away the overgrown endometrium; in hysterec-
tomy the surgeon removes the uterus. In most sit-
uations, hysterectomy is appropriate only when
complex endometrial hyperplasia with atypia
recurs after other treatments or when the risk for
endometrial cancer is high for other reasons,
though women who are past menopause and
have persistent symptoms may opt for hysterec-
tomy to permanently end the hyperplasia.
Risk Factors and Preventive Measures
Any circumstance that increases the presence of
estrogen in the BLOODcirculation underlies the
development of endometrial hyperplasia. The risk
for endometrial hyperplasia is highest in women
who have anovulatory periods (menstrual cycles
without ovulation), who take unopposed estrogen
therapy (estrogen alone), or who take long-term
tamoxifen to treat BREAST CANCER. Other factors
that increase estrogen within the body are OBESITY,
INSULIN RESISTANCE, and type 2 DIABETES. Nutritional
EATING HABITSthat emphasize foods low in fats,
especially saturated fats, and daily physical exer-
cise are the key lifestyle measures that reduce the
risk for endometrial hyperplasia.
See also CANCER RISK FACTORS; CERVICAL INTRAEP-
ITHELIAL NEOPLASIA(CIN); CERVIX; DYSPLASIA; DYSFUNC-
TIONAL UTERINE BLEEDING(DUB); SURGERY BENEFIT AND
RISK ASSESSMENT.
endometriosis A condition in which endome-
trial tissue (the tissue that forms the lining of the
UTERUS) grows abnormally in areas outside the
uterus. The most common sites are the OVARIES,
FALLOPIAN TUBES, peritoneal (abdominal) cavity,
gastrointestinal tract (particularly the COLON), and
BLADDER, though endometrial tissue may appear in
other locations throughout the body. Endometrial
growths, also called implants or tumors, respond
to the body’s changing hormonal environment
through the MENSTRUAL CYCLEin the same ways as
endometrial tissue within the uterus: They
engorge with BLOOD, atrophy, and slough (bleed).
Because there is no pathway for bleeding from
these distant endometrial implants to leave the
body, the blood accumulates in the surrounding
tissues. INFLAMMATION develops as part of the
IMMUNE RESPONSE, initiating a HEALINGprocess that
results in the formation of SCARtissue.
The growth of endometrial tissue in the fallop-
ian tubes or ovaries blocks the ability of these
structures to properly function, a primary conse-
quence of which is impaired FERTILITY.
Endometriosis also appears to instigate an abnor-
mal immune response in which phagocytic cells
(cells that engulf and consume cellular debris),
primarily macrophages, target and kill SPERMand
OVA(eggs). About 40 percent of women who seek
treatment for INFERTILITY have endometriosis.
Endometriosis affects more than five million
women in the United States.
Researchers do not know what causes
endometriosis or how endometrial tissue arises in
sites other than the uterus. Many women who
have endometriosis often also have AUTOIMMUNE
DISORDERSsuch as atopic DERMATITIS, ASTHMA, and
allergies, giving rise to the suspicion of a dysfunc-
tion within the immune system. Some researchers
believe endometrial cells escape from the uterus
via the fallopian tubes, then migrate through the
LY M P Hor blood circulation to implant and grow in
other locations. Endometriosis tends to progres-
sively worsen over time because the endometrial
implants grow under the influence of ESTROGENS,
though this growth usually abates with
MENOPAUSE. For most women menopause, natural
or induced, ends endometriosis.Symptoms and Diagnostic Path
The primary symptoms of endometriosis are PAIN
and infertility. Pain is typically cyclic, following
the pattern of the menstrual cycle, and may be
moderate to debilitating, especially during MEN-
STRUATION. Distant endometrial implants also cause
pain as they swell and then bleed. The diagnostic
path includes comprehensive medical examina-
tion with pelvic examination and often pelvic
ULTRASOUND. Exploratory laparoscopy provides the
definitive diagnosis, allowing the gynecologist to
directly visualize the endometrial implants. Diag-
nostic imaging procedures such as COMPUTED
TOMOGRAPHY(CT) SCANor MAGNETIC RESONANCE IMAG-
ING (MRI) often can detect distant endometrial
implants.Treatment Options and Outlook
At present there is no cure for endometriosis,
though various treatment approaches, medical276 The Reproductive System