Hypoglycemic Syndrome without Hyperinsulinemia. A Diagnostic Challenge

The most common cause of organic fasting hypoglycemia in adults is the presence of an insulin-producing pancreatic adenoma, but when high insulin levels are not found, the differential diagnosis is challenging. Misdiagnosis can lead to an unnecessary pancreatectomy. Insulin concentrations may be low in some cases despite a clinical history suggestive of insulinoma. In these cases, a proinsulinoma should be suspected, although the rarity of this condition requires an extensive workup before reaching a final diagnosis. We describe an unusual case of a 38-year-old man with a severe hypoglycemic syndrome due to a proinsulin-secreting pancreatic adenoma. Insulin was measured by the specific assay and suppressed under the lower detection limit during fasting hypoglycemia. Serum proinsulin and C-peptide levels were abnormally elevated, and further tests revealed an islet cell tumor. The tumor was surgically removed, relieving the fasting hypoglycemia. Histopathological study showed a conventional well-differentiated neuroendocrine tumor with high immunoreactivity against proinsulin and with lesser intensity against insulin. Interestingly, GS-9A8 antibody clone used for immunostaining proinsulin did not cross-react with human insulin or C-peptide, providing an unbiased picture of proinsulin secretion. The resolution of symptoms, the fall of proinsulin concentrations after tumor removal and the histopathology study confirmed the diagnosis of proinsulinoma.

Immunoreactive insulin in portal and hepatic venous blood in patients with insuloma

The insulin level has been determined simultaneously in portal and hepatic venous blood in four patients with insuloma before and after administration of glucose and tolbutamide. Three patients displayed a higher insulin level in hepatic than in portal blood, although no hepatic metastases could be detected by radiologic examination. In contrast, portal insulin concentrations always exceeded hepatic in four control patients investigated in a similar way. The implications of these results are discussed.

Co-expression of ghrelin and its receptor in pancreatic endocrine tumours

OBJECTIVE

Expression of ghrelin has been reported in pancreatic endocrine tumours, but data on ghrelin receptor protein expression are lacking. The aim of this study was to examine the ghrelin receptor, as well as ghrelin, in a selected series of these tumours, including multiple endocrine neoplasia 1 (MEN1) associated tumours, and to correlate data with clinical features including body mass index.

DESIGN

Immunohistochemical detection of ghrelin and its receptor was performed on frozen tissue from 31 tumours: 9 MEN1 and 22 sporadic. Twenty tumours were analysed by quantitative PCR. Plasma ghrelin was assessed in 26 patients.

RESULTS

Twenty-one (68%) of 31 tumours showed immunoreactivity for ghrelin (8/9 MEN1) and 19/20 expressed ghrelin mRNA. Ghrelin receptor protein was detected in 21/30 (70%) tumours (4/8 MEN1), and mRNA was detected in all analysed tumours. Insulinomas had significantly higher levels of receptor mRNA than other tumours. Five patients had elevated plasma ghrelin (> 2 SD above the control group mean). No significant difference in mean plasma ghrelin levels was found between patients (908 +/- 569 ng/l) and controls (952 +/- 164 ng/l). Mean BMI was 24.3 kg/m(2). There was no association between ghrelin or receptor expression and survival.

CONCLUSIONS

We report the first immunohistochemical data on expression of the ghrelin receptor in pancreatic endocrine tumours: 70% of tumours in our material. Concomitant ghrelin and receptor expression was seen in 50% of tumours, indicating an autocrine loop. Ghrelin was expressed in 68% of tumours (8/9 MEN1). Despite frequent ghrelin expression, elevated circulating ghrelin is rare in these patients.

Renal cell carcinoma with non-islet cell tumor hypoglycemia

We report a case of an elderly gentleman with renal cell carcinoma presenting with the rare entity of non-islet cell tumor hypoglycemia (NICTH). Non-islet cell tumor hypoglycemia syndrome is caused by the tumor producing insulin-like growth factor II, causing hypoglycemia. The syndrome is most commonly associated with very large fibromas or fibrosarcomas.

Effect of inhibition of vascular endothelial growth factor signaling on distribution of extravasated antibodies in tumors

Antibodies and other macromolecular therapeutics can gain access to tumor cells via leaky tumor vessels. Inhibition of vascular endothelial growth factor (VEGF) signaling can reduce the vascularity of tumors and leakiness of surviving vessels, but little is known about how these changes affect the distribution of antibodies within tumors. We addressed this issue by examining the distribution of extravasated antibodies in islet cell tumors of RIP-Tag2 transgenic mice and implanted Lewis lung carcinomas using fluorescence and confocal microscopic imaging. Extravasated nonspecific immunoglobulin G (IgG) and antibodies to fibrin or E-cadherin accumulated in irregular patchy regions of stroma. Fibrin also accumulated in these regions. Anti-E-cadherin antibody, which targets epitopes on tumor cells of RIP-Tag2 adenomas, was the only antibody to achieve detectable levels within tumor cell clusters at 6 hours after i.v. injection. Treatment for 7 days with AG-013736, a potent inhibitor of VEGF signaling, reduced the tumor vascularity by 86%. The overall area density of extravasated IgG/antibodies decreased after treatment but the change was less than the reduction in vascularity and actually increased when expressed per surviving tumor vessel. Accumulation of anti-E-cadherin antibody in tumor cell clusters was similarly affected. The patchy pattern of antibodies in stroma after treatment qualitatively resembled untreated tumors and surprisingly coincided with sleeves of basement membrane left behind after pruning of tumor vessels. Together, the findings suggest that antibody transport increases from surviving tumor vessels after normalization by inhibition of VEGF signaling. Basement membrane sleeves may facilitate this transport. Antibodies preferentially distribute to tumor stroma but also accumulate on tumor cells if binding sites are accessible.

Biochemical diagnosis of gastroenteropancreatic endocrine tumors

Functioning gastroenteropancreatic endocrine tumors produce and secrete different substances that can be detected in the plasma and cause hormone-related syndromes. Symptoms such as diarrhea associated either with typical skin rash or peptic ulcer disease may be suggestive of the presence of intestinal carcinoid or gastrinoma. Other clinical manifestations such as severe hypoglycemia, diabetes, necrolytic erythema and gallbladder disease may also indicate an endocrine tumor. Sometimes, patients present no, or just vague, symptoms such as dyspepsia or abdominal pain and nonfunctioning endocrine tumors in these patients can be found incidentally during diagnostic imaging procedures or at operation. Usually, the diagnosis is established by the measurement of the specific tumor marker in the plasma and, sometimes, in the urine. In some cases, normal basal hormone levels are observed even in the presence of typical symptoms. Therefore, stimulatory tests such as the secretin test for gastrinomas are required to establish the diagnosis. General markers for the diagnosis of gastroenteropancreatic endocrine tumors are also available. Among these, chromogranin A has proved to be of great value for diagnosing nonfunctioning tumors and is considered the most sensitive general marker. The availability of both specific and general markers as well as stimulatory tests may enable the clinician to diagnose functioning gastroenteropancreatic endocrine tumors at an early stage and to recognize nonfunctioning tumors.

