Glucose-induced GIP levels in patients with insulinoma

Gastric inhibitory polypeptide (GIP) levels during an oral glucose tolerance test (OGTT) have been determined in eight patients suffering from a single benign beta-cell adenoma. GIP hypersecretion and an absent correlation between the insulin: glucose ratio and plasma GIP concentration have been observed. Our data show that the insulinotropic effect of GIP is almost abolished in insulinoma patients. This finding may help explain blood glucose levels and the inappropriate plasma insulin response to oral glucose often observed in these patients.

Nightly amended IRI/BG ratio in fasting test during sleeping periods in subjects with insulinoma and in normal, diabetic and obese subjects

In order to obtain a dynamic picture of the way abnormal insulinemia, as a function of blood glucose, occurs in the morning in subjects with insulinoma, we have measured amended plasma insulin (IRI)/blood glucose (BG) ratio during the fasting period of 4 sleeping subjects with insulinoma. Healthy subjects and subjects suffering from other diseases were used as reference in order to determine variations of this ratio during the night. BG and IRI were assayed at intervals of 15 or 30 min. Subjects with insulinoma differed from the other subjects by a very elevated ratio dispersion around the mean value with highly significant peaks (greater than 100). Mean value always remained outside the range (7-82) which covers the total range of values measured in healthy and pathological subjects.

Immunologic characterization of plasma glucagon components in a patient with malignant glucagonoma

Plasma immunoreactive glucagon (IRG) components were analyzed by gel filtration on either a Bio-Gel P-30 or a Sephadex G-150 column (1.0 X 68 cm) in a 47-year-old male with biopsy-proven malignant glucagonoma. Plasma samples were obtained before and after 20 courses of streptozotocin treatment as well as after administration of a somatostatin-derivative (SRIF-D, 0.38 mg, subcutaneous), regular insulin (0.2 U/kg, intravenous), and secretin (2 U/kg, intravenous). The fractions from the columns were assayed for IRG by simultaneous radioimmunoassay with C-terminal (Unger 30 K) and N-terminal (OAL 196) antibodies to glucagon. Four IRG components were observed. The largest had a molecular weight of approximately 150,000 daltons and cross-reacted much more strongly with the N-terminal antibody than with the C-terminal. The second IRG component appeared to be about 9000 daltons and cross-reacted more strongly with the N-terminal antibody. The third and major IRG component comprised 51.8% to 88.1% of the total IRG as measured with C-terminal antibody, corresponded in molecular weight to synthetic 3500 dalton glucagon, and reacted roughly equally with each of the two antibodies. The fourth IRG component cross-reacted only with N-terminal antibody and appeared to be smaller than 3500 daltons. The plasma IRG level decreased from 8829 pg/mL to 1421 pg/mL (averages of five consecutive determinations) after 20 courses of treatment with streptozotocin with significant clinical improvement. A marked (74%) but transient decrease in plasma IRG was observed after the SRIF-D injection, whereas secretion and insulin caused increases in plasma IRG level of 53% and 22%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation between plasma adrenal androgens and cortisol in Cushing's disease and ectopic ACTH-producing tumour: relation to adrenarche

To assess the effect of chronic hypersecretion of corticotropin (ACTH) and other peptides derived from proopiomelanocortin , and of cortisol, on plasma adrenal androgen concentration, plasma dehydroepiandrosterone sulphate (DHEA-S), dehydroepiandrosterone (DHEA), androstenedione (delta 4 A), and cortisol were measured in 14 children and adolescents with Cushing's disease, a 9-year-old boy with an ectopic ACTH-producing tumour, and a group of normal, age-related individuals. The plasma DHEA-S concentration was normal for chronological age in 9 of 12 patients and for bone age in 7 of 10 patients. The plasma DHEA level was normal for chronological age in 12 of 14 patients and for bone age in 8 of 10 patients. In contrast, the concentration of plasma delta 4 A was raised for chronological age in 6 of 13 patients and for bone age in 7 of 10 patients. All patients had raised plasma cortisol levels in the afternoon and other laboratory and clinical signs of hypercortisolism. In the boy with an ectopic ACTH-producing tumour, plasma DHEA-S was moderately raised, plasma DHEA was normal, and plasma delta 4 A was very high. This patient's plasma ACTH levels ranged from 1340 to 1520 pg/ml and the cortisol levels from 51 to 95 micrograms/dl. The findings suggest that a factor other than ACTH is also required for adrenal androgen secretion. Since the other proopiomelanocortin -related peptides--ie, the N-terminal peptide (1-76), beta-endorphin (beta-EP), beta-lipotropin (beta-LPH), and gamma-lipotropin (gamma-LPH)--are raised in the plasma of patients with Cushing's disease, one of these is unlikely to be that putative factor.

