A glucagonoma is a rare tumor of the alpha cells of the pancreas that results in the 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.
Signs and symptomsEdit
The primary physiological effect of glucagonoma is an overproduction of the peptide hormone glucagon, which leads to an increase in blood glucose levels through the activation of anabolic and catabolic processes including gluconeogenesis and lipolysis respectively. Gluconeogenesis produces glucose from protein and amino acid materials. It also increases lipolysis, which is the breakdown of fat. The net result is a high level of glucagon in the blood, decreased blood levels of amino acids (hypoaminoacidemia), too few red blood cells, diarrhea, and weight loss of 5 to15 kg.
Necrolytic migratory erythema (NME) is a classical symptom observed in patients with glucagonoma and is the presenting problem in 70% of cases. Associated NME is characterized by the spread of red 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 from a glucagonoma. Diabetes mellitus is present in 80% to 90% of cases of glucagonoma, and is exacerbated by preexisting insulin resistance.
Although the cause is unknown, genetic factors play a role in some cases. A family history of multiple endocrine neoplasia type 1 (MEN 1) is a risk factor. These tumors are usually cancerous, with the cancer spreading and getting worse.
However, recent studies have shown that forty percent of patients have plasma glucagon levels ranging from 500 to 1000 pg/mL. Increased levels have been reported in cases of decreased kidney function, acute pancreatitis, hypercorticism, liver diseases, severe stress, extended fasting, and familial hyperglucagonemia. Rarely do these cases result in levels over 500 pg/mL, except in the case of patients with liver diseases.
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.
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.
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.
Fewer than 251 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 remain unknown.
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- Medline Plus, accessed 4 August 2017.
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