A new classification plot for the C-peptide suppression test

CONTEXT AND OBJECTIVE

To evaluate the C-peptide suppression test as a screening test in patients with symptoms of hypoglycemia as compared to the standard fasting test.

DESIGN

Retrospective discriminant analysis of data from C-peptide suppression tests.

SETTING

Clinical study.

PATIENTS

Patients with insulinomas and patients without insulinomas but having symptoms compatible with hypoglycemia.

INTERVENTIONS

The results from C-peptide suppression tests of 26 patients with insulinomas and 100 patients without insulinomas were compared.

MAIN OUTCOME MEASURES

A classification plot which introduces two discriminant parameters for the C-peptide suppression test: the ratio of [blood glucose]/[C-peptide] at the lowest C-peptide concentration and mean glycemia during insulin infusion.

RESULTS

In patients with insulinomas, minimal serum C-peptide levels were higher (1.81+/- 0.87 ng/mL; median 1.83 ng/mL; maximal suppression 37 +/- 24% of basal C-peptide levels) as compared to patients without insulinoma (0.40 +/- 0.15 ng/mL; median 0.30 ng/mL; maximal suppression of 75 +/- 9%; P<0.001). Mean glycemia during the test was lower in patients with insulinomas (30.8 +/- 3.3 vs. 47.5 +/- 8.3 mg/dL; P<0.001) as was the [blood glucose]/[C-peptide] ratio (21.9 +/- 14.6 vs. 139.2 +/- 43.8; P<0.001). Discriminant analysis revealed a specificity of 96% to rule out the diagnosis of 'insulinoma' at a 1% probability threshold with a sensitivity of 100%.

CONCLUSIONS

We developed a new classification plot for the C-peptide suppression test in order to accurately identify those patients whose symptoms of hypoglycemia are not due to endogenous hyperinsulinemia/insulinomas. Thus, the need for fasting tests and hospitalization costs can be reduced.

The hypothalamic satiety peptide CART is expressed in anorectic and non-anorectic pancreatic islet tumors and in the normal islet of Langerhans

The hypothalamic satiety peptide CART (cocaine and amphetamine regulated transcript) is expressed at high levels in anorectic rat glucagonomas but not in hypoglycemic insulinomas. However, a non-anorectic metastasis derived from the glucagonoma retained high CART expression levels and produced circulating CART levels comparable to that of the anorectic tumors. Moreover, distinct glucagonoma lines derived by stable HES-1 transfection of the insulinoma caused severe anorexia but retained low circulating levels of CART comparable to that of insulinoma bearing or control rats. Islet tumor associated anorexia and circulating CART levels are thus not correlated, and in line with this peripheral administration of CART (5-50 mg/kg) produced no effect on feeding behavior. In the rat two alternatively spliced forms of CART mRNA exist and quantitative PCR revealed expression of both forms in the hypothalamus, in the different islet tumors, and in the islets of Langerhans. Immunocytochemistry as well as in situ hybridization localized CART expression to the somatostatin producing islet D cell. A potential endocrine/paracrine role of islet CART remains to be clarified.

Increased levels of circulating free insulin-like growth factors in patients with non-islet cell tumour hypoglycaemia

Non-islet cell tumour hypoglycaemia (NICTH) is characterised by severe and recurrent fasting hypoglycaemia, and is usually caused by secretion of insulin-like growth factor-II (IGF-II) by the tumour. This induces secondary changes in the circulating levels of insulin, growth hormone (GH), and the IGF-binding proteins (IGFBPs), resulting in an increased insulin-like hypoglycaemic activity of IGF-II. A participating role of IGF-I is not established. We measured serum levels of free IGF-I and free IGF-II, total IGF-I, total IGF-II, big IGF-II and IGFBP-1, IGFBP-2 and IGFBP-3 in patients with NICTH before (n=14) and after surgical removal of the tumour (n=3). A control group (n=20) was included for comparison. In NICTH patients, free IGF-II was 20-fold increased (26.8+/-8.1 [mean+/-SEM] vs. 1.3+/-0.1 microg/l), and free IGF-I was four fold increased (2.8+/-0.4 vs. 0.7+/-0.1 microg/l), as compared to control subjects (p < 0.0001). In accordance with earlier observations levels of total IGF-I, total IGF-II, and IGFBP-3 were decreased, whereas IGFBP-1 and IGFBP-2 were increased in NICTH (all p-values < 0.05). The highly elevated levels of free IGF-I and free IGF-II most likely imply a considerable hypoglycaemic insulin-like activity, and may, by negative feedback explain the marked suppression of the GH/IGF-I axis observed in NICTH. Finally, free IGF-II seems to be a powerful biochemical marker in the diagnosis of NICTH.

Acinar-islet cell carcinoma presenting as insulinoma

A case of acinar-islet cell carcinoma presenting as insulinoma is reported. The patient was a 28-year-old man who presented with two convulsive episodes. Fajans' index [immunoreactive insulin (IRI; microU/ml/ glucose mg/dl)] and Turner's [IRI (microU/ml) x 100/glucose (mg/dl) - 30] index were high (2.8 and 308, respectively), as were serum proinsulin levels (550 pg/ml). Abdominal computed tomography and angiography revealed a highly vascular tumor in the pancreatic tail and several similar tumors in the liver. Histologic features of a biopsy specimen from a hepatic tumor were those of a malignant pancreatic endocrine tumor. Insulin secretion by the liver metastases was confirmed by venous sampling after arterial stimulation with calcium. These findings led us to diagnose malignant insulinoma with liver metastases. Serum levels of alpha-fetoprotein and trypsin were markedly elevated, to 2234 ng/ml (normal < 10) and 22,000 ng/ml (normal < 460) respectively, and these levels continued to rise with further growth of the liver metastases. Immunohistochemically, the metastatic liver tumor specimen was positive for alpha-fetoprotein, alpha 1-antichymotrypsin, chromogranin A, and neuron-specific enolase. These findings of amphicrine features in the tumor were indicative of acinar-islet cell carcinoma that produced alpha-fetoprotein and trypsin in addition to insulin.

