The value of radiologic interventions and (18)F-DOPA PET in diagnosing and localizing focal congenital hyperinsulinism: systematic review and meta-analysis

Molecular imaging of endocrine neoplasms with emphasis on 18F-DOPA PET: a practical approach for well-tailored imaging protocols

6-[18F]-L-fluoro-L-3, 4-dihydroxyphenylalanine (¹⁸F-DOPA) PET/CT can be a useful tool for the detection of different neuroendocrine tumors (NETs). The main determinants of ¹⁸F-DOPA uptake and retention by NETs are related to expression of LAT1/LAT2 transporters, expression and activity of AADC and biochemical phenotype, all being intimately inter-connected to their embryological origin. In order to improve sensitivity of ¹⁸F-DOPA PET, it is of main importance to perform indivisualized imaging protocols across primaries. This review provides a practical approach for performing well-tailored imaging protocols and describes the clinical value of the recommended radiopharmaceuticals.

PET/CT in congenital hyperinsulinism: transforming patient's lives by molecular hybrid imaging

Congenital hyperinsulinism (HI) is a life-threatening condition characterized by severe and recurrent episodes of hypoglycaemia due to defects in key genes involved in regulating insulin secretion. The delay in diagnosis and inappropriate management of HI lead to high risk of permanent hypoglycemic brain injury. The management of HI is challenging as each form of HI (focal, diffuse, and atypical) requires its own therapeutic strategy. In HI diagnostic work-up, integrated PET/CT scan is currently the first-line imaging technique allowing to differentiate between diffuse and focal form and, in the latter case, to localize the focus within the pancreas with high precision. Only in focal HI partial pancreatectomy is the treatment of choice and a curative surgical treatment means a real chance of transforming patient's lives and HI patient's future. The aim of this review is to discuss the role of PET/CT imaging in HI scenario, its technical advantages and limitations and how successful surgery is strongly dependent on accurate preoperative assessment (genetic analysis and PET/CT scan). A multidisciplinary approach in HI diagnosis and treatment inside a single team (involving different expertise) allows to manage children safely and properly, supporting their families in an organized care network.

Congenital hyperinsulinism: recent updates on molecular mechanisms, diagnosis and management

Congenital hyperinsulinism (CHI) is a rare disease characterized by an unregulated insulin release, leading to hypoglycaemia. It is the most frequent cause of persistent and severe hypoglycaemia in the neonatal period and early childhood. Mutations in 16 different key genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, UCP2, HNF4A, HNF1A, HK1, KCNQ1, CACNA1D, FOXA2, EIF2S3, PGM1 and PMM2) that are involved in regulating the insulin secretion from pancreatic β-cells have been described to be responsible for the underlying molecular mechanisms of CHI. CHI can also be associated with specific syndromes and can be secondary to intrauterine growth restriction (IUGR), maternal diabetes, birth asphyxia, etc. It is important to diagnose and promptly initiate appropriate management as untreated hypoglycaemia can be associated with significant neurodisability. CHI can be histopathologically classified into diffuse, focal and atypical forms. Advances in molecular genetics, imaging techniques (18F-fluoro-l-dihydroxyphenylalanine positron emission tomography/computed tomography scanning), novel medical therapies and surgical advances (laparoscopic pancreatectomy) have changed the management and improved the outcome of patients with CHI. This review article provides an overview of the background, clinical presentation, diagnosis, molecular genetics and therapy for children with different forms of CHI.

PET with Different Radiopharmaceuticals in Neuroendocrine Neoplasms: An Umbrella Review of Published Meta-Analyses

Simple Summary

Functional imaging methods and, in particular, positron emission tomography (PET) using several radiopharmaceuticals may play a pivotal role in patients with neuroendocrine neoplasms including neuroendocrine tumors (NETs) located in different sites, paraganglioma (PGL) and neuroblastoma (NB), recurrent medullary thyroid carcinoma (rMTC) and aggressive neuroendocrine neoplasms. Several radiopharmaceuticals can be used in this setting such as Gallium-68 somatostatin analogues (⁶⁸Ga-SSA), Fluorine-18 fluorodihydroxyphenylalanine (¹⁸F-FDOPA), Gallium-68 exendin-4 (⁶⁸Ga-exendin-4), Fluorine-18 fluorodeoxyglucose (¹⁸F-FDG). This umbrella review provides an evidence-based summary about meta-analyses on diagnostic performance, prognostic value, clinical impact and safety of PET with different radiopharmaceuticals in patients with neuroendocrine neoplasms. Overall, evidence-based data support the use of PET with different radiopharmaceuticals in patients with neuroendocrine neoplasms but with specific indications for each radiopharmaceutical.

Abstract

Background: Several meta-analyses have reported quantitative data about the diagnostic performance, the prognostic value, the impact on management and the safety of positron emission tomography (PET) including related hybrid modalities (PET/CT or PET/MRI) using different radiopharmaceuticals in patients with neuroendocrine neoplasms. We performed an umbrella review of published meta-analyses to provide an evidence-based summary. Methods: A comprehensive literature search of meta-analyses listed in PubMed/MEDLINE and Cochrane Library databases was carried out (last search date: 30 June 2021). Results: Thirty-four published meta-analyses were selected and summarized. About the diagnostic performance: ⁶⁸Ga-SSA PET yields high diagnostic performance in patients with NETs and PGL; ¹⁸F-FDOPA PET yields good diagnostic performance in patients with intestinal NETs, PGL, NB, being the best available PET method in detecting rMTC; ⁶⁸Ga-exendin-4 PET has good diagnostic accuracy in detecting insulinomas; ¹⁸F-FDG PET has good diagnostic performance in detecting aggressive neuroendocrine neoplasms. About the prognostic value: ⁶⁸Ga-SSA PET has a recognized prognostic value in well-differentiated NETs, whereas ¹⁸F-FDG PET has a recognized prognostic value in aggressive neuroendocrine neoplasms. A significant clinical impact of ⁶⁸Ga-SSA PET and related hybrid modalities in patients with NETs was demonstrated. There are no major toxicities or safety issues related to the use of PET radiopharmaceuticals in patients with neuroendocrine neoplasms. Conclusions: Evidence-based data support the use of PET with different radiopharmaceuticals in patients with neuroendocrine neoplasms with specific indications for each radiopharmaceutical.

18F-FDOPA and 68Ga-dotatate PET imaging in congenital hyperinsulinism

Congenital hyperinsulinism (CHI) occurs most commonly in infants but may also be discovered in older children. It presents with recurrent episodes of hypoglycemia due to high endogenous insulin levels. There is a focal and diffuse form of the disease depending on the extent of pancreatic involvement. Hyperplasia of the islet cells results in hyperfunctioning pancreatic β cells and the ensuing clinical disease. Medical treatment fails in several patients and surgery has been shown to be very effective in improving prognosis and even resolution of disease in the focal form. Several genetic mutations have been uncovered and these may also be predictive of prognosis. Anatomical imaging alone including ultrasound, CT and MRI are rarely able to detect any abnormality in the pancreas. PET plays a major role in the distinction between the focal and diffuse forms of the disease. It also guides surgical intervention by providing information on the location of the focal hyperfunctioning islet cells. Imaging children and infants in this disease is quite challenging. We propose to show the benefit of using two PET tracers in this disease. ¹⁸F-FDOPA has been used quite successfully in the evaluation of CHI. ⁶⁸Ga-DOTATATE has also been described to be helpful although inferior to ¹⁸F-FDOPA. We illustrate imaging of CHI patients in 3 different scans and briefly review the literature. ¹⁸F-FDOPA as described in the literature is superior but when unavailable ⁶⁸Ga-DOTATATE may be a reasonable alternative.

