glands may become overactive (in a
condition called hyperparathyroidism)
or underactive (see hypoparathyroidism).
parathyroid tumourA growth within
a parathyroid gland. The tumour may
cause excess secretion of parathyroid
hormone, leading to hyperparathyroid-
ism. Cancers of the parathyroid are very
rare; most parathyroid tumours are non-
cancerous adenomas. An adenoma that
causes hyperparathyroidism will be sur-
gically removed (see parathyroidectomy).
This usually provides a complete cure.
paratyphoid feverAn illness identical
in most respects to typhoid fever, except
that it is caused by SALMONELLA PARA-
TYPHIand is usually less severe.
paraumbilical herniaA herniaoccur-
ring near the navel. It may occur in obese
women who have had several children.
parenchymaThe functional (as opposed
to supporting) tissue of an organ.
parenteralA term applied to the admin-
istration of drugs or other substances
by any route other than via the gastro-
intestinal tract (for example, by injection
into a blood vessel).
parenteral nutritionIntravenous feed-
ing (see feeding, artificial).
paresisPartial paralysisor weakness of
1 or more muscles.
parietalA medical term that refers to
the wall of a part of the body.
parity A term that is used to indicate
the number of pregnancies a woman
has undergone that have resulted in the
birth of a baby capable of survival.
parkinsonismAny neurological disor-
der characterized by a mask-like face,
rigidity, and slow movements. The most
common type is Parkinson’s disease.
Parkinson’s diseaseA neurological
disorder that causes muscle tremor, stiff-
ness,and weakness. The characteristic
signs are trembling, rigid posture, slow
movements, and a shuffling, unbalanced
walk. The disease is caused by degener-
ation of, or damage to, cells in the basal
gangliaof the brain, reducing the amount
of dopamine (which is needed for control
of movement). It occurs mainly in elder-
ly people and is more common in men.
The disease usually begins as a slight
tremor of 1 hand, arm, or leg, which is
worse when the hand or limb is at rest.
Later, both sides of the body are affected,
causing a stiff, shuffling, walk; constant
trembling of the hands, sometimes
accompanied by shaking of the head; a
permanent rigid stoop; and an unblink-
ing, fixed expression. The intellect is
unaffected until late in the disease.
There is no cure. Drug treatment is used
to minimize symptoms in later stages.
Levodopa, which the body converts into
dopamine, is usually the most effective
drug. It may be used in combination with
benserazide or carbidopa. The effects of
levodopa gradually wear off. Drugs that
may be used in conjunction with it, or
as substitutes for it, include amantadine
and bromocriptine. Surgical operations
on the brain are occasionally performed.
Untreated, the disease progresses over
10 to 15 years, leading to severe weak-
ness and incapacity. About one third of
sufferers eventually develop dementia.
paronychiaAn infection of the skin fold
at the base or side of the nail. Parony-
chia may be acute (caused by bacteria)
or chronic (usually caused by CANDIDA
ALBICANS). The condition is most com-
mon in women, particularly those with
poor circulation and whose work involves
frequent contact with water. It also
affects people with skin disease involv-
ing the nail fold. Treatmentis with
antifungal drugs or antibiotic drugs.
parotid glandsThe largest of the 3 pairs
of salivary glands. The parotid glands liePARATHYROID TUMOUR PAROTID GLANDS
P
LOCATIONTracheaPARATHYROID GLANDSThyroid
cartilageThyroid
glandParathyroid
glands