Comparison of chromogranin A and pancreastatin levels in plasma of patients with pancreatic islet cell tumor

The plasma levels of chromogranin A (CGA) in patients with islet cell tumor and plasma CGA responses to administration of a somatostatin analogue (Octreotide) in two of these patients were examined in comparison with plasma pancreastatin (PST) levels. There was a significant correlation between the fasting plasma levels of CGA and PST (r = 0.6, P < 0.001). Administration of the somatostatin analogue reduced the plasma concentrations of PST and CGA within 1 h, but the responses of CGA and PST to the analogue were not parallel in either patient. Thus, the suppressive effects of the analogue on the secretions of PST and CGA may be different. The results suggest the value of the PST and CGA assays used in this study.

Embolization in the palliation of complications of inoperable primary pancreatic neoplasms

Primary pancreatic neoplasm typically presents at an advanced stage where surgical management may not be feasible. These patients are often symptomatic due to biliary obstruction but problems may also include gastrointestinal bleeding and endocrinological complications. We describe two cases illustrating the use of palliative embolization in the control of biochemical and haemorrhagic complications of primary pancreatic neoplasm. In one case, massive gastrointestinal bleeding from an inoperable primary pancreatic carcinoma was controlled by two embolization procedures to produce devascularization of the primary lesion. In a second case, life-threatening hypercalcaemia was thought to be due to secretion of a parathormone-like material from an inoperable islet cell tumour. There was no evidence of liver metastases and the pancreatic mass was embolized, following which serum calcium was reduced to near normal levels with considerable clinical improvement. We conclude that there is a role for embolization of inoperable primary pancreatic neoplasm in the palliation of biochemical or haemorrhagic complications of these tumours.

Comparison of plasma pancreastatin and GAWK concentrations, presumed processing products of chromogranin A and B, in plasma of patients with pancreatic islet cell tumors

Plasma pancreastatin (PST) and GAWK, peptides processed from chromogranin A and B, were elevated in patients with various neuroendocrine tumors. In the present study, we measured plasma PST- and GAWK-like immunoreactivity (LI) concentrations in 12 patients with pancreatic islet cell tumors and evaluated them as a marker for these tumors. We also performed the gel filtration of the plasma from a gastrinoma patient and investigated the processing of PST and GAWK in plasma. Elevation of plasma PST-LI was found in 4 of 12 patients (33%) and elevation of plasma GAWK-LI was found in 6 of 12 patients (50%). A significant correlation was not found between plasma PST- and GAWK-LI concentrations of the patients. In the gel permeation chromatography of the plasma from a gastrinoma patient, PST-LI composed of a single peak but GAWK-LI composed of several components with wide range molecular weights.

Distribution and elimination of the somatostatin analogue (111In-DTPA-D-Phe1)-Octreotide (OctreoScan111)

The distribution and elimination characteristics of the 111In-labelled somatostatin analogue OctreoScan111 were studied in 23 patients with malignant tumours. The substance exhibited a rapid blood elimination following a bi-phasic pattern. The initial part of the elimination curves showed a t1/2a of between 0.27 and 3.6 h. The patients investigated had creatinine clearance rates ranging from 33 to 124 ml/min. However, within this range, no apparent correlation was found between the OctreoScan111 elimination rate and kidney function. Also no correlation was observed between the amount of administered activity and the elimination rate of OctreoScan111. The serum radioactivity of 6 patients was analyzed with respect to molecular size. These experiments showed that OctreoScan111 circulated unbound in serum. About 3% of the radioactivity, most probably representing 111In-chloride of DTPA-111In-chloride, circulated protein-bound. The elimination of OctreoScan111 radioactivity in urine displayed a bi-phasic pattern. Size separation of the radioactivity appearing in the urine after 24 h showed a higher molecular weight when compared with OctreoScan111, indicating the existence of a metabolite of the injected substance. The results obtained are discussed in the light of a potential role for the substance in systemic radiotherapy.

Recombinant interferon alpha-2b in patients with metastatic apudomas: effect on tumours and tumour markers

Malignant carcinoid tumours, islet cell tumours and medullary carcinomas of the thyroid are tumours with similar clinical features. In patients with unresectable or metastatic tumours leukocyte interferon (IFN) and recombinant human (rh) IFN have demonstrated efficacy. Twenty-four evaluable patients with progressive tumours were treated with 2.5 megaunits rh IFN alpha-2b, administered once daily subcutaneously, for a median duration of 7 months (range 0.5-37+). Two carcinoid patients demonstrated a response in tumour size, 80% showed stable disease (SD). Sixty percent of the carcinoid patients with elevated urinary 5-hydroxyindoleacetic (5-HIAA) levels reached a biochemical partial response of the urinary 5-HIAA levels (median duration 13.5 months). In the patients with an islet cell or medullary tumour and an elevated tumour marker, the marker did not further increase. Of the 12 carcinoid patients evaluable for a symptomatic response, ten (83%) experienced a relieve of symptoms. IFN alpha-2b dose reduction or discontinuation due to toxicity was necessary in three and ten patients, respectively. No neutralising IFN alpha-2b antibodies developed despite prolonged treatment. In conclusion, IFN alpha-2b had a beneficial effect in patients with progressive tumours, while long-term IFN alpha-2b treatment did not augment neutralising antibodies. In view of the IFN alpha-2b-related toxicity, administration of IFN alpha-2b on alternating days may be preferable.

Production of immunoreactive corticotropin-releasing hormone in various neuroendocrine tumors

The concentrations of immunoreactive (IR) corticotropin-releasing hormone (CRH) in 218 neuroendocrine tumors were determined by CRH radioimmunoassay. The tumors examined were 86 pancreatic endocrine tumors (PET), 22 neuroblastic tumors (NBT), 26 carcinoid tumors (CA), 24 pheochromocytomas (PHEO), 40 small cell lung carcinomas (SCLC) and 20 medullary thyroid carcinomas (MTC). IR-CRH was detectable in 21 neuroendocrine tumors (10 PET, four NBT, three CA, two PHEO and two SCLC) at levels of 10-2,700 ng/g wet weight (9.6%). The 21 patients with these CRH-producing tumors showed no clinical symptoms suggestive of Cushing's syndrome. The levels of plasma IR-CRH extracted by immunoaffinity chromatography were < 7.5 pg/ml in five normal subjects and a patient with a neuroblastic tumor containing 55 ng/g wet weight IR-CRH, but in a patient with a thymic carcinoid tumor containing 1,000 ng/g wet weight IR-CRH, the plasma level was elevated to 180 pg/ml. This patient did not have Cushing's syndrome nor an elevated plasma adrenocorticotropic hormone (ACTH) level. The concentrations of nine peptides (growth hormone-releasing hormone, somatostatin, ACTH, calcitonin, gastrin-releasing peptide, glucagon, vasoactive intestinal peptide, neuropeptide tyrosine and pancreatic polypeptide) were determined in extracts of the 21 IR-CRH-producing tumors. Some of these peptides were frequently found to be produced concomitantly with CRH. The results indicate IR-CRH to be produced by various neuroendocrine tumors, but Cushing's syndrome, due to the CRH, to be very rare. The results also show that CRH-producing tumors produce multiple hormones.

