Glucose-responsive insulinoma in a patient with postprandial hypoglycemia in the morning

A Clinical Case of Insulinoma Presenting with Postprandial Hypoglycemia in a Patient with a History of Gastric Bypass Surgery

A 61-year-old man with a history of total gastrectomy for cancer with Roux-en-Y reconstruction showed severe postprandial hypoglycemia accompanied by endogenous hyperinsulinemia. Abdominal ultrasonography and contrast-enhanced computed tomography showed no abnormal findings in the pancreas. A selective arterial secretagogue injection test showed the marked induction of serum immunoreactive insulin when calcium was injected into the splenic artery. A pathological analysis following distal pancreatectomy with splenectomy revealed a pancreatic neuroendocrine microadenoma containing insulin-producing cells in the resected pancreas. This case highlights the importance of carefully evaluating refractory and severe hypoglycemia in patients with a history of gastric surgery to exclude insulinoma.

Impaired glucose tolerance with neurological manifestations in insulinoma

Insulinoma may have an atypical presentation and it should be suspected in patients with neurological manifestations in spite of an atypical insulin and proinsulin levels associated with hypoglycemia. Fast test is an important tool to reach the diagnosis.

Multiple endocrine neoplasia type 1 (MEN-1) and neuroendocrine neoplasms (NENs)

Neuroendocrine neoplasms (NENs) are relatively rare neoplasms with 6.4-times increasing age-adjusted annual incidence during the last four decades. NENs arise from neuroendocrine cells, which release hormones in response to neuronal stimuli and they are distributed into organs and tissues. The presentation and biological behaviour of the NENs are highly heterogeneous, depending on the organ. The increased incidence is mainly due to increased awareness and improved detection methods both in the majority of sporadic NENs (non-inherited), but also the inherited groups of neoplasms appearing in at least ten genetic syndromes. The most important one is multiple endocrine neoplasia type 1 (MEN-1), caused by mutations in the tumour suppressor gene MEN1. MEN-1 has been associated with different tumour manifestations of NENs e.g. pancreas, gastrointestinal tract, lungs, thymus and pituitary. Pancreatic NENs tend to be less aggressive when arising in the setting of MEN-1 compared to sporadic pancreatic NENs. There have been very important improvements over the past years in both genotyping, genetic counselling and family screening, introduction and validation of various relevant biomarkers, as well as newer imaging modalities. Alongside this development, both medical, surgical and radionuclide treatments have also advanced and improved morbidity, quality of life and mortality in many of these patients. Despite this progress, there is still space for improving insight into the genetic and epigenetic factors in relation to the biological mechanisms determining NENs as part of MEN-1. This review gives a comprehensive update of current evidence for co-occurrence, diagnosis and treatment of MEN-1 and neuroendocrine neoplasms and highlight the important progress now finding its way to international guidelines in order to improve the global management of these patients.

Insulinoma presenting with postprandial hypoglycemia and a low body mass index: A case report

BACKGROUND

Insulinomas are the most common type of functioning endocrine neoplasms of the pancreas presenting hypoglycemic symptoms. Patients characteristically develop symptoms while fasting, but some patients have reported symptoms only in the postprandial state. Repeated and prolonged hypoglycemic episodes can reduce the awareness of adrenergic symptoms, and patients may have amnesia, which delays diagnosis.

CASE SUMMARY

We describe a case of a 24-year-old underweight patient who showed hypoglycemic symptoms for almost 6 years. Although patients with insulinoma characteristically develop symptoms while fasting, this young man had hypoglycemic symptoms up to one hour postprandially, especially after high-sugar meals and after physical activity. The fasting tests and imaging methods performed at local hospitals were evaluated as negative for abnormal results. However, brown adipose tissue exhibited increased metabolic activity, and some muscle groups had histological changes as indicated by positron emission tomography with 2-deoxy-2-[fluorine-18]fluoro-D-glucose integrated with computed tomography. Glycogen deficiency was also histologically confirmed. The patient’s symptoms progressed over the years and occurred more frequently, i.e., several times a month, and the patient had reduced awareness of adrenergic symptoms. The follow-up fasting test was positive, and the imaging results showed a tumor in the head of the pancreas. The patient underwent laparotomy with enucleation of the insulinoma.

CONCLUSION

Weight gain and fasting hypoglycemia are not necessarily characteristics of insulinoma. In prolonged cases, adrenergic symptoms can be suppressed.

Insulinoma Case Admitted with Reactive Hypoglycemia Symptoms

AIM

To present an insulinoma case with post-prandial hypoglycemic symptoms associated with glucose inducible endogenous hyperinsulinemia.

