Medical Glossary Index:

H

Hair follicle- a tiny opening in the skin from which a hair grows

Halitosis- the clinical term for bad breath; commonly caused by poor oral hygiene or eating certain foods; if persistent it can be a sign of illness

Hallucination- a perception that occurs when there is actually nothing there to cause it (such as hearing voices when there are none)

Hammer toe- an abnormality in the tendons of the toe that causes the toe to be flexed at all times

Hamstring muscle- a muscle located at the back of the thigh that bends the leg
at the knee and moves the leg backward

Hardening of the arteries- the common name for arteriosclerosis

Hashimoto’s disease- a disease in which the body’s immune system attacks
cells of the thyroid gland, resulting in a decrease in thyroid hormones

Hay fever- the common name for allergic rhinitis

HDL- see High-density lipoprotein

Heart attack- see Myocardial infarction

Heart block- a disorder of the heart caused by a blockage of the nerve impulses to the heart that regulate heartbeat; may lead to dizziness, fainting, or stroke

Heartburn- a burning sensation experienced in the center of the chest up to the throat; may be caused by overeating, eating spicy food, or drinking alcohol; recurrent heartburn may be caused by acid reflux

Heart disease- see Coronary heart disease

Heart failure- the inability of the heart to pump blood effectively

Heart-lung machine- a machine that takes over the functions of the heart and lungs during certain types of surgery

Heart rate- the rate at which the heart pumps blood, measured in the number of heartbeats per minute

Heart valve- the structure at each exit of the four chambers of the heart that allows blood to exit but not to flow back in

Heat exhaustion- fatigue, dizziness, and nausea experienced because of overexposure to heat; if not treated it can result in heat stroke

Heat stroke- a life-threatening condition resulting from extreme overexposure to heat, which disrupts the body's system of regulating temperature

Heel spur- an abnormal, often painful outgrowth of bone on the back of the heel

Heimlich maneuver- a first-aid technique for choking; dislodges an object that is blocking a person’s airway

Helper T cells- white blood cells, responsible for regulating other cells in the body's immune system, that are the main targets of the AIDS virus; also called CD4 cells

Hemangioma- a purple-red mark on the skin, caused by an excess of blood vessels

Hemarthrosis- bleeding into and swelling of a joint

Hematemesis- vomiting of blood

Hematocrit- the percentage of total blood volume that consists of red blood
cells, which is determined by laboratory testing; can be an indicator of disease or injury

Hematoma- an accumulation of blood from a broken blood vessel

Hematuria- blood in the urine, which can be caused by urinary tract disorders (such as cysts, tumor, or stones) or by an infection

Hemochromatosis- a genetic disorder in which too much iron is absorbed from food

Hemodialysis- a method used to treat kidney failure, in which blood is passed through a machine that purifies it and returns it to the body

Hemoglobin- the pigment in red blood cells that is responsible for carrying oxygen; hemoglobin bound to oxygen gives blood its red color

Hemoglobinuria- hemoglobin in the urine

Hemolysis- the breakdown of red blood cells in the spleen, which is normal but can cause jaundice and anemia when the red blood cells are broken down too
quickly

Hemophilia- an inherited disorder in which a person's blood lacks a certain protein important in forming blood clots, leading to excessive bleeding

Hemorrhage- the medical term for bleeding

Hemorrhoid- a bulging vein either at the opening of the anus or just inside the anus, often caused by childbirth or straining during bowel movements

Hemospermia- blood in the semen

Hemostasis- the stopping of bleeding by the body’s mechanisms

Hemothorax- an accumulation of blood between the chest wall and the lungs

Hepatectomy- surgical removal of all or part of the liver

Hepatic- a term used to describe something that is related to the liver

Hepatitis- inflammation of the liver, which may be caused by a viral infection, poisons, or the use of alcohol or other drugs

Hepatitis A- a form of hepatitis caused by the hepatitis A virus, usually transmitted by contact with contaminated food or water

Hepatitis B- a form of hepatitis (generally more serious than hepatitis A) caused by the hepatitis B virus, which is transmitted through sexual contact or contact with infected blood or body fluids

Hepatitis C- a form of hepatitis caused by the hepatitis C virus, which is transmitted through sexual contact or contact with infected blood or body fluids

Hepatitis D- a form of hepatitis that only causes symptoms when the individual is already infected with hepatitis B

Hepatoma- a cancerous tumor of the liver

Hepatomegaly- enlargement of the liver

Hereditary- describes a genetic trait that is passed from parents to children

Hereditary spherocytosis- a genetic disorder in which red blood cells are smaller, rounder, and more fragile than normal, causing hemolytic anemia

Hermaphroditism- a rare condition in which an individual is born with both male and female reproductive organs

Hernia- the bulging of an organ or tissue through a weakened area in the muscle wall

Herniated disk- see Disk prolapse

Herpes encephalitis- brain inflammation caused by a herpes simplex virus that has spread from another part of the body

Herpes simplex- infection by the herpes simplex virus, which causes blisterlike sores on the face, lips, mouth, or genitals; in rare cases, can also affect the eyes, fingers, or brain

Herpes zoster- see Shingles

Heterosexuality- being sexually attracted to members of the opposite sex

Hiatal hernia- a type of hernia in which the stomach bulges up into the chest cavity through an opening in the diaphragm

Hiccup- involuntary sudden contraction of the diaphragm along with the closing of the vocal cords, producing a "hiccup" sound

High-density lipoprotein- a type of protein found in the blood that removes cholesterol from tissues, protecting against heart disease

Hirschsprung's disease- a condition that is present at birth in which nerve cells do not develop in parts of the intestine, causing the intestine to narrow and block the passage of feces

