T cell

see T-lymphocyte

T-cell leukaemia

a type of leukaemia caused by a virus in which T-lymphocytes divide uncontrollably


a type of white blood cell that fights infections and destroys abnormal cells directly; as compared with releasing antibodies to fight infection

T-lymphocyte killer cell

a type of T-lymphocyte white blood cell that attaches to abnormal cells and releases chemicals that destroy them


a rapid heart rate (over 100 beats per minute)


a parasitic worm that lives in the intestines; causes diarrhoea and abdominal discomfort


the sticky, brown substance in cigarettes that coats the lungs; causes lung and other cancers


a procedure in which the eyelids are sewn shut; performed to protect the corneas


the hard deposit formed on teeth when mineral salts in saliva combine with plaque; can cause dental problems such as gum disease if not controlled

Tay-Sachs disease

a severe genetic disorder that causes nervous system disturbances and death, usually before the age of 3


see Tuberculosis

Tear duct

a tiny passageway that drains lubricating tears from the surface of the eye to the back of the nose


redness of an area of skin, caused by enlargement and proliferation of the underlying small blood vessels

Temperature method

a natural method of family planning in which a woman determines her time of ovulation by changes in her daily temperature

Temporal arteritis

inflammation and narrowing of arteries in the head and neck, including those in the scalp near the temple, which can cause blindness if untreated

Temporomandibular joint syndrome

headache, facial pain, and jaw tenderness caused by irregularities in the way the joints, muscles, and ligaments in the jaw work together


inflammation of a tendon, usually caused by injury, characterised by pain, tenderness, and sometimes limited movement in the attached muscle


strong connective tissue cords that attach muscle to bone or muscle to muscle

Tendon transfer

surgical cutting and repositioning of a tendon so that the muscle attached to it has a new function

Tennis elbow

a form of tendinitis that causes pain and tenderness in the elbow and forearm


inflammation of the inner lining of the sheath that covers a tendon


inflammation of the fibrous wall of the sheath that covers a tendon


see Transcutaneous electrical nerve stimulation

Tension headache

a headache caused by emotional strain or tension in the muscles of the head and neck


anything that causes abnormalities in a developing embryo or foetus, such as a drug or virus


a tumour composed of cells not normally found in the part of the body when the tumour occurred


the two male sex organs that produce sperm and the sex hormone testosterone

Testicular feminisation factor

a genetic disorder in which an individual who is genetically male has the external appearance of a female because the body is unresponsive to testosterone

Testicular torsion

severe pain and swelling of a testicle, due to twisting of the spermatic cord


the sex hormone that stimulates development of male sex characteristics and bone and muscle growth; produced by the testicles and in small amounts by the ovaries


a sometimes fatal disease affecting the brain and spinal cord; caused by infection with bacterium present in soil and manure


a group of antibiotic drugs used to treat a wide variety of infections, including bronchitis and some types of pneumonia

Tetralogy of Fallot

a genetic heart disease involving four structural defects in the heart, which result in insufficient levels of oxygen in the blood


a structure in the brain that relays and processes incoming sensory information from the eyes and ears and from pressure and pain receptors


a group of genetic blood disorders characterised by a defect in the ability to produce haemoglobin, leading to the rupturing of red blood cells (called haemolytic anaemia)

Thallium scanning

a type of radionuclide scanning used to assess the heart

Therapeutic range

the range of doses of a drug that will produce beneficial results without side effects


examination of the membranes covering the lungs using an endoscope


a procedure in which the chest is surgically opened to operate on an organ in the chest cavity


the chest


a vibration felt when the hand is placed flat on the chest; caused by abnormal blood flow through the heart as a result of disease


removal of a blood clot

Thrombocytopenic purpura

a decrease in the number of platelets in the blood, causing abnormal bleeding of blood vessels into the skin


blockage of a blood vessel by a blood clot fragment that has broken off and travelled from another area of the body


inflammation of a vein, along with clot formation in the affected area


a condition in which a blood clot (thrombus) has formed inside a blood vessel


a blood clot in a blood vessel


a candidiasis infection


a tumour of the thymus gland

Thymus gland

an immune system gland located in the upper part of the chest that plays an important role in the production of T-lymphocytes


Thyroglobulin is a protein contained in abundance within the thyroid gland from which the hormone thyroxine is manufactured. It contains tyrosine molecules, which when bound to 4 iodine atoms form thyroxine (T4).

