Symptoms of hypoglycemia, thresholds for their occurrence, and hypoglycemia unawareness

Recurrent spontaneous hypoglycaemia causes loss of neurogenic and neuroglycopaenic signs in infants with congenital hyperinsulinism

OBJECTIVE

Hypoglycaemia-associated autonomic failure (HAAF) with impaired neurogenic and neuroglycopaenic responses occurs in adults following recent, repeated hypoglycaemia. We aimed to evaluate whether HAAF also occurs in patients with infant-onset congenital hyperinsulinism (CHI).

DESIGN, PATIENTS

A controlled fast was performed in (i) seven CHI infants with initial symptomatic hypoglycaemia and three recent episodes of spontaneous recurrent hypoglycaemia each lasting <5 min and in (ii) seven infants with idiopathic ketotic hypoglycaemia for control.

MEASUREMENTS

At the time of hypoglycaemia (blood glucose <3 mmol/l or clinical signs), blood was drawn for serum insulin, cortisol, glucagon, adrenalin and nor-adrenalin. Signs of hypoglycaemia were documented. In CHI patients, the ABCC8 and KCNJ11 genes were analysed by denaturing high performance liquid chromatography (DHPLC) and/or direct bidirectional sequencing.

RESULTS

Two CHI patients had a paternal ABCC8 mutation, five had no mutations. When repeated hypoglycaemia was provoked, all CHI patients exhibited a complete loss of clinical signs of hypoglycaemia, along with a global blunting of the counter-regulatory hormones cortisol, glucagon, growth hormone, adrenalin and nor-adrenalin responses (median values 256 nmol/l, 23 pmol/l, 5·6 mU/l, 390 pmol/l and 2·9 nmol/l, respectively), irrespective of mutational status. In the controls, hypoglycaemia was always clinically overt with normal counter-regulatory cortisol, glucagon, adrenalin and nor-adrenalin responses (530 nmol/l, 60, 920 pmol/l and 4·0 nmol/l, respectively).

CONCLUSION

Recurrent hyperinsulinaemic hypoglycaemia even of short duration blunts the autonomic, neuroglycopaenic and glucose counter-regulatory hormonal responses in patients with infant-onset CHI resulting in clinically silent hypoglycaemia. Tight, or continuous, glucose monitoring is therefore recommended, especially in conservatively treated patients.

Hypoglycemia revisited in the acute care setting

Hypoglycemia is a common finding in both daily clinical practice and acute care settings. The causes of severe hypoglycemia (SH) are multi-factorial and the major etiologies are iatrogenic, infectious diseases with sepsis and tumor or autoimmune diseases. With the advent of aggressive lowering of HbA1c values to achieve optimal glycemic control, patients are at increased risk of hypoglycemic episodes. Iatrogenic hypoglycemia can cause recurrent morbidity, sometime irreversible neurologic complications and even death, and further preclude maintenance of euglycemia over a lifetime of diabetes. Recent studies have shown that hypoglycemia is associated with adverse outcomes in many acute illnesses. In addition, hypoglycemia is associated with increased mortality among elderly and non-diabetic hospitalized patients. Clinicians should have high clinical suspicion of subtle symptoms of hypoglycemia and provide prompt treatment. Clinicians should know that hypoglycemia is associated with considerable adverse outcomes in many acute critical illnesses. In order to reduce hypoglycemia-associated morbidity and mortality, timely health education programs and close monitoring should be applied to those diabetic patients presenting to the Emergency Department with SH. ED disposition strategies should be further validated and justified to achieve balance between the benefits of euglycemia and the risks of SH. We discuss relevant issues regarding hypoglycemia in emergency and critical care settings.

Drug-induced hypoglycaemia: an update

Drugs are the most frequent cause of hypoglycaemia in adults. Although hypoglycaemia is a well known adverse effect of antidiabetic agents, it may occasionally develop in the course of treatment with drugs used in everyday clinical practice, including NSAIDs, analgesics, antibacterials, antimalarials, antiarrhythmics, antidepressants and other miscellaneous agents. They induce hypoglycaemia by stimulating insulin release, reducing insulin clearance or interfering with glucose metabolism. Several drugs may also potentiate the hypoglycaemic effect of antidiabetic agents. Administration of these agents to individuals with diabetes mellitus is of most concern. Many of these drugs, and depending on clinical setting, may also induce hyperglycaemia. Drug-induced hepatotoxicity and nephrotoxicity may lead in certain circumstances to hypoglycaemia. Some drugs may also induce hypoglycaemia by causing pancreatitis. Drug-induced hypoglycaemia is usually mild but may be severe. Effective clinical management can be handled through awareness of this drug-induced adverse effect on blood glucose levels. Herein, we review pertinent clinical information on the incidence of drug-induced hypoglycaemia and discuss the underlying pathophysiological mechanisms, and prevention and management.