Calcitonin immunoreactivity and hypercalcitoninemia in two patients with sporadic, nonfamilial, gastroenteropancreatic neuroendocrine tumors

BACKGROUND

Hypercalcitoninemia in gastroenteropancreatic tumors associated with calcitonin immunoreactivity is rare.

METHODS

We report here two patients in whom pancreatic neuroendocrine tumors both contained and secreted immunoreactive calcitonin. Both patients experienced elevated basal calcitonin immunoreactivity.

RESULTS

The peak responses of immunoreactive calcitonin occurred 5 minutes after pentagastrin administration in these two patients and were 30% and 180% above basal concentrations corresponding to peak increments of 0.39 and 8.78 ng/ml, respectively. The immunoreactive calcitonin response to pentagastrin in these two patients was not significantly different from that seen among five patients with medullary carcinoma of the thyroid gland.

CONCLUSION

It does not appear that immunoreactive calcitonin responses to pentagastrin stimulation will discriminate between patients with medullary carcinoma of the thyroid gland and those with nonfamilial, gastroenteropancreatic neuroendocrine tumors that express calcitonin immunoreactivity. In patients with secretory diarrhea and/or flushing, an elevated level of immunoreactive calcitonin, in the absence of a thyroid mass in the neck, may herald the presence of a gastroenteropancreatic neuroendocrine tumor.

Insulin-secreting pancreatic (islet cell) carcinoma in a cat

A functional, insulin-secreting pancreatic (islet cell) carcinoma was diagnosed in a 17-year-old male Siamese cat. Diagnosis was made on the basis of clinical signs (i.e., seizures and stupor) that resolved temporarily after correction of hypoglycemia with feeding or intravenous administration of glucose, the finding of an inappropriately increased serum insulin concentration in the face of hypoglycemia, and prolonged resolution of hypoglycemia after surgical removal of the tumor. Primary islet cell tumor of the pancreas was confirmed by biopsy. The cat died 18 months later, and necropsy revealed metastases to regional lymph nodes and liver. Specimens of the tumor and metastatic lesions both stained positively for insulin.

Islet amyloid polypeptide-producing pancreatic islet cell tumor. A clinical and biochemical characterization

Islet amyloid peptide (IAPP) or amylin is a recently discovered polypeptide without settled physiology in man. We present a patient with an endocrine pancreatic tumor secreting huge amounts of IAPP-like immunoreactivity (20,000 mol/l) and a concomitant development of diabetes mellitus. The release of insulin and pancreatic polypeptide (PP) was totally absent after an oral glucose load and a mixed meal, respectively. Tumor secretion of IAPP-like immunoreactivity seemed to be influenced by cholinergic mechanisms and by nutrients. The observed effects on insulin and PP secretion by high circulating levels of IAPP-like immunoreactivity may be of beneficial value for further studies of the physiology of IAPP in man.

7B2, a possible marker for nonfunctioning pancreatic islet cell tumor

Plasma 7B2 was measured in 13 patients with pancreatic islet cell tumors, 11 with pancreatic adenocarcinoma and 31 normal subjects as a control. The mean (+/- SD) concentrations of plasma 7B2 in the normal subjects and the patients with pancreatic islet cell tumors were 67 +/- 10 and 1041 +/- 1786 pmol/l, respectively, and the value in the patients with pancreatic islet cell tumors was significantly higher than that in the normal subjects (p less than 0.01). Elevation of plasma 7B2 over the normal range, defined as less than the mean + 3SD value of those in the normal subjects, was found in 10 of 13 patients with pancreatic islet cell tumors including 4 with nonfunctioning tumor. Plasma 7B2 dropped into the normal range postoperatively in 3 patients with nonfunctioning tumor. Plasma 7B2 concentrations in the patients with pancreatic adenocarcinoma remained in the normal range. These results raise a possibility that 7B2 is a useful marker for pancreatic islet cell tumors, in particular nonfunctioning tumor.

Treatment of neuroendocrine carcinomas with combined etoposide and cisplatin. Evidence of major therapeutic activity in the anaplastic variants of these neoplasms

Forty-five patients with metastatic neuroendocrine tumors were treated with a regimen of etoposide 130 mg/m2/d for 3 days plus cisplatin 45 mg/m2/d on days 2 and 3. Both drugs were given by continuous intravenous infusion. Among 27 patients with well-differentiated carcinoid tumors or islet cell carcinomas, only two partial objective tumor regressions were observed (7%). Among 18 patients prospectively classified as having anaplastic neuroendocrine carcinomas, however, there were nine partial regressions and three complete regressions, an overall regression rate of 67%. For anaplastic disease, the median duration of regression was 8 months (range to 21 months). Tumor response was unrelated to primary site, endocrine hyperfunction, or prior therapy experience. The median survival of all patients with anaplastic tumors was 19 months; this seemed favorable when considering the small experiences with these rare tumors reported in the literature. Toxicity, which was severe for most patients, consisted primarily of vomiting, leukopenia, thrombocytopenia, anemia, alopecia, and neuropathy. The anaplastic neuroendocrine tumor is strongly responsive to therapy with combined etoposide and cisplatin. Patients with undifferentiated carcinomas, originating in typical neuroendocrine tumor sites (small and large bowel, pancreas, and stomach) or of unknown origin, who have consistent histologic findings by light microscopy should be evaluated for this possibility with appropriate immune staining or electron microscopy.

Effect of the somatostatin analogue octreotide acetate on hemostasis in humans

Octreotide acetate is a somatostatin analogue that has been shown to ameliorate the side effects of excessive secretion of hormone from benign and malignant tumors. The ability of this drug to inhibit the growth of malignant cells and to control gastrointestinal hemorrhage will prompt additional clinical trials. Because some of these patients may have thrombocytopenia, platelet dysfunction, or a coagulopathy, we studied tests of platelet function and blood coagulation in 15 patients before and after 14 days of therapy with octreotide acetate at a dosage of 500 micrograms three times daily. We found no substantial change in the results of these tests, and no patient experienced bleeding or thrombosis. These results suggest that octreotide acetate does not adversely affect platelet function or the coagulation system in humans.

