Definition A thyroid nuclear medicine scan is a diagnostic procedure to evaluate the thyroid gland, which is located in the front of the neck and controls the body's metabolism. A radioactive substance that concentrates in the thyroid is taken orally or injected into a vein (intravenously), or both. A special camera is used to take an image of the distribution...

Definition Thyroid hormones are artificially made hormones that make up for a lack of natural hormones produced by the thyroid gland. Purpose The thyroid gland, a butterfly-shaped structure in the lower part of the neck, normally produces a hormone called thyroxine. This hormone controls the rate of metabolism—all the physical and chemical processes that occur...

Definition Thyroid function tests are blood tests used to evaluate how effectively the thyroid gland is working. These tests include the thyroid-stimulating hormone test (TSH), free and total thyroxine tests (FT4,T4), the free and total triiodothyronine tests (FT3,T3), the thyroxine-binding globulin test (TBG), and the T-uptake test. Purpose Thyroid function tests are...

Definition Thyroid cancer is a disease in which the cells of the thyroid gland become abnormal, grow uncontrollably and form a mass of cells called a tumor. Description The thyroid is a hormone-producing, butterfly-shaped gland located in the neck at the base of the throat. It has two lobes, the left and the right. The thyroid uses iodine, a mineral found in some foods,...

Definition The thyroid biopsy is a procedure in which a sample of thyroid tissue is withdrawn for laboratory examination. The sample can be withdrawn through a needle or a surgical incision may be made to obtain a piece of thyroid tissue. Purpose The test is generally performed when a lump or a nodule is detected in the thyroid. The test may also be ordered if the thyroid gland...

Definition Thymomas are the most common tumor of the thymus. Description The thymus is located in the upper chest just below the neck. It is a small organ that produces certain types of white blood cells before birth and during childhood. These white blood cells are called lymphocytes and are an important part of the bodyôs immune system. Once released from the thymus, lymphocytes travel to lymph nodes...

Definition Thrombophlebitis is the inflammation of a vein with blood clot formation inside the vein at the site of the inflammation. Thrombophlebitis also is known as phlebitis, phlebothrombosis, and venous thrombosis. Description There are two parts to thrombophlebitis, inflammation of a vein and blood clot formation. If the inflammation is minor, the disease usually is called venous thrombosis...

Definition Thrombolytic therapy is the use of drugs that dissolve blood clots. The name "thrombolytic" comes from two Greek words that mean "clot" and "loosening."  Purpose When a blood clot forms in a blood vessel, it may cut off or severely reduce blood flow to parts of the body that are served by that blood vessel. This event can cause serious damage to those parts...

Definition Thrombocytosis is a blood disorder in which the body produces a surplus of platelets (thrombocytes). Description Thrombocytosis is an abnormally increased number of platelets in the blood. Platelets are blood cells that stick together, helping blood to clot. Thrombocytosis is a condition that may have many causes. Throbocytosis is classified as one of two types. Secondary thrombocytosis can...

Definition Thrombocytopenia is an abnormal drop in the number of blood cells involved in formingblood clots. These cells are called platelets. Description Thrombocytopenia is a blood disease characterized by an abnormally low number of platelets in the bloodstream. The normal amount of platelets is usually between 150,000 and 450,000 cells per microliter of blood. A...

Definition A throat culture is a technique for identifying disease bacteria in material taken from the throat. Most throat cultures are done to rule out infections caused by beta-hemolytic streptococci, which cause strep throat. Hemolytic means that these streptococci destroy red blood cells. Purpose The primary purpose of a throat culture is identification...

Definition Threadworm infection is an intestinal disease, which occasionally spreads to the skin, caused by a type of parasitic roundworm (helminth). In untreated patients, the disease has a high rate of reinfection caused by worms already present in the body. This type of disease recurrence is called autoinfection. Because of autoinfection, threadworms can remain inside humans for as long as 45 years...