Thyroglossal cyst

a swelling at the front of the neck; forms from a duct that fails to disappear during embryonic development

Thyroid antibodies

Thyroid antibodies are immunological weapons that target different proteins in the thyroid gland as part of an autoimmune disease such as Hashimoto’s disease or Graves' disease, where the immune system turns itself onto the body’s own tissues.

Thyroid gland

They thyroid gland is located in the front of the neck below the voice box and plays an important role in metabolism whereby oxygen and calories are converted to energy. The thyroid gland is responsible for producing thyroid hormones Thyroxine (T4) and Triiodothyronine (T3).

Thyroid nodule

Thyroid nodules are very common, especially in people over the age of 60. They are caused when there is abnormal growth of thyroid cells which cause lumps on the thyroid gland. The vast majority of thyroid nodules are benign but a small proportion are cancerous. Normally a thyroid nodule will be investigated through a biopsy. Sometimes thyroid nodules can affect swallowing and breathing, but normally they do not produce any symptoms.

Thyroid Peroxidase

Thyroid peroxidase is an enzyme found within the thyroid gland which is essential for thyroxine hormone production. It converts iodide (which arrives at the thyroid gland in the bloodstream) to iodine which in turn gets bound to tyrosine to form thyroxine.

Thyroid Stimulating Hormone (TSH)

Thyroid Stimulating Hormone (TSH) is produced in the pituitary gland at the base of our brains to stimulate thyroid hormone production. If blood levels of thyroid hormones are high, the pituitary signals the thyroid to stop production, whereas if thyroid hormone levels are low it will signal to increase production. TSH is often measured as a proxy for thyroid hormones.

Thyroid storm

A thyroid storm is caused by extreme hyperthyroidism. Symptoms include rapid heartbeat, raised blood pressure, exhaustion and fever. It is caused by under-treated or untreated hyperthyroidism and can often be fatal.


"Itis" simply means inflammation. Thyroiditis is inflammation of the thyroid gland.


A toxic condition resulting from over-activity of the thyroid gland.

Thyroxine (T4)

Thyroxine is also known as T4 and is the predominant hormone produced by the thyroid gland. It is known as T4 because it uses 4 atoms of iodine (from the food we eat). Thyroxine isn't active in our cells and must convert to Triiodothyronine (T3), the active thyroid hormone, before it can influence our body's metabolism.


see Transient ischemic attack


the thicker of the two long bones in the lower leg; commonly called the shin


an involuntary, repetitive movement such as a twitch

Tic douloureux

see Trigeminal neuralgia


small, eight-legged animals that can attach to humans and animals and feed on blood; sometimes spread infectious organisms via their bites

Tietze's syndrome

inflammation of the cartilage that joins ribs to the breastbone, causing chest pain


a group of common infections occurring on the skin, hair, and nails that are caused by a fungus; commonly referred to as ringworm


a persistent ringing or buzzing sound in the ear

Tipped uterus

an abnormal condition in which the uterus is tilted backward instead of slightly forward

Tissue plasminogen activator

a substance produced by the body and as a genetically engineered drug to prevent abnormal blood clotting

Tissue transglutaminase (tTG)

Tissue transglutaminase (tTG) is an enzyme responsible for joining proteins and is a marker for coeliac disease. High levels are seen in coeliac disease but these reduce and even disappear once the coeliac disease has been treated by excluding gluten in the diet.

Tissue typing

tests used to determine the compatibility of tissues used in grafts and transplants

TMJ syndrome

see Temporomandibular joint syndrome


decreased sensitivity of the body to a certain drug, usually either because the liver becomes more efficient at breaking down the drug or the body's tissues become less sensitive to it; increased tolerance creates a need for a higher dose of the drug in order to have the same effects


the procedure used to measure the pressure within the eye; is useful in detecting glaucoma


surgical removal of the tonsils, usually to treat tonsillitis


infection and inflammation of the tonsils


masses of lymphoid tissue located at either side of the back of the throat

Tourette's syndrome

a movement disorder characterised by involuntary tics and noises, and in some cases uncontrollable shouting of obscenities


a device placed tightly around an arm or leg in order to stop blood flow; can be used to locate veins in order to take a blood sample or to control blood flow during some operations


the presence of bacterial toxins in the blood

Toxic epidermal necrolysis

a severe rash in which the outer layers of skin blister and peel off

Toxic shock syndrome

a life-threatening condition caused by a staphylococci toxin


the extent to which a substance is poisonous


a poisonous substance


human infestation with the larvae of a worm found in the intestines of dogs


a common protozoan infection that is usually only dangerous to a foetus in early pregnancy or a person who is immunocompromised