The utility of circulating levels of human pancreatic polypeptide as a marker for islet cell tumors

The measurement of plasma levels of human pancreatic polypeptide (hPP) has been reported to be clinically useful in predicting the existence of pancreatic islet cell neoplasms in patients with familial multiple endocrine neoplasia type 1 (FMEN-I) and the possible presence of metastatic disease in patients with islet cell tumors. However, these studies have not been prospective and involve small numbers of patients. In this study, fasting plasma samples from 36 patients with biopsy-proved islet cell tumors were analyzed for hPP by radioimmunoassay and compared with age-matched control subjects. Of 13 patients with FMEN-I who had islet cell tumors, 7 (54%) had elevated plasma hPP levels before surgery. After resection of all islet cell tumors, 4 of 12 patients evaluated after surgery still had elevated levels. Fifteen patients had islet cell tumors that were localized (seven insulinomas and eight gastrinomas), but none of these patients had elevated hPP levels, either before or after surgery. Nine patients, including one with FMEN-I, with metastatic islet cell tumors to the liver were studied; three with more advanced disease had elevated hPP levels before surgery. Each of the nine patients underwent resection of all gross disease and the three patients with elevated preoperative levels had normal postoperative hPP levels. Our results indicate that basal plasma levels of hPP were not clinically useful. The hPP levels did not reliably predict the presence of islet cell tumors in patients with FMEN-I, because 46% of patients with tumors did not have elevated plasma levels, and in those with elevated values hPP levels did not reliably predict the resection of all tumor. Plasma levels of hPP have no utility in patients with localized sporadically occurring islet cell tumors and limited utility (33%) in predicting the presence of metastatic islet cell tumors to the liver.

Parathyroid hormone-related peptide in plasma of patients with hypercalcemia and malignant lesions

We developed and validated a radioimmunoassay for circulating human parathyroid hormone-related peptide (PTHrP), based on a commercial antiserum to the synthetic 1-34 fragment of PTHrP, 125I-Tyr degrees-PTHrP(1-34) as radioligand, and prior extraction of the native peptide from plasma with C-2 cartridges. We determined immunoreactive PTHrP concentrations in plasma samples from 48 healthy persons (mean +/- SD, 3.1 +/- 1.0 pmol/liter; range, less than 2 to 5 pmol/liter), 8 patients with primary hyperparathyroidism, 36 patients with hypercalcemia and a concurrent malignant lesion, and 9 normocalcemic patients with cancer and increased serum levels of carcinoembryonic antigen or prostate-specific antigen. PTHrP was normal in samples from patients with primary hyperparathyroidism (3.2 +/- 1.1 pmol/liter), secondary hyperparathyroidism (2.5 +/- 1.3 pmol/liter), and cancer without hypercalcemia (2.4 +/- 1.0 pmol/liter). In contrast, plasma immunoreactive PTHrP levels were increased (6.0 to 85.0 pmol/liter) in 47% of patients with hypercalcemia and cancer of various types, with or without bone metastatic lesions. Large amounts of PTHrP were also found in conditioned medium from cultured human prostatic carcinoma cells. Thus, PTHrP may be a causative factor for hypercalcemia associated with a malignant lesion in at least half of the cases. Measurement of circulating PTHrP may be of differential diagnostic help in hypercalcemic states.

Selective arterial stimulation of secretin in localization of gastrinomas

In two patients with malignant gastrinoma and the Zollinger-Ellison syndrome, we were able to use selective arterial stimulation with secretin as a technique to localize the lesions accurately, allowing resection. The technique of selected arterial secretin stimulation is one of measuring variations in gastrin levels in both the hepatic vein and a peripheral artery at specified times after injection of secretin into a specific artery. When the criteria for localization have been met, one can plot the presence of the gastrinoma within the blood supply of the injected artery and, using angiograms, thus accurately localize the lesion. This method promises to be a valuable additional tumor-localizing procedure, particularly when gastrinomas are extrapancreatic.

Unresponsiveness of insulinoma cells to secretin: significance of the secretin test in patients with insulinoma

It is well known that B cells in the pancreas release insulin when stimulated by secretin, but there have been few reports on the response of insulinoma cells to secretin. In five patients with insulinoma, changes in serum immunoreactive insulin (IRI) concentration were measured after the intravenous injection of secretin into the peripheral vein before and after extirpation of the insulinoma. The extirpated insulinomas were cultured and tested for their response to secretin. The rise in serum IRI in response to secretin in patients with insulinoma was significantly slower and smaller than in normal volunteers. After removal of the insulinoma, the response to secretin became prompt and increased with time. Cultured insulinoma cells did not release insulin when stimulated by secretin. Therefore, it is concluded that the response of insulinoma cells to secretin is quite different from that of normal beta cells, and that the function of beta cells in the insulinoma-bearing pancreas is suppressed by the autonomous hypersecretion of insulin by the insulinoma. The extent of the decrease in function of the beta cells in patients with insulinoma can be estimated by the intravenous secretin test. Thus, the secretin test is sometimes useful in the differentiation of hypoglycemia due to insulinoma from that due to beta cell hyperplasia or alimentary hyperinsulinemia.

Glucose metabolism in a patient with insulinoma complicated by hyperosmolar non-ketotic state

A case of a patient with organic hyperinsulinism complicated by the development of hyperosmolar state is described. The hyperosmolar state was induced by vomiting and dehydration during an acute urinary tract infection. Impairment of glucose metabolism was confirmed by the finding of reduced tissue sensitivity to insulin during a euglycaemic clamp.

Inhibition of streptozotocin-induced islet cell tumors and N-nitrosobis(2-oxopropyl)amine-induced pancreatic exocrine tumors in Syrian hamsters by exogenous insulin

The effects of streptozotocin (SZ) and N-nitrosobis(2-oxopropyl)amine (BOP), separately or in combination, on the pancreas, common duct, and gallbladder, all target tissues of BOP, were studied in Syrian golden hamsters. Groups of hamsters were treated with either a single dose (20 mg/kg body weight) of BOP (BOP group), or a single i.p. dose (50 mg/kg body weight) of SZ and 14 days later with a single s.c. injection of the same dose of BOP (SZ + BOP group). Another group of animals was treated similarly with BOP and SZ except that they received twice daily injections of insulin, beginning 1 day after SZ administration and for the duration of the experiment (52 weeks) (SZ + insulin + BOP group). The control group consisted of hamsters treated with a single dose of BOP and daily doses of insulin (insulin + BOP group). Hamsters treated with SZ recovered spontaneously from their diabetes, although the mortality was high (86%). BOP treatment inhibited the diabetogenic effects of SZ in both SZ + BOP and SZ + insulin + BOP groups and reduced the mortality to 43 and 74%, respectively. SZ pretreatment inhibited the incidence of BOP-induced pancreatic ductal/ductular cell carcinomas in the SZ + BOP group (P less than 0.01); this protective effect of SZ on carcinoma development was potentiated by additional treatment with insulin (SZ + insulin + BOP group, P less than 0.001). Although the frequency of BOP-induced tumors in the gallbladder (all polyps) was not altered by either SZ or insulin, the frequency of the common duct polyps was significantly lower in the SZ + insulin + BOP group than in the BOP group (P less than 0.005). Hamsters in the SZ, SZ + BOP, and SZ + insulin + BOP groups developed islet cell adenomas (insulomas). However, the SZ + insulin + BOP group had significantly fewer insulomas than in the SZ + BOP group (P less than 0.0005). The overall data confirm the inhibitory effect of SZ on BOP-induced pancreatic cancer and suggest that this effect is related to the diabetic condition of hamsters rather than insulin deficiency and that intact islets appear to be prerequisite for exocrine pancreatic cancer induction by BOP. On the other hand, the inhibitory action of insulin on insuloma induction by SZ and on ductal/ductular cancer induction by BOP seems to be related to the suppressive effect of this hormone on beta-cell and ductal/ductular cell replication, respectively.

