Encyclopedia of Health and Medicine

amniocentesis A diagnostic procedure to withdraw
a sample of AMNIOTIC FLUID from the UTERUS of
a pregnant woman to obtain information about
the health status of the FETUS. Obstetricians use
amniocentesis, typically performed during the second
trimester of PREGNANCY, to help diagnose
GENETIC DISORDERS and health conditions of the
developing fetus such as DOWN SYNDROME or SPINA
BIFIDA and other NEURAL TUBE DEFECTS. Amniotic
fluid contains cells from the fetus that can provide
a KARYOTYPE (representation of CHROMOSOME pairamniocentesis
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Age-related hormonal changes are most prominent
in women, who experience significant transformation
in their bodies with menopause. The
cessation of OVULATION means a pronounced drop
in estrogen within the body, affecting not only
reproductive capability but also the functions of
nearly every system in the body. Health concerns
that arise from these changes include increased
risk for OSTEOPOROSIS, CARDIOVASCULAR DISEASE (CVD),
and certain types of cancer. Men also experience
age-related changes in sexuality and reproductive
function. A man’s testosterone level peaks when
he is in his early 20s and gradually declines with
each decade of life. By age 60 most men have
about half the testosterone they had at age 25.
This decline results in changes such as diminished
muscle mass and strength and male pattern baldness
(ALOPECIA). A man’s risk for PROSTATE CANCER
significantly increases after age 60. Though a man
can still father children even into his 80s, declining
testosterone affects LIBIDO (sex drive) and erectile
function.
See also ANDROPAUSE; BENIGN PROSTATIC HYPERPLA-
SIA (BPH); ERECTILE DYSFUNCTION; LIFESTYLE AND
HEALTH; MENSTRUATION; PROGESTERONE.
alpha fetoprotein (AFP) A protein the LIVER produces.
In PREGNANCY the amount of AFP in the
woman’s BLOOD circulation increases, reflecting the
activity of the FETUS’s liver as it develops and
becomes functional. A blood test measures AFP in
the woman’s blood circulation early in the second
trimester, between 15 and 22 weeks of pregnancy.
Elevated AFP levels in pregnancy may indicate
a multiple pregnancy, NEURAL TUBE DEFECTS or
defects in the structure of the abdominal wall that
allow the organs of the gastrointestinal system to
form outside the body. Chronic liver disease, such
as HEPATITIS or CIRRHOSIS, also elevates AFP. Excessive
ALCOHOL consumption and cigarette smoking
are common causes of falsely high measures. Low
AFP levels may indicate a pregnancy that is not as
advanced as the woman believes or suggest the
chromosomal disorder DOWN SYNDROME.
Other health circumstances elevate AFP blood
levels in nonpregnant women and in men. Among
them are liver disease, including LIVER CANCER, TES-
TICULAR CANCER in men, and OVARIAN CANCER in
women. Deviations from normal AFP levels in
pregnancy suggest circumstances that may warrant
further medical evaluation such as ULTRA-
SOUND, AMNIOCENTESIS, and CHORIONIC VILLI SAMPLING
(CVS).
See also ALCOHOLISM; CHROMOSOMAL
GENETIC DISORDERS; PRENATAL CARE.
DISORDERS;
amenorrhea The absence of menstrual periods.
Primary amenorrhea occurs when a young
woman does not begin menstruating by age 16;
secondary amenorrhea occurs in women who
have been menstruating and then stop (miss six or
more consecutive periods).
Primary amenorrhea may result from GENETIC
DISORDERS such as TURNER’S SYNDROME or from hormonal
disorders such as pituitary ADENOMA (a
tumor of the PITUITARY GLAND) or HYPOTHYROIDISM
(underactive THYROID GLAND). PREGNANCY is the
most common cause of secondary amenorrhea.
Other factors that may cause either primary or
secondary amenorrhea include intense physical
exercise, excessive body weight (OBESITY), and
extreme underweight such as may result from
EATING DISORDERS.
Amenorrhea is a symptom of underlying conditions
that affect the function of the OVARIES rather
than itself a health condition. Because the hormones
the ovaries produce affect many other
functions within the body, it is important to identify
its cause. Unresolved primary amenorrhea
may have consequences such as permanent INFER-
TILITY and failure to develop SECONDARY SEXUAL
CHARACTERISTICS.
See also BODY MASS INDEX (BMI); DYSMENORRHEA;
EXERCISE AND HEALTH; FERTILITY; HORMONE; OBESITY
AND HEALTH; OVULATION; PRIMARY OVARIAN FAILURE;
WEIGHT LOSS AND WEIGHT MANAGEMENT.