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Glossaries - A

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

Abdomen (AB-doh-men)

The area between the chest and the hips. Contains the stomach, small intestine, large intestine, liver, gallbladder, pancreas, and spleen.

Abdominal Migraine (ab-DOM-uh-nul MY-grayn)

Absorption (ub-SORP-shun)

The way nutrients from food move from the small intestine into the cells in the body.


acceptable daily intake (ADI)

The amount of chemical that, if ingested daily over a lifetime, appears to be without appreciable effect.

ACE Inhibitor

A type of drug used to lower blood pressure. Studies indicate that it may also help prevent or slow the progression of kidney disease in people with diabetes.

acesulfame K

Acesulfame K, or acesulfame potassium, is a low-calorie sweetener approved for use in the United States in 1988. It is an organic salt consisting of carbon, nitrogen, oxygen, hydrogen, sulphur and potassium atoms. It is 200 times sweeter than sucrose, has a synergistic sweetening effect with other sweeteners, has a stable shelf-life and is heat stable. It is excreted through the human digestive system unchanged, and is therefore non-caloric.


A pill taken to lower the level of glucose (sugar) in the blood. Only some people with noninsulin-dependent diabetes take these pills. See also: Oral hypoglycemic agents.


A chemical formed in the blood when the body uses fat instead of glucose (sugar) for energy. If acetone forms, it usually means that the cells do not have enough insulin, or cannot use the insulin that is in the blood, to use glucose for energy. Acetone passes through the body into the urine. Someone with a lot of acetone in the body can have breath that smells fruity and is called "acetone breath." See also: Ketone bodies.

Acetylcholine (as-e-till-KOH- lean)

a chemical agent that is released by nerve endings; its effects include cardiac inhibition (a slowing down), increase in blood vessel diameter, and other effects.


Achalasia (AK-uh-LAYZ-ya)

A rare disorder of the esophagus. The muscle at the end of the esophagus does not relax enough for the passage to open properly. (See image).

Clear Image


A dry, one-seeded fruit, without a predictable opening and formed from a single carpel. It usually one of many, like an unshelled Sunflower seed.

Clear Image


Specifically, the abnormal buildup of acids in the body, classically caused by diabetes or kidney disease. Broadly, the potential caused by increased protein intake or metabolism, coupled with inadequate intake (or loss) of alkali. For a person with diabetes, this can lead to diabetic ketoacidosis.


In our context, a substance having a pH below that of neutral water (7.0)when in solution. Most metabolic waste products are acidic. Sour.

Achlorhydria (AY-klor-HY-dree-uh)

The lack of free hydrochloric acid in the stomach; more broadly, inadequate or suppressed secretions. Without enough acid, proteins are not broken down, butterfats are not digested, Vitamin B12 may not be absorbed, and there is a long-term risk for the potential of food sensitivities to undigested foreign proteins.

Activated Charcoal (AK-tuh-vay-ted CHAR-kohl)

An over-the-counter product that may help relieve intestinal gas. Also used in various types of filters to remove impurities.

Activated Partial Thromboplastin Time (aPTT) (THROM-boh-plas-tin)

the period required for clot formation in recalcified blood plasma after contact activation and addition of platelet substitutes (e.g., brain cephalin or similar phospholipids); used to assess the intrinsic and common pathways of coagulation. Anticoagulant therapy with heparin or hirudin prolongs the aPTT.

Acute (uh-KYOOT)

A disorder that is sudden and severe but lasts only a short time. The opposite is chronic.

Acute Lymphoblastic Leukemia

A quickly progressing disease in which too many immature white blood cells called lymphoblasts are found in the blood and bone marrow. Also called ALL or acute lymphocytic leukemia.

Acute Myeloid Leukemia

A quickly progressing disease in which too many immature blood-forming cells are found in the blood and bone marrow. Promyelocytic leukemia is a type of acute myeloid leukemia. Also called AML or acute myelogenous leukemia.


A recent term used to describe agents, often botanical, that stimulate non-specific resistance, and that seem to decrease hypothalamus and pituitary over-reactions to perceived...not real...stress.

additives (food additives)

Any natural or synthetic material, other than the basic raw ingredients, used in the production of a food item to enhance the final product. Any substance that may affect the characteristics of any food, including those used in the production, processing, treatment, packaging, transportation or storage of food. Go here for more information.