[Dynamics of the blood serum protein fractions in patients with insulinoma]

Gel electrophoresis was used to study the blood serum of 13 patients with insulinomas who showed marked dysproteinemia in the preoperative period. Enucleation of the tumour or resection of the pancreas were performed depending on the location of the tumours. In the immediate postoperative period dysproteinemia became more pronounced, then a tendency to normalization of the protein spectrum occurred. Dysproteinemia was most pronounced at the zone of the starting peak where insulin-binding proteins are located.

Plasma pancreastatin-like immunoreactivity in various diseases

Plasma pancreastatin (PST)-like immunoreactivity in normal subjects and patients with various diseases was estimated by a RIA, using antiserum raised against a synthetic C-terminal peptide of human PST deduced from the sequence of human chromogranin-A. The mean level +/- SEM was 13.2 +/- 0.6 pmol/L in normal subjects, but was significantly higher in patients with chronic renal failure (526.7 +/- 48.5). An immunoreactive form corresponding to a human PST-like sequence [human chromogranin-A-(250-301)] and a larger form were detected by gel filtration of plasma from these patients, suggesting accumulation of the larger molecular form in these patients. A significant increase in PST-like immunoreactivity was also found in patients with liver cirrhosis (20.8 +/- 3.0 pmol/L), but not in patients with noninsulin-dependent diabetes mellitus, chronic pancreatitis, or pancreatic cancer. Elevated levels were found in 16 of the 21 patients with small cell lung carcinoma examined. High levels were also found in 3 of 11 patients with islet cell tumor.

Fasting insulin levels in normal Kenyan Africans and a case report on insulinoma

The mean fasting insulin level in 30 apparently normal Kenyan Africans was determined by Radio-Immuno Assay (RIA) technique based on coat A-count. The mean value was found as 16.33 microIu/ml with a standard deviation (s.d) of 10.51 microIu/ml. The mean at 95% confidence interval (CI) for the population studied was 16.33 +/- 1.92. The findings are similar to what have been reported among the caucasians. This paper also reports on a case of insulinoma in a young female patient at Kenyatta National Hospital (KNH).

Glucose-stimulated hormone release in rats bearing streptozotocin/nicotinamide-induced islet adenomas: evidence for slow and fast responders

Rats injected with streptozotocin and nicotinamide developed grossly visible islet cell tumors of the pancreas. During i.v. glucose tolerance tests, two populations of tumor-bearing rats were identified: fast responders exhibited significantly lower plasma glucose and markedly elevated plasma immunoreactive insulin (IRI) levels relative to those of the controls. In slow responders, the plasma glucose level was significantly elevated up to 2 h after glucose injection, and the plasma IRI level was lower than that of the controls. During in vitro perfusions with glucose at 300 mg/dl (16.7 mM), tumor-bearing pancreata of fast responders released elevated levels of IRI and immunoreactive somatostatin (IRS); after tumor removal, glucose-stimulated release of these hormones returned to control levels. However, during similar perfusions of pancreata from slow responders, the IRI and IRS release did not decrease after tumor removal, suggesting that the nontumorous pancreatic islets rather than the gross tumors of the slow-responder group were the source of the glucose-stimulated hormone release. These studies demonstrate that gross tumors in the two responder subgroups differ in their glucose-stimulated hormone release.

Lack of diabetogenic action of calcitonin in subjects affected by insulinoma

Calcitonin has been shown to affect calcium handling within cells thus impairing insulin secretion and glucose tolerance in healthy subjects. In the present study we investigate the effects of calcitonin on basal and nutrients-induced plasma glucose and insulin levels variations in healthy subjects (n = 10) and in patients affected by islet cell tumor (n = 6). In healthy subjects calcitonin markedly decreased basal and nutrients-induced plasma insulin levels while in patients with islet cell tumor this calcitonin-mediated effect was lost. So we conclude that the lack of calcitonin effect upon insulin secretion in patients with insulinoma is probably due to the autonomous insulin secretion characterizing islet cell tumor.

Malignant islet cell tumor of the pancreas associated with high plasma calcitonin and somatostatin levels

In this case report we describe a 41-year-old man, without a recognizable preexisting syndrome, who had ascites of massive proportions and died. A malignant tumor of the endocrine pancreas was identified and associated with an extremely high plasma calcitonin level. The plasma somatostatin level was also significantly elevated. Only one previous case report of a tumor with comparable secretory characteristics has been identified.

Suppression of primary and secondary peptides with somatostatin analog in the therapy of functional endocrine tumors

Sandostatin (SMS 201-995 (SMS)), a potent, long acting analog of native somatostatin was used in five patients with functional endocrine tumors (gastrinoma, two patients; insulinoma, one patient; glucagonoma, one, and adult onset nesidioblastosis, one). Primary and secondary peptide levels were obtained during provocation with a test meal, a calcium infusion, a secretin bolus and either a glucagon or tolbutamide bolus. During provocation test, the levels of the primary peptides insulin and C-peptide (nesidioblastosis and insulinoma), gastrin (gastrinoma), glucagon (glucagonoma) and the secondary peptides calcitonin, gastrointestinal peptide, gastrin releasing peptide, motilin, neurotensin, pancreatic polypeptide, somatostatin, substance-P and vasoactive intestinal peptide were obtained at predetermined intervals and quantitated by radioimmunoassay. SMS therapy was begun and peptide levels were again obtained during provocation. SMS suppressed basal primary peptide levels in all patients by more than 50 per cent. In 23 of 26 provocative tests, SMS effectively decreased circulating peptide levels by more than 50 per cent. Thirteen instances of elevated basal secondary peptides were discovered, and SMS universally suppressed these levels by a mean of 54 per cent. Of the 44 provocative tests performed, elevated secondary peptide levels were present in 41. SMS was effective in 31 of these 41 tests. The mean suppression of these provoked secondary peptide levels was 70 per cent. SMS effectively suppresses both basal and provoked peptides and, thus, provides relief of the clinical symptoms induced by pathologic elevations of primary and secondary peptides.

