Medical terms A–Z

Methemoglobin is a chemically altered form of hemoglobin that cannot bind oxygen, and it is normally present in blood only in small amounts.

Methemoglobinemia occurs when methemoglobin, a form of hemoglobin unable to carry oxygen, builds up in the blood beyond its normal small proportion.

The section readers skip is the one that decides whether the result at the end of the paper means anything at all.

A substance being studied in the treatment of cancer.

A substance being studied in the treatment of anemia in patients who are receiving chemotherapy.

A methyl group is a one-carbon chemical unit that, added to or removed from DNA or proteins, can switch nearby gene activity on or off.

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

Adding a single small carbon tag to a molecule, a change tiny in size but large in what it switches off.

A drug used to relieve certain side effects caused by treatment with opiods (pain killers similar to morphine), such as constipation (hard, dry stools), itching, and low urine flow.

Benefit and hazard flow from one action, the blocking of dopamine, in the gut in one case and the brain in the other.

The drug arrives inactive and becomes a poison only inside organisms that live without oxygen, which is the source of its narrow aim.

Continuous or frequent treatment with low doses of anticancer drugs, often given with other methods of therapy.

A machine that uses electricity to form a stream of fast-moving subatomic particles.

A plant whose roots are used as a sedative and to treat certain medical conditions.

A substance being studied in the treatment of cancer.

A substance being studied in the treatment of several types of cancer.

MGUS is a generally symptomless blood finding that carries a modest, ongoing risk of eventually progressing to multiple myeloma or a related condition.

A ball of soap-like molecules hiding a greasy core inside a water-friendly shell, which is how soap lifts fat and how the gut absorbs it.

Any substance or process that kills germs (bacteria, viruses, and other microorganisms that can cause infection and disease).

A tiny deposit of calcium in the breast that cannot be felt but can be detected on a mammogram.

Bacteria and other organisms that live inside the intestines.

An instrument that uses very small amounts of fluid on a microchip to do certain laboratory tests.

A microgram is a metric unit of mass equal to one millionth of a gram, commonly used to measure very small medication doses.

Small numbers of cancer cells that have spread from the primary tumor to other parts of the body and are too few to be picked up in a screening or diagnostic test.

A concentration of 1/1,000,000 (one millionth) molecular weight per liter (mol/L).

Unlike macronutrients such as protein and fat, micronutrients are needed only in small amounts yet remain essential for normal body function.

An organism that can be seen only through a microscope.

MicroRNA is the full name behind the abbreviation miRNA, a short RNA molecule that silences messenger RNAs rather than coding for a protein itself.

A short sequence of DNA, usually 1 to 4 basepairs (a unit of DNA), that is repeated together in a row along the DNA molecule.

A change that occurs in the DNA of certain cells (such as tumor cells) in which the number of repeats of microsatellites (short, repeated sequences of DNA) is different than the number of repeats…

Diagnosis of many conditions rests on magnification, because healthy tissue and diseased tissue often part company only at cellular scale.

Its opposite is gross, meaning visible without help, and the pair marks the boundary between what an eye and a lens can each detect.

A very tiny, hollow, round particle made from glass, ceramic, plastic, or other materials.

A technique used to help determine the stage (extent) of melanoma and certain squamous cell cancers.

A type of acupuncture in which a microwave device is attached to an acupuncture needle to give microwave radiation at an acupuncture point.

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…

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…

Speed in and speed out is the point: it suits a procedure that lasts minutes, not a symptom that lasts months.

The clinician whose training centers on birth as a normal event, with the judgment to recognize when it has stopped being one.

A whole-brain event that happens to hurt: the pain is one stage of an attack starting hours before it and outlasting it.

A thin tube in the breast that carries milk from the breast lobules to the nipple.

One thousandth of a gram, the unit most drug doses are written in and the one most often confused with a microgram.

A measure of volume in the metric system.

Medical findings from skin lesions to blood vessel measurements are commonly sized in millimeters, a metric unit equal to one thousandth of a meter.

The amount of a substance equal to a thousandth of a mole (a measure of the amount of a substance).

A form of exercise that combines body movement with mental focus and controlled breathing to improve strength, balance, flexibility, and overall health.

Unlike vitamins, these are chemical elements: they cannot be built or destroyed by cooking, only taken in and lost again.

A clear, tasteless liquid distilled from crude oil, used to soften skin and to slide stool through the bowel.

A test that measures the strength of the muscles used in breathing.

A type of breast imaging test that is used to detect cancer cells in the breasts of some women who have had abnormal mammograms, or who have dense breast tissue.

miRNA molecules are short strands of RNA that bind messenger RNA to block protein production, providing cells a way to fine-tune gene activity.