An inflammation of one or several lymph nodes, or related lymphoid tissues.


an ordinarily benign (nonmalignant) tumor of skin tissue.

Adjuvant Therapy

Adjuvant therapy can be radiation therapy, chemotherapy, or hormone therapy given before or after primary treatment to try to eliminate any cancer cells that may be left.


The outer covering of the two adrenal glands that lie atop each kidney. Embryonically derived from gonad tissue, they make steroid hormones including DHEA that control electrolytes, the management of fuels, the rate of anabolism, the general response to stress, and maintenance of nonspecific resistance.

Adrenal Glands

Two organs that sit on top of the kidneys and make and release hormones such as adrenalin (epinephrine), cortisol and DHES. This and other hormones, including insulin, control the body's use of glucose (sugar). Go here for detailed information.

Adrenal Medulla

The inner part of the adrenals, derived embryonically from spinal nerve precursors, they secrete epinephrine, norepinephrine and dopamine; used locally as neurotransmitters, sensitive receptors can be mobilized totally by the adrenal medullas.

Ault-onset Diabetes


Called epinephrine in the U.S., this is a substance secreted into the bloodstream and reacted to by specialized receptors throughout the body, initiating a "code blue" or flight-or-fight response. Many receptors are a regular part of sympathetic function, and respond to their own local relative, norepinephrine or noradrenalin, in the course of normal autonomic nervous system interplay.


Pertaining to the adrenal cortex.

Adult-onset Diabetes

Former term for noninsulin-dependent or type II diabetes. See also: diabetes mellitus.

Adverse Effect, Adverse Event

A harmful result; in a clinical trial, an unwanted effect detected in participants.


The parts of plants growing above ground.

Aerobic exercise

Exercise that requires continuous, rhythmic motion of large muscle groups such as the quadriceps. Swimming, running, and walking are examples of aerobic exercise. Aerobic exercise also improves the ability to perform activities of daily living.

Aerophagia (AIR-oh-FAY-jee-uh)

A condition that occurs when a person swallows too much air. Causes gas and frequent belching.

Aflatoxin (af-lah-TOCK-sin)

a toxic chemical produced by the Aspergillus flavus and A. parasiticus molds.


a drug that both binds to receptors and has an intrinsic effect; A drug that triggers an action from a cell or a drug

AIDS (acquired immunodeficiency syndrome)

the late stage of HIV disease, characterized by a deterioration of the immune system and a susceptibility to a range of opportunistic infections and cancers.

Alactasia (ay-lak-TAYZ-ya)

An inherited condition causing the lack of the enzyme needed to digest milk sugar.

Alagille Syndrome(al-uh-GEEL sin-drohm)

A condition of babies in their first year. The bile ducts in the liver disappear, and the bile ducts outside the liver get very narrow. May lead to a buildup of bile in the liver and damage to liver cells and other organs.


More than normal amounts of a protein called albumin in the urine. Albuminuria may be a sign of kidney disease, a problem that can occur in people who have had diabetes for a long time.

Aldose Reductase Inhibitor

A class of drugs being studied as a way to prevent eye and nerve damage in people with diabetes. Aldose reductase is an enzyme that is normally present in the eye and in many other parts of the body. It helps change glucose (sugar) into a sugar alcohol called sorbitol. Too much sorbitol trapped in eye and nerve cells can damage these cells, leading to retinopathy and neuropathy. Drugs that prevent or slow (inhibit) the action of aldose reductase are being studied as a way to prevent or delay these complications of diabetes.


In our context, a substance having a pH above that of neutral water(7.0) when in solution. Signified as pH (potential of Hydrogen), alkaline fluids, such as the blood (pH about 7.4), have the ability to neutralize acids (solutions below pH 7.0). Metabolic wastes are acids, and the alkaline reserve of the blood neutralizes them until they are excreted. See pH

Alimentary Canal (al-uh-MEN-tree kuh-NAL)

See gastrointestinal tract.