Glucagonoma syndrome

A 53-year-old Japanese man with a skin eruption characteristic of glucagonoma syndrome had had misdiagnoses for 10 years. The plasma glucagon level was not abnormally high on the first admission, and 4 years later the level was elevated as determined by the 30 gm arginine tolerance test. An alpha cell carcinoma detected in the tail of the pancreas was associated with a lymph node metastasis; the skin eruption cleared up 10 days after the partial pancreatectomy with lymphadenectomy. The clinical features of glucagonoma syndrome should be given attention.

A standardized meal stimulation test of the endocrine pancreas for early detection of pancreatic endocrine tumors in multiple endocrine neoplasia type 1 syndrome: five years experience

Forty-nine members of 6 families with multiple endocrine neoplasia type 1 (MEN 1) were investigated with a standardized meal stimulation test to detect the presence of pancreatic endocrine tumors. Fifteen age-matched subjects and 4 patients with primary hyperparathyroidism also were studied. Serum pancreatic polypeptide (PP), gastrin, and insulin as well as plasma glucagon and somatostatin concentrations were determined before and during the test meal. Patients with demonstrable pancreatic endocrine tumors had significantly increased mean basal and peak serum PP (P less than 0.001) and gastrin (P less than 0.001) responses to the meal compared with healthy family members and normal subjects. Seven of 12 MEN 1 patients with parathyroid and pituitary disease but no demonstrable pancreatic endocrine tumors had exaggerated PP and/or gastrin responses to the meal; 4 of them developed pancreatic endocrine tumors, detected by abdominal computerized tomography, 0.5-4 yr later. None of the healthy members of the MEN 1 families or the patients with primary hyperparathyroidism had responses different from those of the normal subjects. Our experience with the meal stimulation test indicates that an elevated basal or exaggerated serum PP and/or gastrin response is an earlier sign of pancreatic involvement in the MEN 1 trait than is abdominal computerized tomography.

Alpha-fetoprotein associated with islet cell tumors

Elevated serum levels of alpha-fetoprotein (AFP) (100-1,000 ng/ml) were found in three patients with islet cell tumors. Serial levels correlated with progression of disease, suggesting that AFP could be a useful tumor marker substance for islet cell tumors. Survey sera from an expanded pool of 23 patients with islet cell tumors and nine with carcinoid tumors did not identify additional cases, however, suggesting that elevated AFP levels in these classes of Apudomas are uncommon. Nonetheless, the distinction from other AFP-producing tumors such as hepatocellular carcinoma is clinically important and warrants an awareness of the rare association of AFP with these tumors.

Peptide histidine-methionine immunoreactivity in plasma and tissue from patients with vasoactive intestinal peptide-secreting tumors and watery diarrhea syndrome

The presence of peptide histidine-methionine (PHM)-like peptides has been determined in plasma and tumor specimens from patients with vasoactive intestinal peptide (VIP)-secreting tumors and the watery diarrhea syndrome. All patients had strikingly elevated plasma concentrations of PHM immunoreactivity (median, 1800; range, 500-6800 pmol/liter; n = 12), which were higher than those of VIP (median, 235; range, 50-580 pmol/liter). In patients with other endocrine and nonendocrine pancreatic tumors, plasma PHM concentrations were not significantly different from normal (median, 20; range, 5-60 pmol/liter; n = 28). Plasma samples from patients with diarrhea due to other illnesses also had PHM concentrations that were not significantly different from normal (median, 40; range, 10-80 pmol/liter; n = 23). The gel chromatographic profiles of plasma and tumor extracts from patients with VIP-secreting tumors revealed the presence of at least two molecular forms that reacted with an antiserum directed to the N-terminus of PHM (SY1). The later peak (Kav, 0.50-0.53) corresponded in position to synthetic PHM and also reacted with the PHM-specific antiserum (SY2). The earlier peak (Kav, 0.30-0.37), not reactive with antiserum SY2, corresponded to a large molecular form of PHM-like immunoreactivity previously identified as the predominant form in normal human stomach and plasma, though not in the rest of the intestinal tract. The neuroendocrine nature of the tumors was confirmed by the demonstration of immunostaining with a battery of antisera to neuroendocrine markers. Immunocytochemistry revealed the presence of both VIP and PHM in tumor cells. The presence of high circulating concentrations of PHM-like immunoreactivity in patients with VIP-secreting tumors, as measured with a PHM N-terminus-directed antiserum, SY1, suggests that use of this type of antiserum may provide valuable information in the diagnosis of such tumors. The contribution of the PHM-like peptides to the features of this syndrome is not known.

Lack of suppression of insulin secretion by hyperinsulinemia in a patient with an insulinoma

The regulation of insulin secretion in patients with insulinoma is known to be abnormal. For example, physiological and pharmacological stimuli often fail to stimulate insulin in such patients. Recently, insulin has been found to inhibit its own secretion in normal subjects. To determine if insulin has this effect in patients with insulinoma, we infused insulin at rates of 1 and 10 mU/kg X min in such a patient and in eight normal subjects. Euglycemia was maintained by the euglycemic glucose clamp technique, and endogenous insulin secretion was estimated by measuring plasma C-peptide levels. In the normal subjects, plasma C-peptide declined from 1.60 +/- 0.22 (+/- SEM) to 1.16 +/- 0.17 and 0.82 +/- 0.11 ng/ml during the low and high dose insulin infusions, respectively, indicating 27% (P less than 0.01) and 48% (P less than 0.001) decreases in endogenous insulin secretion at moderately elevated and extremely elevated insulin levels, respectively. In the insulinoma patient, plasma C-peptide was 2.6 ng/ml basally, did not change during the low dose insulin infusion, and rose to 3.4 ng/ml during the high dose insulin infusion. We conclude that the feedback regulation of insulin secretion by insulin that occurs in normal subjects is absent in insulinoma patients. This finding could have pathophysiological and possibly diagnostic significance.

The effect of exogenous hyperinsulinemia on proinsulin secretion in normal man, obese subjects, and patients with insulinoma

To examine possible feedback inhibition of insulin on proinsulin secretion, we measured serum proinsulin levels before and after 120 min of euglycemic hyperinsulinemia (90-100 mU/liter) in 11 normal and 7 obese hyperinsulinemic subjects and 6 patients with beta-cell adenoma (n = 4), carcinoma, or hyperplasia. Baseline proinsulin levels accounted for 19%, 14%, and 56% of the total immunoreactive insulin in the 3 groups, respectively. Compared to normal subjects, baseline proinsulin levels were elevated (P less than 0.02) by 4- and 6-fold in obese subjects and patients with autonomous insulin secretion, respectively, but there was an overlap between the groups. In both normal and obese subjects, hyperinsulinemia suppressed proinsulin secretion by 45-50% (P less than 0.02), whereas no response occurred in the patients. Thus, the 120 min values were clearly different in the patients and the normal or obese subjects. After removal of the adenoma in 4 patients, baseline proinsulin levels and the response to hyperinsulinemia were normalized, but they remained elevated after a partial pancreatectomy or tumor removal in the patients with beta-cell hyperplasia or carcinoma. Thus, proinsulin secretion is under negative feedback control of insulin in both normal man and hyperinsulinemic obese subjects. In patients with insulinoma or beta-cell hyperplasia, this control is lost.

