Glossary

Find definitions for thousands of medical terms, treatments, and tests -- even health-related abbreviations, prefixes, and suffixes.

Filter by First Letter
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

T

The temporomandibular (TM) joints join the skull and lower jawbone (mandible). These gliding "ball and socket" joints are separated by a disc made of cartilage, which keeps the two bones from rubbing together.

These joints are located just in front of each ear. They move when a person opens and closes the mouth.

The TM joints are stabilized by muscles that attach directly to the jawbone. If these muscles are strained or tense, jaw pain may result.

Sometimes TM joint problems result when the cartilage disc tears or moves out of its normal position (disc displacement).

Last Revised: January 11, 2012

Author: Healthwise Staff

Medical Review: Adam Husney, MD - Family Medicine & Arden Christen, DDS, MSD, MA, FACD - Dentistry

Temporomandibular disorder is a jaw problem that causes pain when you talk, chew, swallow, or yawn. The most common cause is tension in your jaw muscles, such as from clenching your jaw or grinding your teeth.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: Adam Husney, MD - Family Medicine & Arden Christen, DDS, MSD, MA, FACD - Dentistry

Tendons are tough, flexible, ropy fibers that connect muscle to bone. Tendons vary in size and shape. And they glide smoothly over muscles as the body moves.

Last Revised: October 16, 2012

Author: Healthwise Staff

Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Kenneth J. Koval, MD - Orthopedic Surgery, Orthopedic Trauma

Testosterone is one of the hormones needed for sexual development and is present in both males and females. Testosterone is considered an androgen, which is a male sex hormone, because it is made in much higher amounts in men than in women.

Testosterone helps strengthen bones and muscles in both men and women. In young men, testosterone signals the body to lower the voice, grow facial hair, and develop sexual characteristics. This hormone is also needed for sperm production.

Last Revised: May 17, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Alan C. Dalkin, MD - Endocrinology

The Therapeutic Lifestyle Changes (TLC) diet is a way to eat that lowers cholesterol. It is low in saturated fat and cholesterol, which can reduce blood cholesterol levels and lower the risk of heart problems.

The TLC diet calls for:

  • Less than 7% of daily calories from saturated fat.
  • No more than 200 mg of dietary cholesterol a day.
  • 25% to 35% of daily calories from fat, mainly from unsaturated fat. Most of the fat should be monounsaturated, and only 10% should be polyunsaturated fat.

The TLC diet is part of the Therapeutic Lifestyle Changes program, which aims to lower cholesterol through diet, exercise, weight loss if needed, and other changes, such as quitting smoking. It is recommended by the National Cholesterol Education Program of the U.S. National Institutes of Health.

Last Revised: June 18, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Rhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator

Thrombin is a substance (enzyme) in the bloodstream that is needed for blood to clot. When a person is cut or wounded, thrombin and a protein called fibrinogen make a stringy material that traps blood cells and then gradually decomposes as the area heals.

Only thrombin located at the area of the injury is activated, and only for a few seconds. This process helps prevent a potentially dangerous blood clot, called a thrombus, from forming and traveling through the bloodstream.

Last Revised: December 28, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Jeffrey S. Ginsberg, MD - Hematology

Thrombophlebitis is inflammation in a vein in an area where a blood clot has formed. Often the term thrombophlebitis is shortened to "phlebitis."

There are two types of phlebitis.

  • Superficial phlebitis occurs when a blood clot and inflammation develop in a small vein near the surface of the skin. This type of phlebitis rarely causes a serious problem.
  • Deep vein thrombosis occurs when a blood clot and inflammation are deep inside a vein in a leg, the lower abdomen (pelvis), or, rarely, the arm. It requires tests and treatment by a doctor.

Last Revised: February 1, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & David A. Szalay, MD - Vascular Surgery

The thyroid is a butterfly-shaped gland that lies in front of the windpipe, also known as the trachea, and just below the voice box, also called the larynx. This gland makes hormones that regulate the way the body uses energy.

The thyroid gland uses iodine from food to make two thyroid hormones: thyroxine (T4) and triiodothyronine (T3). The thyroid gland stores these hormones and releases them into the bloodstream as they are needed.

If the thyroid gland does not produce enough hormones, it is called hypothyroidism. If the gland produces too many hormones, it is called hyperthyroidism. Problems with the thyroid gland can affect many body systems. Changes in weight, heartbeat, body temperature, digestion, and muscle function are common. Both hypothyroidism and hyperthyroidism can be treated, usually with medicine and sometimes with surgery.

