measures a person's average blood glucose (sugar) level for the 2- to 3-month period before the test. See: Hemoglobin A1C.


a hormone that promotes gonad (sex gland) growth and function.


A type of arthritis caused by the reaction of the body to needle-like crystals of uric acid that accumulate in joint spaces. This reaction causes inflammation, swelling, and pain in the affected joint, most commonly the big toe.


abbreviation for glycoprotein. A protein molecule that is glycosylated, that is, coated with a carbohydrate, or sugar. The outer coat proteins of HIV are glycoproteins. The number after the gp (e.g., gp160, gp120, gp41) is the molecular weight of the glycoprotein.


glycoprotein 41. A protein embedded in the outer envelope of HIV that anchors gp120. gp41 plays a key role in HIV's infection of CD4+ T cells by facilitating the fusion of the viral and cell membranes. Antibodies to gp41 can be detected on a screening HIV ELISA.


glycoprotein 120. One of the proteins that forms the envelope of HIV. gp120 projects from the surface of HIV and binds to the CD4 molecule on helper T cells. gp120 has been a logical experimental HIV vaccine because the outer envelope is the first part of the virus that encounters antibody.

Granuloma (gran-yoo-LOH-ma)

A mass of red, irritated tissue in the GI tract found in Crohn's disease.

Granulomatous Colitis (gran-yoo-LOH-muh-tus koh-LY-tis)

Another name for Crohn's disease of the colon.

Granulomatous Enteritis (gran-yoo-LOH-muh-tus en-tuh-RY-tis)

Another name for Crohn's disease of the small intestine.

Growth hormone (gran-yoo-LOH-muh-tus en-tuh-RY-tis)

Hormone produced by the pituitary gland that stimulates growth and development of muscle tissue, energy production, sexual function, skin resilience, bone density, and other important functions. A decline in growth hormone levels often accompanies the degenerative process associated with aging.


a naturally occuring carbohydrate gum used as a thickening agent in foods and in weight-loss preparations.

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