T-cell: A white blood cell made in the thymus gland, a lymphoid structure in the upper chest. (The T in T-cell stands for Thymus). The T-cells coordinate the immune system by secreting lymphokine hormones. There are 3 fundamentally different types of T cells : helper, killer, and suppressor. Each has many subdivisions. T-cells are also called T lymphocytes.

T3: Triiodothyronine, a thyroid hormone. (The number 3 is usually in subscript.) Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.

T4: Thyroxine, a thyroid hormone. (The number 4 is usually in subscript.) Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.

T4 cell: Immune cells that are triggered by antibodies to seek and attack invading organisms. Cells called macrophanges summon T4 cells to the site of the infection and present a protruding antigen onto which the T4 cell locks, thus "recognizing" the invading substance. The T4 cell then reproduces and secretes its potent lymphokine hormones that stimulate B-cell production of antibodies; signal "natural killer" or cytotoxic (cell-killing) T-cells; and summon more macrophanges to the site of the infection. T4 cells are normally twice as common as T8 cells. If a person has AIDS, the proportion of T4 to T8 cells is often reversed. T4 cell are also called T-helper cells.

T8 cell: A type of immune cells, T8 cells close down the immune response after it has destroyed invading organisms. T8 cells are sensitive to high concentrations of circulating lymphokine hormones and release their own lymphokines after an immune response has achieved its goal, signalling all other participants to cease their attack. Some memory B-cells remain to ward off a repeat attack by the invading organism. T8 cells are also called T-suppressor cells.

T-cell lymphoma: A cancer of the immune system that appears in the skin; also called mycosis fungoides.

T-helper cell: Immune cells that are triggered by antibodies to seek and attack invading organisms. Cells called macrophanges summon T-helper cells to the site of the infection and present a protruding antigen onto which the T-helper cell locks, thus "recognizing" the invading substance. The T4-helper cell then reproduces and secretes its potent lymphokine hormones that stimulate B-cell production of antibodies; signal "natural killer" or cytotoxic (cell-killing) T-cells; and summon more macrophanges to the site of the infection. T-helper cells are also called T4 cells and are normally twice as common as T8 cells. If a person has AIDS, the proportion of T4 to T8 cells is often reversed.

T-lymphocyte: A white blood cell made in the thymus gland, a lymphoid structure in the upper chest. T lymphocytes are also called T-cells. (The T in T-cell stands for Thymus). These cells coordinate the immune system by secreting lymphokine hormones. There are 3 fundamentally different types of T lymphocytes : helper, killer, and suppressor.

Tabes dorsalis: The slowly progressive degeneration of the spinal cord that occurs in the late (tertiary) phase of syphilis a decade or more after contracting the infection. Among the terrible features are lancinating lightning pain, ataxia (wobbliness), deterioration of the nerve to the eye (the optic nerve) leading to blindness, urinary incontinence, loss of the sense of position, and degeneration of the joints (Charcot’s joints). Tabes is the Latin word for decay. The term tabes dorsalis was devised in 1836 when the cause of the condition was thought to be wastage of the dorsal (posterior) columns of the spinal cord, well before it was recognized as part of late syphilis.

Tabes spinalis: See Tabes dorsalis.

Tabetic neurosyphilis: See Tabes dorsalis.

Tablespoon: An old-fashionned but convenient household measure of capacity. A tablespoon holds about 5 cc. A tablespoon = 3 teaspoons.

Tache noire: Black spot (in French), a small ulcer covered with a black crust at the site of a tick bite, characteristic of several tick-borne rickettsial diseases.

Tachycardia: A rapid heart rate, usually defined as greater than 100 beats per minute.

Tachycardia, paroxysmal atrial (PAT): Bouts of rapid, regular heart beating originating in the atrium (upper chamber of the heart). Often due to abnormalities in the AV node "relay station" that lead to rapid firing of electrical impulses from the atrium which bypass the AV node under certain conditions. These conditions include alcohol excess, stress, caffeine, overactive thyroid or excessive thyroid hormone intake, and certain drugs. PAT is an example of an arrhythmia where the abnormality is in the electrical system of the heart, while the heart muscle and valves may be normal.

Tachycardia, sinus: Fast heartbeat (tachycardia) occurring because of rapid firing by the SA node, the natural pacemaker of the heart. Electrical signals initiated in the SA node are transmitted to the atria and the ventricles to stimulate heart muscle contractions heartbeats. Sinus tachycardia is usually a rapid contraction of a normal heart in response to a condition, drug, or disease. For examples, pain, fever, excessive thyroid hormone, exertion, excitement, low blood oxygen level (hypoxia), or stimulant drugs such as caffeine, cocaine, and amphetamines can cause tachycardia. However, in some cases, it can be a sign of heart failure or heart valve disease or other illness.

Tachycardia, ventricular: An abnormal heart rhythm that is rapid, regular and originates from an area of the ventricle, the lower chamber of the heart. Ventricular tachycardias are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack.

Tachypnea: Abnormally fast breathing.

Tactile: Having to do with touch.

Taenia: In medicine, it is a genus of large tapeworms. (In Latin, taenia meant a ribbon or tape.)

Taenia saginata: The beef tapeworm. The most common of the big tapeworms that parasitizes people, contracted from infected raw or rare beef. Can grow to be 12-25 feet (3.6-7.5 m) long in the human intestine. Also known as the African tapeworm.