Definition Thoracoscopy is the insertion of an endoscope, a narrow diameter tube with a viewing mirror or camera attachment, through a very small incision (cut) in the chest wall. Purpose Thoracoscopy makes it possible for a physician to examine the lungs or other structures in the chest cavity, without making a large incision. It is an alternative to thoracotomy (opening the chest cavity...

Definition Thoracic surgery is the repair of organs located in the thorax, or chest. The thoracic cavity lies between the neck and the diaphragm, and contains the heart and lungs (cardiopulmonary system), the esophagus, trachea, pleura, mediastinum, chest wall, and diaphragm. Purpose Thoracic surgery repairs diseased or injured organs and tissues in the thoracic cavity....

Definition Thoracic outlet syndromes are a group of disorders that cause pain and abnormal nerve sensations in the neck, shoulder, arm, and/or hand. Description The thoracic outlet is an area at the top of the rib cage, between the neck and the chest. Several anatomical structures pass through this area, including the esophagus, trachea, and nerves and blood vessels that lead...

Definition Also known as pleural fluid analysis, thoracentesis is a procedure that removes an abnormal accumulation of fluid or air from the chest through a needle or tube. Purpose Thoracentesis can be performed as a diagnostic or treatment procedure. For diagnosis, only a small amount of fluid is removed for analysis. For treatment, larger amounts of air or fluid are removed to relieve symptoms. The...

Definition Therapeutic touch, or TT, is a noninvasive method of healing that was derived from an ancient laying—on of hands technique. In TT, the practitioner alters the patient's energy field through an energy transfer that moves from the hands of the practitioner to the patient. Origins Therapeutic touch was developed in 1972 by Dora Kunz, a psychic healer, and Dolores Krieger,Ph.D.,...

Definition Bathing the skin in a variety of preparations in order to remove crusts, scales, and old medications or to relieve inflammation and itching is called taking a therapeutic bath. The term therapeutic bath is also used to refer to various types of warm-water soaks used to speed wound healing, to apply gentle heat to sore muscles or joints, to relieve emotional stress, or...

Definition The thematic apperception test (TAT) is a projective personality test that was designed at Harvard in the 1930s by Christiana D. Morgan and Henry A. Murray. Along with the MMPI and the Rorschach, the TAT is one of the most widely used psychological tests. A projective test is one in which a person's patterns of thought, attitudes, observational...

Definition A thallium heart scan is a test using a special camera and a small amount of radioactive substance injected into the bloodstream to make an image of the blood flow to the heart. Purpose A thallium heart scan is used to evaluate the blood supply to the heart muscle. It can identify areas of the heart that may have a poor blood supply...

Definition Thalassemia describes a group of inherited disorders characterized by reduced or absent amounts of hemoglobin, the oxygen-carrying protein inside the red blood cells. There are two basic groups of thalassemia disorders: alpha thalassemia and beta thalassemia. These conditions cause varying degrees of anemia, which can range from insignificant to life threatening. Description All...

Definition Tetralogy of Fallot is a common syndrome of congenital heart defects. Description The heart is two pumps in one. The ventricle on the left side pumps blood full of oxygen through the body; the ventricle on the right side pumps the same blood through the pulmonary artery to the lungs to take up oxygen. The left ventricle operates at pressures about four times as high as the right ventricle....

Definition Tetracyclines are a group of antibiotics that are useful in treatment of many bacterial infections. Description Tetracyclines are called broad-spectrum antibiotics because they can be used to treat a wide variety of infections. Physicians may prescribe these drugs to treat eye infections, pneumonia , gonorrhea, Rocky Mountain spotted fever , urinary tract infections,...

Definition Tetanus is a rare but often fatal disease that affects the central nervous system by causing painful muscular contractions. It begins when tetanus bacteria enter the body, usually through a wound or cut exposed to contaminated soil. Tetanus is easily preventable through vaccination. Description Tetanus is rare in the United States, with nearly all cases occurring...

Definition Testicular torsion is the twisting of a testis (testicle) such that the spermatic cord becomes twisted, cutting off blood flow to the testis. Description The testes are suspended in the scrotum by a single bundle of tissues called the spermatic cord. Normally this bundle of tissue holds the testes in place. Each testis receives blood through the spermatic cord. When the testicle is not held...

