Find definitions for thousands of medical terms, treatments, and tests -- even health-related abbreviations, prefixes, and suffixes.
HDL (high-density lipoprotein) is sometimes called "good"
cholesterol, because it helps move cholesterol out of the body. HDL does this by binding with cholesterol in the bloodstream and
carrying it back to the liver for disposal.
A high HDL level is linked to a lower risk of heart disease.
June 29, 2012
Kathleen Romito, MD - Family Medicine & Robert A. Kloner, MD, PhD - Cardiology & Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology
A health care agent is a person chosen to make medical decisions
for another, should a severe illness or injury occur that makes communication
impossible. The document that grants this decision-making power to the person
selected is called a medical power of attorney.
A health care agent may also be called a health care proxy or
surrogate or an attorney-in-fact.
Although laws vary by state, a health care agent can usually make
medical treatment decisions at the end of life or anytime a person is not able
to communicate. As soon as a person selects a health care agent, it is
important to thoroughly discuss and document medical care preferences, such as
when to continue or abandon life-support measures.
December 29, 2011
Anne C. Poinier, MD - Internal Medicine & Shelly R. Garone, MD, FACP - Palliative Medicine
A heart attack happens when blood flow to the heart is blocked. Without blood and the oxygen it carries, part of the heart starts to die. The medical name for a heart attack is myocardial infarction, or MI.
A heart attack is often the result of coronary artery disease, in which fatty deposits called plaque (say "plak") build up inside the heart arteries. When plaque breaks open or ruptures, it can form a clot that blocks blood flow to the heart muscle.
Quick treatment that restores blood flow to the heart can help save lives.
October 9, 2012
E. Gregory Thompson, MD - Internal Medicine & John M. Miller, MD, FACC - Cardiology, Electrophysiology
Heart failure means that your heart muscle doesn't pump as much blood as your body needs. In time, this causes fluid to build up in your body, and you have symptoms like swelling in the legs and feeling out of breath and weak.
Heart failure usually gets worse over time. But treatment can slow the disease and help you feel better and live longer.
Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology
A heart murmur is a sound made by blood moving through the chambers
and valves of the heart or through the blood vessels near the heart. The sounds
can be heard through a stethoscope.
Heart murmurs are common in infants and children and are harmless
in most cases. The murmurs usually are not a problem, require no treatment, and
go away on their own. Pregnancy, fever, and some types of anemia can also lead
to temporary heart murmurs. But some adults have harmless heart murmurs that do
not go away.
A heart murmur may sometimes mean there is a more serious problem
with the heart walls or heart valves, such as narrowing or leaking of a heart
valve (stenosis or regurgitation) or an infection of a heart valve
(endocarditis). These problems can cause blood to flow abnormally through the
heart valves or chambers, causing a murmur or other sound that the doctor can
hear with the stethoscope. These conditions require close monitoring and may
July 6, 2012
Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & George Philippides, MD - Cardiology & E. Gregory Thompson, MD - Internal Medicine
Heart valve disease occurs when a heart valve is damaged or
narrowed and does not control or allow the normal flow of blood through and out
of the heart. Causes of heart valve disease include congenital heart disease, an abnormal
valve, or a rupture of a valve.
Heart valves operate like one-way gates, helping blood flow in one
direction between heart chambers as well as into and out of the heart. A normal
heart valve has flaps, called leaflets. When the heart pumps, the leaflets open
one way to allow blood to flow through. Between heartbeats, the leaflets should
close to form a tight seal so that blood does not leak backwards through the
If the heart valve is damaged, the leaflets may not form a tight
seal, and blood may leak backwards through the valve. This leakage is called
Heart valves can also become narrowed,
which may block the flow of blood through the heart. This narrowing is called
Over time, a damaged valve may lead to enlargement of the heart
chambers, heart failure, and atrial fibrillation. It can reduce blood flow to
the muscles of the body, including the heart muscle itself, which can result in
symptoms or damage.
Treatment for heart valve disease depends on the cause and
severity. Close monitoring is sometimes all that is needed for those who have
mild or no symptoms, but a doctor may recommend surgery to repair or replace
the valve in more serious cases.
January 23, 2013
E. Gregory Thompson, MD - Internal Medicine & Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology
Heavy use of alcohol is defined as more than 2 drinks a day for
men and more than 1 drink a day for women. One drink is
12 fl oz (355 mL) of beer,
5 fl oz (148 mL) of wine, or
1.5 fl oz (44 mL) of hard
Heavy use of alcohol increases the risk for many health
January 18, 2012
E. Gregory Thompson, MD - Internal Medicine & Peter Monti, PhD - Alcohol and Addiction
Hemochromatosis is a condition that occurs when too much iron
builds up in the body. Small amounts of iron are normally stored in the liver
and heart, but excess iron will eventually damage these organs.
