Functional studies in patients with the glucagonoma syndrome.

Four patients with glucagon-producing tumours of the pancreas were investigated. Fasting plasma glucagon concentrations ranged from 209--625 pmol/l. Plasma insulin concentrations were normal except in one patient, where the tumour also produced insulin (558 pmol/l). Intravenous glucose (25 g/m2) depressed the glucagon concentration in two patients, while no change was noted in the others. Intravenous arginine stimulated glucagon secretion in three patients, but not in the fourth. Intravenous somatostatin suppressed glucagon secretion in all three patients investigated. All patients had abnormally low plasma levels of individual amino acids; glucogenic and branched-chain amino acids were equally depressed. Surgical removal of the tumours led to complete recovery from dermatosis and the glucagon levels were normalized. Postoperative tests were performed in three patients. The alpha-cell responsiveness to iv glucose was restored. Glucose tolerance (Kg-value) was improved in one patient (0.73 to 1.65), persistently low in one patient (0.75 to 0.72) and impaired in the third patient (1.35 to 1.09). It is concluded that none of these functional tests will be of diagnostic value in cases suspected of glucagonomas. The results also show that glucose homeostasis is remarkably unaffected by the extreme hyperglucagonaemia of these patients and that hypoaminoacidaemia is an important consequence of chronic hyperglucagonaemia.