Definition Testicular surgery is any surgical operation on the testicles. Purpose Testicular surgery is used primarily to correct developmental defects, treat infection or trauma, and treat cancer of the testes. Precautions Testicular surgery, a group of surgical operations performed on the testicles, is considered majorsurgery. In all cases, except when the testes are being...

Definition A testicular self-examination (TSE) is the procedure by which a man checks the appearance and consistency of his testes. Purpose Most testicular cancers are first noticed by the man himself. Men should do a TSE every month to find out if the testes contain any suspicious lumps or other irregularities, which could be signs of cancer or...

Definition Testicular cancer is a disease in which cancer cells are discovered in one or both testicles. The testicles, also known as testes or gonads, are located in a pouch beneath the penis called the scrotum. Description The testicles make up one portion of the male reproductive system. Normally, they are each somewhat smaller than a golf ball in size and are contained within the scrotum....

Definition This most common type of headache is caused by severe muscle contractions triggered by stress or exertion. The American Council for Headache Education (ACHE) estimates that 95% of women and 90% of men in the United States and Canada have had at least one headache in the past twelve months. Tension headaches are considered a type of primary headache,...

Definition Tensilon is the trade name for edrophonium chloride. The Tensilon test is an injection of edrophonium chloride used to diagnosis myasthenia gravis (MG). Purpose Tensilon blocks the action of an enzyme, acetylcholinesterase, an important part of the system regulating neuromuscular transmission. To stimulate a muscle, a nerve cell (neuron) releases the chemical acetylcholine. To prevent prolonged...

Definition Tennis elbow is an inflammation of several structures of the elbow. These include muscles, tendons, bursa, periosteum, and epicondyle (bony projections on the outside and inside of the elbow, where muscles of the forearm attach to the bone of the upper arm). This condition is also called epicondylitis, lateral epicondylitis, medial epicondylitis, or golfer's elbow, where pain is...

Definition Tendinitis is the inflammation of a tendon, a tough rope-like tissue that connects muscle to bone. Description Tendinitis usually occurs in individuals in middle or old age because it is often the result of overuse over a long period of time. Tendinitis does occur in younger patients as a result of acute overuse. tendons that commonly become...

Definition Temporomandibular joint disorder (TMJ) is the name given to a group of symptoms that cause pain in the head, face, and jaw. The symptoms include headaches, soreness in the chewing muscles, and clicking or stiffness of the joints. They often have psychological as well...

Definition The term temporal arteritis literally means "inflammation of the temporal arteries." As implied by the name, these blood vessels run along the temples after they branch off from the carotid artery in the neck. They provide the blood supply to portions of the scalp, jaw muscles, and salivary glands. Inflammation of these arteries, probably resulting from an abnormal...

Definition Teeth whitening is the process of using bleach or other materials to make teeth look whiter. The materials remove stains or other discoloration from the tooth surface. Purpose Teeth whitening is a cosmetic treatment done to improve the appearance of teeth. Teeth are whitened to remove the effects of coffee, cigarettes, and other substances...

Definition The technetium heart scan is a non-invasive nuclear scan that uses a radioactive isotope called technetium to evaluate blood flow after a heart attack. Purpose The technetium heart scan is used to evaluate the heart after a heart attack. It can confirm that a patient had a heart attack when the...

Definition Tay-Sachs disease is a genetic disorder caused by a missing enzyme that results in the accumulation of a fatty substance in the nervous system. This results in disability and death. Description Gangliosides are a fatty substance necessary for the proper development of the brain and nerve cells (nervous system). Under normal conditions, gangliosides are continuously...

Definition Tarsorrhaphy is a rare procedure in which the eyelids are partially sewn together to narrow the opening.  Purpose The eye needs the lid for protection. It also needs tears and periodic blinking to cleanse it and keep it moist. There are many conditions that impair these functions and threaten the eye, specifically the cornea, with drying. Sewing the eyelids partially together helps protect the...