GMP production of 6-[18F]Fluoro-L-DOPA for PET/CT imaging by different synthetic routes: a three center experience

BACKGROUND

The radiofluorinated levodopa analogue 6-[¹⁸F]F-L-DOPA (3,4-dihydroxy-6-¹⁸F-L-phenylalanine) is a commonly employed radiotracer for PET/CT imaging of multiple oncological and neurological indications. An unusually large number of different radiosyntheses have been published to the point where two different Ph. Eur. monographs exist depending on whether the chemistry relies on electrophilic or nucleophilic radiosubstitution of appropriate chemical precursors. For new PET imaging sites wishing to adopt [¹⁸F]FDOPA into clinical practice, selecting the appropriate production process may be difficult and dependent on the clinical needs of the site.

METHODS

Data from four years of [¹⁸F]FDOPA production at three different clinical sites are collected and compared. These three sites, Aarhus University Hospital (AUH), Odense University Hospital (OUH), and Herlev University Hospital (HUH), produce the radiotracer by different radiosynthetic routes with AUH adopting an electrophilic strategy, while OUH and HUH employ two different nucleophilic approaches. Production failure rates, radiochemical yields, and molar activities are compared across sites and time. Additionally, the clinical use of the radiotracer over the time period considered at the different sites are presented and discussed.

RESULTS

The electrophilic substitution route suffers from being demanding in terms of cyclotron operation and maintenance. This challenge, however, was found to be compensated by a production failure rate significantly below that of both nucleophilic approaches; a result of simpler chemistry. The five-step nucleophilic approach employed at HUH produces superior radiochemical yields compared to the three-step approach adopted at OUH but suffers from the need for more comprehensive synthesis equipment given the multi-step nature of the procedure, including HPLC purification. While the procedure at OUH furnishes the lowest radiochemical yield of the synthetic routes considered, it produces the highest molar activity. This is of importance across the clinical applications of the tracer discussed here, including dopamine synthesis in striatum of subjects with schizophrenia and congenital hyperinsulinism in infants.

CONCLUSION

For most sites either of the two nucleophilic substitution strategies should be favored. However, which of the two will depend on whether a given site wishes to optimize the radiochemical yield or the ease of the use.

Clinical application of 18F-DOPA PET/TC in pediatric patients

The use ¹⁸F-DOPA PET/CT for oncologic and non-oncologic pediatric diseases is well consolidated in clinical practice. The indications include brain tumors, neuroendocrine malignancies and congenital hyperinsulinism. The number of papers involving pediatric subjects is steadily growing. However, literature still lacks clinical trials and large multicentric studies in contrast with the extensive literature available for adult patients. The aim of this review is to discuss the main clinical indications of ¹⁸F-DOPA in pediatric oncologic and nononcologic diseases and to analyze its role in diagnosis, staging, biopsy and surgical planning. The high resolution of PET/CT tomographs in addition to the high sensitivity and specificity of ¹⁸F-DOPA imaging exceeds the downsides linked to this nuclear medicine imaging modality. In fact, few potential limitations could discourage the use of PET/CT imaging. For example, similarly to MRI studies the long acquisition time of a PET/CT scan often requires sedation especially in infants. Moreover, the radiation exposure of a PET/CT scan may be high, but the clinical benefit deriving from nuclear medicine imaging outruns the risk connected to the use of ionizing radiations.

Functional characterization of ABCC8 variants of unknown significance based on bioinformatics predictions, splicing assays, and protein analyses: Benefits for the accurate diagnosis of congenital hyperinsulinism

ABCC8 encodes the SUR1 subunit of the β-cell ATP-sensitive potassium channel whose loss of function causes congenital hyperinsulinism (CHI). Molecular diagnosis is critical for optimal management of CHI patients. Unfortunately, assessing the impact of ABCC8 variants on RNA splicing remains very challenging as this gene is poorly expressed in leukocytes. Here, we performed bioinformatics analysis and cell-based minigene assays to assess the impact on splicing of 13 ABCC8 variants identified in 20 CHI patients. Next, channel properties of SUR1 proteins expected to originate from minigene-detected in-frame splicing defects were analyzed after ectopic expression in COSm6 cells. Out of the analyzed variants, seven induced out-of-frame splicing defects and were therefore classified as recessive pathogenic, whereas two led to skipping of in-frame exons. Channel functional analysis of the latter demonstrated their pathogenicity. Interestingly, the common rs757110 SNP increased exon skipping in our system suggesting that it may act as a disease modifier factor. Our strategy allowed determining the pathogenicity of all selected ABCC8 variants, and CHI-inheritance pattern for 16 out of the 20 patients. This study highlights the value of combining RNA and protein functional approaches in variant interpretation and reveals the minigene splicing assay as a new tool for CHI molecular diagnostics.

Continuous spectrum of glucose dysmetabolism due to the KCNJ11 gene mutation-Case reports and review of the literature

The KCNJ11 gene encodes the Kir6.2 subunit of the adenosine triphosphate-sensitive potassium (K_ATP ) channel, which plays a key role in insulin secretion. Monogenic diseases caused by KCNJ11 gene mutation are rare and easily misdiagnosed. It has been shown that mutations in the KCNJ11 gene are associated with neonatal diabetes mellitus (NDM), maturity-onset diabetes of the young 13 (MODY13), type 2 diabetes mellitus (T2DM), and hyperinsulinemic hypoglycemia. We report four patients with KCNJ11 gene mutations and provide a systematic review of the literature. A boy with diabetes onset at the age of 1 month was misdiagnosed as type 1 diabetes mellitus (T1DM) for 12 years and received insulin therapy continuously, resulting in poor glycemic control. He was diagnosed as NDM with KCNJ11 E322K gene mutation, and glibenclamide was given to replace exogenous insulin. The successful transfer time was 4 months, much longer than the previous unsuccessful standard of 4 weeks. The other three patients were two sisters and their mother; the younger sister was misdiagnosed with T1DM at 13 years old, while the elder sister was diagnosed with diabetes (type undefined) at 16 years old. They were treated with insulin for 3 years, with poor glycemic control. Their mother was diagnosed with T2DM and achieved good glycemia control with glimepiride. They were diagnosed as MODY13 because of the autosomal dominant inheritance of two generations, early onset of diabetes before 25 years of age in the two sisters, and the presence of the KCNJ11 N48D gene mutation. All patients successfully transferred to sulfonylureas with excellent glycemic control. Therefore, the wide spectrum of clinical phenotypes of glucose dysmetabolism caused by KCNJ11 should be recognized to reduce misdiagnosis and implement appropriate treatment.

Hyperinsulinemic hypoglycemia in children and adolescents: Recent advances in understanding of pathophysiology and management

Hyperinsulinemic hypoglycemia (HH) is characterized by unregulated insulin release, leading to persistently low blood glucose concentrations with lack of alternative fuels, which increases the risk of neurological damage in these patients. It is the most common cause of persistent and recurrent hypoglycemia in the neonatal period. HH may be primary, Congenital HH (CHH), when it is associated with variants in a number of genes implicated in pancreatic development and function. Alterations in fifteen genes have been recognized to date, being some of the most recently identified mutations in genes HK1, PGM1, PMM2, CACNA1D, FOXA2 and EIF2S3. Alternatively, HH can be secondary when associated with syndromes, intra-uterine growth restriction, maternal diabetes, birth asphyxia, following gastrointestinal surgery, amongst other causes. CHH can be histologically characterized into three groups: diffuse, focal or atypical. Diffuse and focal forms can be determined by scanning using fluorine-18 dihydroxyphenylalanine-positron emission tomography. Newer and improved isotopes are currently in development to provide increased diagnostic accuracy in identifying lesions and performing successful surgical resection with the ultimate aim of curing the condition. Rapid diagnostics and innovative methods of management, including a wider range of treatment options, have resulted in a reduction in co-morbidities associated with HH with improved quality of life and long-term outcomes. Potential future developments in the management of this condition as well as pathways to transition of the care of these highly vulnerable children into adulthood will also be discussed.

