Malignant glucagonoma syndrome: response to chemotherapy

A 58-year-old white woman with known metastatic glucagonoma had widespread necrolytic migratory erythema characteristic of the glucagonoma syndrome. She did not respond to conventional chemotherapy with streptozocin. After one course of dacarbazine therapy, she had remission of the glucagonoma clinically with regression of tumor metastases as defined by liver scanning. After 10 months and additional courses of dacarbazine therapy, she remains in clinical remission. Plasma glucagon levels have decreased although they remain at two to four times the upper limit of normal. On several occasions there was resolution of this patient's rash after intravenous glucose in the absence of supplemental amino acids. We conclude that dacarbazine is an effective mode of chemotherapy for malignant glucagonoma.

Use of a common standard for comparison of insulin C-peptide measurements by different laboratories

A synthetic human C-peptide analogue has been used as a common standard for the comparison of insulin C-peptide measurements in seven assay systems in six laboratories. Even in terms of this common standard there was statistically significant numerical heterogeneity between laboratories for estimates of the C-peptide content of the same plasma samples. However, the consistency in ranking order of estimates of C-peptide in the plasma samples between laboratories suggests that laboratories are in most cases measuring at least similar immunoreactive constituents and that a reference plasma might prove useful in comparing results between laboratories. Until a more suitable reference material is available, the synthetic analogue, 64 formyllysine C-peptide, in ampoules coded 76/561, will be made available for research purposes.

Interrelationships among insulin, glucagon, and gastric inhibitory polypeptide in insulinoma

The interrelationships of serum insulin, glucagon, and gastric inhibitory polypeptide were examined in 13 patients with insulinoma during fed and fasted states. Compared with normal subjects, patients with insulinoma had significantly lower glucose and higher insulin levels during both the fed and the fasted states. Although glucagon concentration was higher at the completion of the fast in patients with insulinoma compared with normals, no significant differences were apparent during the fed state. No difference was noted in gastric inhibitory polypeptide either during the fed state or at the termination of the fast. Under the conditions of the study, no direct suppressive effect of insulin on glucagon or gastric inhibitory polypeptide secretion was apparent. In addition, as opposed to that in normals, the insulinotropic effect of glucagon did not appear to be blunted by hypoglycemia in most of the patients. After glucagon injection, all symptomatically hypoglycemic patients experienced an amelioration of symptoms and restoration of the plasma glucose into the normal range.

Pancreatic polypeptide as screening marker for pancreatic polypeptide apudomas in multiple endocrinopathies

Prospective screening was carried out in 12 members of three families with multiple endocrine adenopathies, type I (MEA,I) and in 14 patients with no multiple endocrine adenopathies with and without other endorcinopathies. Elevated basal and responsive (after a meal) plasma concentrations of a relatively new candidate-hormone, human pancreatic polypeptide (hPP), were associated with pancreatic apudoma tumors in three asymptomatic patients with multiple endocrine adenopathies, type I. Two of these patients had excision of the tumors that resulted in normal plasma hPP concentrations postoperatively. Both tumors contained hPP predominantly by immunocytochemistry; one, a pure pancreatic polypeptide apudoma, was studied extensively demonstrating also by radioimmunoassay a high content of hPP and negligible amounts of insulin, glucagon, somatostatin, vasoactive intestinal polypeptide and gastrin. In this patient plasma concentrations of other polypeptides including insulin, glucagon, somatostatin, vasoactive intestinal polypeptide, gastrin, parathyrin, thyrocalcitonin, prolactin, corticotropin, growth hormone, thyrtropin and amine, serotonin, were within normal limits. The other patient, after excision of an hPP-detected pancreatic mixed hPP-gastrinoma, also became eugastrinemic postoperatively. Normal basal plasma hPP concentrations, but with exaggerated hPP responses to a meal in 11 patients, were associated with various combinations of islet cell hyperplasia, antral G cell hyperplasia with moderate hypergastrinemia and parathyroid hyperplasia. The patients with multiple endocrine adenopathies who have demonstrated this type of increased hPP response to a meal have not been operated on but are at risk for islet hyperplasia. Four of the 12 patients with multiple endocrine adenopathies, type I, with both normal basal and normally responsive hPP concentrations have no evidence as yet of pancreatic involvement.