Taenia solium: The pork tapeworm. Contracted from undercooked or measly pork (pork infected with the larval forms of the tapeworm). Can grow to be 3-6 feet (0.9-1.8 m) long in the human intestine. Also known as the armed tapeworm and the measly tapeworm.

Tag, ear: Common minor anomaly, a rudimentary tag of ear tissue, often containing a core cartilage, usually located just in front of the ear (auricle). Therefore, also called preauricular tag. The presence of 2 or more minor anomalies in a child increases the probability that the child has a major malformation.

Tag, preauricular: See Tag, ear.

Talipes: Clubfoot. The Latin word talipes was compounded from talus (ankle) + pes (foot) since, with the common ("classic") type of clubfoot (talipes equinovarus), the foot is turned in sharply and the person seems to be walking on their ankle. Talipes equinovalgus: Malformation of the foot evident at birth in which the heel is elevated like a horse’s hoof (equino-) and the heel is turned outward (valgus).

Talipes equinovarus: The common ("classic") form of clubfoot. Talipes is made up of the Latin talus (ankle) + pes (foot). Equino- indicates the heel is elevated (like a horse’s) and -varus indicates it is turned inward. With this type of clubfoot, the foot is turned in sharply and the person seems to be walking on their ankle.

Tandem repeat sequences: Multiple copies of the same DNA base sequence on a chromosome; used as a marker in physical mapping of the chromosome.

Tapazol: Trade name for methimazole, an antithyroid medication.

Tapeworm: A worm that is flattened like a tape measure and functions as an intestinal parasite, unable to live freely on its own but able to do so within an animal’s gut.

Tapeworm, African: See Taenia saginata.

Tapeworm, armed: See Taenia solium.

Tapeworm, beef: See Taenia saginata.

Tapeworm, measly: See Taenia solium. The word measly does not imply that this is a puny tapeworm. Measly here refers to meat infested with the larval form of the pork tapeworm (t. solium). From eating the measly meat, you can acquire the tapeworm.

Tapeworm, pork: See Taenia solium.

Tarsal cyst: Also called a Meibomian cyst or a chalazian. A tarsal cyst is an inflammation of the oil gland of the eyelid.

TAR syndrome: TAR stands for Thrombocytopenia (low blood platelets) and Aplasia (absence) of the Radius (the long bone on the thumb-side of the forearm), features characterizing this syndrome. There is phocomelia (flipper-limb) with the thumbs always present. The fibula (the smaller bone in the lower leg) is often absent. The risk of bleeding from too few platelets is high in early infancy but lessens with age. The condition is inherited in an autosomal recessive trait with one gene (on a non-sex chromosome) coming from each parent to the TAR child. Alternative names include thrombocytopenia-absent radius syndrome, radial aplasia-thrombocytopenia syndrome, and tetraphocomelia-thrombocytopenia syndrome.

Tartar: Tartar is the hardened product of longstanding plaque accumulating minerals from the saliva and foods. Plaque is the soft accummulation of food debris and bacteria around teeth. These bacteria feed on left over food in the mouth to excrete toxins that irritate the gums and dissolve the bone. Plaque can be removed by proper brushing and flossing at home. Tartar can become as hard as a rock and then can require a dentist or dental hygienist with special tools to remove it. Dental plaque and tartar cause inflammation of the bone surrounding the teeth referred to as "periodontia."

Td: Adult diphtheria and tetanus toxoids. See Td immunization.

Td immunization: Td is the vaccine given to children over six and adults as a booster for immunity to diphtheria and tetanus.

Teaspoon: Like a tablespoon, a teaspoon is an old-fashionned but convenient household measure. A teaspoon holds about 5 cc. Three teaspoons = a tablespoon.

Technology, recombinant DNA: A series of procedures used to join together (recombine) DNA segments. A recombinant DNA molecule is constructed (recombined) from segments from 2 or more different DNA molecules. Under certain conditions, a recombinant DNA molecule can enter a cell and replicate there, autonomously (on its own) or after it has become integrated into a chromosome.

Technology transfer: The process of converting scientific findings from research laboratories into useful products by the commercial sector.

Telomere: The end of a chromosome. The ends of chromosomes are specialized structures that are involved in the replication and stability of DNA molecules.

Temperature: The temperature is the specific degree of hotness or coldness of the body. It is usually measured with a thermometer.

Temporal arteritis: Also called giant cell arteritis or cranial arteritis, this is a serious disease characterized by inflammation of the walls of the blood vessels (vasculitis). The vessels affected by inflammation are the arteries (hence the name "arteritis"). The age of affected patients is usually over 50 years of age. Giant cell arteritis can lead to blindness and/or stroke. It is detected by a biopsy of an artery. It is treated with high dose cortisone-related medications.

Tempero-mandibular joint (TMJ): The TMJ hinges the lower jaw (mandible) to the skull.

Tempero-mandibular joint (TMJ) syndrome: Disorder of the temporo-mandibular joint(s) causing pain usually in front of the ear(s). Pain in the TMJ can be due to trauma (such as a blow to the face), inflammatory or degenerative arthritis, or by the mandible being pushed back towards the ears whenever the patient chews or swallows. Sometimes, muscles around the TMJ used for chewing can go into spasm, causing head and neck pain and difficulty opening the mouth normally.

Tendon: A tendon is the soft tissue by which muscle attaches to bone. When a tendon becomes inflamed, the condition is referred to as "tendinitis" or "tendonitis."