Immunohistochemical study of neuron-specific enolase and CA 19-9 in pancreatic disorders. The value of neuron-specific enolase as a marker for islet cell and nerve tissue

Immunohistochemical studies of neuron-specific enolase were performed on pancreatic tissues from patients with insulinoma, nonfunctioning islet cell tumor, chronic pancreatitis, and pancreatic adenocarcinoma, and from 5 normal patients. The concentration of neuron-specific enolase was also measured in the sera of patients and in the pancreatic tissue, and the tissues were stained for carbohydrate antigen 19-9 by immunohistochemical techniques. Neuron-specific enolase was localized in nerve fibers, normal islet cells, and islet cell tumors; its concentration was elevated only in the tissue of islet cell tumors and in serum from patients with insulinoma. In the pancreatic tissue of pancreatitis or pancreatic adenocarcinoma, various changes in acini and islets were present. The altered islets stained clearly for neuron-specific enolase and could easily be distinguished from altered, unstained acini in cases of pancreatitis or pancreatic adenocarcinoma. Islets in the pancreatic tissue remained intact with various morphologic changes, although acini had degenerated severely. Carbohydrate antigen 19-9 was localized in all the carcinoma cells in the pancreatic tissue and in some of the normal pancreatic ducts. No cells were simultaneously immunostained by anti-neuron-specific enolase and anti-carbohydrate antigen 19-9 antibodies. Thus, neuron-specific enolase is a good marker for islet cell tumor, and is valuable for examining islets in pancreas with various disorders both alone and in combination with other tumor markers.

Hormonal modification of the growth and metabolic effects of a transplantable rat insulinoma

The growth and metabolic effects of a transplantable radiation-induced rat insulinoma were examined in intact male and female New England Deaconess Hospital (NEDH) rats, and in parathyroidectomised or adrenalectomised male NEDH rats. Subscapular transplantation of insulinoma fragments in intact male rats consistently produced a highly vascularised encapsulated tumour associated with hyperphagia, hyperinsulinaemia and hypoglycaemia which progressed to fatal neuroglycopaenic coma by 30 +/- 0.8 days (mean +/- SEM) and 19 +/- 0.5 days for slow-growing and fast-growing tumour sublines respectively (P less than 0.001). In intact female rats transplanted with the slow-growing subline, the onset of hyperphagia was advanced by 4 days and the severity of hyperinsulinaemia and hypoglycaemia increased (21% and 36%; P less than 0.01 and P less than 0.001, respectively), resulting in a 10% decrease of survival time (P less than 0.05) and a 65% reduction of tumour weight (P less than 0.01). Transplantation of the fast-growing subline into parathyroidectomised male rats, which exhibited a 15-24% (P less than 0.05 - less than 0.01) decrease of plasma calcium, did not modify either the growth or metabolic effects of the tumour. In contrast, transplantation of this subline into adrenalectomised male rats decreased survival time by 32% (P less than 0.001) and reduced final tumour weight by 88% (P less than 0.02) without markedly affecting the onset or magnitude of the hyperinsulinaemia. These results indicate that the growth and metabolic effects of the transplantable NEDH rat insulinoma are modified by the presence of ovarian hormones and by adrenal hormones.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretory response and immunochemical heterogeneity of glucagon in plasma and tumor extracts of a patient with glucagonoma

The secretory response and immunoreactive heterogeneity of glucagon was investigated in a patient with glucagonoma syndrome. After glucose administration, abnormal insulin release accompanied by glucose intolerance were observed, whereas the high glucagon circulating levels were only partially blocked after glucose or somatostatin infusion. Chromatographic fractionation of plasma samples, before and after arginine administration showed that most of the immunoreactivity eluted as true glucagon. Furthermore, when aliquots of the tumor extracts were fractionated by column chromatography or by polyacrylamide gel electrophoresis, most of the immunoreactivity eluted in the 3,500 molecular weight peak. In contrast with previous reports, our results indicate that neoplasia A cells can also manufacture and release into the bloodstream great amounts of genuine glucagon rather than larger glucagon immunoreactive forms. In spite of such findings, in this patient neither diabetes nor hyperglycemia were present.

Euthyroid hyperthyroxinemia and thyroxine-binding prealbumin excess in islet cell carcinoma

This manuscript describes euthyroid hyperthyroxinemia secondary to elevated serum T4-binding prealbumin (TBPA) concentrations in a patient with islet cell carcinoma and reports serum TBPA measurements in other patients with islet cell carcinoma. A 73-yr-old man with a 17-yr history of metastatic islet cell carcinoma was found to have hyperthyroxinemia. His total serum T4 concentration was 18.5 micrograms/dl (normal, 5.5-11.5). Eight years previously, his serum T4 concentration was normal. His free T4 concentration, as determined by equilibrium dialysis, was 1.3 ng/dl (normal, 0.9-2.1). Serum T3, TSH, and T4-binding globulin (TBG) concentrations were normal, as was the TSH response to TRH administration. Polyacrylamide gel electrophoresis of the patient's serum in the presence of tracer amounts of [125I]T4 revealed that, compared to normal sera, [125I]T4 binding to TBPA was increased from 30.0 +/- 6.0% (mean +/- SD) to 52.0%. The distribution of [125I]T3 amont albumin, TBG, and TBPA was normal in this electrophoretic procedure. The concentration of TBPA in the patient's serum was 189 mg/dl. In contrast, the mean serum TBPA concentration in normal men was 40 +/- 4 (mean +/- SD) mg/dl, and that in normal women was 18 +/- 4 mg/dl. Sera from the patient's daughter, his brother, 2 sisters, and 2 male paternal cousins contained normal amounts of TBPA, ranging from 34-47 mg/dl in his male relatives and from 26-30 mg/dl in his female relatives. Serum free T4 index determinations in his relatives also were normal. Serum TBPA concentrations were determined in 14 additional patients with islet cell carcinoma. In 1 of these patients, a man with an insulinoma, serum TBPA was elevated (66 mg/dl). This patient's serum T4 level was 7.3 micrograms/dl, and his free T4 index was 7.0. These data and another study suggest that islet cell carcinoma may rarely produce a TBPA-like protein resulting in an elevated serum TBPA concentration. Markedly elevated serum TBPA is associated with euthyroid hyperthyroxinemia.