Effect of streptozotocin in a case of glucagon-secreting malignant islets-cell tumor

A case of a 65-year-old woman with a pancreatic tumor secreting insulin, glucagon, and associated with high PTH levels and hypercalcemia is reported. The patient underwent two Streptozotocin (STZ) treatments (1 g iv/week for 10 weeks) after liver metastases were found. Hormonal and metabolic parameters were monitorized . Before the first STZ treatment insulin levels ranged between 78 and 132 microU/ml. After STZ administration insulin decreased and then remained lower (8-48 microU/ml) until the death of the patient. Pre-treatment glucagon levels ranged between 1.3 and 3.9 ng/ml. STZ induced a decrease of glucagon to 0.5 ng/ml. Glucagon chromatography revealed the prevalence of high molecular weight (greater than 6,000 mol wt) immunoreactive glucagon (0.9 ng/ml) drastically reduced by STZ treatment (0.15 ng/ml). Hypoaminoacidemia was observed before STZ administration, but at the end of the therapy plasma amino acid concentrations were normal. Hypercalcemia too was sensitive to STZ, but not PTH value, which remained high. The second STZ treatment performed a year later was less effective and so a chemotherapeutic protocol was started. Our findings suggest a cytolitic effect of STZ on malignant A-cell, with reduction of glucagon levels and restoration of amino acid metabolism. This effect would be useful for medical treatment of non-operable glucagon secreting tumors.

The glucagonoma syndrome: stimulus-induced plasma responses of circulating glucagon components IRG9000 and IRG3500

Plasma responses of the major immunoreactive glucagon (IRG) components have been investigated in a case of glucagonoma syndrome. Fasting plasma IRG was 4155 pg/ml. Gel chromatography of plasma revealed that 66% of immunoreactivity was present as IRG9000, while IRG3500 accounted for an additional 26%. The appearance in peripheral plasma of these two glucagon fractions was examined after administration of a number of compounds. IRG levels were clearly elevated after arginine and tolbutamide. Both calcium and calcitonin induced a biphasic rise of IRG, the increase being slower after calcium administration. Somatostatin suppressed plasma IRG levels. All tests induced changes in both IRG3500 and IRG9000. In general, relative changes were more pronounced in IRG3500 than in IRG9000, while absolute changes were greater in IRG9000. The shape of the response curves of IRG3500 and IRG9000 was quite similar after arginine, calcium and somatostatin. After tolbutamide the IRG9000 response was delayed as compared to the IRG3500 component. During the latter part of the calcitonin infusion, IRG9000 remained elevated while IRG3500 was back at its starting level.

Study of hypoglycemic patients by the glucose clamp technique using the artificial pancreas

Using the artificial pancreas, blood glucose levels were maintained at 80 mg/dl in nine hypoglycemic patients (four with histologically proven insulinomas and five with nontumoral hypoglycemia) and in four normal subjects during a 24-h fast. The amount of glucose used, serum insulin levels, and glucose clearance were higher in patients with nontumoral hypoglycemia than in normal subjects and highest in the patients with an insulinoma. Surgical or pharmacological treatment resulted in normalization of all parameters. In contrast to the 72-h fast, the 24-h glucose clamp technique allowed the study of hypoglycemic patients without inducing hazardous hypoglycemia.

Serum markers for pancreatic islet cell and intestinal carcinoid tumors: a comparison of neuron-specific enolase, beta-human chorionic gonadotropin and pancreatic polypeptide

Neuron-specific enolase (NSE) (a glycolytic enzyme that occurs only in neuroendocrine cells), human pancreatic polypeptide (hPP) (a probable peptide hormone), and the beta-subunit of human chorionic gonadotropin (beta hCG) (a glycoprotein hormone), have been suggested as serum markers for the diagnosis and management of apudomas of the pancreas and intestinal tract. Serum levels of NSE, hPP, and beta hCG were measured in 21 patients with pancreatic islet cell cancer (including nine "nonfunctioning" tumors, six gastrinomas, three glucagonomas, two insulinomas, and one somatostatinoma) and in five patients with intestinal carcinoid tumors. Sixteen of the 26 patients (62%) had elevated circulating levels of at least one tumor marker. All three markers were elevated in only one patient, a woman with a "nonfunctioning" islet cell carcinoma. Five patients had increased levels of two serum markers. In three patients both NSE and hPP levels were above normal and in two patients both NSE and beta hCG levels were above normal. In nine patients only one marker was elevated. These included six with elevated NSE levels, two with elevated hPP levels, and one with elevated beta hCG levels. Thus NSE levels were elevated in 12, hPP levels in six, and beta hCG levels in four of the 26 patients. While no single marker was elevated in all patients, each of the three can be elevated in an individual case. When elevated, these markers may be valuable to estimate prognosis or monitor response to therapy.

