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# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

H. pylori

Helicobacter pylori. A type of bacteria that causes inflammation and ulcers in the stomach or small intestine. People with H. pylori infections may be more likely to develop cancer in the stomach, including MALT (mucosa-associated lymphoid tissue) lymphoma.

hA20

A monoclonal antibody that is being studied in the treatment of refractory B-cell non-Hodgkin's lymphoma. Monoclonal antibodies are made in the laboratory and can locate and bind to cancer cells. hA20 binds to the protein CD20, which is found on B cells (a type of immune system cell), and some types of lymphoma cells. Also called IMMU-106 and HCD20.

HAART

Highly active antiretroviral therapy. Treatment for human immunodeficiency virus (HIV) infection that uses a combination of several antiretroviral drugs. The drugs inhibit the ability of the virus to multiply in the body, and they slow down the development of AIDS.

hair follicle (FOL-i-kul)

A shaft or opening on the surface of the skin through which hair grows.

hairy cell leukemia

A rare type of leukemia in which abnormal B-lymphocytes (a type of white blood cell) are present in the bone marrow, spleen, and peripheral blood. When viewed under a microscope, these cells appear to be covered with tiny hair-like projections.

halofuginone hydrobromide

A substance that is being studied for its ability to slow the growth of connective tissue and prevent the growth of new blood vessels to a solid tumor. It belongs to the family of drugs called quinazolinone alkaloids.

Halsted radical mastectomy

Surgery for breast cancer in which the breast, chest muscles, and all of the lymph nodes under the arm are removed. For many years, this was the breast cancer operation used most often, but it is used rarely now. Doctors consider radical mastectomy only when the tumor has spread to the chest muscles. Also called radical mastectomy.

hamartoma (ham-ar-TOE-ma)

A benign (noncancerous) growth made up of an abnormal mixture of cells and tissues normally found in the area of the body where the growth occurs.

hand-foot syndrome

A condition marked by pain, swelling, numbness, tingling, or redness of the hands or feet. It sometimes occurs as a side effect of certain anticancer drugs. Also known as palmar-plantar erythodysthesia.

happy major

Arctium lappa. A plant whose seeds and root have been used in some cultures to treat certain medical problems. It may have antioxidant effects. Also called burdock and lappa.

hard palate (PAL-et)

The front, bony part of the roof of the mouth.

hawthorn fruit

The fruit of the hawthorn tree or bush. It has been used in some cultures to treat certain medical problems, including heart problems and gastrointestinal problems.

HCD20

A monoclonal antibody that is being studied in the treatment of refractory B-cell non-Hodgkin's lymphoma. Monoclonal antibodies are made in the laboratory and can locate and bind to cancer cells. HCD20 binds to the protein CD20, which is found on B cells (a type of immune system cell), and some types of lymphoma cells. Also called IMMU-106 and hA20.

HCP

Healthcare proxy. A type of advance directive that gives a person (such as a relative, lawyer, or friend) the authority to make healthcare decisions for another person. It becomes active when that person loses the ability to make decisions for himself or herself.

hCRF

Human corticotropin-releasing factor. A substance that is being studied in the treatment of brain cancer. It is made naturally by the hypothalamus (a part of the brain) and can also be made in the laboratory. hCRF may help reduce symptoms caused by edema (swelling) of the brain. It belongs to the family of drugs called neurohormones.

HDR

High-dose radiation. An amount of radiation that is greater than that given in typical radiation therapy. HDR is precisely directed at the tumor to avoid damaging healthy tissue, and may kill more cancer cells in fewer treatments.

head and neck cancer

Cancer that arises in the head or neck region (in the nasal cavity, sinuses, lip, mouth, salivary glands, throat, or larynx [voice box]).

healthcare proxy

HCP. A type of advance directive that gives a person (such as a relative, lawyer, or friend) the authority to make healthcare decisions for another person. It becomes active when that person loses the ability to make decisions for himself or herself.

Hedyotis diffusa

An herb used in traditional Chinese medicine to treat certain medical problems. It has been used to boost the immune system and may have anticancer effects.

helical computed tomography

A detailed picture of areas inside the body. The pictures are created by a computer linked to an x-ray machine that scans the body in a spiral path. Also called spiral CT scan.

