HASHISH
HEALING
produce enough
thyroid hormones
,
a
condition known as
hypothyroidism
.
The principal symptoms of Hashimoto's
thyroiditis are tiredness, muscle weak-
ness, and weight gain, and the thyroid
gland becomes enlarged.
Diagnosis is confirmed by
blood tests
.
Treatment is by thyroid hormone replace-
ment therapy, which is life-long.
hashish
Another name for
marijuana
.
hay fever
The popular name for a sea-
sonal form of allergic rhinitis (see
rhinitis,
allergic).
HDL
The abbreviation for
high density
lipoprotein
.
headache
One of the most common
types of pain. A headache is only rarely
a symptom of a serious underlying dis-
order. The pain arises from tension in
the
meninges
, and in the blood vessels
and muscles of the scalp.
Many headaches are simply a resp-
onse to some adverse stimulus, such as
hunger. Such headaches usually clear
up quickly. Tension headaches, caused
by tightening in the face, neck, and scalp
muscles as a result of stress or poor
posture, are also common, and may last
for days or weeks.
Migraine
is a severe,
incapacitating headache preceded or
accompanied by visual and/or stomach
disturbances.
Cluster headaches
cause
intense pain behind
1
eye.
Common causes of headache include
hangover
and noisy or stuffy environ-
ments.
Food additives
may also be a
cause. Some headaches are due to over-
use of painkillers (see
analgesic drugs
).
Other possible causes include
sinusitis
,
toothache
,
cervical osteoarthritis
, and
head injury
. Among the rare causes of
headache are a
brain tumour
,
hyper-
tension
,
temporal arteritis
, an
aneurysm
,
and increased pressure within the skull.
Most headaches can be relieved by
painkillers and rest. If a neurological
cause is suspected,
CT scanning
or
MRI
may be performed.
head-banging
The persistent, rhythmic
banging of the head against a wall or
hard object. Head-banging is seen in
some people with severe
learning dif-
ficulties
, particularly those who lack
stimulation. It also occurs in some
normal toddlers, often when they are
frustrated or angry; most children grow
out of the behaviour.
head injury
Injury to the head may
occur as a result of a blow or a fall. The
severity
of the
injury
depends
on
whether the brain is affected. A blow
may shake or bruise the brain (see
brain
damage
). If the skull is broken (see
skull,
fracture of
), foreign material or bone
may enter the brain and lead to infec-
tion. A blow or a penetrating injury may
cause swelling of the brain, or tear
blood vessels, which may lead to
brain
haemorrhage
.
If the head injury is mild, there may
only be a slight headache. In some
cases there is
concussion
.
More severe
head injuries may result in uncon-
sciousness or
coma
,
which may be fatal.
Amnesia
may occur. After a severe brain
injury, there may be some muscular
weakness or
paralysis
and loss of sen-
sation. Symptoms such as persistent
vomiting, double vision, or a deteri-
orating level of consciousness could
suggest progressive brain damage.
Investigations may include
skull X-rays
and
CT scanning
. A blood clot inside
the skull may be life-threatening and
requires surgical removal; severe skull
fractures
may
also
require
surgery.
Recovery from concussion may take
several days. There may be permanent
physical or mental disability if the brain
has been damaged. Recovery from a
major head injury can be very slow,
but there may be signs of progressive
improvement for several years after
the injury occurred.
head lag
The backward flopping of the
head that occurs when an infant is placed
in a sitting position. Head lag is obvi-
ous in a newborn because the neck
muscles are still weak, but by 4 months
the baby can hold his or her head up-
right (see
child development
).
Heaf test
A type of
tuberculin test
.
healing
The process by which the body
repairs bone, tissue, or organ damage
caused by injury, infection, or disease.
The initial stages of healing are the
same in all parts of the body. After injury,
blood clots
form in damaged tissues.
White
blood cells
,
enzymes
,
histamine,
other chemicals, and
proteins
from which
H
269
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