Definition Tapeworms are a group of parasitic worms that live in the intestinal tracts of some animals. Several different species of tapeworms can infect humans. Tapeworm disease or cestodiasis occurs most commonly after eating raw or undercooked meat or fish that contains the immature form of the tapeworm. Description Tapeworm infections pose a serious public health problem in many less developed...

T'ai chi is an ancient Chinese exercise with movements that originate from the martial arts. While used as a type of self-defense in its most advanced form, t'ai chi is practiced widely for its health andrelaxation benefits. Those in search of well being and a way to combat stress have made what has also been called "Chinese shadow boxing" one of...

Definition Pyruvate kinase deficiency (PKD) is part of a group of disorders called hereditary nonspherocytic hemolytic anemias. Hereditary nonspherocytic anemias are rare genetic conditions that affect the red blood cells. PKD is caused by a deficiency in the enzyme, pyruvate kinase. Although PKD is the second most common of the hereditary nonspherocytic anemias, it is...

Definition Pyloroplasty is an elective surgical procedure in which the lower portion of the stomach, the pylorus, is cut and resutured, to relax the muscle and widen the opening into the intestine.Pyloroplasty is a treatment for high-risk patients for gastric or peptic ulcer disease. A peptic ulcer is a well-defined sore on the stomach where the lining of the stomach or duodenum has been eaten away...

Definition Pyloric stenosis is a disorder that occurs when the pyloric sphincter muscle, which is found at the outlet of the stomach, thickens and becomes enlarged causing the cavity (lumen) of the pylorus to narrow and lengthen. This blocks the passage of food from the stomach to the small intestine (the portion of bowel that continues digestion after food leaves the stomach). Description Pyloric stenosis occurs...

Definition Pyelonephritis is an inflammation of the kidney and upper urinary tract that usually results from noncontagious bacterial infection of the bladder (cystitis ). Description Acute pyelonephritis is most common in adult females but can affect people of either sex and any age. Its onset is usually sudden, with symptoms that often are mistaken as the results of straining the lower back. Pyelonephritis often...

Definition Pulmonary valve stenosis is a congenital heart defect in which blood flow from the heart to the pulmonary artery is blocked. Description Pulmonary valve stenosis is an obstruction in the pulmonary valve, located between the right ventricle and the pulmonary artery. Normally, the pulmonary valve opens to let blood flow from the right...

Definition Pulmonary valve insufficiency is a disorder involving a defect of the valve located in the pulmonary artery. Description This disorder is also known as pulmonary valve regurgitation or pulmonary incompetence. The pulmonary valve is the structure in the pulmonary artery consisting of three flaps, which open and close during...

Definition Pulmonary hypertension is a rare lung disorder characterized by increased pressure in the pulmonary artery. The pulmonary artery carries oxygen-poor blood from the lower chamber on the right side of the heart (right ventricle) to the lungs where it picks up oxygen. Description Pulmonary hypertension is present when the blood pressure in the circulation of the lungs...

Definition Pulmonary function tests are a group of procedures that measure the function of the lungs,revealing problems in the way a patient breathes. These tests can determine the cause of shortness of breath and may help confirm the diagnosis of lung diseases, such as asthma, chronic bronchitis, or emphysema. Th e tests may also be performed before any major lung surgery to make sure the person will not be...

Definition Pulmonary fibrosis is a lung disease characterized by scarring of the deep tissue of the lungs. Description Pulmonary fibrosis belongs to a broad group of lung diseases called “interstitial lung diseases” that includes more than 130 disorders characterized by scarring (fibrosis) and/or inflammation of the lungs. The lungs are a pair of organs located in the chest. They...

Definition A pulmonary embolism occurs when a lung artery is blocked by a blood clot. The blockage is often caused by one or more blood clots that travel to the lungs from another part of the body. Description A pulmonary embolism is a problem of the vascular system, the network of blood vessels that includes the arteries, veins and capillaries that carry blood to and...