Helicobacter pylori (HEEL-ih-koh-BAK-ter py-LOR-ee)

H. pylori. A type of bacteria that causes inflammation and ulcers in the stomach or small intestine. People with H. pylori infections may be more likely to develop cancer in the stomach, including MALT (mucosa-associated lymphoid tissue) lymphoma.

helper T cell

A type of white blood cell that helps stimulate immune system reactions. Helper T cells help activate cytotoxic T cells and macrophages by secreting cytokines. They also stimulate B cells to make antibodies.

hemagglutinin-neuraminidase

A protein found in the outer coat of paramyxoviruses. This protein helps virus particles bind to cells, making infection easier.

hemangiopericytoma

A type of cancer involving blood vessels and soft tissue.

hemangiosarcoma

A type of cancer that begins in the cells that line blood vessels.

hematogenous

Originating in the blood or spread through the bloodstream.

hematologic malignancy

A cancer of the blood or bone marrow, such as leukemia or lymphoma. Also called hematologic cancer.

hematologist (hee-ma-TOL-o-jist)

A doctor who specializes in treating blood disorders.

hematopoiesis

The forming of new blood cells.

hematopoietic growth factor

A group of proteins that causes blood cells to grow and mature.

hematopoietic tissue

Tissue in which new blood cells are formed.

hematoporphyrin derivative

A drug used in photodynamic therapy that is absorbed by tumor cells. When exposed to light, it becomes active and kills the cancer cells.

hemilaryngectomy (HEM-ee-LAIR-in-JEK-tuh-mee)

An operation to remove one side of the larynx (voicebox).

hemoglobin (HE-muh-GLOW-bun)

The substance inside red blood cells that binds to oxygen and carries it from the lungs to the tissues.

hemophilia

Group of hereditary disorders in which affected individuals fail to make enough of certain proteins needed to form blood clots.

hemorrhage

In medicine, loss of blood from damaged blood vessels. A hemorrhage may be internal or external, and usually involves a lot of bleeding in a short time.

hemorrhoid (HEM-uh-roid)

An enlarged or swollen blood vessel, usually located near the anus or the rectum.

heparin

A drug that helps prevent blood clots from forming. It belongs to the family of drugs called anticoagulants (blood thinners).

hepatectomy

Surgery to remove all or part of the liver.

hepatic

Refers to the liver.

hepatic arterial infusion

A procedure to deliver chemotherapy directly to the liver. Catheters are put into an artery in the groin that leads directly to the liver, and drugs are given through the catheters.

hepatic artery

The major blood vessel that carries blood to the liver.

hepatic portal vein

A blood vessel that carries blood to the liver from the stomach, small and large intestines, spleen, pancreas, and gallbladder. Also called portal vein.

hepatic veno-occlusive disease

A condition in which some of the veins in the liver are blocked. It is sometimes a complication of high-dose chemotherapy given before a bone marrow transplant and is marked by increases in weight, liver size, and blood levels of bilirubin.

hepatitis (hep-a-TYE-tis)

Disease of the liver causing inflammation. Symptoms include an enlarged liver, fever, nausea, vomiting, abdominal pain, and dark urine.

hepatitis B virus

A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through blood or sexual contact. Also, infants born to infected mothers may become infected with the virus.

hepatitis C virus

A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through blood or sexual contact. Also, infants born to infected mothers may become infected with the virus.

hepatobiliary

Having to do with the liver, bile ducts, and/or gallbladder.

hepatoblastoma (HEP-a-toe-blas-TOE-ma)

A type of liver tumor that occurs in infants and children.

hepatocellular carcinoma (HEP-a-toe-SEL-yoo-ler KAR-sih-NOH-muh)

A type of adenocarcinoma, the most common type of liver tumor.

hepatocyte (HEP-a-toe-site)

A liver cell.

hepatoma (hep-a-TOE-ma)

A liver tumor.

hepatomegaly

Enlarged liver.

HER1

Epidermal growth factor receptor. The protein found on the surface of some cells and to which epidermal growth factor binds, causing the cells to divide. It is found at abnormally high levels on the surface of many types of cancer cells, so these cells may divide excessively in the presence of epidermal growth factor. Also known as EGFR or ErbB1.