Visual interpretation, not SUV ratios, is the ideal method to interpret 18F-DOPA PET scans to aid in the cure of patients with focal congenital hyperinsulinism

INTRODUCTION

Congenital hyperinsulinism is characterized by abnormal regulation of insulin secretion from the pancreas causing profound hypoketotic hypoglycemia and is the leading cause of persistent hypoglycemia in infants and children. The main objective of this study is to highlight the different mechanisms to interpret the 18F-DOPA PET scans and how this can influence outcomes.

MATERIALS AND METHODS

After 18F-Fluoro-L-DOPA was injected intravenously into 50 subjects' arm at a dose of 2.96-5.92 MBq/kg, three to four single-bed position PET scans were acquired at 20, 30, 40 and 50-minute post injection. The radiologist interpreted the scans for focal and diffuse hyperinsulinism using a visual interpretation method, as well as determining the Standard Uptake Value ratios with varying cut-offs.

RESULTS

Visual interpretation had the combination of the best sensitivity and positive prediction values.

CONCLUSIONS

In patients with focal disease, SUV ratios are not as accurate in identifying the focal lesion as visual inspection, and cases of focal disease may be missed by those relying on SUV ratios, thereby denying the patients a chance of cure. We recommend treating patients with diazoxide-resistant hyperinsulinism in centers with dedicated multidisciplinary team comprising of at least a pediatric endocrinologist with a special interest in hyperinsulinism, a radiologist experienced in interpretation of 18F-Fluoro-L-DOPA PET/CT scans, a histopathologist with experience in frozen section analysis of the pancreas and a pancreatic surgeon experienced in partial pancreatectomies in patients with hyperinsulinism.

Case report: contradictory genetics and imaging in focal congenital hyperinsulinism reinforces the need for pancreatic biopsy

Background

Congenital Hyperinsulinism (CHI) is an important cause of severe hypoglycaemia in infancy due to excessive, dysregulated insulin secretion. In focal CHI, a localised lesion within the pancreas hypersecretes insulin and, importantly, hypoglycaemia resolution is possible through limited surgical resection of the lesion. Diagnosis of focal CHI is based on a crucial combination of compatible genetics and specialised imaging. Specifically, a focal lesion arises due to a paternal mutation in one of the ATP-sensitive potassium channel genes, KCNJ11 or ABCC8, in combination with post-zygotic loss of maternal heterozygosity within the affected pancreatic tissue. 6-[18F]Fluoro-L-3,4-dihydroxyphenylalanine (¹⁸F-DOPA) positron emission tomography (PET)/computed tomography (CT) imaging is used to detect and localise the lesion prior to surgery. However, its accuracy is imperfect and needs recognition in individual case management.

Case presentation

We report the case of an infant with hypoglycaemia due to CHI and a paternally inherited KCNJ11 mutation, c.286G > A (p.Ala96Thr), leading to a high probability of focal CHI. However,¹⁸F-DOPA PET/CT scanning demonstrated diffuse uptake and failed to conclusively identify a focal lesion. Due to unresponsiveness to medical therapy and ongoing significant hypoglycaemia, surgery was undertaken and a small 4.9 × 1.7 mm focal lesion was discovered at the pancreatic neck. This is the second case where this particular KCNJ11 mutation has been incorrectly associated with diffuse ¹⁸F-DOPA uptake, in contrast to the correct diagnosis of focal CHI confirmed by pancreatic biopsy.

Conclusions

Identifying discrepancies between genetic and imaging investigations is crucial as this may negatively impact upon the diagnosis and surgical treatment of focal CHI. This case highlights the need for pancreatic biopsy when a strong suspicion of focal CHI is present even if ¹⁸F-DOPA imaging fails to demonstrate a discrete lesion.

Inheritance of a paternal ABCC8 variant and maternal loss of heterozygosity at 11p15 retrospectively unmasks the etiology in a case of Congenital hyperinsulinism

Advances in genomics and 18F-DOPA PET-CT imaging have transformed the management of infants with Congenital Hyperinsulinism. Preoperative diagnosis of focal hyperinsulinism permits limited pancreatectomy with improved clinical outcomes while knowledge of the molecular etiology informs genetic counseling and provides a more accurate recurrence risk to families.

The role of 18F-DOPA PET/CT in the diagnosis of the congenital focal form of hyperinsulinism in children

BACKGROUND

Congenital hyperinsulinism (CHI) is a neuroendocrine disease with focal or diffuse abnormalities in pancreas. While drug-resistant diffuse forms require near-total pancreatectomy or prolonged pharmacotherapy, focal CHI may be treated by targeted surgical resection. We evaluated the usefulness of ¹⁸F-DOPA PET/CT to identify the focal pancreatic form.

SUBJECTS AND METHODS

Nineteen children (11 boys, 8 girls, aged 2-54 months) with clinical signs of neonatal CHI and positive genetic examinations were enrolled in the study. After i.v. administration of ¹⁸F-DOPA, early PET and late PET/CT acquisition covering one-bed length over thoraco-abdominal region were performed. Both acquisitions were done in dynamic mode to allow exclusion of frames with motion artefacts. Standardized uptake values were adjusted to bodyweight (SUV_bw). The finding was considered as focal when the ratio of SUV_bw^max between the suspicious region and the rest of pancreas was greater than 1.2.

RESULTS

Focal forms were recorded in 10/19 children and 4 of them underwent surgical resection with complete recovery. Focal uptake was significantly higher than the uptake in the normal pancreatic tissue (p=0.0059). Focal and diffuse forms of CHI did not differ significantly in normal pancreatic tissue uptake. We found no advantage in the measurement of SUV_bw^mean ratio compared to SUV_bw^max ratio (p=0.50).

CONCLUSION

¹⁸F-DOPA PET/CT is a useful tool for the localization of focal CHI and planning of surgical treatment.

Spleen Scan for 68Ga-DOTATOC PET-Positive Pancreatic Tail Lesion: Differential Diagnosis of Neuroendocrine Tumor from Accessory Spleen

⁶⁸Ga-DOTATOC PET/CT is widely used as a functional imaging technique in the detection and characterization of neuroendocrine tumors (NETs). Pancreatic NET and intrapancreatic accessory spleen (IPAS) have similar radiologic characteristics in anatomical imaging and usually show high uptake of ⁶⁸Ga-DOTATOC. Thus, it is challenging to make a differential diagnosis between NET and IPAS when the tumor-like lesion is located in the pancreatic tail. Here, we present a case of ⁶⁸Ga-DOTATOC PET-positive pancreatic tail lesion with high arterial enhancement on CT and MRI. Since ^99mTc-labeled damaged red blood cell does not accumulate on NET, a negative spleen scan finding was a crucial diagnostic step to decide surgical resection, which was histologically proven as insulinoma. Our case shows a promising role of additional use of spleen scan with SPECT/CT for the differential diagnosis of ⁶⁸Ga-DOTATOC PET-positive pancreatic NET from the accessory spleen.