One drug with two unrelated jobs: it shields the stomach lining from anti-inflammatory damage and it makes the uterus contract.

A plant that lives partly off the tree it grows on, and the source of a widely debated injected therapy.

A substance that comes from the mistletoe plant and that is being studied as a treatment for cancer.

A drug used to treat some types of testicular cancer.

A deliberately modest word: it promises less of a problem, never none of it, which is why precision about the amount matters.

Muscle and nerve fail first when these break down, because those tissues burn the most energy and store the least.

A substance being studied in the treatment of some leukemias and lymphomas.

Mitomycin is an antitumor antibiotic that damages DNA to treat certain cancers and is also applied topically during some eye surgeries.

Cells rely on mitosis for both growth and the routine replacement of worn out tissue, producing two daughter cells with matching genetic material.

Having to do with the presence of dividing (proliferating) cells.

The process a cell goes through each time it divides.

In a population of cells, the ratio of the number of cells undergoing mitosis (cell division) to the number of cells not undergoing mitosis.

Chemotherapy drugs that jam the machinery pulling chromosomes apart, so a dividing cell stalls partway through and dies.

A drug used to treat advanced prostate cancer that does not respond to hormones, adult acute nonlymphocytic leukemia, and advanced or chronic multiple sclerosis.

A brain tumor that forms from more than one type of brain cell, usually astrocytes and oligodendrocytes.

A substance being studied in the treatment of many types of cancer.

Concentration is what turns a volume into a dose, which is why milliliters and milligrams can never be swapped for each other.

A substance being studied as a treatment for atherosclerosis (a build-up of fat in the arteries).

A substance being studied in the treatment of some types of cancer.

A substance that is being studied in the treatment of prostate cancer.

Easy to confuse with mm for millimeter and with mmol for a plain amount, the capital M is the part that signals a concentration.

A substance being studied in the treatment of cancer.

A substance being studied in the treatment of myelodysplastic syndromes and some types of leukemia.

A placeholder word: it signals that one method among several is meant, and the surrounding sentence has to supply which.

Removal of the whole breast together with the armpit lymph nodes, sparing the chest muscles the older operation sacrificed.

Surgery to remove most, but not all, of the vulva (the external female genital organs, including the clitoris, vaginal lips, and the opening to the vagina).

Modulate means to adjust the strength or activity of a biological process or treatment up or down, rather than switching it fully on or off.

A surgical procedure used to treat skin cancer.

A surgical procedure used to treat skin cancer.

A molar pregnancy occurs when abnormal fertilization causes placental tissue to overgrow into fluid filled cysts instead of a viable embryo.

Whether mold matters to health depends far more on the species and on the person exposed than on the presence of mold itself.

A benign (not cancer) growth on the skin that is formed by a cluster of melanocytes (cells that make a substance called melanin, which gives color to skin and eyes).

The process of identifying a disease by studying molecules, such as proteins, DNA, and RNA, in a tissue or fluid.

A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease.

The sum of the atomic masses of all atoms in a molecule, based on a scale in which the atomic masses of hydrogen, carbon, nitrogen, and oxygen are 1, 12, 14, and 16, respectively.

A branch of medicine that develops ways to diagnose and treat disease by understanding the way genes, proteins, and other cellular molecules work.

A series of actions among molecules in a cell that leads to a certain end point or cell function.

In cancer treatment, substances that kill cancer cells by targeting key molecules involved in cancer cell growth.

Molecules form when atoms bond together, and biological versions such as proteins and DNA can involve thousands of atoms arranged in specific structures.

Three delivery routes, one purpose: putting a steroid exactly where the inflammation is so the rest of the body sees very little of it.

Monitor refers both to the ongoing observation of a person's condition over time and to a device that records or displays patient data.

A monoclonal antibody is a laboratory-made protein engineered to bind one specific target, with uses spanning cancer, autoimmune disease, and infection.

A laboratory finding rather than an illness: identical B cells circulating in numbers too low to count as leukemia.

Time in the bloodstream is a transit stage rather than the job; the real work begins once the cell settles in tissue.

The single unit a chain is built from, whether that chain is a plastic, a starch, a protein or a strand of DNA.

A mixture of oil and water that is combined with a specific antigen to boost the immune response to that antigen.

Taken regularly to prevent symptoms rather than to relieve an attack, montelukast also carries a prominent warning about mood and behavior changes.

An abbreviation for a chemotherapy combination used alone or with radiation therapy to treat Hodgkin lymphoma.

A monoclonal antibody being studied in the treatment of some types of cancer.