Is hyperinsulinemia a possible clinical explanation underlying the myth of Erysichthon?

BACKGROUND: An insulinoma is an endocrine tumor of the pancreas, originating from the beta cells, and has a prevalence of 4 cases per 1 million patients. Insulinomas often follow a "90% rule": 90% are benign [1, 2], 90% originate in the pancreas, 90% are approximately 2 cm wide, and 90% are isolated. Individuals with an insulinoma may have episodic bouts of hyperinsulinemic hypoglycemia. Typically, an insulinoma is indicated by hypoglycemic symptoms which are a result of catecholamine reaction and neuroglycopenia. There is increased secretion of insulin in patients with an insulinoma despite having lower glucose levels. PURPOSE: This paper examines the myth of Erysichthon and speculates whether the symptoms experienced by him are possibly related to those found in patients with an hyperinsulinoma. METHODS: The myth of Erysichthon was taken from various sources (i.e. Hesiod, Callimachus, Ovid) and examined. Symptoms of Erysichthon were then examined. RESULTS: The myth of Erysichthon depicts various sympathoadrenal and neuroglycopenic symptoms including anxiety and abnormal behaviour which can be found in insulinomas. Insulinomas may often present a diagnostic challenge due to their deceptive nature and overlapping symptoms with other disorders such as neurologic disease. Insulinomas inducing weight loss resemble Calamachus's account of Erysichthon whose body is finally emaciated, even though having polyphagia. CONCLUSION: The myth of Erysichthon provides an interesting range of clinical symptoms which I have argued relate to symptoms found in patients with an insulinoma. Although, insulinomas were unknown in ancient medical lore, this paper has speculated that based on Erysichthon's symptoms, the possibility of an insulinoma cannot be ruled out.

Comparison Between Sporadic and Multiple Endocrine Neoplasia Type 1-Associated Insulinoma.

BACKGROUND: The differences between sporadic and multiple endocrine neoplasia type 1 (MEN-1)-associated insulinoma are not well described. Herein, we compared demographics, neoplasm characteristics, presentation, and survival in patients with sporadic vs MEN-1 insulinomas including benign and malignant disease. STUDY DESIGN: A retrospective study identified insulinoma patients. MEN-1 was defined based on genetic testing or clinically in patients with 2 or more primary MEN-1 tumor types. RESULTS: A total of 311 patients were identified: 84% benign and 16% malignant. The incidence of malignancy was similar (18% vs 16%, MEN-1 vs sporadic, p = 0.76). Within malignant patients, the median (interquartile range) age was 33 (25 ,44) years in MEN-1 vs 54 (41, 70) years in sporadic insulinoma (p = 0.04). There was no difference in sex or tumor size between MEN-1 and sporadic malignant insulinoma (p > 0.05). Of the 260 patients with benign insulinoma, 7% had MEN-1 syndrome. MEN-1 patients presented with insulinoma at a younger age: median (interquartile range) age was 38 (24, 49) years vs 52 (43, 65) years (p < 0.01). Resection of benign insulinoma was performed in 78% of the MEN-1 and 94% of the sporadic group (p = 0.03). Resected benign tumors were larger in the MEN-1 group: 2.0 (1.65, 2.45) cm vs 1.5 (1.2, 2.0) cm, respectively (p = 0.03). Concurrent insulinomas were more common in MEN-1 (17% vs 2%; p < 0.01). CONCLUSIONS: MEN-1 patients present with insulinoma at younger age and have larger benign pancreatic lesions at the time of resection compared with sporadic neoplasms. Younger patients and those with multifocal pancreatic neuroendocrine tumor in the setting of endogenous hyperinsulinism should be evaluated for MEN-1.

Long-term morbidity and mortality in patients diagnosed with an insulinoma.