see Tissue plasminogen activator


the tube running from the larynx (the voice box) down the neck and into the upper part of the chest, where it divides to form the two bronchi of the lungs; commonly called the windpipe


inflammation of the trachea


insertion of a tube through a surgical opening in the trachea to maintain an open airway


a persistent, contagious form of conjunctivitis that can lead to complications such as blindness if untreated


the use of tension to hold a body part in place or to correct or prevent an alignment problem


through the skin

Transcutaneous electrical nerve stimulation

a method of relieving pain by applying tiny electrical impulses to nerve endings beneath the skin


a substance in the blood that transports iron throughout the body

Transient ischemic attack

a temporary block in the supply of blood to the brain, resulting in temporary loss of sensation, movement, vision, or speech; often called mini-strokes and can be precursors to a real stroke


able to be passed from one organism to another


transferring a healthy tissue or organ to replace a damaged tissue or organ; also refers to the tissue or organ transplanted

Transurethral prostatectomy

removal of cancerous tissue from the prostate gland using a resectoscope (a long, narrow instrument passed up the urethra), which allows the surgeon to simultaneously view the prostate and cut away the cancerous tissue


physical injury or emotional shock

Travellers' diarrhoea

diarrhoea when travelling in a foreign country, caused by contaminated food or water


an involuntary, rhythmic, shaking movement caused by alternating contraction and relaxation of muscles; can be the normal result of age or the abnormal effect of a disorder


a system used to classify sick or injured people according to the severity of their conditions


growth of the eyelashes inward toward the cornea, causing persistent irritation of the eyeball


infestation by the larvae of the parasitic worm Trichinella spiralis, usually acquired by eating undercooked pork


infection of the vagina by the single-celled parasite Trichomonas vaginilis, which may cause inflammation, itchiness, and discharge from the vagina

Tricuspid valve

the valve located between the two left chambers of the heart (the left atrium and the left ventricle)

Tricyclic antidepressants

drugs used in the treatment of clinical depression

Trigeminal neuralgia

a disorder of the trigeminal nerve (a cranial nerve) that causes brief attacks of severe pain in the lips, cheeks, gums, or chin on one side of the face


the main form of fat in the blood; determining levels of triglyceride is useful in diagnosing and treating diabetes, high blood pressure, and heart disease

Triiodothyronine (T3)

Triiodothyronine (T3) is a potent thyroid hormone which governs metabolism in our body's cells. The thyroid gland produces some triiodothyronine, but most of is derived from thyroxine (T4) which loses an atom of iodine to become T3.


one of three periods lasting about 3 months each; the stages into which pregnancy is divided

Triple X syndrome

the presence of an extra X chromosome in a woman, which may cause some degree of mental retardation


the medical term for lockjaw


the presence in the cells of three copies of a certain chromosome instead of the normal two copies

Trisomy 21

see Down syndrome

Tubal ligation

a procedure in which the fallopian tubes are cut and tied off; usually a permanent form of sterilisation

Tubal pregnancy

a pregnancy that occurs in the fallopian tubes, with a fertilised egg implanting in the tube instead of the uterus; severely painful and can be fatal if not detected and treated

Tuberculin test

skin tests performed to determine previous infection with tuberculosis; can help rule out the possibility of being currently infected with tuberculosis


an infectious bacterial disease transmitted through the air that mainly affects the lungs

Tuberous sclerosis

a genetic disorder of the skin and nervous system characterised by epilepsy, mental retardation, and a skin condition resembling acne


surgical repair of a damaged fallopian tube to treat infertility


an abnormal mass that occurs when cells in a certain area reproduce unchecked; can be cancerous (malignant) or noncancerous (benign)

Tunnel vision

loss of peripheral vision so that only objects directly ahead can be seen; most commonly due to damage caused by increased pressure within the eye (glaucoma)

Turner's syndrome

a genetic disorder in women in which only one X chromosome is present, or both chromosomes are present but one is defective

Tympanic membrane

the medical term for the eardrum


a surgical procedure used to treat hearing loss in which the eardrum or structures in the middle ear are repaired

Typhoid fever

an acute bacterial infection causing fever, headache, abdominal discomfort, and enlargement of the liver and spleen


a group of diseases caused by the micro-organism rickettsia, spread by the bites of fleas, mites, or ticks; symptoms include headache, fever, rash, and a series of complications if untreated

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