HER2/neu

Human epidermal growth factor receptor 2. The HER2/neu protein is involved in the growth of some cancer cells. Also called c-erbB-2.

HER2/neu gene

The gene that makes the human epidermal growth factor receptor 2. The protein produced is HER2/neu, which is involved in the growth of some cancer cells. Also called c-erbB-2.

herba scutellaria barbatae

An herb used in traditional Chinese medicine to treat certain medical problems. It may have anticancer effects.

herbicide

A chemical that kills plants.

Herceptin (her-SEP-tin)

A type of monoclonal antibody used to detect or treat some types of cancer. Monoclonal antibodies are laboratory-produced substances that can locate and bind to cancer cells. Herceptin blocks the effects of the growth factor protein HER2, which transmits growth signals to breast cancer cells. Also called trastuzumab.

hereditary (ha-RED-ih-tair-ee)

Transmitted from parent to child by information contained in the genes.

hereditary leiomyomatosis and renal cell cancer syndrome

HLRCC. A rare inherited disorder that increases the risk of developing benign (noncancerous) tumors of the skin and the uterus (leiomyomas) and malignant (cancerous) tumors of the uterus (leiomyosarcoma) and the kidney.

hereditary mutation

A gene change in the body's reproductive cells (egg or sperm) that becomes incorporated into the DNA of every cell in the body of offspring; hereditary mutations are passed on from parents to offspring. Also called germline mutation.

hereditary nonpolyposis colon cancer

HNPCC. An inherited disorder in which affected individuals have a higher-than-normal chance of developing colorectal cancer and certain other types of cancer, often before the age of 50. Also called Lynch syndrome.

herpesvirus (HER-peez-VYE-rus)

A member of the herpes family of viruses.

heterogeneous

Made up of elements or ingredients that are not alike.

heterogenic (het-er-o-JEN-ik)

Derived from a different source or species. Also called heterogenous.

heterogenous

Derived from a different source or species. Also called heterogenic.

heterozygous genotype

Occurs when the two alleles at a particular gene locus are different. A heterozygous genotype may include one normal allele and one mutation, or two different mutations. The latter is called a compound heterozygote.

hexyl 5-aminolevulinate

A substance that is used to find and kill tumor cells. It enters tumor cells and becomes activated when exposed to a special type of light. A chemical reaction causes the cells to produce fluorescent light and die.

HHV8

Human herpesvirus 8. A type of herpesvirus that may cause Kaposi's sarcoma (a rare cancer that can cause skin lesions) and a type of lymphoma (cancer that begins in the lymph system), especially in patients who have a weak immune system. Also called Kaposi's sarcoma-associated herpesvirus (KSHV).

high grade

When referring to cancerous and precancerous growths, a term used to describe cells that look abnormal under a microscope. These cells are more likely to grow and spread quickly than cells in low-grade cancerous and precancerous growths.

high-dose chemotherapy

An intensive drug treatment to kill cancer cells, but that also destroys the bone marrow and can cause other severe side effects. High-dose chemotherapy is usually followed by bone marrow or stem cell transplantation to rebuild the bone marrow.

high-dose radiation (hy-dose RAY-dee-AY-shun)

HDR. An amount of radiation that is greater than that given in typical radiation therapy. HDR is precisely directed at the tumor to avoid damaging healthy tissue, and may kill more cancer cells in fewer treatments.

high-dose-rate remote brachytherapy

A type of internal radiation treatment in which the radioactive source is removed between treatments. Also called high-dose-rate remote radiation therapy or remote brachytherapy.

high-dose-rate remote radiation therapy

A type of internal radiation treatment in which the radioactive source is removed between treatments. Also called high-dose-rate remote brachytherapy or remote brachytherapy.

high-energy photon therapy

A type of radiation therapy that uses high-energy photons (units of light energy). High-energy photons penetrate deeply into tissues to reach tumors while giving less radiation to superficial tissues such as the skin.

high-grade lymphoma

A type of lymphoma that grows and spreads quickly, and has severe symptoms. It is seen frequently in patients who are HIV-positive (AIDS-related lymphoma). Also called aggressive or intermediate-grade lymphoma.

high-grade squamous intraepithelial lesion

HSIL. A precancerous condition in which the cells of the uterine cervix are moderately or severely abnormal.