OBJECTIVE: Insulinomas are rare functional pancreatic neuroendocrine tumours. As previous data on the long-term prognosis of insulinoma patients are scarce, we studied the morbidity and mortality in the Finnish insulinoma cohort. DESIGN: Retrospective cohort study. METHODS: Incidence of endocrine, cardiovascular, gastrointestinal and psychiatric disorders, and cancers was compared in all the patients diagnosed with an insulinoma in Finland during 1980-2010 (n = 79, including two patients with multiple endocrine neoplasia type 1 syndrome), vs 316 matched controls, using the Mantel-Haenszel method. Overall survival was analysed with Kaplan-Meier and Cox regression analyses. RESULTS: The median length of follow-up was 10.7 years for the patients and 12.2 years for the controls. The long-term incidence of atrial fibrillation (rate ratio (RR): 2.07 (95% CI: 1.02-4.22)), intestinal obstruction (18.65 (2.09-166.86)), and possibly breast (4.46 (1.29-15.39) and kidney cancers (RR not applicable) was increased among insulinoma patients vs controls, P < 0.05 for all comparisons. Endocrine disorders and pancreatic diseases were more frequent in the patients during the first year after insulinoma diagnosis, but not later on. The survival of patients with a non-metastatic insulinoma (n = 70) was similar to that of controls, but for patients with distant metastases (n = 9), the survival was significantly impaired (median 3.4 years). CONCLUSIONS: The long-term prognosis of patients with a non-metastatic insulinoma is similar to the general population, except for an increased incidence of atrial fibrillation, intestinal obstruction, and possibly breast and kidney cancers. These results need to be confirmed in future studies. Metastatic insulinomas entail a markedly decreased survival.

Clinical Characteristics and Incidences of Benign and Malignant Insulinoma Using a National Inpatient Database in Japan.

CONTEXT: Insulinoma is the most common pancreatic functional neuroendocrine neoplasm, yet little information on recent clinical practice in patients with insulinoma, especially malignant insulinoma, is available. OBJECTIVE: This work aims to clarify the characteristics and practice patterns in patients with insulinoma using a national inpatient database. METHODS: Using the Japanese Diagnosis Procedure Combination database, we retrospectively identified patients with insulinoma admitted between 2010 and 2018. We compared background characteristics and therapeutic interventions between patients with benign and malignant insulinoma. We also estimated the incidence of insulinoma using the number of patients with newly diagnosed insulinoma in 2012. RESULTS: We identified 844 patients with benign insulinoma and 102 patients with malignant insulinoma. Patients with malignant insulinoma were younger (median, 55.5 vs 66.0 years, P < .001) and less likely to be female (55.9% vs 65.3%, P = .061) than patients with benign insulinoma. Analysis of therapeutic interventions revealed that patients with malignant insulinoma more frequently received medications (71.6% vs 49.6%, P < .001) but less frequently underwent pancreatic surgery (57.8% vs 72.0%, P = .003). Older patients were a smaller proportion of those undergoing surgery and a larger proportion of those managed with medications without surgery (P < .001). The incidence of insulinoma was estimated to be 3.27 (95% CI, 2.93-3.61) individuals per million Japanese adult population per year. CONCLUSION: The present study using a nationwide database had a larger sample size than previous studies and revealed definitive differences in patient characteristics and therapeutic patterns between benign and malignant insulinoma.

Rare causes of hypoglycemia in adults.

Hypoglycemia is defined by a low blood glucose level associated to clinical symptoms. Hypoglycemia may be related to treatment of diabetes, but also to drugs, alcohol, critical illness, cortisol insufficiency including hypopituitarism, insulinoma, bariatric or gastric surgery, pancreas transplantation or glucagon deficiency, or may be surreptitious. Some hypoglycemic episodes remain unexplained, and genetic, paraneoplastic and immune causes should be considered. Genetic causes may be related to endogenous hyperinsulinism and to inborn errors of metabolism (IEM). Endogenous hyperinsulinism is related to monogenic congenital hyperinsulinism, and especially to mutations of the glucokinase-activating gene or of insulin receptors, both characterised by postprandial hypoglycemia with major hyperinsulinism. In adulthood, IEM-related hypoglycemia can persist in a previously diagnosed childhood disease or may be a presenting sign. It is suggested by systemic involvement (rhabdomyolysis after fasting or exercising, heart disease, hepatomegaly), sometimes associated to a family history of hypoglycemia. The timing of hypoglycemic episodes with respect to the last meal also helps to orientate diagnosis. Fasting hypoglycemia may be related to type 0, I or III glycogen synthesis disorder, fatty acid oxidation or gluconeogenesis disorder. Postprandial hypoglycemia may be related to inherited fructose intolerance. Exercise-induced hyperinsulinism is mainly related to activating mutation of the SLC16A1 gene. Besides exceptional ectopic insulin secretion, paraneoplastic causes involve NICTH (Non-Islet-Cell Tumour Hypoglycemia), caused by Big-IGF2 secretion by a large tumour, with low blood levels of insulin, C-peptide and IGF1. Autoimmune causes involve antibodies against insulin (HIRATA syndrome), especially in case of Graves' disease, or against the insulin receptor. Medical history, timing, and insulin level orientate the diagnosis.