Diarrhoea in vipoma patients associated with cosecretion of a second active peptide (peptide histidine isoleucine) explained by single coding gene

Peptide histidine isoleucine (PHI), first isolated from pig intestine, is distributed identically to vasoactive intestinal peptide (VIP) in all mammals. 42 patients with high plasma VIP secondary to VIPoma also had very high plasma PHI-like immunoreactivity, in a constant ratio to VIP. None of 125 patients with other endocrine tumours had high levels of either peptide. VIPoma tissue from 20 patients also contained PHI shown by immunocytochemistry to be produced by the same cell as VIP. Messenger RNA(mRNA) from one of these tumours contained the codes for VIP and a separate PHI-like sequence. Human PHI-like sequence differed from porcine PHI in only two aminoacid residues. A single cell thus produces two separate regulatory peptides with apparently similar potencies but different spectra of activity. In normal tissue the constant coproduction of two active neuropeptides by a single neuron provides further evidence against the doctrine of one neuron producing only one neurotransmitter.

Radioimmunoassay for pancreatic polypeptide, and its age-related changes in concentration

Pancreatic polypeptide (PP), a recently discovered pancreatic hormone, is potentially a marker for endocrine tumors. Consequently, we devised a radioimmunoassay for it, using antisera (raised in rabbits) to bovine PP, 125I-labeled bovine PP (purified by anion-exchange chromatography), and human PP standards. Concentrations circulating in fasting, normal subjects were measured. Statistical analysis of the results revealed a skewed distribution. An age-related increase was also observed. Evaluating PP concentrations in sera from 23 patients with endocrine tumors, we found increased values in a few cases of Zollinger-Ellison syndrome, medullary carcinoma of the thyroid, carcinoid syndrome, and one tumor producing vasoactive intestinal polypeptide (VIPoma). In contrast, values from five insulinomas and one glucagonoma were within the normal reference interval. Thus, an increased value for PP in a fasting individual may suggest the diagnosis of an endocrine tumor but is not a diagnostic prerequisite.

Five cases of somatostatinoma: clinical heterogeneity and diagnostic usefulness of basal and tolbutamide-induced hypersomatostatinemia

Five cases of somatostatinoma are reported, four being primarily located in the pancreas and one in the duodenum. The diagnosis was based upon the histological and immunochemical characteristics of tumoral and metastatic tissue. A marked clinical heterogeneity was noted: one patient presented with gallstones, steatorrhea, and diabetes, two patients suffered from severe hypoglycemic attacks, and two cases were admitted for obstructive jaundice. This varying symptomatology was related to differences in the circulating levels of biologically active somatostatin and to a variable cellular composition of the tumor. In all cases, a basal and/or tolbutamide-induced hypersomatostatinemia was measured. It is concluded that the clinical and hormonal features of the earlier defined somatostatinoma syndrome are no requisite for the diagnosis of somatostatinoma; the analysis of plasma somatostatin immunoreactivity might lead to a higher detection rate of this endocrine tumor.

Recurrent pheochromocytoma associated with glucagonoma. A case report

We treated a hypertensive patient with recurrent pheochromocytoma (paraganglioma) associated with glucagonoma. No clinical symptom of glucagonoma was found and it could be detected only by a slight elevation of plasma immunoreactive glucagon (IRG) while the extirpated pancreatic tumor contained much IRG. This case could not be classified as either multiple endocrine neoplasia (MEN) type I or type II.

Serum neuron-specific enolase: a serum marker for nonfunctioning pancreatic islet cell carcinoma

The isoenzyme, neuron-specific enolase (NSE) was evaluated as a serum marker for nonfunctioning pancreatic islet cell carcinoma. Serum NSE was measured by radioimmunoassay in 6 patients with islet cell cancer and in 22 healthy adults. Mean serum NSE in control subjects was 5 ng/ml (range 3.2 to 8.4 ng/ml). Three of six patients had clearly elevated serum NSE with values that ranged from 22 to 44 ng/ml. One patient had an equivocally elevated serum NSE of 9.2 ng/ml while receiving chemotherapy. When relapse occurred, the NSE level increased to 44 ng/ml. One of two patients with normal serum NSE had undergone radical pancreatectomy and had no evidence of disease when studied. Elevated serum NSE returned to normal limits after removal of all gross tumor in the only patient from whom a preoperative measurement was obtained. Results of this preliminary study suggest that serum NSE levels can aid in the diagnosis and monitoring of the course of nonfunctining islet cell carcinoma.

