Webster's New World Medical Dictionary

endometrial biopsy
A common procedure for
sampling the inner lining of the uterus (the
endometrium). Endometrial biopsy is usually done
to learn the cause of abnormal uterine bleeding,
although it may be used to determine the cause of
infertility, test for uterine infections, and monitor the
response to certain medications. The main prob-
lems resulting from endometrial biopsy are cramp-
ing and pain. Vaginal bleeding, infection, and, very
rarely, perforation of the uterus can also occur.
endometrial hyperplasia
A condition charac-
terized by overgrowth of the lining of the uterus.
endometriosis
A noncancerous condition in
which tissue that looks like endometrial tissue
grows in abnormal places, most often in the
abdomen. Although most women with endometrio-
sis have no symptoms, pelvic pain during menstrua-
tion or ovulation can be a symptom of
endometriosis. Endometriosis can also be sus-
pected by a physician during a physical examination
and confirmed by surgery, usually laparoscopy.
Treatment options include medication for pain, hor-
mone therapy, and laparoscopic surgery to remove
the growths (hysterectomy was once done but is
usually ineffective). Most women with endometrio-
sis are completely unaware of these growths, and
are not harmed by their presence. However,
endometriosis can increase the risk of ectopic preg-
nancy, a potentially life-threatening condition that
can cause infertility. See also 
adenomyosis.
endometritis
Inflammation of the endometrium,
the inner layer of the uterus.
endometrium
The inner layer of the uterus.
endonuclease
An enzyme that cleaves a nucleic
acid (DNA or RNA) at specific sites in the nucleotide
base sequence.
endorphin
A hormonal compound that is made
by the body in response to pain or extreme physical
exertion. Endorphins are similar in structure and
effect to opiate drugs. They are responsible for the
so-called runner’s high, and release of these essen-
tial compounds permits humans to endure child-
birth, accidents, and strenuous everyday activities.
e
ndoscope
A lighted optical instrument that is
used to get a deep look inside the body. An endo-
scope, which may be rigid or flexible, can be used to
examine organs, such as the throat or esophagus.
Specialized endoscopes are named for where they
are intended to look. Examples include the cysto-
scope (bladder), nephroscope (kidney), broncho-
scope (bronchi), laryngoscope (larynx), otoscope
(ear), arthroscope (joint), laparoscope (abdomen),
and gastrointestinal endoscopes.