Surgical management of insulinomas at the Azerbaijan Medical University: a retrospective study of 21 cases over a 10-year period

Background/aim: This study represents the first report that evaluates the experience gathered from diagnosis, surgical treatment and outcome of insulinoma patients from Azerbaijan. Materials and methods: We retrospectively review of insulinoma patients for a 10-year period. Collected data included patient demographics, laboratory and imaging tests, detailed surgical reports, histopathological examination of resected specimens, and clinical follow-up. Results: Twenty-one insulinoma patients were identified. Male patients comprised 52.4%; mean age was 44 years. Mean time to diagnosis was 14 months; 61% patients had ≥3 medical referrals due to hypoglycemia-related symptoms. Diagnosis sensitivity of CT, MRI and US was 85%, 80%, and 55%, respectively. The mean glucose, insulin, C-peptide levels were 35.7 ± 9.5 mg/dL, 33.5 ± 21.9 µU/mL, and 3.74 ± 1.88 ng/mL, respectively. Pancreatic head and tail were the most frequent tumor locations; mean tumor size was 1.5 ± 0.7 cm. No statistical association was found between the tumor size and preoperative glucose, C-peptide and insulin levels. Distal pancreatectomy and enucleation were the most common surgical procedures. Local tumor recurrence rate was 14%. There was no mortality. Conclusions: To prevent delayed diagnoses, physicians should be familiar with the typical symptoms of these rare tumors.

Malignant Insulinoma: A Rare Form of Neuroendocrine Tumor.

INTRODUCTION: Due to the rarity of malignant insulinoma, a lack of the literature describing factors affecting outcomes exists. Our aim was to review malignant insulinoma incidence, characteristics and survival trends. METHODS: We identified all patients with malignant insulinoma in the SEER registries from 1973 to 2015. Incidence, neoplasm characteristics and factors affecting cancer-specific survival (CSS) were described. RESULTS: A total of 121 patients were identified. The crude annual overall incidence was low (range 0.0-0.27 cases per million person years). The largest proportion had localized disease (40%), while 16% had regional disease, 39% distant metastatic disease, and stage was unreported in 5%. Most neoplasms were in the body/tail of the pancreas, followed by the head of the pancreas. Grade was reported in 40% of patients; only a single patient reported as having grade IV with the remainder all grades I/II. Surgical resection was performed in 64% of patients. Within surgical patients, the median primary neoplasm size was 1.8 cm. Regional lymph nodes were examined in 57.1% of surgical patients, while 34% of examined nodes were positive. The median CSS was 183 months. On multivariable analysis, surgical resection, male sex and absence of metastatic disease were associated with superior survival. CONCLUSION: While the greatest proportion of patients with malignant insulinoma present with localized disease, regional lymph node involvement was found in 34% of whose nodes were tested. Further studies are needed to assess the role of lymph node dissection in improving survival and preventing recurrence given the observed frequency of lymph node involvement.

Nationwide survey of endogenous hyperinsulinemic hypoglycemia in Japan (2017-2018): Congenital hyperinsulinism, insulinoma, non-insulinoma pancreatogenous hypoglycemia syndrome and insulin autoimmune syndrome (Hirata's disease).

AIMS/INTRODUCTION: We aimed to investigate the nationwide incidence, treatment details and outcomes of patients with endogenous hyperinsulinemic hypoglycemia (EHH), including those with transient/persistent congenital hyperinsulinism (CHI), insulinoma, non-insulinoma pancreatogenous hypoglycemia syndrome and insulin autoimmune syndrome (Hirata's disease) in Japan. MATERIALS AND METHODS: A nationwide, questionnaire-based survey was carried out to determine the number of patients with EHH who were treated for hypoglycemia or hypoglycemia-related complications in 2017-2018. The questionnaires were sent to all hospitals in Japan with >300 beds, and with pediatric and/or adult clinics likely managing EHH patients. The secondary questionnaires were sent to obtain the patients' date of birth, sex, age at onset, treatment details and post-treatment outcomes. RESULTS: A total of 447 patients with CHI (197 transient CHI, 225 persistent CHI and 25, unknown histology), 205 with insulinoma (118 benign, 18 malignant and 69 unknown subtype), 111 with non-insulinoma pancreatogenous hypoglycemia syndrome (33 post-gastric surgery HH, 57 postprandial HH, 10 nesidioblastosis and 11 unknown subtype) and 22 with insulin autoimmune syndrome were identified. Novel findings included: (i) marked improvement in the prognosis of persistent CHI over the past 10 years; (ii) male dominance in the incidence of transient CHI; (iii) non-insulinoma pancreatogenous hypoglycemia syndrome emerging as the second most common form of EHH in adults; (iv) frequent association of diabetes mellitus with insulin autoimmune syndrome; and (v) frequent post-treatment residual hypoglycemia and impaired quality of life. CONCLUSIONS: The first nationwide, all age group survey of EHH showed the current status of each type of EHH disorder and the unmet needs of the patients.