CASE

A 52-year-old female patient was evaluated for hypoglycemic symptoms especially those occuring within 3 hours after consuming sugary foods. These symptoms were persistent for a year and a half. She was diagnosed with reactive (post-prandial) syndrome and followed a recommended diet and was given acarbose but there was no improvement. The results suggested post-prandial endogenous hyperinsulinemia related hypoglycemia. Multiphasic computerized tomography revealed an 11x15x12 mm size mass lesion, anteriorly in the head and uncinate process of the pancreas and then the patients were treated surgically with pancreatic enucleation and cured.

CONCLUSION

Distinguishing post-prandial syndrome by careful history and clinical evaluation in patients with postprandial symptoms is of great importance in terms of cost-effectivity. However, it should not be forgotten that although organic pathologies are mostly presented with fasting hypoglycemia, they may also cause post-prandial symptoms. Severity and progression of the symptoms that point to neuroglycopenia is important, and in this condition the most convenient clinical approach to the patient should be performed with careful and appropriate assessment steps.

Glucose-responsive Insulinoma with Insulin Hypersecretion Suppressed by Metformin

In type 2 diabetes mellitus, metformin suppresses excessive insulin secretion in relation to the intake of glucose. We herein report the case of a 45-year-old man with glucose-responsive insulinoma whose responsive hypoglycemia was alleviated by metformin. The patient had a history of a postprandial loss of consciousness, resulting in hospital admission. He refused surgery and diazoxide administration. A 75-g oral glucose tolerance test after metformin administration revealed the suppression of glucose-responsive insulin hypersecretion and responsive hypoglycemia. Pancreatic head duodenectomy was performed, which alleviated the symptoms. Metformin administration in patients with glucose-responsive insulinoma may therefore be effective for preventing responsive hypoglycemia and hyperinsulinemia.

Insulinoma Presenting with Reactive Hypoglycemia: Evaluating the Effect of Tumor Resection via Continuous Glucose Monitoring

A 71-year-old woman previously diagnosed with reactive hypoglycemia was transferred to our emergency unit because of loss of consciousness. Her plasma glucose level was 27 mg/dL, and continuous glucose monitoring (CGM) revealed postprandial asymptomatic hypoglycemia. A hypervascular tumor was identified via computed tomography in the distal pancreas, and the diagnosis of insulinoma was confirmed using the selective arterial calcium stimulation test. Although no episodes of hypoglycemia were observed during CGM after resection, a pathological examination identified regional lymph node metastasis. It is important to consider insulinoma as a cause of postprandial hypoglycemia, and CGM is useful for evaluating treatment outcomes.

Concurrent insulinoma and impaired glucose tolerance suspected as owing to obesity

An obese 68-year-old woman was admitted for examination of fasting hypoglycaemia. A prolonged 18 h fast reduced her plasma glucose without suppressing insulin secretion, while plasma β-hydroxybutyrate levels were suppressed. Despite the prolonged fast, the glucose response to glucagon was increased by 25 mg/dL (1.39 mM) glucose, which is compatible with insulinoma. A 75 g oral glucose tolerance test (75 g OGTT) showed impaired glucose tolerance. An abdominal CT scan revealed a mass lesion in the uncinate process of the pancreas, a finding consistent with the results of angiography and selective artery calcium injection test. The patient then underwent a pancreaticoduodenectomy; the pancreatic mass was histologically diagnosed as benign insulinoma. After surgery, a prolonged 24 h fast caused no hypoglycaemia and the glucose tolerance capacity in 75 g OGTT improved. Eight months after surgery, the patient's body weight had reduced by 10 kg. This is therefore a case of concurrent insulinoma and impaired glucose tolerance.

Biochemical markers for gastroenteropancreatic neuroendocrine tumours (GEP-NETs)

Biochemical markers are applied in gastroenteropancreatic neuroendocrine tumours (GEP-NETs) for diagnostic, prognostic or predictive purposes. Chromogranin A is the most important general marker and it is recommended to be measured in every patient with a suspected NET, whereas Neuron Specific Enolase is elevated mainly in poorly differentiated NETs. Pancreatic Polypeptide is used in the diagnosis of pancreatic non-functioning NETs, whereas Chorionic Gonadotrophin has an adjunctive role. In the case of functioning tumours, specific markers should be sought and monitored during follow up. Endogenous hyperinsulinemia is suggested in the presence of non-suppressible insulin and proinsulin levels during hypoglycemia, whereas high fasting or stimulated gastrin levels along with elevated gastric acid output are diagnostic for the Zollinger-Ellison syndrome. Glucagon, vasoactive intestinal polypeptide (VIP) and somatostatin are markers for glucagonoma, VIP-oma and somatostatinoma syndromes respectively. In case of ectopic paraneoplastic syndrome, the relevant hormone serves as a diagnostic and prognostic marker.