There are two types of hemochromatosis:
Hereditary hemochromatosis is one of the most common
genetic disorders in white people, especially those of Northern European
descent. Excess iron
builds up slowly throughout life. Most people with hemochromatosis notice
symptoms when they are age 40 to 60. These symptoms include fatigue, joint
pain, weakness, excess urination, and weight loss.
hemochromatosis is recognized early, it can be treated before other problems
start. It is treated by removing excess iron from the blood, either by removing
blood from the body (phlebotomy) or by taking a medicine (chelating agent) that
binds to and removes iron from the body. Hereditary hemochromatosis requires
treatment throughout a person's life. Acquired hemochromatosis does not need
further treatment after the condition has been corrected.
October 15, 2012
Kathleen Romito, MD - Family Medicine & Brian Leber, MDCM, FRCPC - Hematology
Dialysis is a mechanical process that partly does the work
that healthy kidneys would do. Hemodialysis uses a man-made membrane (dialyzer)
to filter wastes, remove extra fluid from the blood, restore the proper balance
of chemicals in the blood, and eliminate extra fluid (edema) from the
Before hemodialysis treatments can begin, a doctor will need
to create an access where blood can flow in and out of the body (dialysis
access). This is
usually done by joining an artery and a vein in the forearm or by using a small
tube to connect an artery and a vein.
Hemodialysis is usually done in a hospital or
dialysis center on a set schedule. It is usually done 3 days a week and takes 3
to 5 hours a day. In some cases, hemodialysis can be done at home. Home
hemodialysis can be done on more days of the week. Some types of home
hemodialysis are done during the night.
September 15, 2011
Anne C. Poinier, MD - Internal Medicine & Mitchell H. Rosner, MD - Nephrology
Hemoglobin is the protein in red blood cells that carries oxygen
from the lungs to the rest of the body. It also helps carry carbon dioxide back
to the lungs, where it can be breathed out of the body.
Abnormally low levels of hemoglobin result in anemia.
August 6, 2012
E. Gregory Thompson, MD - Internal Medicine & Joseph O'Donnell, MD - Hematology, Oncology
Hemophilia is a rare genetic bleeding disorder in which a person
inherits problems with certain blood clotting factors, making them unable to
work properly. Blood-clotting factors are needed to help stop bleeding after a
cut or injury and to prevent spontaneous bleeding.
The hemophilia gene can contain many different errors, leading to
different degrees of abnormality in the amount of clotting factor produced.
People who have hemophilia are at risk of abnormal bleeding throughout the
body, especially in the joints and muscles, which may lead to disabling joint
Hemophilia occurs almost exclusively in men. The disease can be
passed from a mother who is a carrier of the genetic
defect (but who does not have the disease) to her son. Rarely, a girl can have
hemophilia. This occurs only if she inherits a defective gene from both her
mother and her father.
Symptoms of hemophilia are usually first noticed during infancy or
childhood. However, some people who have milder forms of hemophilia may not
develop symptoms until later in life.
The following are signs of hemophilia that may be noticed shortly
Other symptoms of hemophilia include easy bruising, frequent
nosebleeds, blood in the urine, and bleeding after dental work.
Some people who have hemophilia may need to inject (infuse)
themselves with clotting factors to prevent uncontrolled bleeding. They may
need to do this either regularly or only before activities or situations (such
as surgery) when injury or bleeding may occur.
August 3, 2011
E. Gregory Thompson, MD - Internal Medicine & Brian Leber, MDCM, FRCPC - Hematology
Hepatitis is a disease that causes inflammation of the liver and
interferes with its normal function. Hepatitis can be caused by infection
(usually by a virus), excessive alcohol use, medicine, or a problem with the
The three most common types of viral hepatitis are hepatitis A,
hepatitis B, and hepatitis C. Viral hepatitis is contagious. All three types of
viral hepatitis (A, B, and C) can be spread through contact with body fluids. Hepatitis A can also spread when people consume food or water contaminated by
stool (feces) containing the virus.
Symptoms of hepatitis can last for weeks to months. They
Some types of hepatitis can cause serious, long-term complications,
such as severe and permanent liver damage.
October 29, 2012
Kathleen Romito, MD - Family Medicine & W. Thomas London, MD - Hepatology
Hepatitis B is a virus that infects the liver. Most adults who get it have it for a short time and then get better. But sometimes the virus causes a long-term infection, called chronic hepatitis B. Over time, this can lead to liver damage or liver cancer.