Utility of contrast-enhanced computed tomography in the evaluation of canine insulinoma location.

OBJECTIVES: To determine 1) the sensitivity of contrast-enhanced CT (CECT) for detection of primary canine insulinomas and metastases 2) the sensitivity of CECT to locate canine insulinomas within the pancreas and 3) the CECT attenuation pattern of canine insulinomas and post-contrast phase in which insulinomas have the best visibility. METHODS: A retrospective review was performed of the medical records of 27 canine insulinoma patients. Simultaneous occurrence of blood glucose < 3.5 mmol/L (reference interval: 4.2-5.8 mmol/L) and plasma insulin > 10 mIU/L (reference interval: 1.4-24.5 mIU/L) were considered diagnostic for insulinoma. The dogs had a mean age of 9.0 ± 1.7 (SD) years and comprised 11 males and 17 females. RESULTS: Using CECT-scans, 26/27 insulinomas were successfully detected. However, CECT-scans predicted the correct location of insulinomas within the pancreas in only 14/27 dogs. In 9/13 inaccurately located insulinoma cases, the location error was major. There was no significant difference between triple, double and single-phase CECT-scans with location accuracies of 54%, 50% and 50%, respectively. Also, there was no specific post-contrast phase in which insulinomas could be visualised best. Detection of lymph node metastases with CECT-scans had a sensitivity of 67% (10/15 lymph node metastases). Detection of liver metastases had a sensitivity of 75% (6/8 liver metastases). This study highlights that major location errors mainly occurred if single- or double-phase CECT-scans were used (6/9 cases). CONCLUSION: It is suggested that triple-phase CECT-scans have superior outcome over single- or double-phase CECT-scans in pre-operative imaging of canine insulinomas.

[Insulinomas in Tampere University Hospital Special Responsibility Area in 1980-2010]. / Insulinoomat Tampereen yliopistollisen sairaalan erityisvastuualueella 1980-2010.

BACKGROUND: Insulin-producing neuroendocrine tumours (iNETs) are rare, but their incidence is increasing. We studied the incidence, clinical picture, diagnostics, and treatment of insulinomas diagnosed in 1980 to 2010. METHODS: Retrospective analysis of insulinomas diagnosed in Tampere University Hospital. RESULTS: We found 23 iNET cases corresponding to an incidence of 0.7/million/year. All had neuroglycopenic symptoms and 83% had autonomic ones. The median diagnostic delay (from first symptoms up to diagnosis) was 25 months. Preoperative imaging found the tumor in 87%. Twenty-one out of 22 patients who underwent surgery recovered completely. CONCLUSIONS: Despite improved imaging the diagnostic delay of iNETs remained unchanged. Hypoglycemia and insulinoma should be considered as a cause of unspecific, symptomatic attacks.

Insulinoma: a multicenter, retrospective analysis of three decades of experience (1983-2014).