Terminal ileitis: Crohn’s disease, a chronic inflammatory disease of the intestine involving only the end of the small intestine (the terminal ileum). Crohn’s disease affects primarilythe small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease often strikes persons in their teens or early twenties. It tends to be chronic, recurrent with periods of remission and exacerbation. In the early stages, It causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery.

Test, Fisher’s exact: A statistical test of independence much used in medical research. It tests the independence of rows and columns in a 2 X 2 contingency table (with 2 horizontal rows crossing 2 vertical columns creating 4 places for data) based on the exact sampling distribution of the observed frequencies. Hence it is an "exact" test. Devised by the great British statistician R. A. Fisher (1890-1962).

Test, glucose tolerance (GTT): After fasting, a specific amount (100 grams) of glucose is given by mouth, and the blood levels of this sugar are measured every hour. Normally, the blood glucose should return to normal within 2 to 2 ½ hours. The GTT is considered a classic test of carbohydrate metabolism. It is much used in the diagnosis of diabetes. The GTT depends on a number of factors including the ability of the intestine to absorb glucose, the power of the liver to take up and store glucose, the capacity of the pancreas to produce insulin, and the amount of "active" insulin.

Test, skin, for allergy: Test done on the skin to identify the allergy substance (allergen) triggering the allergic reaction. A small amount of the suspected allergy substance is placed on the skin. The skin is then gently scratched through the small drop with a special sterile needle. If the skin reddens and, more importantly, swells, then allergy to that substance is probable.

Testicles: The male sex glands. The testicles produce and store sperm and are the major source of testosterone.

Testing, anonymous: Testing in which no name or other means is used to identify the person tested. There is total anonymity. For example, the State of Florida requires that each county have a site for anonymous HIV testing.

Testosterone: A male sex hormone.

Tetanus: An often fatal infectious disease due to a bacteria (Clostridium tetani) that usually enters the body through a puncture, cut or open wound. Tetanus leads to profound painful spasms of muscles, including"locking" of the jaw so the mouth cannot open (lockjaw), and death. Tetanus is the "T" in the DPT, DTaP, DT, and Td vaccines.

Tetraphocomelia-thrombocytopenia syndrome: See TAR syndrome.

Thalassemia: Not just one disease but rather a complex series of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of hemoglobin is made up of 4 polypeptide chains (usually 2 chains of one type and 2 chains of another type of chain). In thalassemia, there is a mutation (change) in one of the types of globin chains. Depending upon which globin chain is affected, the mutation typically leads to underproduction (or absence) of that globin chain, a deficiency of hemoglobin, and anemia.

Thalassemia, beta: Also known as thalassemia major .The clinical picture of this important type of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley.. Other names for the disease are Cooley’s anemia and Mediterranean anemia. The name thalassemia was coined by the Nobel Prize winning pathologist George Whipple and the professor of pediatrics Wm Bradford at U. of Rochester because thalassa in Greek means the sea (like the Mediterrranean Sea) + -emia means in the blood so thalassemia means sea in the blood. Thalassemia is not just one disease. It is a complex contingent of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of normal adult hemoglobin is made up of 2 alpha and 2 beta polypeptide chains. In beta thalassemia, there is a mutation (change) in both beta globin chains leading to underproduction (or absence) of beta chains, underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin (for example, from Italy and Greece). Children with this disease inherit one gene for it from each parent. The parents are carriers (heterozygotes) with just one thalassemia gene, are said to have thalassemia minor, and are essentially normal. Their children affected with beta thalassemia seem entirely normal at birth because at birth we still have predominantly fetal hemoglobin which does not contain beta chains. The anemia surfaces in the first few months after birth and becomes progressively more severe leading to pallor and easy fatiguability, failure to thrive (grow), bouts of fever (due to infections) and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease.

Thalassemia major: The dire disease also known as beta thalassemia. The clinical picture of this form of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley. Other names for the disease are Cooley’s anemia and Mediterranean anemia. The term thalassemia was coined by the Nobel Prize winning pathologist George Whipple and the professor of pediatrics William Bradford at U. of Rochester because thalassa in Greek means the sea (like the Mediterrranean Sea) + -emia means in the blood so thalassemia means sea in the blood. Thalassemia is not just one disease. It is a complex contingent of genetic (inherited) disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. The globin part of normal adult hemoglobin is made up of 2 alpha and 2 beta polypeptide chains. In beta thalassemia, there is a mutation (change) in both beta globin chains leading to underproduction (or absence) of beta chains, underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin (for example, from Italy and Greece). Children with this disease inherit one gene for it from each parent (and so are said to be homozygous for beta thalassemia). The parents are carriers (heterozygotes) with just one thalassemia gene, are said to have thalassemia minor, and are essentially normal. Their children affected with beta thalassemia seem entirely normal at birth (because at birth we still have predominantly fetal hemoglobin which does not contain beta chains) but the anemia emerges in the first few months of life and becomes progressively more severe leading to pallor and easy fatiguability, failure to thrive (grow), bouts of fever (due to infections) and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease.

Thalassemia minor: Also called thalassemia trait, thalassemia minor is the carrier state for beta thalassemia. People who are carriers (heterozygotes) have just one thalassemia gene, are said to have thalassemia minor, and are essentially normal.

Therapy, gene: Insertion of normal DNA directly into cells to correct a genetic defect. Gene therapy is the treatment of disease by replacing, altering, or supplementing a gene responsible for the disease. In gene therapy for cancer, for example, researchers are trying to bolster the body’s natural capacity to combat cancer and make the tumor more sensitive to other kinds of therapy. Gene therapy, still in its early stages, holds great promise for the treatment of many diseases.