Hyperinsulinaemic hypoglycaemia-an overview of a complex clinical condition

Hyperinsulinaemic hypoglycaemia (HH) is a major cause of hypoglycaemia in the neonatal period, infancy and childhood. It is caused by unsuppressed insulin secretion in the setting of hypoglycaemia and carries a high risk of significant neurological sequelae, such as cognitive impairment. Genetic mutations have been implicated in the pathogenesis of the condition. Other causes include intra-uterine growth retardation, perinatal asphyxia, maternal diabetes mellitus and syndromes, such as Beckwith-Wiedemann. Based on the aetiology, the clinical presentation can range from absence of symptoms to the typical adrenergic symptoms and coma and even death. The diagnosis is based on biochemical findings and the gold-standard imaging technique is 18F-DOPA PET/CT scanning. Treatment options involve medications, such as diazoxide, nifedipine, glucagon and octreotide, as well as surgery. Novel treatment, such as long-acting octreotide, lanreotide and sirolimus, may be used as an alternative to pancreatectomy. Potential future medical treatments include exendin, a GLP-1 receptor antagonist, and glucagon infusion via a pump.Conclusion: Advances in the fields of genetic testing, imaging techniques and medical treatment are beginning to provide novel insights into earlier detection, less invasive treatment approaches and fewer complications associated with the complex entity of hyperinsulinaemic hypoglycaemia. What is Known: • HH is caused by dysregulated insulin release from the β cell due to genetic mutations and carries a risk for complications, such as neurocognitive impairment. 18F-DOPA PET/CT scanning is presented as the gold-standard imaging technique currently in children with hyperinsulinaemic hypoglycaemia. • Clinical presentation is heterogeneous and treatment options include medical therapy and pancreatectomy. What is New: • 18F-DOPA PET/CT is indicated in suspected focal CHI due to paternal transmitted mutations in ABCC8 or KCNJ11. • Novel treatment options have been introduced, such as long-acting octreotide, lanreotide, sirolimus and selective nonpeptide somatostatin receptor subtype 5 (SSTR5) agonists. Future medical treatments include exendin, a GLP-1 antagonist, and glucagon infusion via a pump. However, all these options are off-label at present.

Imaging of pancreatic neuroendocrine tumors: recent advances, current status, and controversies

INTRODUCTION

Recently, there have been a number of advances in imaging pancreatic neuroendocrine tumors (panNETs), as well as other neuroendocrine tumors (NETs), which have had a profound effect on the management and treatment of these patients, but in some cases are also associated with controversies. Areas covered: These advances are the result of numerous studies attempting to better define the roles of both cross-sectional imaging, endoscopic ultrasound, with or without fine-needle aspiration, and molecular imaging in both sporadic and inherited panNET syndromes; the increased attempt to develop imaging parameters that correlate with tumor classification or have prognostic value; the rapidly increasing use of molecular imaging in these tumors and the attempt to develop imaging parameters that correlate with treatment/outcome results. Each of these areas and the associated controversies are reviewed. Expert commentary: There have been numerous advances in all aspects of the imaging of panNETs, as well as other NETs, in the last few years. The advances are leading to expanded roles of imaging in the management of these patients and the results being seen in panNETs/GI-NETs with these newer techniques are already being used in more common tumors.

Diagnosis and management of hyperinsulinaemic hypoglycaemia

Hyperinsulinaemic hypoglycaemia (HH) is a heterogeneous condition with dysregulated insulin secretion which persists in the presence of low blood glucose levels. It is the most common cause of severe and persistent hypoglycaemia in neonates and children. Recent advances in genetics have linked congenital HH to mutations in 14 different genes that play a key role in regulating insulin secretion (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, UCP2, HNF4A, HNF1A, HK1, PGM1, PPM2, CACNA1D, FOXA2). Histologically, congenital HH can be divided into 3 types: diffuse, focal and atypical. Due to the biochemical basis of this condition, it is essential to diagnose and treat HH promptly in order to avoid the irreversible hypoglycaemic brain damage. Recent advances in the field of HH include new rapid molecular genetic testing, novel imaging methods (18F-DOPA PET/CT), novel medical therapy (long-acting octreotide formulations, mTOR inhibitors, GLP-1 receptor antagonists) and surgical approach (laparoscopic surgery). The review article summarizes the current diagnostic methods and management strategies for HH in children.

Clinical Diversity in Focal Congenital Hyperinsulinism in Infancy Correlates With Histological Heterogeneity of Islet Cell Lesions

Background: Congenital Hyperinsulinism (CHI) is an important cause of severe and persistent hypoglycaemia in infancy and childhood. The focal form (CHI-F) of CHI can be potentially cured by pancreatic lesionectomy. While diagnostic characteristics of CHI-F pancreatic histopathology are well-recognized, correlation with clinical phenotype has not been established. Aims: We aimed to correlate the diversity in clinical profiles of patients with islet cell organization in CHI-F pancreatic tissue. Methods: Clinical datasets were obtained from 25 patients with CHI-F due to ABCC8/KCNJ11 mutations. ¹⁸F-DOPA PET-CT was used to localize focal lesions prior to surgery. Immunohistochemistry was used to support protein expression studies. Results: In 28% (n = 7) of patient tissues focal lesions were amorphous and projected into adjoining normal pancreatic tissue without clear delineation from normal tissue. In these cases, severe hypoglycaemia was detected within, on average, 2.8 ± 0.8 (range 1-7) days following birth. By contrast, in 72% (n = 18) of tissues focal lesions were encapsulated within a defined matrix capsule. In this group, the onset of severe hypoglycaemia was generally delayed; on average 46.6 ± 14.3 (range 1-180) days following birth. For patients with encapsulated lesions and later-onset hypoglycaemia, we found that surgical procedures were curative and less complex. Conclusion: CHI-F is associated with heterogeneity in the organization of focal lesions, which correlates well with clinical presentation and surgical outcomes.

Pancreatic uptake and radiation dosimetry of 6-[18F]fluoro-L-DOPA from PET imaging studies in infants with congenital hyperinsulinism

METHODS

After injecting 25.6 ± 8.8 MBq (0.7 ± 0.2 mCi) of 18F-Fluoro-L-DOPA intravenously, three static PET scans were acquired at 20, 30, and 40 min post injection in 3-D mode on 10 patients (6 male, 4 female) with congenital hyperinsulinism. Regions of interest (ROIs) were drawn over several organs visible in the reconstructed PET/CT images and time activity curves (TACs) were generated. Residence times were calculated using the TAC data. The radiation absorbed dose for the whole body was calculated by entering the residence times in the OLINDA/EXM 1.0 software.

RESULTS

The mean residence times for the 18F-Fluoro-L-DOPA in the liver, lungs, kidneys, muscles, and pancreas were 11.54 ± 2.84, 1.25 ± 0.38, 4.65 ± 0.97, 17.13 ± 2.62, and 0.89 ± 0.34 min, respectively. The mean effective dose equivalent for 18F-Fluoro-L-DOPA was 0.40 ± 0.04 mSv/MBq. The CT scan used for attenuation correction delivered an additional radiation dose of 5.7 mSv. The organs receiving the highest radiation absorbed dose from 18F-Fluoro-L-DOPA were the urinary bladder wall (2.76 ± 0.95 mGy/MBq), pancreas (0.87 ± 0.30 mGy/MBq), liver (0.34 ± 0.07 mGy/MBq), and kidneys (0.61 ± 0.11 mGy/MBq). The renal system was the primary route for the radioactivity clearance and excretion.

CONCLUSIONS

The estimated radiation dose burden from 18F-Fluoro-L-DOPA is relatively modest to newborns.