OBJECTIVE: To analyze the clinical features, diagnostic procedures, treatment, and clinical outcome of insulinomas diagnosed and treated in the period 1983-2014 in four Spanish hospitals. METHODS: All patients with either biochemical and morphological criteria of insulinoma and/or histological demonstration of insulin-secreting tumor were included. RESULTS: Twenty-nine patients [23 women (79.3%); mean age 48.7±17.4 years (range, 16-74)] were recruited. Twenty-six patients (89.7%) had sporadic tumors, and the rest (3 women, 10.3%) developed in the context of multiple endocrine neoplasia type 1. There were 3 (10.3%) multiple insulinomas, one associated with multiple endocrine neoplasia type 1, and two (6.9%) malignant insulinomas, both sporadic. Most patients (n=18, 62.1%) had fasting hypoglycemia, about a third (31%) both postprandial and fasting hypoglycemia, and 6.9% postprandial hypoglycemia only. Time to glucose nadir (37.3±6.5mg/dL) in the fasting test was 9.0±4.4h, with maximal insulin levels of 25.0±20.3µU/mL. Abdominal CT detected insulinoma in 75% of patients. Twenty-seven (93.1%) patients underwent surgery [enucleation, 18 (66.7%) and subtotal pancreatectomy, 9 (33.3%); tumor size, 1,7±0,7cm]. Surgery achieved cure in the majority (n=24, 88.9%) of patients. CONCLUSION: In our setting, insulinoma is usually a benign, small, and solitary tumor, mainly affecting women aged 45-50 years, and usually localized with abdominal CT. The most commonly used surgical technique is enucleation, which achieves a high cure rate.

MEN1 disease occurring before 21 years old: a 160-patient cohort study from the Groupe d'étude des Tumeurs Endocrines.

CONTEXT: Multiple endocrine neoplasia Type-1 (MEN1) in young patients is only described by case reports. OBJECTIVE: To improve the knowledge of MEN1 natural history before 21 years old. METHODS: Obtain a description of the first symptoms occurring before 21 years old (clinical symptoms, biological or imaging abnormalities), surgical outcomes related to MEN1 Neuro Endocrine Tumors (NETs) occurring in a group of 160 patients extracted from the "Groupe d'étude des Tumeurs Endocrines" MEN1 cohort. RESULTS: The first symptoms were related to hyperparathyroidism in 122 cases (75%), pituitary adenoma in 55 cases (34%), nonsecreting pancreatic tumor (NSPT) in 14 cases (9%), insulinoma in 20 cases (12%), gastrinoma in three cases (2%), malignant adrenal tumors in 2 cases (1%), and malignant thymic-NET in one case (1%). Hyperparathyrodism was the first lesion in 90 cases (56%). The first symptoms occurred before 10 years old in 22 cases (14%) and before 5 years old in five cases (3%). Surgery was performed before age 21 in 66 patients (41%) with a total of 74 operations: pituitary adenoma (n = 9, 16%), hyperparathyroidism (n = 38, 31%), gastrinoma (n = 1, 33%), NSPT (n = 5, 36%), and all cases of insulinoma, adrenal tumors, and thymic-NET. One patient died before age 21 due to a thymic-NET. Overall, lesions were malignant in four cases. CONCLUSIONS: Various MEN1 lesions occurred frequently before 21 years old, but mainly after 10 years of age. Rare, aggressive tumors may develop at any age. Hyperparathyroidism was the most frequently encountered lesion but was not always the first biological or clinical abnormality to appear during the course of MEN1.

[A rare case of hypoglycemia in an elderly patient with type 2 diabetes mellitus: malignant metastasizing insulinoma].

The incidence of insulinoma, an insulin-producing tumour arising from pancreatic beta-cells and responsible for the development of fasting hypoglycemia, in the general population is 1-4 per 1,000,000 yearly, mostly at the age of 25-55 yr. Malignization of this neoplasm occurs in 10-15% of the cases. One third of the tumours produce metastases. The most characteristic clinical manifestation of insulinoma is the Whipple's triad, with episodes of fasting hypoglycemia (below 2.8 mmol/l) correctable by intravenous glucose injection or intake of sugar. The authors report a case of intravital diagnosis of malignant metastasizing insulinoma in a 82 year old woman with type 2 diabetes mellitus. A review of relevant literature is presented.

A 60-year expirience in the treatment of pancreatic insulinoma in the Military Medical Academy, Belgrade, Serbia.

