Medical Dictionary: T

T cells: A family of lymphocytes. Some T cells are directly involved in fighting a pathogen. Memory T cells stimulated during an immune response retain a memory of the pathogen as insurance against future attacks. Helper T cells play a prominent roll in the allergic response.

tachycardia: An abnormally fast heart rate that tops 100 beats per minute. It can be a sign of

tarsal coalition: An inherited condition in which two bones of the foot are fused together; can result in rigid flat feet.

TDD: Telecommunications device for the deaf. Machinery that allows a hearing-impaired person to send and receive typed messages over the telephone.

tendinitis: Inflammation of a tendon, usually caused by injury, that may cause pain and restrict movement of the muscle attached to the tendon.

tendon: A tough, fibrous band of tissue that attaches muscle to bone.

tendonitis: Inflammation of a tendon, usually caused by injury, which may restrict movement of the muscle attached to the tendon.

tenosynovitis: swelling and inflammation of the tendon sheath, which decreases the sheath’s production of synovial fluid.

tension headache: A headache, usually mild or moderate in intensity, not accompanied by other symptoms; pain is usually felt throughout the head, across the forehead, or in the back of the head.

thalamus: A brain structure located just above the hippocampus that is crucial for integrating and relaying sensory information throughout the brain and has a role in memory consolidation.

thrombolytic agents: Agents or medications that dissolve blood clots and restore blood flow through a blocked artery; used to treat heart attack and stroke. Also called “clot busters.” One example is recombinant tissue plasminogen activator.

thrombus: A blood clot that has formed inside an intact blood vessel.

thunderclap headache: A sudden, excruciating headache that may be the result of bleeding in the head.

thymus: A primary organ of the lymph system located in the upper-middle chest. Home to maturing T cells; hence the “T” in their name.

thyroidectomy: A surgical procedure to remove all or part of the thyroid.

thyroiditis: Inflammation of the thyroid. Types of thyroiditis include Hashimoto’s thyroiditis, subacute thyroiditis, and postpartum or silent thyroiditis.

thyroid-stimulating hormone (TSH): A hormone secreted into the bloodstream by the pituitary gland that stimulates the thyroid gland. The amount of hormone produced by the thyroid gland depends on how much TSH is in the blood. Doctors measure levels of TSH to determine whether a person’s thyroid hormone levels are normal.

thyrotoxicosis: The presence of too much thyroid hormone in the body. This may be caused by an overproductive thyroid, inflammation of the thyroid, or taking too much thyroid hormone.

thyroxine (T4): One of two types of major thyroid hormone manufactured by the thyroid gland. It contains four iodine atoms.

tibia: The shinbone; the large bone of the calf.

tincture: An herbal product made by soaking an herb in a mixture of water and alcohol to extract certain constituents. The strength is then noted as a ratio of the percent of herbal product used to the amount of alcohol or water.

tinea pedis: Athlete’s foot.

tinnitus: A ringing in the ears or some other sound that has no external cause.

tolerable upper intake level (UL): The highest amount of a nutrient deemed likely to have no harmful health effects for almost all healthy people when taken consistently. When people take more than the UL, the risk for ill effects rises along with the dose.

tonic: An agent believed to invigorate a specific body organ.

tonometry: A glaucoma screening test that measures pressure inside the eye.

toxic nodular goiter: An enlarged thyroid gland with nodules that produce excess thyroid hormone. This type of goiter is to blame for hyperthyroidism in many people over 60.

toxoid vaccines: Vaccines that protect against harmful bacterial toxins. These vaccines contain toxins that have been detoxified and rendered inactive.

trabecular bone: Bone tissue arranged in a meshwork of thin plates or beams that is commonly found at the center of long bones and that composes a large part of the hip and vertebrae. Also called cancellous bone or spongy bone.

trans fatty acids (trans fats): Unhealthy fats that occur naturally in meat but come mainly from processed foods made with hydrogenated oils. Hydrogenated oils are polyunsaturated fats that have been chemically altered to be made more like saturated fats. These processed fats are solid at room temperature and are often found in commercial baked goods. They have an unhealthy effect on blood lipid levels.

transcranial Doppler scanning: An ultrasound technique that makes images of the major arteries at the base of the brain.

transcutaneous electrical nerve stimulation (TENS): The use of low-voltage electrical currents to treat pain. The electric current prevents pain signals traveling through small nerve fibers from reaching the brain.

transient ischemic attack (TIA): A brain attack that resolves within 24 hours; often the first sign of an impending stroke, but may cause damage on its own.

transient pain: Minor, fleeting pain.

transrectal ultrasonography (TRUS): A procedure that uses sound waves to create an image of the prostate as a means of detecting cancer. Sound waves are directed to the prostate from a probe inserted in the rectum.

transurethral incision of the prostate (TUIP): An operation used to treat BPH in which incisions are made in the prostate tissue to relieve pressure on the urethra and alleviate urinary difficulties.

transurethral microwave thermotherapy (TUMT): A heat therapy for BPH that uses microwaves to destroy prostate tissue that obstructs urine flow.

transurethral needle ablation (TUNA): A procedure that uses radio waves to heat and destroy prostate cells obstructing the urethra.

transurethral resection of the prostate (TURP): The most common procedure for BPH, in which excess prostate tissue is cut away.

transverse processes: The ringlike projection on each side of a vertebra to which muscles and ligaments are attached and, in the chest area, to which the ribs are connected.

tricyclic antidepressants (TCAs): A class of medications that are thought to work by increasing the availability of serotonin and norepinephrine to nerve cell receptors.

trigger point: A tender area that, when stimulated, also elicits pain elsewhere in the body — such as the arm, the shoulder, or another area of the neck.

trigger: Anything that can set off asthma symptoms.

triglyceride: The primary type of fat in the body and in the diet, formed from three fatty-acid molecules and one glycerol molecule. This fat can raise the risk for heart disease when elevated.

triiodothyronine (T3): One of two types of major thyroid hormone manufactured by the thyroid gland. It contains three iodine atoms. Outside the thyroid gland, the liver and other organs convert T4 to T3.

triptans: A class of medications that work by constricting blood vessels in the head and perhaps by inhibiting inflammation.

trochlea: A groove in front of the femur where the patella moves as the knee bends and straightens.

trust: A legal entity in which assets are gathered during a person’s lifetime. That person may control distributions directly or through trustees elected to carry out wishes at a time or point specified. After death, remaining assets are distributed to beneficiaries.

tumor: An abnormal growth of cells. It can be benign or malignant.

tympanic membrane: The eardrum.

tympanometry: A diagnostic test involving a probe that sends sound waves to the eardrum to help determine if the person’s hearing loss is due to a problem in the middle ear. Also known as impedance testing.

type 1 diabetes: An autoimmune disorder in which the pancreas stops producing insulin.

type 2 diabetes: A disorder in which the body can’t use insulin effectively.