ABSTRACT
Ghucagon is a pancreatic peptide, secreted by the A cells of the pancreatic islets of Langerhans under the influence of a certain number of regulating factors. This 29 amino-acids peptide has essentially a hyperglycemic action because it mobilizes all the organism's energetic reserves, and will therefore oppose insulin hypoglycemias. Its other actions are less known and are only expressed at supraphysiological levels such as its muscle relaxant effect on the digestive smooth muscle fibers, or its cardiac stimulant effect. Some authors have attributed recently to glucagons a role in the regulation of thirst and satiety, and that may lead to some interesting therapeutic actions such as in obesity. Its regulating action on liver cells has not been proven yet at least in severe hepatic lesions. Glucagonomas are rare neuroendocrine tumors, usually malignant, that develop in the endocrine pancreas and have a clinical picture characterized by the presence of the 4 D syndrome [migratory necrolytic dermatitis, diabetes mellitus, deep-vein thrombosis, and depression]. The tumor causing the hyperglucagonemia has a slow growth that explains its often important volume and the existence of metastasis in 60% of the cases at the time of diagnosis. Apart from the metastatic invasion, and as is the case in other neuroendocrine tumors, there are no definite criteria of histological malignancy. The definitive treatment of glucagonoma is surgical removal of the tumor, flanked or not by a treatment with somatostatin analogues that are active because of the existence of somatostatin receptors in neuroendocrine tumors. Radioactive somatostatin is utilized for the detection of metastatic sites but also as a therapeutic tool. Concerning whole-body scanning, the use of radiolabeled somatostatin has proven to be one of the high-performance techniques, but also a very sensitive one. As far as treatment is concerned, somatostatin radioactive analogues are increasingly replacing conventional radiotherapy as well as conventional chemotherapy