Anticonvulsant and proconvulsant actions of 2-deoxy-D-glucose

PURPOSE

2-Deoxy-D-glucose (2-DG), a glucose analog that accumulates in cells and interferes with carbohydrate metabolism by inhibiting glycolytic enzymes, has anticonvulsant actions. Recognizing that severe glucose deprivation can induce seizures, we sought to determine whether acute treatment with 2-DG can promote seizure susceptibility by assessing its effects on seizure threshold. For comparison, we studied 3-methyl-glucose (3-MG), which like 2-DG accumulates in cells and reduces glucose uptake, but does not inhibit glycolysis.

METHODS

Mice were treated with 2-DG or 3-MG and the seizure threshold determined in the 6-Hz test, the mouse electroshock seizure threshold (MEST) test, and the intravenous pentylenetetrazol (i.v. PTZ) or kainic acid (i.v. KA) seizure threshold tests. 2-DG was also tested in fully amygdala-kindled rats.

RESULTS

2-DG (125-500 mg/kg, i.p., 30 min before testing) significantly elevated the seizure threshold in the 6-Hz seizure test. 2-DG (250-500 mg/kg) decreased the threshold in the MEST and i.v. PTZ and i.v. KA tests. 3-MG had no effect on seizure threshold in the 6-Hz test but, like 2-DG, decreased seizure threshold in the i.v. PTZ test. 2-DG (250 and 500 mg/kg, i.p., 30 min before testing) had no effect on amygdala-kindled seizures.

CONCLUSIONS

Although 2-DG protects against seizures in the 6-Hz seizure test, it promotes seizures in some other models. The proconvulsant action may relate to reduced glucose uptake, whereas the anticonvulsant action may require inhibition of glycolysis and shunting of glucose metabolism through the pentose phosphate pathway.

[Hypoglycemia and insulinoma]

Insulinomas are rare causes of hypoglycemia. After having ruled out non insulinomatous causes of hypoglycemia in a patient in whom Whipple's triad is documented, hyperinsulinism must be demonstrated biochemically, either during a spontaneous hypoglycemic episode or, more often, during a supervised fast which may be prolonged up to 72 h. A mixed-meal test may also help to diagnose the very rare cases of postprandial hypoglycemia related to non insulinoma pancreatogenic hypoglycemic syndrome (NIPHS) or to some rare insulinomas. Only when diagnosis of hypoglycemic hyperinsulinism is made, the tumor localization process may be initiated. This may be difficult due to the small size of insulinomas (generally < 1 cm). Multimodal approach is necessary. The association of endoscopic ultrasound and CT-scan or MRI seems optimal. Octreoscan will be also performed. First results with a very new technique, the GLP-1 receptor imaging, are promising for localizing very small tumors. This localization aims to allow a sparing surgery; enucleation of benign tumors, if possible, allows a pancreatic tissue preservation in patients with quite normal survival.

Human cerebral neuropathology of Type 2 diabetes mellitus

The cerebral neuropathology of Type 2 diabetes (CNDM2) has not been positively defined. This review includes a description of CNDM2 research from before the 'Pubmed Era'. Recent neuroimaging studies have focused on cerebrovascular and white matter pathology. These and prior studies about cerebrovascular histopathology in diabetes are reviewed. Evidence is also described for and against the link between CNDM2 and Alzheimer's disease pathogenesis. To study this matter directly, we evaluated data from University of Kentucky Alzheimer's Disease Center (UK ADC) patients recruited while non-demented and followed longitudinally. Of patients who had come to autopsy (N = 234), 139 met inclusion criteria. These patients provided the basis for comparing the prevalence of pathological and clinical indices between well-characterized cases with (N = 50) or without (N = 89) the premortem diagnosis of diabetes. In diabetics, cerebrovascular pathology was more frequent and Alzheimer-type pathology was less frequent than in non-diabetics. Finally, a series of photomicrographs demonstrates histopathological features (including clinical-radiographical correlation) observed in brains of persons that died after a history of diabetes. These preliminary, correlative, and descriptive studies may help develop new hypotheses about CNDM2. We conclude that more work should be performed on human material in the context of CNDM2.