highly active antiretroviral therapy

HAART. Treatment for human immunodeficiency virus (HIV) infection that uses a combination of several antiretroviral drugs. The drugs inhibit the ability of the virus to multiply in the body, and they slow down the development of AIDS.

high-risk cancer

Cancer that is likely to recur (come back), or spread.

hilar

Refers to the area where nerves and blood vessels attach to an organ.

histamine dihydrochloride

A drug being studied for its ability to enhance the effectiveness of IL-2 in treating acute myeloid leukemia.

histiocytic lymphoma

An outdated term referring to non-Hodgkin's lymphomas made up of large abnormal lymphoid cells. Histiocytic lymphomas include mature B-cell and T-cell non-Hodgkin's lymphomas. Many tumors that were once called histiocytic lymphomas are now considered to be a type of large cell lymphoma.

histologic examination

The examination of tissue specimens under a microscope.

histology

The study of tissues and cells under a microscope.

histone

A type of protein found in chromosomes. Histones bind to DNA, help give chromosomes their shape, and help control the activity of genes.

histone deacetylase

HDAC. An enzyme that changes the way histone binds to DNA. HDAC inhibitors are being studied as a treatment for cancer.

historic cohort study

A research study in which the medical records of groups of individuals who are alike in many ways but differ by a certain characteristic (for example, female nurses who smoke and those who do not smoke) are compared for a particular outcome (such as lung cancer). Also called a retrospective cohort study.

historical control subject

An individual treated in the past and used in a comparison group when researchers analyze the results of a clinical study that had no control group. The use of a control, or comparison, group helps researchers determine the effects of a new treatment more accurately.

HIV

Human immunodeficiency virus, the cause of acquired immunodeficiency syndrome (AIDS).

HIV antibody

A substance produced by certain white blood cells in reaction to contact with HIV, the human immunodeficiency virus.

HIV positive

Infected with the human immunodeficiency virus (HIV), the cause of acquired immunodeficiency syndrome (AIDS).

HLA

Human lymphocyte antigen. One of a group of proteins found on the surface of white blood cells and other cells that play an important part in the body's immune response to foreign substances. These antigens vary from person to person, and an HLA test is done before organ transplantation to find out if tissues match between a donor and a recipient. Also called human leukocyte antigen.

HMG-CoA reductase inhibitor (HMG-koh-EN-zime-A ree-DUK-tayz in-HIH-bih-ter)

Hydroxymethylglutaryl-coenzyme A reductase inhibitor. A substance that blocks an enzyme needed by the body to make cholesterol and lowers the amount of cholesterol in the blood. HMG-CoA reductase inhibitor drugs are called statins.

HNPCC

Hereditary nonpolyposis colon cancer. An inherited disorder in which affected individuals have a higher-than-normal chance of developing colorectal cancer and certain other types of cancer, often before the age of 50. Also called Lynch syndrome.

Hodgkin's disease (HOJ-kinz...)

A cancer of the immune system that is marked by the presence of a type of cell called the Reed Sternberg cell. Symptoms include the painless enlarged lymph nodes, spleen, or other immune tissue. Other symptoms include fever, weight loss, fatigue, or night sweats. Also called Hodgkin's lymphoma.

Hodgkin's lymphoma (HOJ-kinz lim-FOH-muh)

A cancer of the immune system that is marked by the presence of a type of cell called the Reed Sternberg cell. Symptoms include the painless enlarged lymph nodes, spleen, or other immune tissue. Other symptoms include fever, weight loss, fatigue, or night sweats. Also called Hodgkin's disease.

holmium Ho 166 DOTMP

A drug containing a radioactive isotope that is used in the diagnosis and treatment of cancer.

holy thistle

Cnicus benedictus. A plant whose leaves, stems, and flowers have been used in some cultures to treat certain medical problems. Holy thistle may have anti-inflammatory and anticancer effects. Also called blessed thistle, St. Benedict's thistle, cardin, and spotted thistle.

homeopathic medicine

An alternative approach to medicine based on the belief that natural substances, prepared in a special way and used most often in very small amounts, restore health. According to these beliefs, in order for a remedy to be effective, it must cause in a healthy person the same symptoms being treated in the patient. Also called homeopathy.

homoharringtonine

An anticancer drug that belongs to the plant alkaloid family of drugs.