Allergen (food allergen)

A food allergen is the part of a food (a protein) that stimulates the immune system of food allergic individuals. A single food can contain multiple food allergens. Carbohydrates or fats are not allergens.

Allergy (AL-ur-jee)

A condition in which the body is not able to tolerate certain foods, animals, plants, or other substances.

Alkylating Agents

A family of anticancer drugs that combine with a cancer cell's DNA to prevent normal cell division.

Alopecia (al-oh-PEE-she-ah)

loss of hair

Alpha Cell

A type of cell in the pancreas (in areas called the islets of Langerhans). Alpha cells make and release a hormone called glucagon, which raises the level of glucose (sugar) in the blood.

Amebiasis (uh-mee-BY-uh-sis)

An acute or chronic infection. Symptoms vary from mild diarrhea to frequent watery diarrhea and loss of water and fluids in the body. See also Gastroenteritis.

Amino Acid (ah-ME- no)

a component part of every protein, in which up to 20 different amino acids are strung together into polymer chains like beads in a necklace; the sequence of its amino acids determines a protein's structure and function; many proteins catalyze chemical reactions in the body. A deficiency of even a single amino acid can impair the body's production of many proteins, and result in hormone imbalances, breakdown of muscle tissue, and weakened immune function. Detailed information can be found here.


A type of diabetic neuropathy that causes muscle weakness and wasting.


The building up of proteins from simpler molecules in the body, (such as proteins forming from amino acids). This generative process results in increased lean muscle mass, stronger bones, and a greater energy supply. Anabolic hormones include DHEA, testosterone, and growth hormone.


the building up in the body of complex chemical compounds from smaller simpler compounds (e.g., proteins from amino acids); see catabolism for comparison.


Drugs that reduce pain. These drugs include aspirin, acetaminophen, and ibuprofen.


Anal Fissure

A small tear in the anus that may cause itching, pain, or bleeding.


Anal Fistula (AY-nul FIST-yoo-luh)

A channel that develops between the anus and the skin. Most fistulas are the result of an abscess (infection) that spreads to the skin.


Anamnestic response

the heightened immunologic reaction elicited by a second or subsequent exposure to a particular pathogenic microorganism (e.g., bacterium, fungus, virus), toxin, or antigen. (See also memory cells.)


resembling anaphylaxis, an immediate, transient allergic reaction.

Anaphylaxis (an-ah-fuh-LACK-siss)

an immediate allergic reaction to a pharmacologic agent.


Refers to cancer cells that grow and divide rapidly.

Anastomosis (AN-nuh-stuh-MOH-sis)

An operation to connect two body parts. An example is an operation in which a part of the colon is removed and the two remaining ends are rejoined.

ancrod (AN-crod)

a protease derived from the venom of the Malayan pit viper that acts specifically on fibrinogen; used as an anticoagulant (Arvin, Knoll Pharmaceuticals).


any substance that produces masculinization, such as testosterone.

Androgen Ablation

The use of hormone therapy to suppress or block the production of male hormones in order to reduce the spread of prostate cancer.

Androgen Suppression

Stopping the production of male sex hormones. Androgen suppression is achieved by removing the testicles, by taking female sex hormones, or by taking drugs. Also called androgen ablation.

Anemia (uh-NEE-mee-uh)

Anemia is a condition in which a deficiency in the size or number of erythrocytes (red blood cells) or the amount of hemoglobin they contain limits the exchange of oxygen and carbon dioxide between the blood and the tissue cells. Most anemias are caused by a lack of nutrients required for normal erythrocyte synthesis, principally iron, vitamin B-12, and folic acid. Others result from a variety of conditions, such as hemorrhage, genetic abnormalities, chronic disease states or drug toxicity. Hemoglobin is a protein in the blood that contains iron.



the loss or weakening of immune response to an irritating agent or antigen. Anergy can be thought of as the opposite of allergy, which is an overreaction to a substance. The strength of the immune response is often quantitatively evaluated by standardized skin tests. A small amount of solution containing an antigen known to cause a response, such as tetanus, mumps, or candida, is injected under the skin and the area checked for a localized skin reaction after 48 to 72 hours. Healthy people will develop a measurable area of redness at the injection site; people who are immune suppressed, such as people with AIDS, will have no measurable response to these skin tests.

