Advances in the diagnosis and management of hyperinsulinemic hypoglycemia

Glucagon treatment for post-gastric bypass hypoglycemia

Hyperinsulinemic hypoglycemia is a recently described complication of Roux-en-Y gastric bypass (RYGB). We hypothesized that glucagon administration would help maintain normal postprandial plasma glucose concentrations by stimulating hepatic glucose output, and if so, represent a new therapeutic option for postbypass hypoglycemia. In this study, we compared the insulin and glycemic response to a mixed meal with and without concomitant glucagon infusion in a patient with severe recurrent hypoglycemia after RYGB. Although effective in transiently raising postprandial plasma glucose values, glucagon infusion was also associated with higher insulin concentrations, and failed to prevent symptomatic hypoglycemia. This case demonstrates that glucagon may have limited clinical utility in the treatment of post-RYGB hyperinsulinemic hypoglycemia.

Neonatal hypoglycemia

PURPOSE OF REVIEW

Hypoglycemia in the newborn may be associated with both acute decompensation and long-term neuronal loss. Studies of the cause of hypoglycemic brain damage and the relationship of hypoglycemia to disorders associated with hyperinsulinism have aided in our understanding of this common clinical finding.

RECENT FINDINGS

A recent consensus workshop concluded that there has been little progress toward a precise numerical definition of neonatal hypoglycemia. Nonetheless, newer brain imaging modalities have provided insight into the relationship between neuronal energy deficiency and central nervous system damage. Laboratory studies have begun to reveal the mechanism of hypoglycemic damage. In addition, there is new information about hyperinsulinemic hypoglycemia of genetic, environmental, and iatrogenic origin.

SUMMARY

The quantitative definition of hypoglycemia in the newborn remains elusive because it is a surrogate marker for central nervous system energy deficiency. Nonetheless, the recognition that hyperinsulinemic hypoglycemia, which produces profound central nervous system energy deficiency, is most likely to lead to long-term central nervous system damage, has altered management of children with hypoglycemia. In addition, imaging studies on neonates and laboratory evaluation in animal models have provided insight into the mechanism of neuronal damage.

PET and PET/CT in endocrine tumours

Functional information provided by PET tracers together with the superior image quality and the better data quantification by PET technology had a changing effect on the significance of nuclear medicine in medical issues. Recently introduced hybrid PET/CT systems together with the introduction of novel PET radiopharmaceuticals have contributed to the fact that nuclear medicine has become a growing diagnostic impact on endocrinology. In this review imaging strategies, different radiopharmaceuticals including the basic mechanism of their cell uptake, and the diagnostic value of PET and PET/CT in endocrine tumours except differentiated thyroid carcinomas will be discussed.

Investigation and management of congenital hyperinsulinism

Insulin is a powerful hormone produced by the beta-cells in the pancreas. Its major function is to regulate blood glucose levels, facilitating the transport of glucose into the body's cells. Congenital hyperinsulinism is characterized by the presence of insulin that is inappropriately high for the concentration of blood glucose. Because high levels of insulin also switch off all alternative fuels for the brain to use, this condition can cause brain injury if not detected quickly. Nurses are in a unique position by the bedside to identify the symptoms and treat the hypoglycaemia through very simple nursing interventions, such as safe administration of glucose and frequent blood glucose monitoring. Congenital hyperinsulinism can be transient or persistent. Persistent congenital hyperinsulinism can be further divided into focal or diffuse disease. Focal congenital hyperinsulinism can now be cured, and the management of congenital hyperinsulinism has radically changed with the help of genetics and research. Now pancreatectomy surgery is only used as the last resort.

Rapid genetic analysis, imaging with 18F-DOPA-PET/CT scan and laparoscopic surgery in congenital hyperinsulinism

Congenital hyperinsulinism (CHI) is responsible for profound hypoglycaemia which needs aggressive treatment in order to prevent neurological damage. Mutations in seven different genes have been held responsible for the inappropriate insulin secretion, typical of this condition. The most common cause of CHI is autosomal recessive mutations in the ABCC8 and KCNJ11 genes which encode for two subunits (SUR 1 and Kir6.2, respectively) of the pancreatic B-cell ATP-sensitive potassium channel. Furthermore, histopathological lesions, diffuse and focal, have been associated with different genetic alterations. [18F]Fluorodopa PET/CT imaging, in most cases, differentiates focal from diffuse disease and is 100% accurate in localizing the focal lesion. Recently laparoscopic pancreatectomy has been performed and is curative in the focal form. We report a case in which clinical experience together with rapid genetic analysis, imaging with 18F-DOPA-PET/CT and laparoscopic surgery, were able to guide the correct clinical management of this condition.

Persistent hyperinsulinemic hypoglycemia with left ventricular hypertrophy and dysrhythmia: a case report

Persistent hyperinsulinemic hypoglycemia in neonatal period is characterized by insulin hypersecretion. The major feature is severe hypoglycemia, generally unresponsive to routine medical treatment. Subtotal or total pancreatectomy is performed in unresponsive cases. In this case report, we present a newborn with persistent hypoglycemia unresponsive to medical treatment with dysrhythmic left ventricular hypertrophy. The insulin/C-peptide ratio was 58 as a confirmation of diagnosis. Since hypoglycemia persisted after the initial medical treatment, a subtotal pancreatectomy was performed followed by near-total pancreatectomy. A histologic examination revealed diffuse insulin islets. At the 70th post-natal day, death occurred due to heart failure and ventricular dysrhythmia. To our knowledge, severe dysrhythmia and left ventricular hypertrophy in persistent hyperinsulinemic hypoglycemia (PPH) is identified in the patient.

18F-FDOPA: a multiple-target molecule

Although 6-(18)F-fluoro-L-dopa ((18)F-FDOPA) has been available to study the striatal dopaminergic system for more than 2 decades, the full potential of the tracer was not realized before the introduction of (18)F-FDOPA PET and PET/CT to image a variety of neuroendocrine tumors (NETs) and pancreatic beta-cell hyperplasia. Together with receptor-based imaging, (18)F-FDOPA offers a formerly unforeseen means to assist in the management of NETs and infants with persistent hyperinsulinemic hyperplasia. Institutions with special expertise in surgical, oncologic, and radiologic therapeutic modalities for NETs derive the highest benefit from (18)F-FDOPA PET/CT. (18)F-FDOPA-guided therapy may add to NET control by ensuring maximal cytoreduction.

Primers on molecular pathways - ion channels: key regulators of pancreatic physiology

Ion transport across the cellular plasma membrane is important in almost every physiological process. This phenomenon is driven by the coordinated action of carriers, pumps and channels, which move ions in and out the cells and between different organelles. Ion channels are transmembrane proteins that provide a continuous aqueous pore through which ions can selectively move. The interest in these molecules has increased due to the recognition of diverse pathologies related with mutations in genes encoding these transmembrane proteins, now known as channelopathies. Ion channels play a variety of functions in the pancreas. Here, we briefly describe ion transport characteristics as well as their role in pancreas physiology and pathophysiology.