Webster's New World Medical Dictionary

thelarche
The time that breast development
starts in girls.
T-helper cell
See 
T-4 cell.
therapeutic
Relating to therapeutics, the branch
of medicine that is concerned specifically with the
treatment of disease. The therapeutic dose of a drug
is the amount needed to treat a disease.
therapeutic abortion
An abortion that is
brought about intentionally. Also known as induced
abortion.
therapeutic cloning
Cloning designed as ther-
apy for a disease. In therapeutic cloning, the
nucleus of a cell, typically a skin cell, is inserted into
a fertilized egg whose nucleus has been removed.
The nucleated egg begins to divide repeatedly to
form a blastocyst. Scientists then extract stem cells
from the blastocyst and use them to grow cells that
are a perfect genetic match for the patient. The cells
created via therapeutic cloning can then be trans-
planted into the patient to treat a disease from
which the patient suffers. In contrast to the goal of
therapeutic cloning, the goal of reproductive
cloning is to create a new individual, an idea that
has stirred great controversy and met with almost
uniform disapproval.
therapy
The treatment of disease. Therapy is syn-
onymous with treatment.
thermometer
In medicine, a device used to meas-
ure the temperature of the human body. There are
many types of medical thermometers, including oral
thermometers (placed under the tongue), rectal
thermometers (placed within the rectum), multipur-
pose thermometers (placed under the tongue, in the
rectum, or under the armpit), eardrum thermome-
ters (placed inside the ear), and basal thermometers
(highly sensitive thermometers placed under the
tongue or in the rectum to measure slight tempera-
ture changes indicating that ovulation has taken place
in a woman). See also 
fever; temperature.
thiamine
Vitamin B1, which acts as a coenzyme
in the metabolism of the body. In its active form, thi-
amine participates in a range of biochemical reac-
tions, including certain reactions that are important
to carbohydrate metabolism. Deficiency of thiamine
leads to the disease beriberi. See also Appendix C,
“Vitamins.”
thigh
The thick, muscular portion of the leg that
extends from the hip to the knee. The thigh has only
one bone, the femur, which is the largest bone in the
human body.