Angiodysplasia (AN-jee-oh-dis-PLAYZ-ya)

Abnormal or enlarged blood vessels in the gastrointestinal tract.

Angiography (AN-jee-AW-gruh-fee)

An imaging technique that provides a picture, called an angiogram, of blood vessels; an x-ray that uses dye to detect bleeding in the gastrointestinal tract.


Disease of the blood vessels (arteries, veins, and capillaries) that occurs when someone has diabetes for a long time. There are two types of angiopathy: macroangiopathy and microangiopathy. In macroangiopathy, fat and blood clots build up in the large blood vessels, stick to the vessel walls, and block the flow of blood. In microangiopathy, the walls of the smaller blood vessels become so thick and weak that they bleed, leak protein, and slow the flow of blood through the body. Then the cells, for example, the ones in the center of the eye, do not get enough blood and may be damaged.

Ankylosing spondylitis

Anorectal Atresia (AY-noh-REK-tul uh-TREEZ-ya)

Lack of a normal opening between the rectum and anus.


a drug or substance that leads to anorexia or diminished appetite; appetite suppressant.

Anorexia Nervosa

An eating disorder characterized by refusal to maintain a minimally normal weight for height and age. The condition includes weight loss leading to maintenance of body weight 15 percent below normal; an intense fear of weight gain or becoming fat, despite the individual's underweight status; a disturbance in the self-awareness of one's own body weight or shape; and in females, the absence of at least three consecutive menstrual cycles that would otherwise be expected to occur.

Anoscopy (ay-Naw-skuh-pee)

A test to look for fissures, fistulae, and hemorrhoids. The doctor uses a special instrument, called an anoscope, to look into the anus.

Antacids (ant-ASS-idz)

Medicines that balance acids and gas in the stomach. Examples are Maalox, Mylanta, and Di-Gel.


a drug that impedes the action of another chemical substance in the body; One agent that opposes or fights the action of another. For example, insulin lowers the level of glucose (sugar) in the blood, whereas glucagon raises it; therefore, insulin and glucagon are antagonists.


Antihormone agents (also called androgen blockers) used to block the production of male hormones.


Drugs that fight infection caused by bacteria. Antibiotic drugs include amikacin, amoxicillin (amoxicillin-clavulanic acid), ceftriaxone, ciprofloxacin, clarithromycin, metronidazole, novobiocin, penicillin, and tetracycline.

Antibody, Antibodies

Proteins that the body makes to protect itself from foreign substances; an infection-fighting protein molecule in blood or secretory fluids that tags, neutralizes, and helps destroy pathogenic microorganisms (e.g., bacteria, viruses) or toxins. Antibodies, known generally as immunoglobulins, are made and secreted by B lymphocytes in response to stimulation by antigens. Each specific antibody binds only to the specific antigen that stimulated its production. (See also immunoglobulin; enhancing antibody; functional antibody; neutralizing antibody.)

In diabetes, the body sometimes makes antibodies to work against pork or beef insulins because they are not exactly the same as human insulin or because they have impurities. The antibodies can keep the insulin from working well and may even cause the person with diabetes to have an allergic or bad reaction to the beef or pork insulins.

Antibody-mediated immunity

also called humoral immunity. Immunity that results from the activity of antibodies in blood and lymphoid tissue.

Anticoagulant (an-tee-ko-AG-u-lent)

any substance that prevents blood clotting; administered for prophylaxis or treatment of thromboembolic disorders. Parenteral anticoagulants include heparin, low molecular weight heparins, hirudin, and ancrod, all of which inactivate thrombin and other clotting factors. The oral anticoagulants inhibit the synthesis of vitamin K-dependent coagulation factors.

Anticholinergics (an-tee-koh-lih-NURJ-iks)

Medicines that calm muscle spasms in the intestine. Examples are dicyclomine (dy-SY-kloh-meen) (Bentyl) and hyoscyamine (HY-oh-SY-uh-meen) (Levsin).


A drug that prevents or relieves convulsions or seizures.