Measurement of human proinsulin by an indirect two-site immunoradiometric assay

An indirect two-site immunoradiometric assay is described for the measurement of human proinsulin in plasma. Polyethylene tubes coated with purified guinea-pig antibodies to insulin were used to extract proinsulin and insulin from plasma. Rabbit antibody to human C peptide was then added to react with the C-peptide moiety of the bound proinsulin. The uptake of this antibody was measured by the subsequent binding of 125I-sheep antibody to rabbit IgG. The binding of radioactivity to the tubes was a function of the proinsulin concentration in the sample. The sensitivity of the assay was 0.006 pmol/ml. Only 200 microliters of plasma was required in the assay and the 125I-labelled antibody was produced from readily available reagents. The polyethylene tubes remained stable for at least 5 months after coating. The mean fasting proinsulin level was 0.009 pmol/ml in sixteen normal subjects and 0.025 pmol/ml in twelve maturity onset diabetics. Oral glucose produced an 8 fold increase in proinsulin concentration but a decline in the plasma proinsulin/insulin molar ratio. Four patients with insulinoma had extremely elevated proinsulin levels and proinsulin/insulin ratios.

Calcium infusion: a new provocative test for insulinomas

Calcium gluconate (10 mg Ca(++)/kg) was administered intravenously over a 2-hour period to 16 adult patients who were evaluated for hypoglycemia. In nine of ten patients with benign or malignant insulinomas (eight proven at operation, and two with positive chemical tests and angiographic localization awaiting operation), significant hypoglycemia and hyperinsulinemia occurred within 60 to 90 minutes after the start of the calcium infusion. Serum proinsulin and Cpeptide concentrations increased at the time of the calciuminduced hyperinsulinemia in several patients in whom these parameters were studied. The one individual who did not respond to the calcium infusion was found to have a benign insulinoma. His basal glucose/insulin ratio of 0.64 was the lowest of the insulinoma group and thus his failure to respond to calcium may indicate that his tumor was secreting maximally at the time of the infusion. Following successful removal of the insulinoma, calcium infusion did not result in changes in serum glucose or insulin concentrations (tested in five patients). In contrast, neither a patient with pathologically documented islet cell hyperplasia, five others with reactive, fupctional or drug-induced hypoglycemia, nor four healthy volunteers showed any changes in circulating glucose or insulin levels while receiving calcium intravenously. Calcium infusion is a safe, rapid and effective provocative test for the diagnosis of insulin-secreting, islet cell tumors of the pancreas.

Effects of somatostatin on insulin and glucagon in patients with insulinoma

Effects of somatostatin on fasting and arginine-or tolbutamide-stimulated insulin release were studied in four patients with insulinoma. Somatostatin (bolus or bolus + infusion) reduced fasting insulin values in all patients; insulin response to tolbutamide was partially reduced in two patients; somatostatin bolus impaired the insulin response to arginine. Fasting glucagon levels and glucagon response to arginine were also reduced by somatostatin. These results indicate the potential usefulness of somatostatin in the diagnosis of insulinoma even if its effect on insulin is only partial.

Localizaiton of insulinomas by radioimmunoassay of blood obtained by the transport route

Transhepatic catheterization of the portal system was performed to obtain blood for RIA of insulin. This technique localized insulinomas in two patients after negative celiac, superior mesenteric, and subselective gastroduodenal arteriograms. The tumors were found in the predicted locations at surgery.

The surgical aspects of insulinomas

The clinical diagnosis of insulinoma rests on the demonstration of Whipple's triad (symptoms of hypoglycimia, low circulating glucose and prompt relief of symptoms after glucose administration). Biochemically, the association of an increased value of immunoreactive insulin with a low glucose value is diagnostic of insulin-mediated hypoglycemia. Angiographic localization of these tumors is accomplished in more than 90% of cases. The pathologic changes are usually due to a single adenoma, for which surgical enucleation is the procedure of choice. Malignancy and persistent hypoglycemia occur in slightly less than 10% of cases and can be fairly successfully managed by diazoxide and streptozotocin.

Islet cell tumors of the pancreas: clinico-biochemical correlations

Islet cell tumors produce a spectrum of syndromes. Intensive investigations of these tumors have enhanced our understanding of cellular origin, physiology and biochemistry of the islet hormones. Biochemical studies on the hormones are helpful in the diagnosis and treatment planning of the islet tumors. For example, insulinoma and glucagonoma can be diagnosed more readily by demonstration of proinsulin and proglucagon-like components, respectively, in the blood. Similarly, measurement of vasoactive intestinal polypeptide is not only useful in the diagnosis, but also in the follow-up of patients with pancreatic cholera syndrome. This mini-review examines these and other clinico-biochemical correlates seen in islet tumors.