18F-DOPA PET/CT and 68Ga-DOTANOC PET/CT scans as diagnostic tools in focal congenital hyperinsulinism: a blinded evaluation

Purpose

Focal congenital hyperinsulinism (CHI) is curable by surgery, which is why identification of the focal lesion is crucial. We aimed to determine the use of 18F–fluoro-dihydroxyphenylalanine (18F-DOPA) PET/CT vs. 68Ga-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic-acid-1-Nal3-octreotide (68Ga-DOTANOC) PET/CT as diagnostic tools in focal CHI.

Methods

PET/CT scans of children with CHI admitted to Odense University Hospital between August 2005 and June 2016 were retrospectively evaluated visually and by their maximal standardized uptake values (SUV_max) by two independent examiners, blinded for clinical, surgical and pathological data. Pancreatic histology was used as the gold standard. For patients without surgery, the genetic profile served as the gold standard.

Results

Fifty-five CHI patients were examined by PET/CT (18F-DOPA n = 53, 68Ga-DOTANOC n = 18). Surgery was performed in 34 patients, no surgery in 21 patients. Fifty-one patients had a classifiable outcome, either by histology (n = 33, 22 focal lesions, 11 non-focal) or by genetics (n = 18, all non-focal). The predictive performance of 18F-DOPA PET/CT to identify focal CHI was identical by visual- and cut-off-based evaluation: sensitivity (95% CI) of 1 (0.85–1); specificity of 0.96 (0.82–0.99). The optimal 18F-DOPA PET SUV_max ratio cut-off was 1.44 and the optimal 68Ga-DOTANOC PET SUV_max cut-off was 6.77 g/ml. The area under the receiver operating curve was 0.98 (0.93–1) for 18F-DOPA PET vs. 0.71 (0.43–0.95) for 68Ga-DOTANOC PET (p < 0.03). In patients subjected to surgery, localization of the focal lesion was correct in 91%, and 100%, by 18F-DOPA PET/CT and 68Ga-DOTANOC PET/CT, respectively.

Conclusion

18F-DOPA PET/CT was excellent in predicting focal CHI and superior compared to 68Ga-DOTANOC PET/CT. Further use of 68GA-DOTANOC PET/CT in predicting focal CHI is discouraged.

Electronic supplementary material

The online version of this article (10.1007/s00259-017-3867-1) contains supplementary material, which is available to authorized users.

Efficacy and safety of octreotide for the treatment of congenital hyperinsulinism: a prospective, open-label clinical trial and an observational study in Japan using a nationwide registry

Octreotide, a long-acting somatostatin analog, has been used for treating hypoglycemia caused by congenital hyperinsulinism (CHI). However, octreotide has not been evaluated in clinical trials and has not been approved in any developed country. We aimed to test the efficacy and safety of octreotide for diazoxide-unresponsive CHI through a combination of a single-arm, open-label clinical trial (SCORCH study) and an observational study to collect data on the clinical course of patients treated off-label in Japan (SCORCH registry). In the SCORCH study, 5 patients were stabilized (blood glucose > 45 mg/dL) by hypertonic glucose infusion, and treated by continuous subcutaneous octreotide infusion at a dose of 5-25 μg/kg/day. Continuous blood glucose monitoring was performed between -24 and +48 hours. In 3 patients, a clinically meaningful rise in blood glucose was achieved and therapy was continued. The glucose infusion was gradually decreased and stopped after 5, 11, and 174 days, respectively. In one case, remission of CHI was reached after 606 days and octreotide was discontinued. The SCORCH registry included 19 diazoxide-unresponsive patients treated by subcutaneous octreotide, by continuous infusion or multiple daily injections. Of the 17 patients treated with hypertonic glucose infusion, the infusion rate was reduced after 4 weeks to less than 50% in 11 patients (64.7%) and stopped in 9 (52.9%). During the combined observation period of 695.4 patient-months in both studies, no severe adverse events related to octreotide were observed. In conclusion, subcutaneous octreotide injection was effective and well tolerated in the majority of patients with diazoxide-unresponsive CHI.

Clinical practice guidelines for congenital hyperinsulinism

Congenital hyperinsulinism is a rare condition, and following recent advances in diagnosis and treatment, it was considered necessary to formulate evidence-based clinical practice guidelines reflecting the most recent progress, to guide the practice of neonatologists, pediatric endocrinologists, general pediatricians, and pediatric surgeons. These guidelines cover a range of aspects, including general features of congenital hyperinsulinism, diagnostic criteria and tools for diagnosis, first- and second-line medical treatment, criteria for and details of surgical treatment, and future perspectives. These guidelines were generated as a collaborative effort between The Japanese Society for Pediatric Endocrinology and The Japanese Society of Pediatric Surgeons, and followed the official procedures of guideline generation to identify important clinical questions, perform a systematic literature review (April 2016), assess the evidence level of each paper, formulate the guidelines, and obtain public comments.

Hyperinsulinemic hypoglycemia: clinical, molecular and therapeutical novelties

Hyperinsulinemic hypoglycemia (HI) is the most common cause of hypoglycemia in children. Impairment of cellular pathways involved in insulin secretion from pancreatic β-cells, broadly classified as channelopathies and metabolopathies, have been discovered in the past two decades. The increasing use of NGS target panels, combined with clinical, biochemical and imaging findings allows differentiating the diagnostic management of children with focal forms, surgically curable, from those with diffuse forms, more conservatively treated with pharmacological and nutritional interventions. Specific approaches according to the subtype of HI have been established and novel therapies are currently under investigation. Despite diagnostic and therapeutic advances, HI remains an important cause of morbidity in children, still accounting for 26-44% of permanent intellectual disabilities, especially in neonatal-onset patients. Initial insult from recurrent hypoglycemia in early life greatly contributes to the poor outcomes. Therefore, patients need to be rapidly identified and treated aggressively, and require at follow-up a complex and regular monitoring, managed by a multidisciplinary HI team. This review gives an overview on the more recent diagnostic and therapeutic tools, on the novel drug and nutritional therapies, and on the long-term neurological outcomes.

Systematic reviews of diagnostic tests in endocrinology: an audit of methods, reporting, and performance

BACKGROUND

Systematic reviews provide clinicians and policymakers estimates of diagnostic test accuracy and their usefulness in clinical practice. We identified all available systematic reviews of diagnosis in endocrinology, summarized the diagnostic accuracy of the tests included, and assessed the credibility and clinical usefulness of the methods and reporting.

METHODS

We searched Ovid MEDLINE, EMBASE, and Cochrane CENTRAL from inception to December 2015 for systematic reviews and meta-analyses reporting accuracy measures of diagnostic tests in endocrinology. Experienced reviewers independently screened for eligible studies and collected data. We summarized the results, methods, and reporting of the reviews. We performed subgroup analyses to categorize diagnostic tests as most useful based on their accuracy.

RESULTS

We identified 84 systematic reviews; half of the tests included were classified as helpful when positive, one-fourth as helpful when negative. Most authors adequately reported how studies were identified and selected and how their trustworthiness (risk of bias) was judged. Only one in three reviews, however, reported an overall judgment about trustworthiness and one in five reported using adequate meta-analytic methods. One in four reported contacting authors for further information and about half included only patients with diagnostic uncertainty.

CONCLUSION

Up to half of the diagnostic endocrine tests in which the likelihood ratio was calculated or provided are likely to be helpful in practice when positive as are one-quarter when negative. Most diagnostic systematic reviews in endocrine lack methodological rigor, protection against bias, and offer limited credibility. Substantial efforts, therefore, seem necessary to improve the quality of diagnostic systematic reviews in endocrinology.

mTOR Inhibitors for the Treatment of Severe Congenital Hyperinsulinism: Perspectives on Limited Therapeutic Success

CONTEXT

Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycemia in neonates and infants. In medically unresponsive CHI, subtotal pancreatectomy is performed to achieve euglycemia with consequent diabetes in later life. Sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been reported to obviate the need for pancreatectomy, but experience is limited.