Last Revised: August 7, 2012

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Matthew I. Kim, MD - Endocrinology

Total cholesterol is the sum of all cholesterol measured in a person's blood. This total includes high-density lipoprotein (HDL), which is sometimes called the "good cholesterol," and low-density lipoprotein (LDL), sometimes called the "bad cholesterol," and very low-density lipoprotein (VLDL).

Cholesterol is measured either in milligrams per deciliter of blood (mg/dL) or in millimoles per liter of blood (mmol/L).

  • A total cholesterol level of less than 200 mg/dL (5.17 mmol/L) is desirable.
  • 200 to 239 mg/dL (5.17 to 6.18 mmol/L) is considered borderline high cholesterol.
  • 240 mg/dL (6.21 mmol/L) or higher is considered high cholesterol.

The ratio of total cholesterol to "good" (HDL) cholesterol is also important, especially if total cholesterol is high.

Last Revised: July 13, 2011

Author: Healthwise Staff

Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & Carl Orringer, MD - Cardiology, Clinical Lipidology

Trans fats are primarily created through hydrogenation, a process that turns liquid oils into solids like hard margarine and shortening. Some foods with trans fats include vegetable shortening, some margarines, crackers, cookies, and many packaged snack foods. Some animal-based foods have small amounts of naturally occurring trans fats.

Trans fats do not spoil as quickly as liquid fats, which makes them better in foods that are packaged for a long time.

Trans fat can increase cholesterol levels the same way as saturated fat. The best way to check for trans fat in a food is to look at the list of ingredients. Food made with partially hydrogenated or hydrogenated oil will have trans fat.

Last Revised: January 25, 2013

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Rhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator

A transcutaneous blood oxygen monitor is used to help doctors find out whether a person needs supplemental oxygen or an adjustment to the amount of supplemental oxygen they are already receiving. A sensor attached to the person's finger connects to a machine that gives a reading of the oxygen level in the person's blood.

This test does not require taking a sample of a person's blood.

Last Revised: October 11, 2011

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & Larry A. Latson, MD - Pediatric Cardiology

Transcutaneous electrical nerve stimulation (TENS) is a therapy that uses mild electrical current to treat pain.

Current is delivered through small pieces of material that conduct electricity (electrodes). These are placed on the skin near the source of pain. When the current is delivered, some people experience less pain. This may be because electricity from the electrodes stimulates the nerves in an affected area and sends signals to the brain that "scramble" normal pain signals. Another theory is that the electrical stimulation of the nerve may help the body to produce natural painkillers called endorphins, which may block the perception of pain.

Last Revised: January 9, 2013

Author: Healthwise Staff

Medical Review: Anne C. Poinier, MD - Internal Medicine & Nancy Greenwald, MD - Physical Medicine and Rehabilitation

In a transesophageal echocardiogram, a transducer is inserted through the mouth and down the throat into the esophagus. High-pitched sound waves (ultrasound) are sent through the transducer to produce an image of the heart and sometimes the aorta.

Normally the transducer is moved over the surface of the skin on the chest.

A transesophageal echocardiogram is often used for obese people because evaluating the heart through a thick chest wall is hard. This method allows a clear view of the valves and their ability to function. It provides a better view of heart valves than a standard transthoracic echocardiogram, but the procedure is more complicated.

Last Revised: December 9, 2011

Author: Healthwise Staff

Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & George Philippides, MD - Cardiology

A transient ischemic attack (TIA) happens when blood flow to part of the brain is stopped for a short time. It's also called a mini-stroke because the symptoms are like those of a stroke but they don't last long or cause lasting damage.

A TIA is a warning that you may have a stroke in the future. Early treatment can help prevent a stroke.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Richard D. Zorowitz, MD - Physical Medicine and Rehabilitation

In transposition of the great vessels, the major blood vessels attached to the heart—the aorta and the pulmonary artery—are reversed. This reversal results in the blood going to the wrong places. This leads to low oxygen levels in the body.

The aorta, which normally carries oxygen-rich blood from the left side of the heart to the body, instead receives oxygen-poor blood from the right side of the heart. The pulmonary artery, which normally carries oxygen-poor blood from the right side of the heart to the lungs, instead receives oxygen-rich blood from the left side of the heart.

In transposition of the great vessels, the right lower chamber of the heart (rather than the left lower chamber) pumps blood to the body. But the right side of the heart normally is not strong enough to pump blood effectively to the whole body. This increased workload on the right side of the heart can lead to a weakened heart.