[Vasoactive intestinal peptide (VIP) in the Verner-Morrison syndrome (author's transl)]

An early diagnosis of the Verner-Morrison syndrome will greatly enhance the chances of curative resection. There is a striking need for a simple diagnostic test. A number of suggestions have been made for the presumed hormone mediator of this syndrome. Numerous reports have led to a wide acceptance that vasoactive intestinal peptide (VIP) is the responsible mediator for the pharmacologic actions of this peptide are similar to the physiological characteristics noted in the watery diarrhea syndrome. A raised plasma VIP concentration, on the other hand, would suggest the presence of a tumour. These observations argue for the radioimmunoassay measurement of plasma VIP in a patient with the watery diarrhea syndrome.

Pancreatic islet cell adenocarcinoma: clinical and diagnostic features of six cases

The clinicopathologic aspects of pancreatic islet cell adenocarcinoma in 6 dogs were compared. Diagnosis was based on insulin-glucose ratios in 5 dogs. Surgical excision of the tumor resulted in absence of clinical signs for at least 1 year in 3 dogs.

Responses of patients with insulinomas to stimulators and inhibitors of insulin release that have been linked with cyclic adenosine monophosphate

The study comprises nine consecutive patients who had pancreatic beta-cell tumors and spontaneous hypoglycemia, seven of whom had verified, benign insulinomas and one a malignant insulinoma with metastases to the liver. The ninth patient, who refused surgery, was followed for three years without displaying any signs of malignancy. Among the patients with benign insulinomas, three showed exaggerated, two normal, and two unusual insulin responses to glucose. One such patient as well as the one with a malignant tumor did not respond to glucose. In general, the insulin responses to glucagon were similar to those to glucose. Somatostatin reduced basal insulin levels as well as the responses to glucose and glucagon only in subjects with normal or exaggerated responses to these agents. Einephrine behaved like somatostatin when insulin release was stimulated by glucose, but it was a weak inhibitor of the glucagon-stimulated response. The subject with the malignant insulinoma did not respond to either glucose or somatostatin. The remission of the disease, which followed streptozotocin treatment, was accompanied by restoration of the normal responsiveness to the above agents.

Glucagon stimulates insulin release by increasing the intracellular level of cyclic adenosine monophosphate (AMP). The effects of glucose, somatostatin, and epinephrine are supposed to be mediated, at least partially, by way of the adenylcyclase-cyclic AMP system. Therefore, the present data suggest that the variability of the beta-cell responsiveness to glucose and glucagon in patients with insulinoma reflects the responsiveness of the adenylcyclase-cyclic AMP system of the beta-cell tumor, which may be exaggerated, normal, or absent.

Insulin release in response to calcium in the diagnosis of insulinoma

A calcium infusion (4 mg Ca++/kg/hr) significantly increased plasma insulin levels and reduced blood glucose in 4 patients with insulin-secreting pancreatic islet cell tumors. These parameters were not altered by a similar infusion of calcium in normal volunteers, 2 patients with alimentary hypoglycemia, and 2 with functional hypoglycemia. No difference in response was observed between patients with benign and malignant beta-cell tumors. Infusion of diazoxide (600 mg) with calcium blocked the stimulation of the latter on insulin secretion. The results indicate the usefulness of calcium infusion in the diagnosis of insulin-secreting tumor.

Localization of occult insulinoma by super-selective pancreatic venous sampling for insulin assay through percutaneous transhepatic catheterization

Preoperative localization of insulinomas by arteriography is successful only 66% of the time. With small tumors, intraoperative localization is usually unsuccessful also. Because surgical morbidity and mortality are increased greatly when major, blind, pancreatic resections or reoperations are performed, additional preoperative localization procedures are needed. We now report the successful localization of an occult insulinoma by means of blood sampling for insulin radioimmunoassay, obtained by selective pancreatic vein sampling through percutaneous transhepatic catheterization.

Our patient had symptoms of fasting hypoglycemia for 11 months. Routine studies were normal and two fasting plasma glucose concentrations were 34 and 16 mg/dl to correspond with insulin values of 33 and 75 μU/ml. Celiac arteriography was normal. Percutaneous transhepatic portal and pancreatic venous catheterization revealed insulin concentrations (μU/ml) of between 23 and 36 in portal and splenic veins, 17 in the short, gastric vein, 17 in the dorsal pancreatic vein, 19 in the superior, mesenteric vein, and 61 and 288 in two pancreatic magna veins draining the tail. An insulinoma of 2 × 3 cm was resected from the tail. On the basis of our experience with this patient, it is clear that selective venous sampling may facilitate the localization of occult insulinomas at surgery and thereby avoid extensive, blind, pancreatic resections and the need for reoperation.