Third and fourth pharyngeal pouch syndrome: Also called the DiGeorge syndrome (DGS), this disorder is characterized by (1) low blood calcium levels (hypocalcemia) due to underdevelopment (hypoplasia) of the parathyroid glands which control calcium; (2) underdevelopment (hypoplasia) of the thymus, an organ behind the breastbone in which lymphocytes mature and multiply; and (3) defects of the heart involving the outflow tracts > from the heart. Most cases of DGS are due to a microdeletion in chromosome band 22q11.2. A small number of cases have defects in other chromosomes, notably 10p13. Named after the American pediatric endocrinologist Angelo DiGeorge. Another name for DGS is hypoplasia of the thymus and parathyroids.

Thombi: Just the plural of thrombus. See: Thrombus.

Thoracic: Pertaining to the chest.

Thoracic duct: A vascular structure which recirculates lymph into the blood stream. It begins in the abdomen and tracks alongside the aorta and esophagus to eventually join with the left brachiocephalic vein.

Thoracic outlet syndrome: Condition due to compromise of blood vessels or nerve fibers between the armpit (axilla) and base of the neck.

Thoracotomy: An operation to open the chest.

Thorax: The thorax is the area of the body located between the abdomen and the neck. It is also commonly referred to as the chest. Within the thorax are the lungs, heart and first section of the aorta.

Thrombectomy: Procedure to remove a clot (a thrombus).

Thrombin: A key clot promoter, thrombin is an enzyme that presides over the conversion of a substance called fibrinogen to fibrin, the right stuff for a clot.

Thrombinogen: A coagulation factor needed for the normal clotting of blood. In the cascade of events leading to the final clot, thrombinogen precedes thrombin (and so is a precursor to thrombin). In fact, thrombinogen gives rise to thrombin, and also called prothrombin.

Thrombocyte: A platelet. Crucial to normal blood clotting. Although platelets are sometimes classed as blood cells, they are not. They are fragments of a large cell called a megakaryocyte (literally, a large cell).

Thrombocytopenia-absent radius syndrome: See TAR syndrome.

Thoracentesis: Removal of fluid in the pleura through a needle.

Thrombocytopenia-absent radius syndrome: See TAR syndrome.

Thrombolytic agents: Medications such as plasminogen-activator (t-PA) and streptokinase that are effective in dissolving clots and re-opening arteries. Used, for example, in the treatment of heart attacks.

Thrombophlebitis: Inflammation of a vein that occurs when a blood clot forms.

Thrombotic disease due to protein C deficiency: Protein C is a protein in plasma that enters into the cascade of biochemical events leading to the formation of a clot. Deficiency of protein C results in thrombotic (clotting) disease and excess platelets with recurrent thrombophlebitis (inflammation of the vein that occurs when a clot forms). The clot can break loose and travel through the blood stream (thromboembolism) to the lungs causing a pulmonary embolism, brain causing a stroke (cerebrovascular accident), heart causing an early heart attack, skin causing what in the newborn is called neonatal purpura fulminans, the adrenal gland causing hemorrhage with abdominal pain, abnormally low blood pressure (hypotension), and salt loss. Protein C deficiency is due to possession of one gene (heterozygosity) in chromosome band 2q13-14. The possession of two such genes (homozygosity) is usually lethal.

Thrombus: A clot in a blood vessel or within the heart.

Thymine (T): One member of the base pair A-T (adenine-thymine) in DNA.

Thymus: An organ in which lymphocytes mature and multiply. It lies behind the breastbone.

Thymus and parathyroids, hypoplasia of: See Third and fourth pharyngeal pouch syndrome.

Thyroglossal cyst: A thyroglossal cyst is a fluid-filled sac that is present at birth and located in the midline of the neck. A thyroglossal cyst is a result of incomplete closure of a segent of a tube-like structure (the thyroglossal duct) that is present, and normally closes, as the embryo develops. A thyroglossal cyst is also called a thyrolingual cyst.

Thyroid: Gland located in the lower part of the neck, below the Adam’s apple, wrapped around the windpipe (trachea). The thyroid has the shape of a butterfly, since it is formed by two wings (lobes) which are attached by a middle part. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.

Thyroid scan: A picture taken of the thyroid gland after radioactive iodine is taken by mouth.

Thyroid hormones: Chemical substances made by the thyroid gland which is located in the front of the neck. The thyroid gland uses iodine to make thyroid hormones. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3).

Thyroid stimulating hormone (TSH): A hormone produced by the pituitary gland (at the base of the brain) that promotes the growth of the thyroid gland (in the neck) and stimulates it. Normally, the rate of thyroid hormone production is controlled by the pituitary. When there are insufficient thyroid hormones in the body for normal functioning of the cells, the pituitary releases TSH. TSH in turn "stimulates" the thyroid gland to produce more thyroid hormones. In contrast, when there is excessive amount of thyroid hormones, the pituitary gland stops producing TSH. The TSH level then falls and thyroid hormone production is reduced. This mechanism maintains a relatively constant level of thyroid hormones circulating in the blood. This phenomenon is analogous to a thermostat used for temperature regulation in a room: when the temperature rises, the thermostat shuts the heater off and the room temperature falls back to normal. High levels of thyroid hormones cause the TSH level to fall, resulting in no further stimulation of the thyroid gland. In hyperthyroidism, there are continuously elevated levels of the thyroid hormones. TSH is also known as thyrotropin.

