infertilityThe inability to produce off-
spring, which may result from a problem
in either the male or the female repro-
ductivesystem, or, in many cases, from
a combination of problems in both.
The main cause of male infertility is a
lack of healthy sperm. In azoospermia,
no sperm are produced; in oligospermia
only a few sperm are produced. In some
cases, sperm are produced but are mal-
formed or short-lived. The underlying
cause of these problems may be block-
age of the spermatic tubes or damage
to the spermatic ducts, usually due to a
sexually transmitted infection. Abnormal
development of the testes due to an
endocrine disorder (see hypogonadism)
or damage to the testes by orchitismay
also cause defective sperm. Smoking,
toxins, or various drugs can lower the
sperm count. Other causes are disorders
affecting ejaculation (seeejaculation,
disorders of). Rarely, male infertility is
due to a chromosomal abnormality, such
as Klinefelter’s syndrome, or a genetic
disease, such as cystic fibrosis.
The most common cause of female
infertility is failure to ovulate. Other
causes are blocked, damaged or absent
fallopian tubes; disorders of the uterus,
such as fibroidsand endometriosis; prob-
lems with fertilization, or implantation
in the uterus (see implantation, egg).
Infertility also occurs if the woman’s
cervical mucus provides antibodies that
kill or immobilize her partner’s sperm.
Rarely, a chromosomal abnormality, such
as Turner’s syndrome, is the cause of a
woman’s infertility.
Investigations to discover the cause of
a woman’s infertility may include blood
and urine tests, to check that ovulation
is occurring, and laparoscopyto deter-
mine whether or not an abnormality is
present. The initial investigation for male
infertility is seminal fluid analysis.
Treatment of male infertility is limited.
The only option for azoospermia is adop-
tion of children or artificial insemination
by a donor. If the sperm count is low, arti-
ficial insemination by the male partner
may be tried. In some cases of male
infertility due to a hormonal imbalance,
drugs such as clomifeneor gonadotro-
phin hormonetherapy may prove useful.
Failure of the woman to ovulate re-
quires ovarian stimulation with a drug
such as clomifene, either with or without
a gonadotrophin hormone. Microsurgery
can sometimes repair damage to the
fallopian tubes. If surgery is unsuccess-
ful, in vitro fertilization(IVF) is the only
option. Uterine abnormalities or disor-
ders, such as fibroids, may require
treatment. In some cases, provided the
woman has normal fallopian tubes,
gamete intrafallopian transfer (GIFT) or
zygote intrafallopian transfer(ZIFT) may
be carried out.
infestationThe presence of animal par-
asites (such as mites, ticks, or lice) in
the skin or hair, or of worms (such as
tapeworms) inside the body.
infibulationA form of female circumci-
sion in which the labia majora (the
outer lips surrounding the vagina) are
removed and the entrance to the vagina
narrowed (see circumcision, female).
infiltrateBuild-up of substances or cells
within a tissue that are either not nor-
mally found in it or are usually
present only in smaller amounts. Infil-
trate may refer to a drug (such as a local
anaesthetic) that has been injected into
a tissue, or to the build-up of a sub-
stance within an organ (for example, fat
in the liver caused by excessive alcohol
consumption). Radiologists use the term
to refer to the presence of abnormali-
ties, most commonly on a chest X-ray,
due to conditions such as infection.
inflammationRedness, swelling, heat,
and pain in a tissue due to injury or
infection. When body tissues become
damaged, mast cells release the chemical
histamineand other substances. His-
tamine increases the flow of blood to
the damaged tissue and also makes the
blood capillaries more leaky; fluid then
oozes out and into the tissues, causing
localized swelling. Pain is caused by the
stimulation of nerve endings by the
inflammatory chemicals.
Inflammation is usually accompanied
by a local increase in the number of
white blood cells. These cells help to
destroy any invading microorganisms
and are involved in repairing the dam-
aged tissue. Inappropriate inflammation
(as in rheumatoid arthritisand someINFERTILITY INFLAMMATION
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