The effect of propranolol on hypoglycaemia. Observations in five insulinoma patients

Five hypoglycaemic hyperinsulinaemic patients (three with proven benign insulinoma, one with proven metastasizing insulinoma, one with probable insulinoma not found at surgery) were treated with propranolol for a variable time ranging from two weeks to one year. Three patients showed favourable clinical results and a significant increase of the mean basal blood glucose level was found while two patients showed no improvement of the frequency of neuroglycopenic episodes and no significant increase of their mean blood glucose level. No patient showed a significant decrease in mean basal IRI concentration. A decrease of insulinaemic responses was observed during oral and intravenous glucose tolerance tests, a prolonged fast, and tolbutamide and glucagon tests performed in some patients. The results suggest that propranolol may induce in certain patients an improvement of basal clinical status through not understood effects (probably hepatic), which leave the peripheral concentrations of insulin unchanged, whereas inhibition of insulin secretion may represent the main way by which the improvement of metabolic situation during physiological or pharmacological stimulation may have been achieved.

Insulinoma resection facilitated by the artificial endocrine pancreas

The artificial endocrine pancreas was adapted to assist with the intraoperative localization of an insulin-secreting islet cell adenoma in a 23-year-old patient with a five-month history of hypoglycemic attacks. Glycemia was monitored in continuously withdrawn whole blood, and dextrose was infused to maintain euglycemia by an artificial endocrine pancreas with a closed loop that excluded its usual insulin delivery capability. The dextrose infusion rate was established in accordance with a control algorithm whose parameters were chosen to amplify changes in dextrose delivery rate for small alterations in the measured baseline glucose concentration. The dextrose infusion rate preoperatively was 155 mg. per minute and decreased to 100 mg. per minute with initiation of surgery. An area in the tail of the pancreas suspected of containing the insulinoma was excluded from the circulation by a noncrushing clamp. After 14 minutes the dextrose infusion progressively decreased to 27 mg. per minute reflecting a glycemic rise of 15 mg. per deciliter. These changes were taken to represent a fall in ambient insulin activity. This was subsequently confirmed directly by the demonstration of reduction in immunoreactive insulin and progressive increase in both plasma free fatty acid levels and postoperative glucose intolerance. Exclusion of the insulinoma from the circulation resulted also in a rapid decrease of circulating proinsulin concentration giving an estimated half-life of 25 minutes.

Insulinoma: poor recognition of clinical features is the major problem in diagnosis

Traditionally it is taught that hypoglycaemia may cause a clinical picture which mimics a variety of neurological and psychiatric disorders. Yet patients with insulinoma continue to baffle many medical specialists, who presumably are not sufficiently aware of the clinical features of hypoglycaemia. After examining medical records of seventeen patients, diagnosed as suffering from "insulinoma" in major Melbourne hospitals from 1971 to 1976, it was evident that these patients frequently undergo extensive investigations for supposed neurological disorders, the correct diagnosis being missed until they develop catastrophic symptoms. Of these seventeen patients, the diagnosis was made with reasonable speed in only six cases, while eight patients were initially discharged from hospital with a completely erroneous diagnosis. It seems likely that a number of patients with insulinoma, whose symptoms are less dramatic than those reported here, are being mistakenly treated as having epileptiform or psychiatric disorders.

Blood amine acid levels in patients with insulin excess (functioning insulinoma) and insulin deficiency (diabetic ketosis)

Blood amino acid concentrations were determined in the postabsorptive state in nine patients with insulin excess (functioning insulinomas), nine juvenile-type diabetics with insulin deficiency (diabetic ketosis due to insulin withdrawal), six juvenile diabetics in moderate metabolic control, and five healthy control subjects. Blood branched-chain amino acid (BCAA) levels were elevated in diabetic ketosis and decreased in patients with insulinomas. Blood concentrations of BCAA were significantly correlated to blood glucose levels, and in diabetics they were also correlated to blood ketone bodies, serum free fatty acids, and glycerol levels. These data indicate an inverse relationship between circulating effective insulin levels and blood BCAA concentrations. It is suggested that blood levels of BCAA might represent an indicator of insulin-dependent alterations of protein metabolism.