Hirsutism- excessive hair or hair growth in unusual places, especially in women

Histamine- a chemical in some cells of the body that is released during allergic reactions, causing inflammation; also causes production of acid in the stomach and narrowing of the airways

H1 (histamine) blocker- a drug that blocks the action ofhistamine; used to treat inflammation

H2 (histamine) blocker- a drug used in the treatment of peptic ulcers that blocks histamine from causing acid production in the stomach

Histoplasmosis- a respiratory disease acquired by inhaling the spores of a fungus found in soil, especially where there are bird or bat droppings

HIV- see Human immunodeficiency virus

Hives- the common term for urticaria, an itchy, inflamed rash that results from an allergic reaction

Hodgkin's disease- a cancer of lymphoid tissue (found in lymph nodes and the spleen) that causes the lymph nodes to enlarge and function improperly; may cause illness, fever, loss of appetite, and weight loss

Homeostasis- the body's coordinated maintenance of the stable, internal environment by regulating blood pressure, blood sugar, body temperature, etc

Homocystinuria- a genetic disorder in which an enzyme deficiency causes a substance called homocystine to build up in the blood, leading to mental handicap
and skeletal abnormalities

Homosexuality- being sexually attracted to members of the same sex

Hookworm- infestation by a small, round, blood-sucking parasite; commonly causes a rash on the foot, but can also cause cough, pneumonia, and anemia

Hormonal implant- surgical insertion of a small object just under the skin that slowly releases a synthetic hormone for purposes such as birth control

Hormone- a chemical produced by a gland or tissue that is released into the bloodstream; controls body functions such as growth and sexual development

Hormone replacement therapy- the use of natural or artificial hormones to
treat hormone deficiencies

Hospice- a hospital or an area of a hospital dedicated to treating people who are dying, often of a specific cause

Hot flash- a sudden, temporary feeling of heat and sometimes sweating; usually occurs as a result of low estrogen levels in women because of menopause or after a hysterectomy

HTLV- see Human T-cell lymphotrophic virus

Human immunodeficiency virus- a retrovirus that attacks helper T cells of the immune system and causes acquired immunodeficiency syndrome (AIDS);
transmitted through sexual intercourse or contact with infected blood

Human T-cell lymphotrophic virus- a virus similar to HIV that affects the same helper T cells, but usually accompanies adult T-cell leukemia or T-cell lymphomas

Hydramnios- an excess of amniotic fluid in the uterus during pregnancy

Hydrocele- a painless swelling of the scrotum, caused by a collection of fluid around the testicle; commonly occurs in middle aged men

Hydrocephalus- excess cerebrospinal fluid within the brain; commonly referred
to as "water on the brain"

Hydrocortisone- a corticoseroid drug that is used to treat inflammation and allergies

Hygiene- the practice, maintenance, and study of health; commonly refers to cleanliness

Hymen- a thin fold of membrane partly closing the opening of the vagina; usually torn during first sexual intercourse or insertion of a tampon

Hyperactivity- a type of behavior characterized by excessive physical activity, sometimes associated with neurological or psychological causes

Hyperalimentation- a method of providing nutrients by the use of a tube or intravenously to a person who cannot eat food or needs nutrients because of an
illness

Hyperbilirubinemia- a condition in which there is too much bilirubin, a substance produced when red blood cells are broken down; can lead to jaundice

Hypercalcemia- a condition marked by abnormally high levels of calcium in the blood; can lead to disturbance of cell function in the nerves and muscles and, if not treated, can be fatal

Hypercholesterolemia- an abnormally high level of cholesterol in the blood, which can be the result of an inherited disorder or a diet that is high in fat

Hyperglycemia- a condition characterized by abnormally high levels of glucose
in the blood, usually as a result of untreated or improperly controlled diabetes mellitus

Hyperlipidemia- a general term for a group of disorders in which lipid levels in the blood are abnormally high, including hypercholesterolemia

Hyperparathyroidism- overactivity of the parathyroid glands, which increases calcium levels in the blood (called hypercalcemia) and decreases calcium in bones (causing osteoporosis)

Hyperplasia- the enlargement of an organ or tissue

Hypersensitivity- an excessive response of the body’s immune system to a foreign protein

Hypertension- abnormally high blood pressure, even when at rest

Hyperthermia- an abnormally high body temperature

Hyperthyroidism- overactivity of the thyroid gland, causing nervousness, weight loss, fatigue, and diarrhea

Hypertrophy- increase in the size of an organ due to an increase in the size of its cells

Hyperventilation- abnormally rapid breathing

Hypochondriasis- an abnormal condition in which a person is overly concerned with health and believes that he or she is suffering from a major illness despite
medical opinion to the contrary

Hypodermic needle- a thin, hollow needle attached to a syringe; used to inject a medication under the skin, into a vein, or into a muscle

Hypoglycemia- abnormally low levels of glucose in the blood

Hypoplasia- failure of a tissue or organ to develop normally

Hypotension- the medical term for abnormally low blood pressure, which results in reduced blood flow to the brain, causing dizziness and fainting

Hypothermia- an abnormally low body temperature

Hypothyroidism- underactivity of the thyroid gland, causing tiredness, cramps,
a slowed heart rate, and possibly weight gain

Hypoventilation- a slower-than-normal breathing rate

Hypoxemia- a reduced level of oxygen in the blood

Hypoxia- a reduced level of oxygen in tissues

Hysterectomy- surgical removal of the uterus

Hysteria- a term used to describe symptoms that are caused by mental stress
and occur in someone who does not have a mental disorder

Hysterosalpingography- an X-ray examination performed to examine the inside of the uterus and fallopian tubes, in order to investigate and possibly treat infertility

Hysteroscopy- a method used to examine the inside of the uterus and the cervix using a viewing instrument