Glucagonoma
A
glucagonoma
is a rare
tumor of the
alpha cells
of the
pancreas
that results
in up to a
1000-fold
overproduction
of the
hormone
glucagon.
Alpha cell
tumors are
commonly
associated
with
glucagonoma
syndrome,
though
similar
symptoms are
present in
cases of
pseudoglucagonoma
syndrome in
the absence
of a
glucagon-secreting
tumor.
History
Fewer than
250 cases of
glucagonoma
have been
described in
the
literature
since their
first
description
by Becker in
1942.
Because of
its rarity
(fewer than
one in 20
million
worldwide),
long-term
survival
rates are as
yet unknown.
Symptoms
The primary
physiological
effect of
glucagonoma
is an
overproduction
of the
peptide
hormone
glucagon,
which
enhances
blood
glucose
levels
through the
activation
of catabolic
processes
including
gluconeogenesis
and
lipolysis.
Gluconeogenesis
produces
glucose from
protein and
amino acid
materials;
lipolysis is
the
breakdown of
fat. The net
result is
hyperglucagonemia,
decreased
blood levels
of amino
acids (hypoaminoacidemia),
anemia,
diarrhea,
and weight
loss of 5-15
kg.
Necrolytic
migratory
erythema (NME)
is a
classical
symptom
observed in
patients
with
glucagonoma
and is
present in
80% of
cases.
Associated
NME is
characterized
by the
spread of
erythematous
blisters and
swelling
across areas
subject to
greater
friction and
pressure,
including
the lower
abdomen,
buttocks,
perineum,
and groin.
Diabetes
mellitus
also
frequently
results from
the insulin
and glucagon
imbalance
that occurs
in
glucagonoma.
Diabetes
mellitus is
present in
80-90% of
cases of
glucagonoma,
and is
exacerbated
by
preexisting
insulin
resistance.
Diagnosis
A blood
serum
glucagon
concentration
of 1000 pg/mL
or greater
is
indicative
of
glucagonoma
(the normal
range is
50-200 pg/mL).
Blood tests
may also
reveal
abnormally
low
concentrations
of amino
acids, zinc,
and
essential
fatty acids,
which are
thought to
play a role
in the
development
of NME. Skin
biopsies may
also be
taken to
confirm the
presence of
NME.
A CBC can
uncover
anemia,
which is an
abnormally
low level of
hemoglobin.
The tumor
itself may
be localized
by any
number of
radiographic
modalities,
including
angiography,
CT, MRI,
PET, and
endoscopic
ultrasound.
Laparotomy
is useful
for
obtaining
histologic
samples for
analysis and
confirmation
of the
glucagonoma.
Treatment
Heightened
glucagon
secretion
can be
treated with
the
administration
of
octreotide,
a
somatostatin
analog,
which
inhibits the
release of
glucagon.
Doxorubicin
and
streptozotocin
have also
been used
successfully
to
selectively
damage alpha
cells of the
pancreatic
islets.
These do not
destroy the
tumor, but
help to
minimize
progression
of
symptoms.
The only
curative
therapy for
glucagonoma
is surgical
resection,
where the
tumor is
removed.
Resection
has been
known to
reverse
symptoms in
some
patients.
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