homozygous genotype

Occurs when both alleles at a particular gene locus are the same. A person may be homozygous for the normal allele or for a mutation.

hormonal therapy

Treatment that adds, blocks, or removes hormones. For certain conditions (such as diabetes or menopause), hormones are given to adjust low hormone levels. To slow or stop the growth of certain cancers (such as prostate and breast cancer), synthetic hormones or other drugs may be given to block the body's natural hormones. Sometimes surgery is needed to remove the gland that makes a certain hormone. Also called hormone therapy, hormone treatment, or endocrine therapy.

hormone

A chemical made by glands in the body. Hormones circulate in the bloodstream and control the actions of certain cells or organs. Some hormones can also be made in a laboratory.

hormone receptor

A protein on the surface of a cell that binds to a specific hormone. The hormone causes many changes to take place in the cell.

hormone receptor test

A test to measure the amount of certain proteins, called hormone receptors, in cancer tissue. Hormones can attach to these proteins. A high level of hormone receptors may mean that hormones help the cancer grow.

hormone replacement therapy

HRT. Hormones (estrogen, progesterone, or both) given to women after menopause to replace the hormones no longer produced by the ovaries. Also called menopausal hormone therapy.

hormone responsive

In oncology, describes cancer that responds to hormone treatment.

hormone therapy

Treatment that adds, blocks, or removes hormones. For certain conditions (such as diabetes or menopause), hormones are given to adjust low hormone levels. To slow or stop the growth of certain cancers (such as prostate and breast cancer), synthetic hormones or other drugs may be given to block the body's natural hormones. Sometimes surgery is needed to remove the gland that makes a certain hormone. Also called hormonal therapy, hormone treatment, or endocrine therapy.

hormone treatment

Treatment that adds, blocks, or removes hormones. For certain conditions (such as diabetes or menopause), hormones are given to adjust low hormone levels. To slow or stop the growth of certain cancers (such as prostate and breast cancer), synthetic hormones or other drugs may be given to block the body's natural hormones. Sometimes surgery is needed to remove the gland that makes a certain hormone. Also called hormonal therapy, hormone therapy, or endocrine therapy.

Horner's syndrome

A condition in which one side of the face is flushed, does not produce sweat, and has a constricted pupil and drooping eyelid. It can be caused by an injury to, or paralysis of, nerves in the neck, or by a tumor.

hospice (HOS-pis)

A program that provides special care for people who are near the end of life and for their families, either at home, in freestanding facilities, or within hospitals.

host cell

A cell that is infected by a virus or another type of microorganism.

hot flash

A sudden, temporary onset of body warmth, flushing, and sweating (often associated with menopause).

hot nodule

When radioactive material is used to examine the thyroid with a scanner, nodules that collect more radioactive material than the surrounding thyroid tissue are considered "hot." Hot nodules are rarely malignant. Hot nodules are sometimes called hyperfunctioning nodules.

hotspot

In genetics, an area of DNA that is likely to mutate (change).

HPPH

2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a. A drug that is used in photodynamic therapy that is absorbed by tumor cells; when exposed to light, it becomes active and kills the cancer cells.

HPV

Human papillomavirus. A member of a family of viruses that can cause abnormal tissue growth (for example, genital warts) and other changes to cells. Infection with certain types of HPV may increase the risk of developing some types of cancer.

HRT

Hormone replacement therapy. Hormones (estrogen, progesterone, or both) given to women after menopause to replace the hormones no longer produced by the ovaries. Also called menopausal hormone therapy.

HSIL

High-grade squamous intraepithelial lesion. A precancerous condition in which the cells of the uterine cervix are moderately or severely abnormal.

HTLV-1

Human T-cell leukemia virus type 1. A retrovirus that infects T-cells (a type of white blood cell) and can cause leukemia and lymphoma. HTLV-1 is spread by sharing syringes or needles used to inject drugs, through sexual contact, and from mother to child at birth or through breast-feeding.

hu14.18-interleukin-2 fusion protein

An anticancer drug in which hu14.18, a monoclonal antibody, is combined with interleukin-2. The monoclonal antibody binds to the cancer cells and delivers IL-2, which stimulates the immune system to destroy the cancer cells.