OBJECTIVE

We have investigated the efficacy and adverse effect profile of mTOR inhibitors in the treatment of severe CHI.

DESIGN, SETTING, AND PATIENTS

This was an observational review of 10 severe CHI patients treated with mTOR inhibitors, in France and the United Kingdom, with the intention of achieving glycemic control without pancreatectomy. Safety information was recorded.

MAIN OUTCOME MEASURE(S)

We examined whether mTOR inhibitors achieved glycemic control, fasting tolerance, and weaning of supportive medical therapy.

RESULTS

mTOR inhibition achieved euglycemia, fasting tolerance, and reduced medical therapy in only three patients (30%). Triglyceride levels were elevated in five patients (50%). One child required a blood transfusion for anemia, four had stomatitis, two had sepsis, one developed varicella zoster, and two patients developed gut dysmotility in association with exocrine pancreatic insufficiency. In silico analysis of transcriptome arrays from CHI patients revealed no significant association between mTOR signaling and disease. Pancreatic tissue from two patients who did not respond to sirolimus showed no reduction in cell proliferation, further suggesting that mTOR signaling did not down-regulate proliferation in the CHI pancreas.

CONCLUSION

mTOR inhibitor treatment is associated with very limited success and must be used with caution in children with severe CHI.

Role of (18) F-FDOPA PET/CT imaging in endocrinology

(18) F-FDOPA (6-[18F]-L-fluoro-L-3, 4-dihydroxyphenylalanine)-based PET/CT imaging can be a useful tool for the detection of different neuroendocrine tumours (NETs). (18) F-FDOPA is taken up into the cells via the neutral amino acid transporter (LAT1/4F2hc). This transporter is also coupled to the mammalian target of rapamycin (mTOR) signalling pathway. (18) F-FDOPA PET/CT may be performed for confirmation of diagnosis of pheochromocytoma/paraganglioma, staging at initial presentation, restaging and follow-up of patients. In SDHx-related syndromes, (18) F-FDG PET/CT should be performed in addition to (18) F-FDOPA PET/CT. (18) F-FDOPA PET/CT is also invaluable in the detection staging/restaging of carcinoid tumours and has greater sensitivity as compared to somatostatin receptor scintigraphy. (18) F-FDOPA PET/CT can also distinguish between focal vs diffuse CHI. It is not as useful in adult hyperinsulinism due to increased background uptake, but the problem may be overcome with the help of premedication with carbidopa. It has limited use in pancreatic NETs. (18) F-FDOPA PET/CT is a good modality for detection of persistent and residual medullary thyroid cancer (MTC), but (18) F-FDG PET/CT may be needed in aggressive tumours. In summary, F-DOPA PET/CT has widespread utility in the diagnosis of different neuroendocrine tumours.

Clinical and histological heterogeneity of congenital hyperinsulinism due to paternally inherited heterozygous ABCC8/KCNJ11 mutations

CONTEXT

Congenital hyperinsulinism (CHI) has two main histological types: diffuse and focal. Heterozygous paternally inherited ABCC8/KCNJ11 mutations (depending upon whether recessive or dominant acting and occurrence of somatic maternal allele loss) can give rise to either phenotype. However, the relative proportion of these two phenotypes in a large cohort of CHI patients due to paternally inherited heterozygous ABCC8/KCNJ11 mutations has not been reported.

OBJECTIVE

The purpose of this study is to highlight the variable clinical phenotype and to characterise the distribution of diffuse and focal disease in a large cohort of CHI patients due to paternally inherited heterozygous ABCC8/KCNJ11 mutations.

DESIGN

A retrospective chart review of the CHI patients due to heterozygous paternally inherited ABCC8/KCNJ11 mutations from 2000 to 2013 was conducted.

RESULTS

Paternally inherited heterozygous ABCC8/KCNJ11 mutations were identified in 53 CHI patients. Of these, 18 (34%) either responded to diazoxide or resolved spontaneously. Fluorine-18 l-3, 4-dihydroxyphenylalanine positron emission tomography computerised tomography 18F DOPA-PET CT) scanning in 3/18 children showed diffuse disease. The remaining 35 (66%) diazoxide-unresponsive children either had pancreatic venous sampling (n=8) or 18F DOPA-PET CT (n=27). Diffuse, indeterminate and focal disease was identified in 13, 1 and 21 patients respectively. Two patients with suspected diffuse disease were identified to have focal disease on histology.

CONCLUSIONS

Paternally inherited heterozygous ABCC8/KCNJ11 mutations can manifest as a wide spectrum of CHI with variable 18F DOPA-PET CT/histological findings and clinical outcomes. Focal disease was histologically confirmed in 24/53 (45%) of CHI patients with paternally inherited heterozygous ABCC8/KCNJ11 mutations.

Occurrence of giant focal forms of congenital hyperinsulinism with incorrect visualization by (18) F DOPA-PET/CT scanning

CONTEXT

Congenital hyperinsulinism (CHI) is a rare disease characterized by severe hypoglycaemic episodes due to pathologically increased insulin secretion from the pancreatic beta cells. When untreated, CHI might result in irreversible brain damage and death. Currently, two major subtypes of CHI are known: a focal form, associated with local distribution of affected beta cells and a nonfocal form, affecting every single beta cell. The identification of focal forms is important, as the patients can be cured by limited surgery. (18) F DOPA-PET/CT is an established non-invasive approach to differentiate focal from nonfocal CHI.

OBJECTIVE

The purpose of this study was to identify possible limitations of (18) F DOPA-PET/CT scan in patients with focal forms nonfocal CHI.

DESIGN

A retrospective chart review of 32 patients (from 2008 through 2013) who underwent (18) F DOPA-PET/CT and partial pancreatectomy for focal CHI at the reference centres in Berlin, Germany and London, UK.

RESULTS

In most cases (n = 29, 90·7%), (18) F DOPA-PET/CT was sufficient to localize the complete focal lesion. However, in some patients (n = 3, 9·3%), (18) F DOPA-PET/CT wrongly visualized only a small portion of the focal lesion. In this group of patients, a so-called 'giant focus' was detected in histopathological analysis during the surgery.

CONCLUSIONS

Our data show that in most patients with focal CHI (18) F DOPA-PET/CT correctly predicts the size and anatomical localisation of the lesion. However, in those patients with a 'giant focal' lesion (18) F DOPA-PET/CT is unreliable for correct identification of 'giant focus' cases.

Strengths and limitations of using 18fluorine-fluorodihydroxyphenylalanine PET/CT for congenital hyperinsulinism

¹⁸fluorine-fluorodihydroxyphenylalanine (FDOPA) PET/CT is currently the first-line imaging technique to distinguish between focal and diffuse forms of congenital hyperinsulinism (CHI) and to accurately localize focal forms. However, this technique has a number of limitations, mainly the very small size of focal forms or inversely a very large focal form mimicking a diffuse form, and misinterpretation of physiologic uptake masking hot spots or inversely mimicking focal forms. The other limitation is the limited availability of the radiopharmaceutical. FDOPA PET/CT has no recognized competitor to date among the available morphologic and functional imaging techniques. Other potential approaches using specific tracers for positron emission tomography (PET) are discussed, using radiopharmaceuticals specific for β cell mass or targeting somatostatin receptors. These radiopharmaceuticals can be labeled with gallium-68, a PET emitter readily available in PET centers equipped with 68Ge/68Ga generators.

