Bma Illustrated Medical Dictionary

G6PD deficiencyAn X-linked disorder
that affects the chemistry of red blood
cells, making them prone to damage by
infectious illness or certain drugs or foods.
Red blood cells are missing G6PD (the
enzymeglucose 6 phosphate dehydroge-
nase). Thedisorder most often affects
southern European and black men.
Women are unaffected but can carry the
abnormal gene.
Some antimalarial drugsand antibiotics
can precipitate destruction of red cells
in affected people. In one form of G6PD
deficiency called favism,affected people
are sensitive to a chemical in broad
beans, which they must avoid eating.
After taking a precipitating drugor food,
or during an infectious illness, a person
with G6PD deficiency develops the
symptoms (see anaemia, haemolytic).
G6PD deficiency is diagnosed with a
blood test. There is no particular treat-
ment but symptoms caused by a drug
or food can be relieved by avoiding it.
GABA The abbreviation for gamma-
aminobutyric acid, a neurotransmitter.
GABA controls the flow of nerve impulses
by blocking the release of other neuro-
transmitters (e.g. noradrenaline and
dopamine) that stimulate nerve activity.
GABA activity is increased by benzodi-
azepine drugsand anticonvulsants.
gabapentinAn anticonvulsant drug used
either alone or with other anticonvul-
sants to treat some types of epilepsy.
Common side effects include dizziness,
unsteadiness, and fatigue.
galactorrhoeaSpontaneous, persistent
production of milk by a woman who is
not pregnant or lactating (see lactation),
or, very rarely, by a man.
Lactation is initiated by a rise in the
level of prolactin, a hormone produced
by the pituitary gland. Galactorrhoea is
caused by excessive secretion of pro-
lactin due to a pituitary tumouror other

endocrine disease, such as hypothy-

roidism. Some antipsychotic drugsmay

also cause excessive secretion. Treat-

ment with bromocriptine suppresses

prolactin production, but the underlying

cause may also need treatment.

galactosaemiaA rare, inherited condi-

tion in which the body is unable to

convert the sugar galactose into glucose

due to the absence of a liver enzyme.

It causes no symptoms at birth, but

jaundice, diarrhoea, and vomiting soon

develop and the baby fails to gain weight.

Untreated, the condition results in liver

disease, cataract, and learning difficulties.

The diagnosis is confirmed by urine and

blood tests. The major source of galac-

tose is the milk sugar lactose. Lactose-

free milk must be used throughout life.

gallbladderA small, pear-shaped sac

situated under the liver that stores bile.

Bile, produced by the liver, passes into

the gallbladder via the hepatic and cystic

ducts. It is released into the intestine

via the common bile duct.

gallbladder cancerA rare cancerof

unknown cause that occurs mainly in the

elderly. The cancer may cause jaundice

and tenderness in the abdomen, but

it is sometimes symptomless. It is usu-

ally diagnosed by ultrasound scanning.

G6PD DEFICIENCY GALLBLADDER CANCER

G

Cystic duct

Wall of

gallbladder

Muscle

Fibrous

tissue

LOCATION

Liver

Pancreas

Hepatic

ducts

from

liver

GALLBLADDER

Common

bile

duct

Gallbladder

lining

G