Thyroid stimulating immunoglobulin (TSI): The TSI level is abnormally high in persons with hyperthyroidism (too much thyroid hormone) due to Graves’ disease.

Thyroidectomy: Surgery to remove part or all of the thyroid gland. This might be done to remove a tumor or treat hyperthyroidism or goiter (enlarged thyroid gland). The goal of surgery in hyperthyroidism is to remove just enough thyroid gland so that a normal amount of thyroid hormone is produced. If too much thyroid is removed, the patient will produce too little thyroid hormone (hypothyroidism) and need treatment to return the thyroid status to normal (euthyroid). The complications of surgery can include vocal cord paralysis and accidental removal of the parathyroid glands (located behind the thyroid gland), resulting in low calcium levels (the parathyroid glands regulate calcium).

Thyroiditis: Inflammation of the thyroid gland. The inflamed thyroid gland can releases an excess of thyroid hormones into the blood stream, resulting in a temporary hyperthyroid state. Once the thyroid gland is depleted of thyroid hormones, the patient commonly goes through a hypothyroid (low thyroid) phase. This phase can last 3-6 months until the thyroid gland fully recovers. Thyroiditis can be diagnosed by a thyroid scan (a picture taken of the thyroid gland after radioactive iodine is taken by mouth).

Thyroiditis, autoimmune: A progressive disease of the thyroid gland with antibodies in the blood stream directed against the thyroid and infiltration of the gland by lymphoctes (a key type of white blood cells involved in the immune response). This immune response is against one’s own thyroid. (It is autoimmune.) Predominantly affects women. Can be familial. Also called Hashimoto’s disease or Hashimoto’s thyroiditis.

Thyroiditis, Hashimoto’s: Autoimmune thyroiditis. A progressive disease of the thyroid gland with antibodies in the blood stream directed against the thyroid and infiltration of the gland by lymphoctes (a key type of white blood cells involved in the immune response). This immune response is against one’s own thyroid. (It is autoimmune.) Predominantly affects women. Can be familial. Also called Hashimoto’s disease.

Thyroiditis, postpartum: Inflammation of the thyroid gland after pregnancy.

Thyroiditis, subacute: Inflammation of the thyroid gland after a viral illness.

Thyrolingual cyst: A thyrolingual cyst is a fluid-filled sac that is present at birth and located in the midline of the neck. A thyrolingual cyst is a result of incomplete closure of a segent of a tube-like structure (the thyrolingual duct) that is present, and normally closes, as the embryo develops. A thyrolingual cyst is also called a thyroglossal cyst.

Thyrotropin: A hormone produced by the pituitary gland (at the base of the brain) that promotes the growth of the thyroid gland (in the neck) and stimulates it. The suffix -tropin indicates "an affinity for". Thyrotropin has an affinity for the thyroid. Thyrotropin is known also as thyroid stimulating hormone (TSH).

Thyroxine: A chemical substance made by the thyroid gland The thyroid gland uses iodine to make thyroid hormones. Thyroxine (T4), one of the most important thypoid hormones, has four iodine molecules attached to its molecular structure. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.

Tick-borne rickettsioses of the eastern hemisphere: Thare are 3 known diseases caused by infection with rickettsial agents. They are North Asian tick-borne rickettsiosis, Queensland tick typhus, and African tick typhus (fièvre boutonneuse).

Tick-borne rickettsiosis, north Asian: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.

Tick fever: See Rocky Mountain spotted fever.

Tick typhus: See Typhus, tick.

Tick typhus, African: See Typhus, African tick.

Tick typhus, Queensland: See Typhus, Queensland tick.

Tinea unguium: The most common fungus infection of the nails (onychomycosis). Onychomycosis makes the nails look white and opaque, thickened, and brittle. Older women (perhaps because estrogen deficiency may increase the risk of infection). and men and women with diabetes or disease of the small blood vessels (peripheral vacscular disease) are at increased risk. Artificial nails (acrylic or "wraps") increase the risk because when an artificial nail is applied, the nail surface is usually abraded with an emery board damaging it, emery boards can carry infection, and. water can collect under the nail creating a moist, warm environment for fungal growth. Alternative names include ringworm of the nails and dermatophytic onychomycosis.

Tinnitus: Ringing in the ears. Tinnitus has many causes including medications (such as aspirin, and other antiinflammatory drugs), aging, and ear trauma.

Tissue: A group or layer of cells that perform specific functions.

TMA: See Trimethylaminuria

TMJ: Tempero-mandibular joint, the joint that hinges the lower jaw (mandible) to the skull.

TMJ syndrome: Disorder of the temporo-mandibular joint(s) causing pain usually in front of the ear(s).

Tonsillectomy: The surgical removal of both tonsils.

Tonsillitis: Inflammation of the of a tonsil, typically as a result of infection by either a virus or bacteria.

Tonsils: Small masses of lymphoid tissue at the back of the throat, on either side of the throat.

Tooth, cracked, syndrome: A toothache caused by a broken tooth (tooth fracture) without associated cavity or advanced gum disease. Biting on the area of tooth fracture can cause severe sharp pains. These fractures are usually due to chewing or biting hard objects such as hard candies, pencils, nuts, etc. Sometimes, the fracture can be seen by painting a special dye on the cracked tooth. Treatment usually is to protect the tooth with a crown. However, if placing a crown does not relieve pain symptoms, a root canal procedure may be necessary.

