trichomoniasis Infection with the parasite Trichomonas vaginalis. The infection is sexually transmitted, and the vagina is the most common site of infection in women, while the urethra (urine canal) is the most common site of infection in men. Most men with trichomoniasis have no signs or symptoms; however, some men may have an irritation inside…
trichotillomania Compulsive hair pulling. An impulse control disorder characterized by the repeated urge to pull out scalp hair, eyelashes, eye brows, or other body hair. Treatment may include cognitive-behavior therapy and medications.
tricuspid Having three flaps or cusps. For example, the aortic valve and the tricuspid valve in the heart each have three cusps.
tricuspid valve One of the four heart valves, the first one that blood encounters as it enters the heart. The tricuspid valve stands between the right atrium and the right ventricle, and it allows blood to flow only from the atrium into the ventricle.
tricyclic antidepressant One of a family of medications that affect the neurotransmitters norepinephrine, serotonin, and acetylcholine. The tricyclic antidepressants are used to treat clinical depression, fibromyalgia, and other pain conditions.
trigeminal nerve The chief nerve of sensation for the face, which is also the motor nerve that controls the muscles used for chewing. Problems with the sensory part of the trigeminal nerve result in pain or loss of sensation in the face. Problems with the motor root of the trigeminal nerve result in deviation of…
trigeminal neuralgia Inflammation of the trigeminal nerve (the fifth cranial nerve) that most commonly causes paroxysms of very intense lightning pain in the areas of the face that the nerve supplies—the lips, eye, nose, scalp, forehead, gums, cheek, and chin—on the involved side of the face. Triggers for attacks can include touching the face, brushing…
triglyceride The major form of fat, which consists of three molecules of fatty acid combined with one molecule of the alcohol glycerol. Triglycerides serve as the backbone of many types of lipids (fats). Triglycerides come from food and are also produced by the body. See also triglyceride test.
triglyceride test A simple blood test to measure the level of triglycerides in the blood. Triglyceride levels are influenced by recent fat and alcohol intake, so a person being tested should fast from food and alcohol for at least 12 hours before being tested. The normal level of triglycerides depends on the age and sex…
triiodothyronine A hormone that is made by the thyroid gland. Triiodothyronine has three iodine molecules attached to its molecular structure. It is the most powerful thyroid hormone, and it affects almost every process in the body, including body temperature, growth, and heart rate. Also known as T3 and liothyronine.
trimester In obstetrics, one of the three divisions of three months each during pregnancy, in which different phases of fetal development take place. The first trimester is a time of basic cell differentiation. The second trimester is a period of rapid growth and maturation of body systems. A secondtrimester fetus that is born prematurely may…
trimethylaminuria See fish-odor syndrome.