Antidiabetic agent

A substance that helps a person with diabetes control the level of glucose (sugar) in the blood so that the body works as it should. See also: Insulin; oral hypoglycemic agents.

Antidiarrheals (AN-tee-dy-uh-REE-ulz)

Medicines that help control diarrhea. An example is loperamide (lo-PEH-ruh-myd) (Imodium).

Antiemetics (an-tee-ee-MET-iks)

Medicines that prevent and control nausea and vomiting. Examples are promethazine (pro-MEH-thuh-zeen) (Phenergan) and prochlorperazine (pro-klor-PEH-ruh-zeen) (Compazine).


A drug to treat infections caused by funguses. Antifungal drugs include metronidazole, amphotericin B, nystatin, fluconazole, and voriconazole.


any substance that stimulates the immune system to produce antibodies. Antigens are often foreign substances such as invading bacteria or viruses. (See also immunogen.)

Antigen-presenting cell (APC)

B cell, macrophage, dendritic cell or other cell that ingests and processes foreign bodies such as viruses and displays the resulting antigen fragments on its surface to attract and activate the CD4+ T cells that respond specifically to that antigen. (See also dendritic cell; macrophage.)



an antibody that recognizes and binds to the antigen-binding site of another antibody. In HIV vaccines, anti-idiotype vaccines are made from antibodies generated against antibodies to the virus.


A substance that works to slow or prevent the generation of free radical molecular groups in the body, thereby protecting against degenerative cell damage associated with oxidative stress.


An agent that kills bacteria. Alcohol is a common antiseptic. Before injecting insulin, many people use alcohol to clean their skin to avoid infection.

Antispasmodics (an-tee-spaz-MAW-diks)

Medicines that help reduce or stop muscle spasms in the intestines. Examples are dicyclomine (dy-SY-klo-meen) (Bentyl) and atropine (AH-tro-peen) (Donnatal).

Antithrombin (an-tee-THROM-bin)

a general term for a naturally occurring substance that neutralizes the action of thrombin and thus limits or restricts blood coagulation. Six antithrombins have been designated by Roman numbers I- IV; of these, antithrombin I and III appear to be of most importance.

Antithrombin III

a protein that inactivates thrombin in a time-dependent irreversible reaction and serves as a cofactor of heparin and its anticoagulant activities. Antithrombin III also inhibits certain coagulation factors.

Antithrombotic (an-tee-throm-BOT-ik)

an agent that prevents or interferes with the formation of thrombin.


The term arthritis literally means joint inflammation, but it also is used to refer to more than 100 rheumatic diseases. These diseases can cause pain, stiffness, and swelling in joints and may also affect other parts of the body.


Aspartame is a low-calorie sweetener used in a variety of foods and beverages and as a tabletop sweetener. It is about 200 times sweeter than sugar. Aspartame is made by joining two protein components, aspartic acid and phenylalanine.


Asthma is a chronic medical condition, affecting approximately 10 million Americans (3 to 4 percent of the population). Asthma results when irritants (or trigger substances) cause swelling of the tissues in the air passage of the lungs, making it difficult to breathe. Typical symptoms of asthma include wheezing, shortness of breath and coughing.


A condition that exists when too much cholesterol builds up in the blood and accumulates in the walls of the blood vessels.

atonic colon

Commonly called "Lazy Bowel Syndrome"; Lazy bowel syndrome, also known as slow transit constipation (STC), is a condition characterized by the slow movement of waste through the digestive system, primarily due to reduced motility of the large intestine. It is a type of functional constipation, or constipation without a clear cause. Other types of functional constipation include normal transit constipation and defecating disorder. Normal transit constipation occurs when the digestive system operates normally and waste moves at a normal speed; however, stool may be difficult to pass. Defecating disorder is defined as the inability to evacuate contents from the rectum despite excessive straining.

Attention Deficit Hyperactivity Disorder (ADHD)

Commonly called "hyperactivity"; Attention Deficit Hyperactivity Disorder is a clinical diagnosis based on specific criteria. These include excessive motor activity, impulsiveness, short attention span, low tolerance to frustration and onset before 7 years of age.

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