Tooth root sensitivities: Oversensitivity of exposed roots of teeth to cold, hot, and sour foods because those roots are no longer protected by healthy gum and bone. Chronic gum disease contributes to toothache due to root sensitivities. The roots are the lower 2/3 of the teeth that are normally buried in bone. The bacterial toxins dissolve the bone around the roots and cause the gum and the bone to recede, exposing the roots. The sensitivities may be so severe that the person avoids any cold or sour foods.

Topical chemotherapy: Treatment with anticancer drugs in a lotion or cream.

Tophaceous gout: Nodular masses of uric acid crystals (tophi) are deposited in different soft tissue areas of the body. Even though tophi are most commonly found as hard nodules around the fingers, at the tips of the elbows, and around the big toe, tophi nodules can appear anywhere in the body. They have been reported in unexpected areas such as in the ears, vocal cords, or around the spinal cord! Tophaceous gout is always a result of chronic gout.

Tophi: The plural of tophus.

Tophus: A nodular mass of uric acid crystals. Tophi are characteristically deposited in different soft tissue areas of the body in gout. The word tophus comes via Latin from the Greek tophos meaning a porous volcanic stone. In chronic (tophaceous) gout, nodular masses of uric acid crystals (tophi) deposit in different soft tissue areas of the body. Even though tophi are most commonly found as hard nodules around the fingers, at the tips of the elbows, and around the big toe, tophi nodules can appear anywhere in the body. They have been reported in unexpected areas such as in the ears, vocal cords, or around the spinal cord!

Torsion dystonia: A form of dystonia known as early-onset torsion dystonia (also called idiopathic or generalized torsion dystonia) that begins in childhood around the age of 12. Symptoms typically start in one part of the body, usually in an arm or leg, and eventually spread to the rest of the body within about 5 years. Early-onset torsion dystonia is not fatal, but it can be severely debilitating. Most children with the disorder are unable to perform the simplest of motor tasks and are confined to a wheelchair by the time they reach adulthood.

Torticollis, spasmodic: Spasmodic torticollis, or torticollis, is the most common of the focal dystonias. In torticollis, the muscles in the neck that control the position of the head are affected, causing the head to twist and turn to one side. In addition, the head may be pulled forward or backward. Called wry neck.

Total hysterectomy: Complete surgical removal of the uterus and cervix. Also called a complete hysterectomy.

Toxic shock: See Toxic shock syndrome.

Toxic multinodular goiter: Condition in which the thyroid gland contains multiple lumps (nodules) that are overactive, produce excess thyroid hormones and thereby cause hyperthyroidism. This condition is also known as Parry’s disease or Plummer’s disease.

Toxic shock syndrome: A grave condition occurring predominantly in menstruating women using tampons, toxic shock is characterized by a highly toxic state (with sudden high fever, vomiting, diarrhea, muscle aching) followed by low blood pressure (hypotension) which can lead to shock (and death). There may be a rash resembling sunburn with peeling of skin. The Channing Laboratory in Boston under Dr. Edw. Kass discovered that toxic shock was due to a toxin produced by Staph (Staphylococcus) aureus bacteria growing under conditions with little or no oxygen. The syndrome occurs rarely in women not using tampons and in men.

Toxins: Poisons produced by certain animals, plants, or bacteria.

Trachea: The trachea is a tube-like portion of the breathing or "respiratory" tract that connects the "voice box" (larynx) with the bronchial parts of the lungs. It is also called the "windpipe."

Tracheoesophageal puncture: A small opening made by a surgeon between the esophagus and the trachea. A valve keeps food out of the trachea but lets air into the esophagus for esophageal speech.

Tracheostomy: Surgery to create an opening (stoma) into the windpipe. The opening itself may also be called a tracheostomy.

Tracheostomy button: A 1/2- to 1 1/2-inch-long plastic tube placed in the stoma to keep it open.

Tracheostomy tube: A 2- to 3-inch metal or plastic tube that keeps the stoma and trachea open. Also called a trach ("trake") tube.

Transcription: Making an RNA copy from a sequence of DNA (a gene). Transcription is the first step in gene expression.

Transfusion: The transfer of blood or blood products from one person to another.

Transitional cell carcinoma: Cancer that develops in the lining of the renal pelvis. This type of cancer also occurs in the ureter and the bladder.

Transfer RNA (tRNA): A class of RNA that has triplet nucleotide sequence complementary to the triplet nucleotide coding sequences of messenger RNA (mRNA). The role of tRNAs is to bond with amino acids and transfer them to the ribosomes, where proteins are assembled according to the genetic code carried by mRNA

Translation: To go from RNA to protein, translation is needed. Translation is the process by which the genetic code carried by messenger RNA (mRNA) directs the production of proteins from amino acids.

Transsexual: A person who desires or has achieved transsexualism (by having a sex change operation, etc.). A transsexual is different from a transvestite who is a person who masquerades by dressing in the clothing of the opposite sex (cross-dressing). See: Transsexualism.

Transsexualism: Consistently strong desire to change ones anatomic sex and belong to the opposite sex, to change gender and do so by all available means (including surgery, hormonal treatment, dress, and life style). "Trans-" is related to the Latin verb "transire", meaning "to pass or cross over, or pass beyond." In transsexualism, one crosses over or passes beyond ones sex to the opposite sex. Transsexualism is thus distinct from mere cross-dressing which is termed transvestism (from the Latin "vestitus" meaning "clothed"). (A publicized instance of transsexualism involved the ophthalmologist Dr. Richard Raskind who became the professional tennis player, Renée Richards, on the ladies’ tour.)