The virus spreads through the blood of an infected person or through sexual contact with an infected person.
A hernia is tissue from inside the abdomen that bulges out through
a weak spot in the muscles of the abdominal (belly) wall. The weak spot may have been
present since birth or may develop after surgery or from violent or ongoing
coughing, lifting heavy objects, or aging.
There are several types of hernias:
A person with a hernia often feels pain, pressure, or burning or
feels like something has given way.
November 15, 2012
E. Gregory Thompson, MD - Internal Medicine & Kenneth Bark, MD - Surgery, Colon and Rectal
The bones that form your spine are cushioned by small discs that act as shock absorbers and keep the spine flexible. When a disc is damaged, it may bulge or break open. This is called a herniated disc, slipped disc, or ruptured disc. It may push on the nerves and cause pain, numbness, or weakness in the area where that nerve travels. Most herniated discs happen in the lower back.
October 9, 2012
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Robert B. Keller, MD - Orthopedics
A hiatal hernia occurs when a small portion of the stomach pushes
upward through the diaphragm, a sheetlike muscle that separates the lungs from
the abdomen. Usually this doesn't cause any symptoms, but it increases the risk
of stomach acid backing up into the esophagus (reflux), which can lead to
Normally the entire stomach sits below the diaphragm. The esophagus
passes through an opening in the diaphragm called the hiatus before it enters
the stomach. Weakened tissues within and around the hiatus allow a hiatal
hernia to develop.
A hiatal hernia that is not causing symptoms does not usually need
any treatment. Treatment for a hiatal hernia that causes heartburn is the same
as for gastroesophageal reflux disease (GERD). This may include home treatment
with nonprescription antacids, acid reducers, or acid blockers; prescription
medicines; or, in severe cases, surgery.
March 6, 2012
Adam Husney, MD - Family Medicine & Peter J. Kahrilas, MD - Gastroenterology
Blood pressure is a measure of how hard the blood pushes against the walls of your arteries as it moves through your body. Blood pressure readings consist of an upper number and a lower number (such as 120 over 90 or 120/90). High blood pressure is 140/90 or higher.
When blood pressure is high, it starts to damage the blood vessels, heart, and kidneys. This can lead to heart attack, stroke, and other problems.
High blood pressure is also called hypertension. It can be managed with lifestyle changes and medicines.
September 26, 2012
Adam Husney, MD - Family Medicine
Cholesterol is a type of fat (lipid) in your blood. Your body needs some cholesterol. But if you have too much, it can build up in your arteries and increase your risk of heart disease and stroke.
You can get high cholesterol by eating foods that have too much cholesterol and saturated fat or by having an inherited condition that causes high cholesterol.
HIV (human immunodeficiency virus) is a virus that attacks the immune system, the body's natural defense system. Without a strong immune system, the body has trouble fighting off disease.
HIV is treated with medicines that slow or stop the damage to the immune system. If it's not treated, in time HIV will cause AIDS (acquired immunodeficiency syndrome).
E. Gregory Thompson, MD - Internal Medicine & Peter Shalit, MD, PhD - Internal Medicine
Hives (urticaria) are an allergic reaction of the skin that may
last a few minutes or can persist for a few days. They appear as raised, red,
itchy bumps (wheals) of different shapes and sizes, with defined red margins
and pale centers.
Hives may appear and then disappear at random and seem to move from
place to place on the skin. Hives may range in size from less than
0.25 in. (0.6 cm) to
3 in. (7.6 cm) across or
larger. Patches of hives may combine to form raised, reddened skin over large
areas of the body.
Hives may appear as a reaction to a medication, food, or infection.
A single area of swelling often occurs after an insect bite at the site of the
bite. Other possible causes include contact with plants, things you breathe in
(inhalants), stress, makeup, and exposure to heat, cold, or sunlight. Often a
cause cannot be found.
Hives are often minor, but they can also be the first sign of a
life-threatening allergic reaction (anaphylaxis) that requires emergency
April 29, 2011
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine
Homocysteine is an amino acid normally found in small amounts
in the blood. Abnormal levels may mean that you are not getting enough vitamins like folic acid, vitamin B6, and vitamin B12.
Homocysteine tests might be used to check for other conditions or diseases.
January 15, 2013
E. Gregory Thompson, MD - Internal Medicine & George Philippides, MD - Cardiology
A hormone, such as insulin or estrogen, is a substance released by
an organ or tissue that controls the activity of organs or cells in another
part of the body. The organs or glands that release hormones are part of the
Hormones may also be taken as medicines, such as birth control
pills or estrogen therapy.