Assessing the quality of studies on the diagnostic accuracy of tumor markers

OBJECTIVES

With rapidly increasing numbers of publications, assessments of study quality, reporting quality, and classification of studies according to their level of evidence or developmental stage have become key issues in weighing the relevance of new information reported. Diagnostic marker studies are often criticized for yielding highly discrepant and even controversial results. Much of this discrepancy has been attributed to differences in study quality. So far, numerous tools for measuring study quality have been developed, but few of them have been used for systematic reviews and meta-analysis. This is owing to the fact that most tools are complicated and time consuming, suffer from poor reproducibility, and do not permit quantitative scoring.

METHODS

The International Bladder Cancer Network (IBCN) has adopted this problem and has systematically identified the more commonly used tools developed since 2000.

RESULTS

In this review, those tools addressing study quality (Quality Assessment of Studies of Diagnostic Accuracy and Newcastle-Ottawa Scale), reporting quality (Standards for Reporting of Diagnostic Accuracy), and developmental stage (IBCN phases) of studies on diagnostic markers in bladder cancer are introduced and critically analyzed. Based upon this, the IBCN has launched an initiative to assess and validate existing tools with emphasis on diagnostic bladder cancer studies.

CONCLUSIONS

The development of simple and reproducible tools for quality assessment of diagnostic marker studies permitting quantitative scoring is suggested.

Congenital hyperinsulinism: Role of fluorine-18L-3, 4 hydroxyphenylalanine positron emission tomography scanning

Congenital hyperinsulinism (CHI) is a rare but complex heterogeneous disorder caused by unregulated secretion of insulin from the β-cells of the pancreas leading to severe hypoglycaemia and neuroglycopaenia. Swift diagnosis and institution of appropriate management is crucial to prevent or minimise adverse neurodevelopmental outcome in children with CHI. Histologically there are two major subtypes of CHI, diffuse and focal disease and the management approach will significantly differ depending on the type of the lesion. Patients with medically unresponsive diffuse disease require a near total pancreatectomy, which then leads on to the development of iatrogenic diabetes mellitus and pancreatic exocrine insufficiency. However patients with focal disease only require a limited pancreatectomy to remove only the focal lesion thus providing complete cure to the patient. Hence the preoperative differentiation of the histological subtypes of CHI becomes paramount in the management of CHI. Fluorine-18L-3, 4-hydroxyphenylalanine positron emission tomography (¹⁸F-DOPA-PET) is now the gold standard for pre-operative differentiation of focal from diffuse disease and localisation of the focal lesion. The aim of this review article is to give a clinical overview of CHI, then review the role of dopamine in β-cell physiology and finally discuss the role of ¹⁸F-DOPA-PET imaging in the management of CHI.

Congenital hyperinsulinism: current status and future perspectives

The diagnosis and treatment of congenital hyperinsulinism (CHI) have made a remarkable progress over the past 20 years and, currently, it is relatively rare to see patients who are left with severe psychomotor delay. The improvement was made possible by the recent developments in the understanding of the molecular and pathological basis of CHI. Known etiologies include inactivating mutations of the KATP channel genes (ABCC8 and KCNJ11) and HNF4A, HNF1A, HADH, and UCP2 or activating mutations of GLUD1, GCK, and SLC16A1. The understanding of the focal form of KATP channel CHI and its detection by (18)F-fluoro-L-DOPA positron emission tomography have revolutionized the management of CHI, and many patients can be cured without postoperative diabetes mellitus. The incidence of the focal form appears to be higher in Asian countries; therefore, the establishment of treatment systems is even more important in this population. In addition to diazoxide or long-term subcutaneous infusion of octreotide or glucagon, long-acting octreotide or lanreotide have also been used successfully until spontaneous remission. Because of these medications, near-total pancreatectomy is less often performed even for the diazoxide-unresponsive diffuse form of CHI. Other promising medications include pasireotide, small-molecule correctors such as sulfonylurea or carbamazepine, GLP1 receptor antagonists, or mammalian target of rapamycin inhibitors. Unsolved questions in this field include the identification of the remaining genes responsible for CHI, the mechanisms leading to transient CHI, and the mechanisms responsible for the spontaneous remission of CHI. This article reviews recent developments and hypothesis regarding these questions.

Update on neonatal hypoglycemia

PURPOSE OF REVIEW

Neonatal hypoglycemia is one of the most common biochemical abnormalities encountered in the newborn. However, controversy remains surrounding its definition and management especially in asymptomatic patients.

RECENT FINDINGS

New information has been published that describes the incidence and timing of low glucose concentrations in the groups most at risk for asymptomatic neonatal hypoglycemia. Furthermore, one large prospective study failed to find an association between repetitive low glucose concentrations and poor neurodevelopmental outcomes in preterm infants. But hypoglycemia due to hyperinsulinism, especially genetic causes, continued to be associated with brain injury. New advances were made in the diagnosis and management of hyperinsulinism, including acquired hyperinsulinism in small for gestational age infants and others. Continuous glucose monitoring remains an attractive strategy for future research in this area.

SUMMARY

The fundamental question of how best to manage asymptomatic newborns with low glucose concentrations remains unanswered. Balancing the risks of overtreating newborns with low glucose concentrations who are undergoing a normal transition following birth against the risks of undertreating those in whom low glucose concentrations are pathological, dangerous, and/or a harbinger of serious metabolic disease remains a challenge.

Beta-cell imaging: call for evidence-based and scientific approach

INTRODUCTION

Advances in positron emission tomography (PET) imaging have provided opportunities to develop radiotracers specific for imaging insulin-producing pancreatic β-cells. However, a host of lingering questions should be addressed before these radiotracers are advocated for noninvasive quantification of β-cell mass (BCM) in vivo in the native pancreas.

METHOD

We provide an overview of tetrabenazine-based PET tracers developed to image and quantify BCM and discuss several theoretical, technical, and biological limitations of applying these tracers in clinical practice.

DISCUSSION

VMAT2, a transporter protein expressed on pancreatic β-cells, has been advocated as a promising target for PET imaging tracers, such as dihydrotetrabenazine. However, the lack of radiotracer specificity for these proteins hampers their clinical application. Another important argument against their use is a striking discrepancy between radiotracer uptake and BCM in subjects with type I diabetes mellitus and healthy controls. Additionally, technical issues, such as the finite spatial resolution of PET, partial volume effects, and movement of the pancreas during respiration, impede PET imaging as a viable option for BCM quantification in the foreseeable future.

CONCLUSION

The assertion that BCM can be accurately quantified by tetrabenazine derived β-cell-specific radiotracers as density per unit volume of pancreatic tissue is not justifiable at this time. The fallacy of these claims can be explained by technical as well as biological facts that have been disregarded and ignored in the literature.

