ADRENOGENITAL SYNDROME
Adrenal gland disorders are a range of
uncommon but sometimes serious
conditions that result from deficient or
excessive production of hormones by
one or both of the adrenal glands.
Congenitaldefects
A genetic defect causes congenital
adrenal hyperplasia,
in which the
adrenal cortex is unable to make
sufficient hydrocortisone and
aldosterone.As
a side effect of the
reduced hydrocortisone production,
the glands are stimulated into
producing excess androgens (male
sex hormones); this can cause
masculinization of female babies.
Autoimmune disorders
Deficient production of hormones by
the adrenal cortex is called
adrenal
failure;
if the deficiency is due to disease
of the adrenal glands themselves, it is
called
Addison's disease.The
most
common cause of Addison’s disease is
an autoimmune process (in which the
body’s immune system attacks its own
tissues). Addison’s disease can take a
chronic course characterized by
weakness, weight loss, and skin
darkening, or an acute form
(Addisonian crisis or acute adrenal
failure), in which the patient may
become confused and comatose.
Infection
Destruction of the adrenal glands by
tuberculosis
was once a major cause of
Addison’s disease but is now
uncommon. The onset of an infection
or other acute illness in someone with
Addison’s disease can precipitate acute
adrenal failure.
Impaired blood supply
Loss or obstruction of the blood supply to
the adrenal glands, sometimes as a result of
arterial disease, is another possible cause of
Addison’s disease or acute adrenal failure.
Tumours
Cancerous or noncancerous growths in
the adrenal glands are rare but generally
lead to excess secretion of hormones. A
tumour of the adrenal cortex can secrete
aldosterone, causing primary
aldosteronism
(also called Conn’s syndrome), a
condition that is characterized by thirst
and high blood pressure. A tumour can
also secrete hydrocortisone, causing
Cushing's syndrome,
which has various
features including muscle-wasting and
obesity of the trunk. Androgens may
also be produced in excess, causing
masculinization in females.
Two types of tumour affect the
adrenal medulla,
phaeochromocytoma
and
neuroblastoma,
which affects children.
These tumours may cause excess secretion
of adrenaline (epinephrine) and
noradrenaline (norepinephrine).
Other disorders
In many cases, disturbed activity of the
adrenals is caused, not by disease of the
glands themselves, but by an increase or
decrease in the blood level of hormones
that influence the activity of the glands.
Hydrocortisone production by the
adrenal cortex is controlled by the
secretion of ACTH (adrenocorticotrophic
hormone) by the pituitary gland.
A tumour or other pituitary gland
disorder, or tumours in the lung, breast,
and elsewhere, can cause excess ACTH
secretion, leading to excess production
of hydrocortisone by the adrenals and,
hence, to Cushing’s syndrome. Pituitary
disease is a cause of Cushing’s syndrome.
INVESTIGATION
Blood and/or urine tests can detect the
high levels of adrenal hormones that
occur with adrenal tumours.They can
also detect the high levels of natural
corticosteroids that occur in Cushing’s
syndrome, and the low levels that occur
in congenital adrenal hyperplasia. Blood
tests are used to measure salt and
potassium levels if Addison’s disease is
suspected; further blood tests may be
carried out to measure corticosteroid
hormone levels. Diagnosis o f Addison’s
disease can be confirmed by the
response to an injection o f ACTH,
w hich, under normal circumstances,
will stimulate the adrenal glands. MRI or
CT scanning can detect abnormalities
of the adrenal glands and can confirm
the presence of an adrenal tumour.
They can also distinguish between
raised hormone levels due to an
adrenal tumour, or those due to a
pituitary tumour. Ultrasound scanning
can rule out an adrenal tumour as the
cause of congenital adrenal hyperplasia.
A
adrenogenital syndrome
See
adrenal hyperplasia, congenital.
advanced life support
Treatment of
cardiac arrest
(a halt in the
heart’s pumping action) by medical or
paramedical professionals when
basic life
support,
(which may be performed by a
first-aider) has failed to restore a normal
heartbeat and spontaneous breathing.
Advanced life support involves the use
of drugs and medical equipment.
An
ECG
monitor is used to record the
electrical activity of the heart muscle.
Ventilation
delivers oxygen by way of an
endotracheal
tube
inserted,
via
the
mouth, into the trachea (windpipe). A
cannula
(a thin plastic tube inserted into
a vein) allows administration of drugs
such as
adrenaline
(epinephrine). In the
event of
ventricular fibrillation
(rapid un-
coordinated contractions of the heart),
defibrillation
(a brief electric shock to
the heart using two paddles placed on
the chest) may be used.
adverse reaction
See
side effect.
Aedes
A genus of disease-transmitting mos-
quitoes.
Many
species
of AEDES
are
responsible
for
spreading
important
viral infections; AEDES AEGYPTI
is the
main vector of
dengue
and
yellow fever
.
(See also
mosquito bites.
)
aerobic
A term that refers to anything that
requires oxygen to live, function, and
grow. Humans and many other forms
of life are dependent on oxygen for
“burning” foods in order to produce
energy
(see
metabolism).
Because
of
this dependence, they are described as
obligate aerobes.
In contrast, many bacteria have fund-
amentally
different metabolisms
and
thrive without oxygen (some are even
killed by exposure to oxygen); such
microorganisms are described as
anaero-
bic.
There are also certain bacteria and
yeasts, known as facultative aerobes,
that flourish in oxygen but can also live
without it. (See also
aerobics.)
20
previous page 19 BMA A Z Family Medical Encyclopedia   2004 read online next page 21 BMA A Z Family Medical Encyclopedia   2004 read online Home Toggle text on/off