Hu3S193

A monoclonal antibody that is being studied in the treatment of some types of cancer. Monoclonal antibodies are made in the laboratory and can locate and bind to cancer cells. Hu3S193 binds to the protein Lewis(y), which is found on colon, breast, lung, ovary, and prostate cancer cells.

Huang Lian

A Chinese herb that has been used as a treatment for a variety of medical problems. It is being studied as an anticancer drug.

HuHMFG1

A monoclonal antibody that binds to the protein MUC1, which is found on breast, ovarian, pancreatic, gastric, and colon cancer cells. Monoclonal antibodies are laboratory-produced substances that can locate and bind to cancer cells. HuHMFG1 is being studied in the treatment of some types of cancer.

human corticotropin-releasing factor

hCRF. A substance that is being studied in the treatment of brain cancer. It is made naturally by the hypothalamus (a part of the brain) and can also be made in the laboratory. hCRF may help reduce symptoms caused by edema (swelling) of the brain. It belongs to the family of drugs called neurohormones.

human epidermal growth factor receptor 2

HER2/neu. The HER2/neu protein is involved in growth of some cancer cells. Also called c-erbB-2.

human herpesvirus 8

HHV8. A type of herpesvirus that may cause Kaposi's sarcoma (a rare cancer that can cause skin lesions) and a type of lymphoma (cancer that begins in the lymph system), especially in patients who have a weak immune system. Also called Kaposi's sarcoma-associated herpesvirus (KSHV).

human immunodeficiency virus

HIV. The cause of acquired immunodeficiency syndrome (AIDS).

human leukocyte antigen

HLA. One of a group of proteins found on the surface of white blood cells and other cells that play an important part in the body's immune response to foreign substances. These antigens vary from person to person, and an HLA test is done before organ transplantation to find out if tissues match between a donor and a recipient. Also called human lymphocyte antigen.

human lymphocyte antigen

HLA. One of a group of proteins found on the surface of white blood cells and other cells that play an important part in the body's immune response to foreign substances. These antigens vary from person to person, and an HLA test is done before organ transplantation to find out if tissues match between a donor and a recipient. Also called human leukocyte antigen.

human papillomavirus (pap-ih-LO-ma-VYE-rus)

HPV. A member of a family of viruses that can cause abnormal tissue growth (for example, genital warts) and other changes to cells. Infection with certain types of HPV may increase the risk of developing some types of cancer.

human T-cell leukemia virus type 1

A type of virus that infects T cells (a type of white blood cell) and can cause leukemia and lymphoma. HTLV-1 is spread by sharing syringes or needles used to inject drugs, through blood transfusions, through sexual contact, and from mother to child at birth or through breast-feeding.

humidifier (hyoo-MID-ih-fye-er)

A machine that puts moisture in the air.

Hürthle cell neoplasm (HER-tel cell)

An uncommon type of thyroid tumor that can be benign or malignant.

Hycamtin (hy-KAM-tin)

A drug used to treat some types of cancer. It belongs to the family of drugs called topoisomerase inhibitors. Also called topotecan.

hydration

Combining with water.

hydrazine sulfate

A substance that has been studied as a treatment for cancer and as a treatment for cachexia (body wasting) associated with advanced cancer.

hydrocephalus (hye-dro-SEF-uh-lus)

The abnormal buildup of cerebrospinal fluid in the ventricles of the brain.

hydrocortisone

A drug used to relieve the symptoms of certain hormone shortages and to suppress an immune response.

hydrogen peroxide

A chemical used in bleaches, dyes, cleansers, antiseptics, and disinfectants. In a concentrated form, it is toxic and irritating to tissues.

hydrolysis

A chemical reaction that uses water to break down a compound.

hydromorphone

A drug used to relieve pain.

hydronephrosis

Abnormal enlargement of a kidney, which may be caused by blockage of the ureter (such as by a kidney stone) or chronic kidney disease that prevents urine from draining into the bladder.

hydroureter

Abnormal enlargement of the ureter caused by any blockage that prevents urine from draining into the bladder.

hydroxychloroquine

A substance that decreases immune responses in the body. It is used to treat some autoimmune diseases, and is being studied as a treatment for graft-versus-host disease. Hydroxychloroquine belongs to the family of drugs called antiprotozoals.