K(ATP) channels and islet hormone secretion: new insights and controversies

ATP-sensitive potassium channels (K(ATP) channels) link cell metabolism to electrical activity by controlling the cell membrane potential. They participate in many physiological processes but have a particularly important role in systemic glucose homeostasis by regulating hormone secretion from pancreatic islet cells. Glucose-induced closure of K(ATP) channels is crucial for insulin secretion. Emerging data suggest that K(ATP) channels also play a key part in glucagon secretion, although precisely how they do so remains controversial. This Review highlights the role of K(ATP) channels in insulin and glucagon secretion. We discuss how K(ATP) channels might contribute not only to the initiation of insulin release but also to the graded stimulation of insulin secretion that occurs with increasing glucose concentrations. The various hypotheses concerning the role of K(ATP) channels in glucagon release are also reviewed. Furthermore, we illustrate how mutations in K(ATP) channel genes can cause hyposecretion or hypersecretion of insulin, as in neonatal diabetes mellitus and congenital hyperinsulinism, and how defective metabolic regulation of the channel may underlie the hypoinsulinaemia and the hyperglucagonaemia that characterize type 2 diabetes mellitus. Finally, we outline how sulphonylureas, which inhibit K(ATP) channels, stimulate insulin secretion in patients with neonatal diabetes mellitus or type 2 diabetes mellitus, and suggest their potential use to target the glucagon secretory defects found in diabetes mellitus.

Integrating genetic and imaging investigations into the clinical management of congenital hyperinsulinism

Congenital Hyperinsulinism (CHI) is a rare but important cause of hypoglycaemia in infancy. CHI is a heterogeneous disease, but has a strong genetic basis; a number of genetic causes have been identified with CHI in about a third of individuals, chiefly in the genes that code for the ATP sensitive K(+) channels (KATP ) in the pancreatic β-cells. Rapid KATP channel gene testing is a critical early step in the diagnostic algorithm of CHI, with paternal heterozygosity correlating with the occurrence of focal lesions. Imaging investigations to diagnose and localize solitary pancreatic foci have evolved over the last decade with (18)F-DOPA PET-CT scanning as the current diagnostic tool of choice. Although clinical management of CHI has improved significantly with the application of genetic screening and imaging investigations, much remains to be uncovered. This includes a better understanding of the molecular mechanisms for dysregulated insulin release in those patients without known genetic mutations, and the development of biomarkers that could characterize CHI, including long-term prognosis and targeted treatment planning, i.e. 'personalised medicine'. From the perspective of pancreatic imaging, it would be important to achieve greater specificity of diagnosis not only for focal lesions but also for diffuse and atypical forms of the disease.

Congenital hyperinsulinism

PURPOSE OF REVIEW

Congenital hyperinsulinism (CHI) is a multifaceted disease and continues to be the most common cause of persistent hypoglycemia in infants. The purpose of the review is to highlight important recent developments regarding CHI.

RECENT FINDINGS

Several recent studies have highlighted the advances in medical genetics, imaging techniques, histological variety, and surgical decision making regarding CHI. The advancements have resulted in the ability to often distinguish between diffuse and focal disease, thus allowing a more focused medical and surgical approach to the patient. When genetic information is combined with advanced imaging and intraoperative histological analysis, surgical results have improved. Despite medical and surgical advancements, recent studies also reveal the need for better medical options for patients and that aggressive surgery may lead to the onset of diabetes.

SUMMARY

Current advances have improved the overall care of the patient with CHI, although there are still improvements to be achieved. The ability to apply these advancements is best accomplished with an experienced team consisting of geneticists, radiologists, endocrinologists, pathologists, and surgeons. Utilizing a team approach results in a complete evaluation and allows a customized care plan for each patient.

18F-fluorodihydroxyphenylalanine vs other radiopharmaceuticals for imaging neuroendocrine tumours according to their type

6-Fluoro-(¹⁸F)-L-3,4-dihydroxyphenylalanine (FDOPA) is an amino acid analogue for positron emission tomography (PET) imaging which has been registered since 2006 in several European Union (EU) countries and by several pharmaceutical firms. Neuroendocrine tumour (NET) imaging is part of its registered indications. NET functional imaging is a very competitive niche, competitors of FDOPA being two well-established radiopharmaceuticals for scintigraphy, ¹²³I-metaiodobenzylguanidine (MIBG) and ¹¹¹In-pentetreotide, and even more radiopharmaceuticals for PET, including fluorodeoxyglucose (FDG) and somatostatin analogues. Nevertheless, there is no universal single photon emission computed tomography (SPECT) or PET tracer for NET imaging, at least for the moment. FDOPA, as the other PET tracers, is superior in diagnostic performance in a limited number of precise NET types which are currently medullary thyroid cancer, catecholamine-producing tumours with a low aggressiveness and well-differentiated carcinoid tumours of the midgut, and in cases of congenital hyperinsulinism. This article reports on diagnostic performance and impact on management of FDOPA according to the NET type, emphasising the results of comparative studies with other radiopharmaceuticals. By pooling the results of the published studies with a defined standard of truth, patient-based sensitivity to detect recurrent medullary thyroid cancer was 70 % [95 % confidence interval (CI) 62.1–77.6] for FDOPA vs 44 % (95 % CI 35–53.4) for FDG; patient-based sensitivity to detect phaeochromocytoma/paraganglioma was 94 % (95 % CI 91.4–97.1) for FDOPA vs 69 % (95 % CI 60.2–77.1) for ¹²³I-MIBG; and patient-based sensitivity to detect midgut NET was 89 % (95 % CI 80.3–95.3) for FDOPA vs 80 % (95 % CI 69.2–88.4) for somatostatin receptor scintigraphy with a larger gap in lesion-based sensitivity (97 vs 49 %). Previously unpublished FDOPA results from our team are reported in some rare NET, such as small cell prostate cancer, or in emerging indications, such as metastatic NET of unknown primary (CUP-NET) or adrenocorticotropic hormone (ACTH) ectopic production. An evidence-based strategy in NET functional imaging is as yet affected by a low number of comparative studies. Then the suggested diagnostic trees, being a consequence of the analysis of present data, could be modified, for some indications, by a wider experience mainly involving face-to-face studies comparing FDOPA and ⁶⁸Ga-labelled peptides.

Monogenic hyperinsulinemic hypoglycemia: current insights into the pathogenesis and management

Hyperinsulinism (HI) is the leading cause of persistent hypoglycemia in children, which if unrecognized may lead to development delays and permanent neurologic damage. Prompt recognition and appropriate treatment of HI are essential to avoid these sequelae. Major advances have been made over the past two decades in understanding the molecular basis of hyperinsulinism and mutations in nine genes are currently known to cause HI. Inactivating K_ATP channel mutations cause the most common and severe type of HI, which occurs in both a focal and a diffuse form. Activating mutations of glutamate dehydrogenase (GDH) lead to hyperinsulinism/hyperammonemia syndrome, while activating mutations of glucokinase (GK), the “glucose sensor” of the beta cell, causes hyperinsulinism with a variable clinical phenotype. More recently identified genetic causes include mutations in the genes encoding short-chain 3-hydroxyacyl-CoA (SCHAD), uncoupling protein 2 (UCP2), hepatocyte nuclear factor 4-alpha (HNF-4α), hepatocyte nuclear factor 1-alpha (HNF-1α), and monocarboyxlate transporter 1 (MCT-1), which results in a very rare form of HI triggered by exercise. For a timely diagnosis, a critical sample and a glucagon stimulation test should be done when plasma glucose is < 50 mg/dL. A failure to respond to a trial of diazoxide, a K_ATP channel agonist, suggests a K_ATP defect, which frequently requires pancreatectomy. Surgery is palliative for children with diffuse K_ATPHI, but children with focal K_ATPHI are cured with a limited pancreatectomy. Therefore, distinguishing between diffuse and focal disease and localizing the focal lesion in the pancreas are crucial aspects of HI management. Since 2003, ¹⁸ F-DOPA PET scans have been used to differentiate diffuse and focal disease and localize focal lesions with higher sensitivity and specificity than more invasive interventional radiology techniques. Hyperinsulinism remains a challenging disorder, but recent advances in the understanding of its genetic basis and breakthroughs in management should lead to improved outcomes for these children.