Lab Test Glossary

Lab Test Glossary T

Testosterone: Testosterone is the primary male sex hormone, controlling male sexual development. Testosterone levels increase during puberty to an adult peak but may decrease in the elderly male. In women, testosterone levels are 5% to 10% of those in males. Only 2% to 3% of testosterone is circulating in the blood as free testosterone, with the rest bound to sex hormone binding globulin and albumin. Testosterone levels may be increased with gonadal and adrenal tumors, use of androgens (also called anabolic steroids), adrenal hyperplasia and polycystic ovarian syndrome. Decreased testosterone levels occur in hypogonadism, hypopituitarism, orchiectomy, estrogen therapy and some genetic diseases. Additionally, low testosterone levels are associated with obesity, which, in turn, is linked to insulin resistance, type 2 diabetes, and the metabolic syndrome.
Tetanus Toxin IG Antibody: Tetanus, also known as lockjaw, is caused by tetanospasmin (tetanus toxin); a powerful protein toxin produced by the bacterium Clostridium tetani. Immunity to tetanus toxin is induced only by immunization, as previous tetanus exposure does not result in protection against further attacks. Immunization against the tetanus toxin is a very effective preventative measure.
Thrombopoietin (TPO): Thrombopoietin (TPO) is the most potent cytokine protein involved in platelet cell production. Platelets are a type of cell involved in the blood clotting process. TPO increases both the size and number of megakaryocytes (cells that are broken down to create platelets). TPO is produced mainly by the liver, but also by the kidneys. It levels rise in response to an increased need for platelets.
Thyroglobulin IG Antibody: Although there are several causes of hypothyroidism, a relatively common cause is autoimmune thyroiditis (Hashimoto?s thyroiditis). In this condition, one or more antibodies directed against the thyroid gland eventually result in hypothyroidism. The two most common thyroid auto-antibodies seen in people with hypothyroidism are thyroid microsomal antibody (also known as thyroid peroxidase antibody) and thyroglobulin antibody. People with elevated levels of both thyroglobulin antibody levels and thyroid stimulating hormone (TSH) progress to overt hypothyroidism at a rate of 3% to 5% per year.
Thyroglobulin Antigen: Thyroglobulin is a protein that binds to thyroxine (T4). Its levels may be elevated in inflammatory conditions of the thyroid as well as in thyroid cancer. Thyroglobulin levels may also be elevated in Graves’ disease, goiter and thyroiditis. Serum thyroglobulin levels are particularly useful in thyroid cancer monitoring, since levels rise with localized or metastatic thyroid cancers and fall after thyroid removal and other types of therapy
Thyroid Microsomal IG Antibody: Although there are several causes of hypothyroidism, a relatively common cause is autoimmune thyroiditis (Hashimoto's thyroiditis). In this condition, one or more antibodies directed against the thyroid gland eventually result in hypothyroidism. The two most common thyroid autoantibodies seen in people with hypothyroidism are thyroid microsomal antibody (also known as thyroid peroxidase antibody) and thyroglobulin antibody. People with elevated levels of both thyroid microsomal antibodies and thyroid stimulating hormone (TSH) progress to overt hypothyroidism at a rate of 3% to 5% per year.
Thyroid Stimulating Hormone (TSH): Thyroid stimulating hormone (TSH) is produced in the pituitary gland and stimulates the thyroid to secrete T4 and T3 thyroid hormones. Abnormal levels of TSH may indicate various thyroid and pituitary gland conditions. Low levels of TSH may result in high levels of T4 and T3 (primary hyperthyroidism), while excess levels of TSH can result in low levels of T4 and T3 (primary hypothyroidism). TSH is a sensitive marker for monitoring the effects of thyroid hormone replacement therapy.
Thyroxine (T4): Thyroxine (T4) is the most abundant hormone produced by the thyroid gland and plays an important role in the control of metabolism. Increased levels are seen with Graves’ disease (hyperthyroidism), toxic multinodular goiter, thyroiditis and (rarely) thyroid cancer. Decreased levels may result from thyroiditis, hypothryroidism, pituitary dysfunction, hypothalamic disease, or the use of certain medications.
Thyroxine IG Antibody (T4 Ab): The thyroxine antibody test measures antibodies to thyroxine (T4) thyroid hormone. T4 plays an important role in the control of metabolism. Autoantibodies to T4 can alter the results of the T4 test and may indicate an underlying autoimmune condition.
Thyroxine Binding Globulin (TBG): In the bloodstream, thyroxine (T4) is bound to thyroxine binding globulin (TBG). The most common causes for an increased TBG level are increased estrogen; liver disease; drugs such as tamoxifen, perphenazine and methadone; and familial or genetic causes. Determination of TBG levels is useful when total thyroid hormone levels do not correlate with the thyro- metabolic status, as in pregnancy, contraceptive steroid use or hereditary excesses or deficiencies of TBG.
Tissue Factor (TF): Tissue factor (TF) is a receptor protein that behaves like a cytokine (a cell signaling molecule). It is involved in blood coagulation and helps to signal other cells involved in inflammatory reactions. Levels of TF may be elevated in cancer and certain inflammatory conditions.