May 17, 2012
E. Gregory Thompson, MD - Internal Medicine & Alan C. Dalkin, MD - Endocrinology
Hormone therapy (HT) is a general term for the use of man-made
(synthetic) estrogen, with or without progestin, to treat symptoms caused by
the changing hormone levels that occur before and after menopause. Hormone
therapy carries some health risks, and its use should be discussed carefully
with a health professional.
Hormone therapy includes:
When taken after menopause, hormone therapy is also called hormone
replacement therapy. But more experts are using the term "hormone therapy"
(HT) to avoid the misleading message that women should have premenopausal
levels ("replacement") of hormones after menopause.
April 26, 2012
Anne C. Poinier, MD - Internal Medicine & Carla J. Herman, MD, MPH - Geriatric Medicine
Hormone therapy is used to change the way hormones stimulate cancer
growth. These medicines either block the effects hormones have on the cancer
cells or block the production of the hormones.
If tests show that the breast cancer cells have estrogen and
progesterone receptors (ER/PR-positive), hormone therapy may be used. Tamoxifen
and aromatase inhibitors are the most commonly used hormonal therapies. Other
hormonal therapies include progestins, such as megestrol (Megace), and
antiestrogen, such as fulvestrant.
June 28, 2011
Sarah Marshall, MD - Family Medicine & Douglas A. Stewart, MD - Medical Oncology
Hospice care provides medical services, emotional support, and
spiritual resources for people who are in the late stages of an incurable
illness, such as cancer or Alzheimer's disease. Hospice care also helps family
members manage the practical details and emotional challenges of caring for a
dying loved one.
Hospice services are provided by a team of
caregivers that may include health professionals, volunteers, and spiritual
advisors. Services typically include:
December 29, 2011
A hot flash is a sudden sensation of intense body heat, often
with profuse sweating and reddening of the head, neck, and chest. These
symptoms can be accompanied by mild to severe heart palpitations, anxiety,
irritability and, in rare cases, panic.
Hot flashes are the most
common symptom of a woman's changing estrogen levels around the time of
menopause. They strike unexpectedly, often at night, and usually last several
seconds to minutes. Hot flashes:
Hot flashes are less commonly caused by thyroid problems,
cancers, and psychological stress. Men commonly have hot flashes when taking
hormone therapy for prostate cancer.
Several medicines are
available to treat hot flashes.
April 26, 2012
Huntington's disease is a rare inherited (genetic) disorder that
causes parts of the brain to break down and lose some normal functions
(degeneration). It is also called Huntington's chorea.
Symptoms of the disease usually develop after age 40 and include
rapid, jerky movements (twitches in the face and jerks of the arms) that cannot
be controlled (chorea) and the gradual loss of mental abilities (dementia),
leading to personality changes, behavior problems, and memory loss.
There is no known cure for the disease. Treatment with medications
may help control the involuntary movements.
November 3, 2011
Sarah Marshall, MD - Family Medicine & Siobhan M. Dolan, MD, MPH - Reproductive Genetics
Hyperbaric oxygen therapy is a treatment to increase a person's
blood oxygen level, which can prevent tissue death, promote healing, and help
fight infection. This treatment involves a person being in an enclosed chamber
while 100% oxygen is pumped in at high pressure.
Hyperbaric oxygen therapy may be used to treat conditions such as
severe carbon monoxide poisoning, some types of infections, decompression
sickness, burns, extreme blood loss, and injuries that cut off oxygen supply to
the muscles and other soft tissues.
Large medical centers can often provide hyperbaric oxygen therapy,
but it may not be available in smaller hospitals.
March 1, 2012
Anne C. Poinier, MD - Internal Medicine & R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology
A hyperosmolar state develops
when a person with type 2 diabetes has very high blood sugar—usually 600
milligrams per deciliter (mg/dL) or more. Sometimes this condition is the first time a person learns that he or she has type 2 diabetes.
A hyperosmolar state can develop when a person is very sick and/or dehydrated, such as from the flu, a severe infection, a heart
attack, or water pills (diuretics). If the
person does not drink enough liquids, he or she may become confused. Older people are at increased risk for
developing a hyperosmolar state.
Symptoms of a hyperosmolar state include:
Hyperosmolar state is treated in a hospital with insulin to reduce
the blood sugar level and extra fluids through a vein (IV) to replace the lost
The best way to prevent a hyperosmolar state is to treat high blood sugar levels early and drink enough liquids.