hydroxymethylglutaryl-coenzyme A reductase inhibitor (hy-DROK-see-MEH-thul-GLOO-tuh-ril koh-EN-zime-A ree-DUK-tayz in-HIH-bih-ter)

HMG-CoA reductase inhibitor. A substance that blocks an enzyme needed by the body to make cholesterol and lowers the amount of cholesterol in the blood. HMG-CoA reductase inhibitor drugs are called statins.

hydroxyurea

An anticancer drug that belongs to the family of drugs called antimetabolites.

hygiene (HY-jeen)

The science of health, and the practice of cleanliness that promotes good health and well-being.

hyperalimentation

A form of nutrition that is delivered into a vein. Hyperalimentation does not use the digestive system. It may be given to people who are unable to absorb nutrients through the intestinal tract because of vomiting that won't stop, severe diarrhea, or intestinal disease. It may also be given to those undergoing high-dose chemotherapy or radiation and bone marrow transplantation. It is possible to give all of the protein, calories, vitamins and minerals a person needs using parenteral nutrition. Also known as parenteral or total parenteral nutrition (TPN).

hyperbaric oxygen

Oxygen that is at an atmospheric pressure higher than the pressure at sea level. Breathing hyperbaric oxygen to enhance the effectiveness of radiation therapy is being studied.

hypercalcemia (hye-per-kal-SEE-mee-a)

Abnormally high blood calcium.

hyperfractionation

A way of giving radiation therapy in smaller-than-usual doses two or three times a day instead of once a day.

hyperglycemia

Abnormally high blood sugar.

hypericum perforatum

St. John's wort. An herbal product sold as an over-the-counter treatment for depression. It is being studied for its ability to lessen certain side effects of cancer treatment.

hyperkeratosis

A condition marked by thickening of the outer layer of the skin, which is made of keratin (a tough, protective protein). It can result from normal use (corns, calluses), chronic inflammation (eczema), or genetic disorders (X-linked ichthyosis, ichthyosis vulgaris).

hypernephroma (HYE-per-neh-FRO-ma)

The most common type of kidney cancer. It begins in the lining of the renal tubules in the kidney. The renal tubules filter the blood and produce urine. Also called renal cell cancer.

hyperplasia (hye-per-PLAY-zha)

An abnormal increase in the number of cells in an organ or tissue.

hypersensitivity

An exaggerated response by the immune system to a drug or other substance.

hypertension

Abnormally high blood pressure.

hyperthermia therapy (hy-per-THER-mee-a)

A type of treatment in which body tissue is exposed to high temperatures to damage and kill cancer cells or to make cancer cells more sensitive to the effects of radiation and certain anticancer drugs.

hyperthermic perfusion

A procedure in which a warmed solution containing anticancer drugs is used to bathe, or is passed through the blood vessels of, the tissue or organ containing the tumor.

hyperthyroidism

Too much thyroid hormone. Symptoms include weight loss, chest pain, cramps, diarrhea, and nervousness. Also called overactive thyroid.

hyperuricemia

A buildup of uric acid (a byproduct of metabolism) in the blood; a side effect of some anticancer drugs.

hypervascular

Having a large number of blood vessels.

hypnosis

A trance-like state in which a person becomes more aware and focused and is more open to suggestion.

hypoglycemia

Abnormally low blood sugar.

hypopharynx

The bottom part of the throat. Cancer of the hypopharynx is also called hypopharyngeal cancer.

hypotension

Abnormally low blood pressure.

hypothalamus (hye-po-THAL-uh-mus)

The area of the brain that controls body temperature, hunger, and thirst.

hypothesis

A tentative proposal made to explain certain observations or facts that requires further investigation to be verified.

hypothyroidism

Too little thyroid hormone. Symptoms include weight gain, constipation, dry skin, and sensitivity to the cold. Also called underactive thyroid.

hypoxia

A condition in which there is a decrease in the oxygen supply to a tissue. In cancer treatment, the level of hypoxia in a tumor may help predict the response of the tumor to the treatment.

hypoxic

Having too little oxygen.

hysterectomy (hiss-ter-EK-toe-mee)

Surgery to remove the uterus and, sometimes, the cervix. When the uterus and part or all of the cervix are removed, it is called a total hysterectomy. When only the uterus is removed, it is called a partial hysterectomy.