Transurethral resection: Surgery performed with a special instrument inserted through the urethra. Also called TUR.

Transvaginal ultrasound: Sound waves sent out by a probe inserted in the vagina. The waves bounce off the ovaries, and a computer uses the echoes to create a picture called a sonogram. Also called TVS.

Transvestism: Dressing in the clothing of the opposite sex. Also called cross-dressing. The prefix "trans-" relates to the Latin verb "transire", meaning "to pass or cross over, or pass beyond" while the "-vestism" stems from "vestitus" meaning "clothed." In centuries past, the Catholic Church forbade women from acting in the theater. Therefore, stage roles for females had to be played by males who dressed as females—male transvestism, at least for the duration of the performance.

Transvestite: A person who dresses in the clothing of the opposite sex, i.e., a person who cross-dresses.

Treadmill, exercise: A continuous EKG recording of the heart as the patient performs increasing levels of exercise. In addition to detecting abnormal heart rhythms (arrhythmias), the exercise treadmill is a screening test for the presence of narrowed coronary arteries that can limit the supply of oxygenated blood to the heart muscle during exercise.

Tremor: A tremor is an abnormal repetitive shaking movement of the body. Tremors have many causes and can be inherited, related to illnesses (such as thyroid disease), fever, hypothermia, drugs or fear.

Trench fever: A louse-borne disease first recognized in the trenches of World War I, again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Also called Wolhynia fever, shin bone fever, quintan fever, five-day fever, Meuse fever, His’ disease, His-Werner disease, Werner-His disease.

Treponema pallidum: The cause of syphilis, this is a microscopic bacterial organism called a spirochete, a worm-like spiral-shaped organism that wiggles vigorously when viewed under a microscope. Treponema pallidum was discovered in 1905 by the German bacteriologist Fritz Schaudinn (1871-1906) who named it, putting together the Greek trepo (I turn) and nema (thread) with the Latin pallida (pale) to make a pale turning thread.

Tricuspid valve: The heart valve between the right atrium and right ventricle. Normally allows blood to flow only from the atrium into the ventricle.

Triiodothyronine: A hormone made by the thyroid gland. The thyroid gland uses iodine to make thyroid hormones. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body. Triiodothyronine (T3) has three iodine molecules attached to its molecular structure. Iodine is found in seafood, bread, seaweed, and ordinary table salt.

Trimethylaminuria (TMA): An inborn error of metabolism associated with an offensive body odor, the smell of rotting fish, due to the excessive excretion of TMA in urine, sweat, and breath. Persons with TMA may experience tachycardia (fast heart rate) and severe hypertension (high blood pressure) after eating cheese (which contains tyramine) and after using nasal sprays containing epinephrine. TMA is caused by a mutation (change) in the gene for an enzyme, flavin-containing monooxygenase-3 (FMO3) encoded by a gene on chromosome #1. The FMO3 enzyme metabolizes tyramine (which is in cheese). The syndrome is associated with various psychosocial reactions, including social isolation, clinical depression and attempted suicide.

Trisomy 13 syndrome: Condition with three rather than the normal two chromosomes #13. Children born with this syndrome have multiple malformations and mental retardation due to the extra chromosome #13. The congenital malformations (birth defects) commonly include scalp defects, hemangiomas (blood vessel malformations) of the face and nape of the neck, cleft lip and palate, malformations of the heart and abdominal organs, and flexed fingers with extra digits. The mental retardation is profound. The IQ is untestably low. The majority of trisomy 13 babies die soon after birth or in infancy. The condition is also called Patau syndrome after the late geneticist Klaus Patau (at the University of Wisconsin) who discovered the extra chromosome in 1960.

Trisomy 18 syndrome: There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is profound with the IQ too low to even test. Nineteen out of 20 (95%) of these children die before their first birthday. The condition is also called Edwards syndrome in honor of the British physician and geneticist John Edwards who discovered the extra chromosome in 1960.

Trisomy 21 syndrome: A common chromosome disorder due to an extra chromosome number 21 (trisomy 21). The syndrome causes mental retardation, a characteristic face, and multiple malformations. It is associated with a major risk for heart problems, a lesser risk of duodenal atresia (part of the intestines not developed), and a minor but still significant risk of acute leukemia. Trisome 21 syndr0ome is also commonly called Down syndrome after the 19th century English doctor Langdon Down who was curiously enough not the first person to describe the condition, added little to knowledge and, in great error, attributed the condition to a "reversion" to the mongoloid race. The disorder was also once called mongolism, a term now considered slang.

tRNA: Transfer RNA.

Tropical typhus: See Typhus, scrub.

TSH: Stands for Thyroid Stimulating Hormone. Also known as thyrotropin.

TSI: Stands for Thyroid Stimulating Immunoglobulin. The TSI level is abnormally high in persons with hyperthyroidism (too much thyroid hormone) due to Graves’ disease. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body.

Tsutsugamushi disease: See Typhus, scrub.

T-suppressor cell: A type of immune cells, also called T8 cells, these cells close down the immune response after it has destroyed invading organisms. T8 cells are sensitive to high concentrations of circulating lymphokine hormones and release their own lymphokines after an immune response has achieved its goal, signalling all other participants to cease their attack. Some memory B-cells remain to ward off a repeat attack by the invading organism.