June 29, 2011
E. Gregory Thompson, MD - Internal Medicine & Jennifer Hone, MD - Endocrinology, Diabetes and Metabolism
Hyperthyroidism means that your body has too much thyroid hormone, which controls how your body uses energy. Too much thyroid hormone can make you lose weight quickly, have a fast heartbeat, sweat a lot, or feel nervous and moody. If it isn't treated, it can cause serious problems.
E. Gregory Thompson, MD - Internal Medicine & David C.W. Lau, MD, PhD, FRCPC - Endocrinology
Hypertrophic cardiomyopathy is a genetic disease in which the heart
muscle grows abnormally, making the heart muscle thicken. The thickened heart
muscle can interfere with the heart's electrical system, which increases the
risk for life-threatening abnormal heartbeats (arrhythmias) and, rarely, sudden
Symptoms, such as shortness of breath and chest pain, may occur at
any time of life. But some people never have symptoms, even though the
condition may have been present for some time. In some cases, the thickened
heart muscle is unable to relax between heartbeats, and the heart muscle itself
does not get enough blood or oxygen, which causes chest pain. In rare cases,
the thickened heart muscle becomes unable to pump enough blood to meet the
body's needs, resulting in heart failure.
July 23, 2012
Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & Robert A. Kloner, MD, PhD - Cardiology & George Philippides, MD - Cardiology
Hyperventilation is breathing that is deeper and more rapid than
normal, which causes the amount of carbon dioxide (CO2) in the blood to drop
too low. This may result in lightheadedness, a rapid heartbeat, shortness of
breath, numbness or tingling in the hands or feet, anxiety, fainting, and sore
Some causes of hyperventilation include extreme anxiety, asthma,
emphysema, head injury, fever, exposure to altitude above
6000 ft (2000 m), and some
In many cases, hyperventilation can be controlled with home
treatment, such as focusing on proper breathing techniques.
August 29, 2012
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & David Messenger, MD
Hypoglycemia is a low level of blood sugar. A person may
tremble, feel nervous or jittery, break out in a cold sweat, have a headache,
or feel sick to his or her stomach.
Blood sugar levels are measured in mg/dL. A fasting blood sugar
level of 70 to 99 mg/dL is normal, 50 to 70 mg/dL is mildly low, and less than
50 mg/dL is very low.
If blood sugar, also called glucose,
continues to fall, a person may experience mood changes, such as irritability,
anxiety, restlessness, anger, or confusion. And he or she may have symptoms
such as weakness, blurred vision, dizziness, fatigue, and poor coordination.
Hypoglycemia may also result from taking certain medicines or drinking alcohol. It can also be caused by certain health problems, such as not processing
carbohydrates properly or having an enzyme deficiency. Sometimes the cause is
Treatment for a sudden (acute) episode of hypoglycemia
involves eating or drinking some form of sugar to restore blood sugar to a
normal level. Episodes of hypoglycemia caused by a long-term (chronic) health
condition are treated the same way. But to prevent future episodes of
hypoglycemia, treatment or cure of the long-term condition is needed.
March 16, 2011
Hypoglycemia (or hypoglycemic) unawareness is the inability to
recognize early symptoms of low blood sugar until they become severe. Once
symptoms reach this stage, urgent treatment is needed to prevent further
progression and life-threatening health problems, such as a seizure or
Severe symptoms of low blood sugar include confusion, slurred
speech, unsteadiness when standing or walking, muscle twitching, and
personality changes. People with diabetes who tightly control their blood sugar
levels are more likely to have episodes of low blood sugar. Frequent and severe
low blood sugar episodes are likely to evolve into hypoglycemia unawareness.
Once a person has had one hypoglycemia unawareness episode, more are likely to
September 20, 2012
Hypoplastic left heart syndrome is a heart defect that is present
at birth (congenital) in which the left side of the heart and aorta are very
small or underdeveloped. The small left ventricle makes the right ventricle responsible for pumping blood to the
lungs and body.
Over time, too little blood may be pumped to the body, leading to
heart failure. Without a series of major heart operations, this defect almost always
October 11, 2011
John Pope, MD - Pediatrics & Larry A. Latson, MD - Pediatric Cardiology
Hypothyroidism happens when your thyroid gland doesn't make enough thyroid hormone. Thyroid hormone controls the way your body uses energy. A low thyroid level can make you feel tired and weak.
Medicine can correct your thyroid level. Most people need to keep taking the thyroid medicine throughout their lives.
September 27, 2012
Kathleen Romito, MD - Family Medicine & Matthew I. Kim, MD - Endocrinology