There are several types of transposition of the great vessels. Each has slightly different placement of the vessels and openings that result in mixing of blood between the two sides of the heart. The most common form of transposition of the great vessels results in oxygen-poor blood being pumped to the body.

Certain other heart defects must be present to allow a child with transposition of the great vessels to live. Other defects ultimately compensate for the transposition of the great vessels by allowing oxygen-rich blood to mix with oxygen-poor blood so that some oxygen can get to the tissues of the body. Surgery is usually needed for long-term survival.

Last Revised: October 11, 2011

Author: Healthwise Staff

Medical Review: John Pope, MD - Pediatrics & Larry A. Latson, MD - Pediatric Cardiology

Trigeminal neuralgia (sometimes called tic douloureux) is a sudden, sharp pain on one side of the face. The pain commonly starts near one side of the mouth, then shoots toward the ear, eye, or nostril on the same side of the face.

The pain may start with a touch, movement, air drafts, eating, or for no known reason. Symptom-free periods, called remissions, may last several months or longer. As the condition gets worse, though, the episodes of pain become more frequent, remissions become shorter and less common, and a dull ache may remain between the episodes of stabbing pain.

Trigeminal neuralgia is most common in middle and late life. It affects women more often than men. When trigeminal neuralgia occurs in young people, it is often caused by multiple sclerosis.

Treatment with medicine is usually helpful. Surgery may be helpful if a structural problem (such as a blood vessel pressing on the trigeminal nerve) is the cause.

Last Revised: July 20, 2012

Author: Healthwise Staff

Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine

Triglycerides are a type of fat found in your blood. You need some triglycerides for good health. But high levels of triglycerides raise your risk for heart disease and other serious problems.

Your triglycerides are measured by the same blood test that measures your cholesterol.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: Kathleen Romito, MD - Family Medicine & Robert A. Kloner, MD, PhD - Cardiology & Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology

A normal pregnancy lasts about 40 weeks from conception to the birth of a baby. This time is roughly divided into 3 periods: the first trimester, from conception to about the 12th week of pregnancy; the second trimester, from about 13 to 27 weeks of pregnancy; and the third trimester, from about 28 weeks of pregnancy until birth.

Each trimester of pregnancy is marked by developmental changes in the fetus.

  • By the end of the first trimester (about week 12 of pregnancy), the fetus has a recognizable human form.
  • By the end of the second trimester (about week 27 of pregnancy), all the vital organs of the fetus have developed. Also, the mother begins to feel the fetus begin to move (quickening), usually starting between weeks 16 and 20.
  • During the third trimester (about week 28 until birth), the fetus's size increases and organs mature.

Last Revised: July 23, 2012

Author: Healthwise Staff

Medical Review: Sarah Marshall, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology

The trunk, or torso, is the part of the body to which the head, arms, and legs connect. It includes the shoulders, chest, lower abdomen, back, and buttocks.

Last Revised: March 4, 2011

Author: Healthwise Staff

Medical Review: Adam Husney, MD - Family Medicine & David A. Fleckenstein, MPT - Physical Therapy

Tuberculosis (TB) is an infection caused by bacteria. It usually affects the lungs. Symptoms may include fever, extreme fatigue, weight loss, night sweats, and a cough that brings up thick, bloody mucus.

TB can be deadly if it isn't treated.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology

Type 1 diabetes is a lifelong disease that happens when the pancreas stops making insulin. It usually develops in children and young adults.

Insulin lets sugar (glucose) move from the blood into the body's cells, where it can be used for energy or stored. Without insulin, sugar can't get into the cells, and your blood sugar gets too high. Over time, high blood sugar can lead to problems with your eyes, heart, blood vessels, nerves, and kidneys.

Treatment for type 1 diabetes focuses on keeping your blood sugar level in a safe range by eating a balanced diet, taking insulin injections, and getting regular exercise.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Jennifer Hone, MD - Endocrinology, Diabetes and Metabolism

Type 2 diabetes is a lifelong disease that happens when your body can't use insulin the right way or when your pancreas can't make enough insulin. It often affects people who are overweight and not physically active.

Insulin helps sugar (glucose) move from the blood into the body's cells, where it can be used for energy or stored. Without insulin, sugar can't get into the cells, and your blood sugar gets too high. Over time, high blood sugar can lead to problems with your eyes, heart, blood vessels, nerves, and kidneys.

You may be able to manage diabetes by eating a balanced diet and getting regular exercise. But some people need medicines to help control their blood sugar levels.

Last Revised: October 9, 2012

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Jennifer Hone, MD - Endocrinology, Diabetes and Metabolism