Stimulation of insulin release by glucose in a transplantable rat islet cell tumor

A subline of an x-ray-induced transplantable rat insulinoma has been studied in vivo and in vitro. Tumors grew rapidly after sc transplantation and were rich in insulin, but contained only small amounts of glucagon and somatostatin. Despite marked basal hyperinsulinemia, iv glucose administration caused a further increase in plasma insulin in tumor-bearing rats. When the pancreas was functionally excluded by ligation of supplying arteries, glucose still elicited a clear insulin response. In vitro, insulin release from perifused tumor fragments was stimulated by the combination of glucose and 3-isobutyl-1-methylxanthine, but not by glucose alone. In contrast, there was a clear stimulation of insulin release by glucose in primary monolayer cultures of tumor cells. This suggests a better functional capacity of the cultured cells compared to that of the tumor fragments. The results indicate that this transplantable rat islet cell tumor is a convenient source of large quantities of functional beta-cells.

Validation of a rapid solid-phase radioimmunoassay for canine, bovine, and equine insulin

A rapid and convenient commercial radioimmunoassay kit, developed for quantifying hormones in specimens from human beings, was validated for use in measuring insulin in serum of dogs, cattle, and horses. The procedure uses polypropylene assay tubes treated with rabbit anti-porcine insulin serum and porcine [125I]iodoinsulin. Specificity was proven by demonstrating that standard solutions of porcine insulin and serial dilutions of canine, bovine, and equine sera and pancreatic extracts inhibited binding of [125I]iodoinsulin to the antibody in a parallel manner. Gel-filtration chromatography of pancreatic extracts yielded a major peak of immunoreactive material that eluted identically with [125I]iodoinsulin. Immunoreactivity was not associated with fractions that contain larger and smaller molecular weight peptides (eg, proinsulin and C-peptide, respectively). Biological specificity of the assay was shown by demonstrating increased insulin in serum after injection of glucose into heifers and glucagon into dogs and horses. Purified insulin and insulin in pancreatic extracts could be quantitatively recovered from serum, thereby demonstrating accuracy of the assay. Interassay precision of 5 control specimens run in 20 consecutive assays ranged from 6.7% to 20.1% (coefficient of variation) and intra-assay precision of 6 control specimens each assayed 10 times ranged from 4.4% to 10.7% (coefficient of variation). Sensitivity of the assay was 3.2 microIU/ml. This radioimmunoassay for insulin is ideal for veterinary research and diagnosis, because a single set of reagents and procedures can be used for at least 3 species.

Plasma insulin response to various secretagogues in insulinoma

Since the development of radioimmunoassay for insulin, the diagnosis of insulinoma has been made easily. However, it has been assumed that insulinoma is heterogenous in the histological structure as well as in clinical findings. Therefore, the present study was performed to investigate the insulin response to various stimuli and to evaluate the various insulin response tests in 19 patients with insulinoma. The fasting blood glucose was 19 to 90 mg/100 ml in insulinoma and 81 +/- 5 (mean +/- S.D.) mg/100 ml in normal controls. Plasma insulin (IRI) in insulinoma ranged from 10 to 255 microU/ml, while in the control it was 14 +/- 9 microU/ml. However, insulin/blood glucose ratio increased in insulinoma (0.2-11.2) compared with the normal control (0.18 +/- 0.11). In oral glucose tolerance tests, plasma IRI increased and reached peak levels of 48-244 microU/ml, remaining elevated in most cases. In the intravenous tolbutamide test, plasma IRI increased conspicuously to 82-1,330 microU/ml and hypoglycemic coma was provoked in 54%. Plasma IRI was elevated in the intravenous glucagon test and reached the peak levels of 85-400 microU/ml, which exceeded those of the control group. Plasma IRI increased to more than 100 microU/ml after arginine infusion and formed bizarre curves. There were no correlations between plasma IRI response to various stimuli and malignancy, type of B-granule or insulin content of insulinoma tumors. It is concluded that fasting plasma IRI, insulin/glucose ratio, tolbutamide test and glucagon test are highly valuable for the diagnosis of insulinoma.