Tubes, Fallopian: The Fallopian tubes normally transport the egg of the female from the egg sac, or ovary, to the womb, or uterus. Normal tubes have small hair like projections on the lining cells called cilia. These cilia are important to movement of the egg through the fallopian tube and into the uterus. If the tubal cilia are damaged by infection, the egg may not get ‘pushed along’ normally and can settle in the tube. Likewise, if infection causes partial blockage of the tube with scar tissue, this can also act to prevent the egg from getting to the uterus. Any process that narrows the tube and thus decrease the caliber of the passage way can increase the chance of an ectopic pregnancy. Examples of these would be endometriosis, tumors, or scar tissue in the pelvis (pelvic adhesions) that cause twisting or chinking of the tube.

Tumor: An abnormal mass of tissue. A classic sign of inflammation. Tumors can be benign or malignant.

Tumor debulking: Surgically removing as much of the tumor as possible.

Tumor markers: Substances found in abnormal amounts in the blood, in other body fluids, or in tumor tissue of some patients with certain types of cancer. Examples are alphafetoprotein (AFP), human chorionic gonadotropin, and lactate dehydrogenase (LDH).

Tumor registry: Recorded information about the status of patients with tumors. Although a registry was originally the place (like Registry House in Edinburgh) where information was collected (in registers), the word registry has also come to mean the collection itself. A tumor registry is organized so the data can be analyzed. For example, analysis of data in a tumor registry maintained at a hospital may show a rise in lung cancer among women.

Tunica albuginea: The whitish membrane within the penis that surrounds the spongy chambers (corpora cavernosa) in the penis and which helps to trap the blood in the corpora cavernosa, thereby sustaining erection of the penis. The term comes straight from the Latin tunica (covering or coat) + albuginea (white) = a covering that is white, like the white (albumen) of an egg.

Tunica albuginea: Literally, the white coat. In anatomy, a dense white fibrous covering.

Tunica albuginea of the testis: The layer of dense whitish inelastic tissue that surrounds the testis.

Turner-Kieser syndrome: See nail-patella syndrome (Turner in 1933 described two families with the disease. The name Turner is more closely associated with the XO syndrome).

Tympanic membrane: Just the ear drum.

Tympanoplasty: A surgical operation to correct damage to the middle ear and restore the integrity of the ear drum. Tympano- comes from the Greek tympanon meaning drum.

Tympanum: The anatomic name for the cavity of the middle ear which is separated from the outer ear by the ear drum.

Tympany: A hollow drum-like sound produced when a gas-containing cavity is tapped sharply. Tympany is heard if the chest contains free air(pneumothorax) or the abdomen is distended with gas.

Typist’s cramp: A dystonia that affects the muscles of the hand and sometimes the forearm and only occurs during handwriting. Similar focal dystonias have also been called writer’s cramp, pianist’s cramp, musician’s cramp, and golfer’s cramp.

Typhus, African tick: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (tache noire) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash. Also called fièvre boutonneuse.

Typhus, classic: See Typhus, epidemic.

Typhus, endemic: See Typhus, murine.

Typhus, epidemic: A severe acute disease with prolonged high fever up to 40° C (104° F), intractable headache, and a pink-to-red raised rash. The cause is a microorganism called Rickettsia prowazekii. It is found worldwide and is transmitted by lice. The lice become infected on typhus patients and transmit illness to other people. The mortality increases with age and over half of untreated persons age 50 or more die. Also called European, classic, or louse-borne typhus and jail fever.

Typhus, European: See Typhus, epidemic.

Typhus, louse-borne: See Typhus, epidemic.

Typhus, mite-borne: See Typhus, scrub.

Typhus, murine: An acute infectious disease with fever, headache, and rash, all quite similar to, but milder than, epidemic typhus, caused by a related microoganism, Rickettsia typhi (mooseri), transmitted to humans by rat fleas (Xenopsylla cheopis). The animal reservoir includes rats, mice and other rodents. Murine typhus occurs sporadically worldwide but is more prevalent in congested rat-infested urban areas. Also known as endemic typhus, rat-flea typhus, and urban typhus of Malaya.

Typhus, Queensland tick: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.

Typhus, scrub: A mite-borne infectious disease caused by a microorganism, Rickettsia tsutsugamushi, characteristically with fever, headache, a raised (macular) rash, swollen glands (lymphadenopathy) and a dark crusted ulcer (called an eschar or tache noire) at the site of the chigger (mite larva) bite. This disease occurs in the area bounded by Japan, India, and Australia. Known also as Tsutsugamushi disease, mite-borne typhus, and tropical typhus.

Typhus, rat-flea: See Typhus, murine.

Typhus, tick: Rocky Mountain spotted fever (RMSF), an acute febrile (feverish) disease initially recognized in the Rocky Mountain states, caused by Rickettsia rickettsii transmitted by hard-shelled (ixodid) ticks. Occurs only in the Western Hemisphere. Anyone frequenting tick-infested areas is at risk for RMSF. Onset of symptoms is abrupt with headache, high fever, chills, muscle pain. and then a rash .The rickettsiae grow within damaged cells lining blood vessels which may become blocked by clots. Blood vessel inflammation (vasculitis) is widespread Early recognition of RMSF and prompt antibiotic treatment is important in reducing mortality. Also called spotted fever and tick fever.

Typhus, tropical: See Typhus, scrub.

Typhus, urban. of Malaysia: See Typhus, murine.