Glossary T

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Glossary T
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Telangiectasias

Small enlarged blood vessels near the surface of the skin 1 to 3 mm in width and several mm to centimeters in length.

Teratogen

Anything that can cause a birth defect such as a maternal condition (diabetes, PKU) , a drug (alcohol), a medication (valproic acid, isotretinoin) , an infectious agent (toxoplasmosis, cytomegalovirus) or a physical agent (ionizing radiation).

Testicle (Testis)

Either of the two male reproductive organ found in the pouch (scrotum) below the penis. The testicles produce sperm and sex hormones.

Testosterone

A steroid hormone produced by the Leydig cells of the testicles (and to a lesser extent the ovaries and adrenal glands) that promotes the development of secondary male sexual characteristics.

Normal Values
Male: 10 - 35 nmol/L (3 - 10 ng/mL)
Female: Less than 3.5 nmol/L ( < 1 ng/mL)
Prepubertal boys and girls: 0.17 - 0.7 nmol/L (0.05 -0.2 ng/mL)

Tetralogy of Fallot

A complex congenital heart defect named after the French physician Louis Arthur Fallot who made the first complete description of this heart disease. TOF is thought to be caused by malalignment of the conal septum during early development. Although TOF has been associated with chromosome 22 deletions and some chromosomal abnormalities most cases of TOF have no known cause.

TOF has the following four features:

1) A ventricular septal defect (VSD)
2) Pulmonary stenosis causing obstruction of blood flow from the right ventricle to the lungs
3) An overriding aorta -the aorta lies directly over the VSD between the left and right ventricles.
4) Right ventricle hypertrophy due resistance to blood flow from the right ventricle.

As a result of these features, oxygen-poor blood from the right ventricle flows preferentially across the VSD directly into the aorta instead of into the pulmonary artery to the lungs. This is known as a right-to-left shunt and causes the infant to appear cyanotic (blue).

After delivery a Blalock-Thomas-Taussig shunt may be performed on infants with severe variants such as TOF with pulmonary atresia (pseudotruncus arteriosus). Otherwise surgery to relieve the right ventricular outflow tract stenosis (by resection of muscle), and repair the VSD is usually done in infants at 1 year of age or younger. Pulmonary valve replacement is often required as an adolescent or young adult.

Differential diagnosis includes pulmonary atresia with VSD, double outlet right ventricle (DORV), and perimembranous VSD.

See Also

The Fetus.net
OMIM

Thalassemia A group of inherited blood disorders characterized by moderate to severe anemia. Thalassemias are caused by defects in the genes that control production of globins, the building blocks of hemoglobin (the oxygen carrying molecule in red blood cells). The two main types of thalassemia are alpha-thalassemia and beta-thalassemia .
	Hemoglobin

Thrombocytopenia

A lower than normal number (count) of platelets in the blood. Platelets are cell fragments in the blood that help to form blood clots.

150,000 to 450,000 platelets per microliter (x 10^–6/Liter)

Persons with low platelet numbers may experience nosebleeds, gum bleeding , bruises and small red pinpoints on the skin (petechiae). Rarely persons will experience bleeding into the urine, gastrointestinal tract, or into the head with very low platelet numbers.

Common causes of thrombocytopenia during pregnancy include:

Gestational thrombocytopenia

Pre-eclampsia

HELLP syndrome

Immune thrombocytopenic purpura

Drugs

Heparin, quinine, quinidine, zidovudine, sulfonamides, trimethoprim-sulfamethoxazole, gold compounds, sulfonamides, rifampin, valproic acid, phenytoin , digitalis ranitidine, cimetidine, procainamide, ampicillin, penicillin, alpha-methyl dopa, ethanol, aspirin, acetaminophen, indocin

Less common:

Systemic lupus Erythematosus, antiphospholipid syndrome, human immunodeficiency virus (HIV) infection , B12 or folate deficiency, hyperthyroidism, massive transfusion, prosthetic heart valves, thrombotic Thrombocytopenic Purpura (TTP), sepsis , disseminated intravascular coagulation (DIC) , hypersplenism, hemolytic uremic syndrome, hereditary thrombocytopenias, alcoholism, leukemia, aplastic anemia

Thrush (Candidiasis)

A yeast (Candida) infection of the tongue , mouth , and throat characterized by white patches and ulcers. Thrush is usually seen in infants , but occurs with increased frequency in adults with diabetes or HIV.

Titer

The concentration of an antibody in the blood. The titer is measured by diluting a sample until the antibody is no longer detectable. The result is given as the reciprocal (inverse) of the last dilution giving a measurable effect.

Example:

A blood sample (tube 1) has been diluted by 1/2 to produce tube 2, tube 2 was

diluted by 1/2 to produce tube 3 and so forth.

A substance was added to each tube to detect antibody.
The 4th tube is the last dilution at which the antibody is detected, and it is 1/8 th the

strength of the original sample.

The titer of the antibody is therefore 8.

1	2	3	4	5	6
1:1	1:2	1:4	1:8	1:16	1:32

Tocolytic

A substance that decreases uterine contractions.

Total iron-binding capacity (TIBC)

A measurement of the amount of iron that can potentially be bound by transferrin.

If the iron stores in the body are low, fewer sites on the transferrin molecules will be filled by iron, and the TIBC will be higher. If the amount of transferrin is increased the TIBC will also be increased.
If the iron stores in the body are very high the or transferrin is decreased then the TIBC will be low because most of the binding sites are filled. A low TIBC may be seen in hemochromatosis, sideroblastic anemia, and liver disease.

Toxemia (Preeclampsia)

Toxoplasmosis

An illness caused by the parasite, Toxoplasma gondii. Toxoplasma gondii is found in raw and undercooked meat; unwashed fruits and vegetables; dirty cat-litter boxes; and outdoor places where cat feces can be found.Fetal infection can occur via transplacental transmission.

http://www.cdc.gov/toxoplasmosis/

Transferrin

The protein found in blood that carries iron. The liver produces transferrin, and increases its production of transferrin in response to iron deficiency and pregnancy.

Transferrin saturation (%)

SEE Percent transferrin saturation (TSAT)

Transposition of the great arteries (TGA, Transposition of the Great Vessels, TGV )

A birth defect of the heart in which the the aorta and the pulmonary artery are switched (transposed). The aorta arises from the right ventricle instead of from the left ventricle, and the pulmonary artery arises from the left ventricle instead of arising from the right ventricle. In transposition of the great arteries the blood from the body enters the right side of the heart and flows into the aorta back to the body without receiving oxygen from the lungs.

While in the uterus the fetus is able to maintain adequate delivery of oxygen to the body because the formen ovale allows mixing of blood between the right and left atrium and the ductus arteriosus allows mixing of the blood between the pulmonary artery and the aorta. After delivery the baby will become blue due to lack of oxygen if these structures are not kept open.

The ductus may be kept open using drugs,and the foramen ovale can be enlarged with a catheter procedure which is performed in the first few days of life. An "Arterial Switch Operation" carried out in the first week or two of life corrects the primary abnormality. The small coronary arteries, which feed the heart muscle are transferred as well.

T-sign

On ultrasound examination the junction of two amniotic sacs forms a 90 degree angle with the placenta, a T-shaped junction. There is no placental tissue extending between the amniotic membranes. The T-sign strongly indicates that there is a single placenta (monochorionic).

Twin peak sign, Lambda sign

On ultrasound examination the presence of a triangular projection of placental tissue extending between two amniotic sacs. The twin peak sign strongly indicates that there are two separate placentas (dichorionic).