Glucagonoma

A glucagonoma is a rare tumorof the alpha cellsof the pancreasthat results in up to a 1000-fold overproduction of the hormoneglucagon. Alpha cell tumors are commonly associated with glucagonoma syndrome, though similar symptoms are present in cases of pseudoglucagonoma syndromein 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 physiologicaleffect of glucagonoma is an overproduction of the peptidehormone glucagon, which enhances blood glucoselevels through the activation of catabolicprocesses including gluconeogenesisand lipolysis. Gluconeogenesis produces glucosefrom proteinand amino acidmaterials; 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 mellitusalso frequently results from the insulinand glucagonimbalance 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 serumglucagon concentration of 1000 pg/mLor 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 biopsiesmay also be taken to confirm the presence of NME.

A CBCcan 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. Laparotomyis useful for obtaining histologicsamples 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. Doxorubicinand streptozotocinhave 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 surgicalresection, where the tumor is removed. Resection has been known to reverse symptoms in some patients.

References

• eMedicine - Glucagonoma
• Malignant glucagonoma of the pancreas diagnoses through anemia and diabetes mellitus
• Somatostatin analogue in treatment of coexisting glucagonoma and pancreatic pseudocyst: dissociation of responses

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It uses material from the http://en.wikipedia.org/wiki/Glucagonoma Wikipedia article Glucagonoma.