Tissue Inhibitor of Metalloproteinase 1 (TIMP-1): Tissue inhibitors of metalloproteinases (TIMPs) block the activity of matrix metalloproteinases (MMPs). MMPs are enzymes that break down structural proteins and connective tissue such as collagens, proteoglycans, gelatin, fibronectin, laminin, and elastin under both normal and disease conditions. It is believed that levels of TIMPs and MMPs should be balanced for good health.
Tissue Transglutaminase IG Antibody (TTG Ab): The presence of antibodies against tissue transglutaminase is associated with celiac disease, a digestive condition associated with poor absorption of nutrients. Symptoms include abdominal pain, constipation, diarrhea and bloating. Celiac disease occurs most often in childhood and in the third to fifth decades of life, but can develop at any age. The typical presentation is malabsorption, but subclinical disease, particularly in adults, can be intestinal or extraintestinal and can include symptoms similar to irritable bowel syndrome, including bloating, abdominal pain, constipation or diarrhea. Other symptoms can include anemia, fatigue, dyspepsia, infertility, miscarriages, bone pain, tooth enamel defects, oral ulcers, elevated aminotransferases and neurologic or neuropsychiatric manifestations. Although many patients present with multiple symptoms, it is not uncommon for a patient to have a single sign or symptom.
Total Protein: Total protein is a measure of the total protein content in the blood. Total protein levels are used in the evaluation of nutritional status, nephrotic (kidney) syndromes, malabsorption, and cancers including myeloma. Protein levels may be elevated due to dehydration, vomiting, diarrhea, Addison’s disease, diabetic acidosis, or muliple myeloma. They are decreased in nephrotic syndrome, salt retention syndromes, severe burns, extensive bleeding, pregnancy, intestinal malabsorption, and severe protein starvation (kwashiokor).
Toxoplasma Ggondii IGM Antibody (t. gondii Ab): Toxoplasmosis is a common infectious disease, caused by the Toxoplasma gondii (T. gondii) parasite. It may be fatal to immounocompromised patients. In healthy individuals, it causes only mild symptoms. Antibodies against the parasite that causes toxoplasmosis indicates recent infection or exposure to this parasite. Acute toxoplasmosis in pregnant women can result in severe damage or death to the fetus.
Triglycerides: Triglycerides are common fats found in the food we eat and in our bodies. High blood levels of triglycerides are related to dietary intake as well as metabolic factors. Triglycerides are often measured as a reflection of fat ingestion and metabolism or as part of an evaluation of coronary risk factors. High triglyceride levels appear to be associated with an increased risk of cardiovascular events, particularly in conjunction with other risk factors. High triglyceride levels may occur in cirrhosis, chronic renal insufficiency, familial hyperlipoproteinemia (rare), acute myocardial infarction, hypothyroidism, diabetes mellitus, Cushing’s syndrome, nephrotic syndrome, glycogen storage disease and pancreatitis. Low levels may indicate malabsorption syndrome, malnutrition, or abetalipoproteinemia.
Triiodothyronine (t3): Triidothyronine (T3), a hormone produced by the thyroid gland, is important to regulation of many components of body metabolism. Elevated T3 levels in conjunction with elevated thyroxine (T4) levels and decreased thyroid stimulating hormone (TSH) may indicate hyperthyroidism. Elevated T3 levels can also be seen with pregnancy, hepatitis and other thyroid diseases. Decreased T3 levels in conjunction with decreased T4 levels and increased TSH levels may indicate hypothyroidism. Decreased T3 levels can also be seen with pituitary insufficiency, hypothalamic failure, protein malnutrition and liver diseases.
Triiodothyronine IG Antibody (T3 Ab): This test measures antibodies to triidothyronine (T3) thyroid hormone. T3 is important to regulation of many components of body metabolism. Autoantibodies to T3 can alter the results of the T3 test and may indicate an underlying autoimmune condition.
Trypanosoma Cruzi IGM Antibody (T. Cruzi Ab): Trypanosoma cruzi (T. cruzi) is an infectious parasite that can cause Chagas disease or American trypanosomiasis. This is relatively common in South America and other developing regions, but rare in the United States. The presence of IGM antibodies against T. cruzi indicates recent exposure to or infection with T. cruzi.
Tumor Necrosis Factor Alpha (TNF-Alpha): Tumor necrosis factor alpha (TNF-alpha) is produced by various white blood cells. Levels of TNF-alpha may be elevated in some cancers (especially lung cancer and certain leukemias) and some inflammatory conditions. TNF-alpha is also found in the joint fluid of arthritis patients. Clinical trials investigating TNF-alpha as a cancer treatment option are underway, however, they have yet to demonstrate significant efficacy.
Tumor Necrosis Factor Beta (TNF-beta): Tumor necrosis factor beta (TNF-beta) is produced by white blood cells and promotes the generation of cells involved in wound healing. TNF-beta may also inhibit the growth of some cancers by decreasing their production of new blood vessels. Levels of TNF-beta may be elevated in certain infections, especially meningococcal septicemia, and some tumors. TNF-beta may have therapeutic benefits in the treatment of some cancers and other conditions, however, research and clinical applications are only in the initial stages.
Tumor Necrosis factor Receptor 2 (TNF r2): Tumor necrosis factor receptor 2 (TNF R2) is involved in the destruction of various types of normal and abnormal proteins. Low levels of TNF R2 are associated with cancer of the kidney.
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