a sensation of not being able to take a
full breath. Breathing into a paper bag
may help to reduce the symptoms in
people with anxiety.
hyphaemaBlood in the front chamber
of the eye, usually caused by an injury
that ruptures a small blood vessel in
the irisor ciliary body. Initially, there
may be blurred vision, but the blood
usually disappears completely within a
few days and vision is restored.
hypnosisA trance-like state of altered
awareness characterized by extreme sug-
gestibility. Some psychoanalysts induce
a hypnotic state as a means of helping
patients remember and come to terms
with disturbing events. More often, hyp-
nosis is used to help patients to relax. It
may be useful in people suffering from
anxiety, panic attacks, or phobias, or in
those wishing to correct addictive habits.
hypnotherapyThe use ofhypnosisas
part of a psychological therapy.
hypnotic drugsDrugs that induce sleep
(see sleeping drugs).
hypo-A prefix meaning under, below, or
less than normal.
hypoaldosteronismA rare deficiency
of the hormone aldosterone, which is
produced by the adrenal glands. The
condition may be caused by damage or
disease affecting the adrenal glands. It
may produce weakness, and is treated
by the drug fludrocortisone.
hypocalcaemiaAn abnormally low level
of calciumin the blood. The most com-
mon cause is vitamin Ddeficiency. Rarer
causes include chronic kidney failureand
hypoparathyroidism. In mild cases, hypo-
calcaemia is symptomless; in severe
cases, it leads to tetany. It may also result
in bone softening, causing ricketsin chil-
dren and osteomalaciain adults.
hypochondriasisA person’s unrealis-
tic belief that he or she is suffering
from a serious illness, despite medical
reassurance. Hypochondriacs worry con-
stantly about their health and interpret
any symptom, however trivial, as evi-
dence of disease.
Hypochondriasis may be a complica-
tion of other psychological disorders,
including phobia, obsessive–compulsive
disorder, generalized anxiety disorder,
and brain diseases such as dementia.Other factors include social stresses
and personality type. Where possible,
treatment is of the underlying mental
disorder. Hypochondriasis without an
underlying cause is difficult to treat.
hypochondriumThe region on each
side of the upper abdomen, situated
below the lower ribs.
hypoglossal nerveThe 12th cranial
nerve, which controls tongue movement.
hypoglycaemiaAn abnormally low level
of glucosein the blood. Almost all cases
of hypoglycaemia occur in people with
diabetes mellitus, in whom the pancreas
fails to produce enough insulin, result-
ing in an abnormally high level of
glucose. To lower the blood glucose
level, hypoglycaemic drugsor insulin
are given. Too high a dose of either can
reduce the blood glucose to too low a
level. Hypoglycaemia can also occur if a
diabetic person misses a meal or takes
strenuous exercise. Rarely, the condi-
tion can result from drinking too much
alcohol or from an insulin-producing
pancreatic tumour.
The main symptoms include sweating,
hunger, dizziness, trembling, headache,
palpitations, confusion, and sometimes
double vision. Behaviour is often irra-
tional and aggressive. Comamay occur
in severe cases. Hypoglycaemia may
also be the cause of seizures and jittery
behaviour in newborns.
Sugar should be eaten at the first sign
of a diabetic attack. An injection of either
glucose solution or the hormone gluca-
gon may be given in an emergency.
hypoglycaemics, oralA group of anti-
diabetic drugsthat are used to lower
blood glucose. Too high a dose may
provoke the onset of hypoglycaemia.
hypogonadismUnderactivity of the tes-
tesor ovaries. Hypogonadism may be
caused by disorders of the gonads or a
disorder of the pituitary glandthat causes
deficient production of gonadotrophin
hormones. In men, hypogonadism causes
the symptoms and signs of androgen
hormonedeficiency; in women, it causes
those of oestrogendeficiency.
hypohidrosisReduced activity of the
sweat glands. Hypohidrosis is a feature
of hypohidrotic ectodermal dysplasia, a
rare, inherited, incurable condition thatHYPHAEMA HYPOHIDROSISH