some psychological disorders, particu-
larly depression. Regular weightbearing
exercise, such as running, increases the
density of, and thereby strengthens, the
bones. The bone disease osteoporosisis
less common in people who have exer-
cised throughout their adult lives.
However, vigorous exercise may cause
injury and increase the risk of a heart
attack in people who are out of condi-
tion. Professional sportsmen such as
footballers have an increased risk of
osteoarthritisin later life because of re-
peated minor damage to the joints.
exercise ECG The use of electrocardio-
graphy (see ECG) to assess the function
of the heart when it is put under the
stress of exercise. Exercise ECG is usu-
ally carried out when coronary artery
diseaseis suspected. It involves raising
the heart rate by exercising, usually on
a treadmill with an adjustable gradient
or an exercise bicycle, and recording the
heart’s electrical activity for analysis.
exfoliationFlaking off, shedding, or peel-
ing from a surface in scales or thin
layers, as in exfoliative dermatitis.
exfoliative dermatitisA skin disorder
characterized by inflammation, redness,
and scaling of the skin over most of the
body. Exfoliative dermatitis may be the
result of an allergic response to a drug
or may be due to worsening of a skin
condition such as psoriasisor eczema.
The condition sometimes occurs in lym-
phomaand leukaemia.
There is a widespread rash with severe
flaking of the skin, which results in in-
creased loss of water and protein from
the surface of the body. Protein loss
may cause oedema and muscle wasting.
Further possible complications include
heart failureand infection. The treat-
ment and outlook depend on the cause.
exhibitionismThe habit of deliberately
exposing the genitaliaas a deviant sexu-
al act. This type of behaviour is almost
always confined to men. Psychotherapy
or behaviour therapymay help persis-
tent offenders.
exocrine glandA glandthat secretes
substances through a ducton to the
inner surface of an organ or the outer
surface of the body. Examples include
the salivary glandsand sweat glands.
The release of exocrine secretions can
be triggered by a hormone or a neuro-
transmitter. (See also endocrine gland.)
exogenousOf a disease or disorder,
having a cause that is external to the
body, such as infection, poisoning, or
injury. (See also endogenous.)
exomphalosA rare birth defect, in
which a membranous sac containing
part of the intestines protrudes through
the navel. The condition may some-
times be diagnosed before birth by
ultrasoundexamination. Exomphalos is
treated by surgery, the success of which
depends on the extent of the defect.
exophthalmosProtrusion of one or
both eyeballs caused by a swelling of
the soft tissue in the eye socket. It is
most commonly associated with thyro-
toxicosis. Other causes include an eye
tumour, inflammation, or an aneurysm
behind the eye. Exophthalmos may re-
strict eye movement and cause double
vision. In severe cases, increased pres-
sure in the socket may restrict blood
supply to the optic nerve, causing blind-
ness. The eyelids may be unable to
close, and vision may become blurred
due to drying of the cornea.
In exophthalmos due to thyroid dis-
ease, treatment of the thyroid disorder
may relieve the exophthalmos, but, if
the cause is Graves’ disease, exophthal-
mos may persist even if thyroid function
returns to normal. Early treatment of
the condition usually returns vision to
normal. Occasionally, surgery may be
required to relieve pressure on the eye-
ball and optic nerve.
exostosisThe most common type of
benign bone tumour, in which there is
an outgrowth of bone. Exostosis occurs
most frequently at the end of the femur
or tibia. It may be due to hereditary fac-
tors or prolonged pressure on a bone.
In most cases, exostosis produces no
symptoms. Often, it is recognized only
after an injury, when it appears as a
hard swelling. Occasionally, the tumour
presses on a nerve, causing pain or
weakness in the affected area. Diagnosis
can be confirmed by X-rays. Treatment,
by surgical removal, may be carried out
if the tumour is causing symptoms or
for cosmetic reasons.EXERCISE ECG EXOSTOSIS
E