BACKGROUND/AIM: Insulinomas are rare benign tumors in the most cases and the most frequent endocrine tumors of the pancreas. A wide spectrum of clinical manifestations in patients with insulinoma is the reason for difficult recognition of the disease with a long period of time between the onset of symptoms and the diagnosis. Diagnostic procedures include Whipple's triad, 72-hour fast test and topographic assessment. The only currative therapy for patients with insulinoma is operative treatment. METHODS: This retrospective study included 42 patients with diagnosis of insulinoma treated in our institution in a 60-year period. In all the patients a demographic and clinical data, types of biochemical methods for diagnosis, and diagnostic procedures for insulinoma localization were analyzed. Tumor size and localization, surgical procedures, postoperative complications and outcome were assessed. RESULTS: A study included 42 patients, 29 women and 13 men. The median age at diagnosis was 43 years. Median time between the onset of symptoms and diagnosis was 3 years. The most common clinical symptoms and signs were disturbance of consciousness and abnormal behavior in 73%, confusion and convulsions in 61% of patients. The diagnosis of insulinoma was estimated by Whipple's triad and 72-hour fast test in 14 patients. Determination of insulinoma localization was assessed by angiography in 16 (36%) of the patients, by ultrasound (US) in 3 of 16 (18.8%) patients, by abdominal computed tomography (CT) in 8 of 18 (44.5%) patients, and magnetic resonance imaging (MRI) in 2 of 8 (25%) patients. Insulinoma was found in 13 of 13 (100%) patients by arterial stimulation with venous sampling (ASVS) and in 13 of 14 (93%) patients by endoscopic ultrasound (EUS). Of the 42 patients, 38 (90.5%) underwent operative procedure. Minimal resection was performed in 28 (73.6%) of the patients [tumor enucleation in 27 (71%) and central pancreatectomy in one (2.6%) of the patients], and the major resection was performed in 9 (23.6%) of the operated patients [distal splenopancreatectomy in 8 (21%) and pancreaticoduodenectomy in one (2.6%) patient]. The overall mortality rate in postoperative period was 2.6% (one patient). CONCLUSION: A combination of ASVS and EUS as diagnostic procedures ensures high accuracy for preoperative determination of insulinoma localization. Minimal resection such as enucleation shoud be performed whenever it is possible.

Risk factors for the occurrence of insulinoma: a case-control study.

BACKGROUND: The etiology of insulinoma is poorly understood. Few studies investigated the possible roles of environmental factors and lifestyle in the pathogenesis of insulinoma. The aim of this study is to identify risk factors associated with occurrence of insulinoma in the Chinese population. METHODS: This study consisted of 196 patients with insulinoma and 233 controls. Demographic information of the patients and controls and risk factors of the disease were analyzed. Univariate and unconditional multivariable logistic regression analyses were made to estimate odds ratios (ORs) and possible risk factors. RESULTS: Approximately 68.88% (135/196) of the patients were from rural areas in contrast to 10.30% (24/233) of the controls (P<0.0001). This difference was confirmed by the multivariate analysis (OR=4.950; 95% CI: 2.928-8.370). Family history of pancreatic endocrine tumor (OR=16.754; 95% CI: 2.125-132.057) and other cancers (OR=2.360; 95% CI: 1.052-5.291) was also related to a high-risk population of insulinoma. CONCLUSION: Rural residents or people who have a family history of pancreatic endocrine tumor and other cancers are a high-risk population of insulinoma.

Clinical features of insulinoma in patients with multiple endocrine neoplasia type 1: analysis of the database of the MEN Consortium of Japan.

More than 50% of patients with multiple endocrine neoplasia type 1 (MEN1) develop gastroenteropancreatic neuroendocrine tumors (GEPNETs), and insulinoma is the second most common functioning GEPNET. Compared to other functioning and nonfunctioning GEPNETs in MEN1, insulinoma is considered to develop at a younger age. To clarify the clinical features of insulinoma developed in Japanese patients with MEN1, a recently constructed database of Japanese MEN1 patients was analyzed. Among 560 registered cases, insulinoma was seen in 69 patients and information on age at diagnosis was available for 54 patients. Tumors predominantly occurred in the body and tail of the pancreas. The mean age at diagnosis of insulinoma (34.8 ± 16.7 yrs) was significantly younger than that of gastrinoma (50.6 ± 14.3 yrs) and nonfunctioning tumor (44.7 ± 13.3 yrs) in patients with MEN1. Patients diagnosed as having insulinoma during middle-age (30 - 49 yrs) tended to have a long period from appearance of hypoglycemic symptoms to diagnosis of the tumor. Of note, 13 patients (24%) were diagnosed as having insulinoma before 20 yrs of age. Such young onset was not seen in other GEPNETs. Since the development of GEPNETs during adolescence is quite rare, insulinoma diagnosed before 20 yrs strongly suggests the presence of MEN1 and warrants further investigation, including MEN1 genetic testing. Also, clinicians should be aware that insulinoma can often be missed in middle-aged patients.