Advances in the diagnosis and management of hyperinsulinemic hypoglycemia

Hyperinsulinemic hypoglycemia (HH) is a consequence of unregulated insulin secretion by pancreatic beta-cells and is a major cause of hypoglycemic brain injury and mental retardation. Congenital HH is caused by mutations in genes involved in regulation of insulin secretion, seven of which have been identified (ABCC8, KCNJ11, GLUD1, CGK, HADH, SLC16A1 and HNF4A). Severe forms of congenital HH are caused by mutations in ABCC8 and KCNJ11, which encode the two components of the pancreatic beta-cell ATP-sensitive potassium channel. Mutations in HNF4A, GLUD1, CGK, and HADH lead to transient or persistent HH, whereas mutations in SLC16A1 cause exercise-induced HH. Rapid genetic analysis combined with an understanding of the histological features (focal or diffuse disease) of congenital HH and the introduction of (18)F-L-3,4-dihydroxyphenylalanine PET-CT to guide laparoscopic surgery have totally transformed the clinical approach to this complex disease. Adult-onset HH is mostly caused by an insulinoma; however, it has also been reported to present as postprandial HH in patients with noninsulinoma pancreatogenous hypoglycemia syndrome, in those who have undergone gastric-bypass surgery for morbid obesity, and in those with mutations in the insulin-receptor gene.

Portal vein glucose sensors do not play a major role in modulating physiological responses to insulin-induced hypoglycemia in humans

OBJECTIVE

Experimental data from animal studies indicate that portal vein glucose sensors play a key role in the responses to slow-fall hypoglycemia. However, their role in modulating these responses in humans is not well understood. The aim of the present study was to examine in humans the potential role of portal vein glucose sensors in physiological responses to insulin-induced hypoglycemia mimicking the slow fall of insulin-treated diabetic subjects.

RESEARCH DESIGN AND METHODS

Ten nondiabetic subjects were studied on two different occasions during intravenous insulin (2 mU . kg(-1) . min(-1)) plus variable glucose for 160 minutes. In both studies, after 60 min of normal plasma glucose concentrations, hypoglycemia (47 mg/dl) was induced slowly (60 min) and maintained for 60 min. Hypoglycemia was preceded by the ingestion of either oral placebo or glucose (28 g) given at 30 min.

RESULTS

Plasma glucose and insulin were not different with either placebo or glucose (P > 0.2). Similarly, counterregulatory hormones, substrates, and symptoms were not different with either placebo or glucose. The Stroop color and colored words subtest of the Stroop test deteriorated less (P < 0.05) with glucose than placebo.

CONCLUSIONS

In contrast to animals, in humans, prevention of portal hypoglycemia with oral glucose from the beginning of insulin-induced slow-fall hypoglycemia has no effect on sympathoadrenal and symptomatic responses to hypoglycemia.

Clinicopathological characteristics and non-adhesive organ culture of insulinomas

BACKGROUND AND AIMS

Insulinoma is a very rare type of islet cell tumour, but nevertheless the most common endocrine tumour of the pancreas. We aimed at reviewing our clinical experience with this tumour type and to assess whether organ culture could be obtained from surgically resected insulinoma material.

MATERIAL AND METHODS

All patients with insulinomas (6 men and 10 women) referred to Haukeland University Hospital between 1986 and 2006 were included in the study. Median age of onset was 53 years (range 21-74). Biochemical diagnosis was established during a 72 h fast test. Imaging and localization of the tumours were performed with intra-operative ultrasonography, endoscopic ultrasonography, CT-scan and/or transcutaneous ultrasonography. For six patients, organ cultures were set up from tumour tissue fragments.

RESULTS

The annual incidence of insulinoma was 0.8 per million. The patients generally presented with non-specific, episodic symptoms, which often were mistaken for cardiovascular, neurological or diabetic disease and in some cases delayed the diagnosis with several years. Two patients had diabetes prior to the diagnosis of insulinoma. Patient weight gain was probably due to increased food intake, compensating for the hypoglycemia. Intra-operative ultrasonography detected all tumours correctly, whereas 73% were detected by endoscopic ultrasonography and 38% by CT scan. Five insulinomas were located in the head, eight in the body and three in the tail of the pancreas. All were removed by open-access surgery, eleven cases by resection and five by enucleation. One tumour was malignant with liver metastases and two patients had tumours defined as borderline. Insulinoma tissue fragments developed into spheroids during the first week of culturing and insulin secretion into the media was demonstrated.

CONCLUSIONS

Insulinomas are rare and diagnostically challenging tumours. Intra-operative ultrasonography was superior to other imaging modalities to locate the lesion. In organ culture, insulinomas readily form spheroids which may be used to yield insight into beta-cell biology.

Effect of oral amino acids on counterregulatory responses and cognitive function during insulin-induced hypoglycemia in nondiabetic and type 1 diabetic people

OBJECTIVE

Amino acids stimulate glucagon responses to hypoglycemia and may be utilized by the brain. The aim of this study was to assess the responses to hypoglycemia in nondiabetic and type 1 diabetic subjects after ingestion of an amino acid mixture.

RESEARCH DESIGN AND METHODS

Ten nondiabetic and 10 diabetic type 1 subjects were studied on three different occasions during intravenous insulin (2 mU . kg(-1) . min(-1)) plus variable glucose for 160 min. In two studies, clamped hypoglycemia (47 mg/dl plasma glucose for 40 min) was induced and either oral placebo or an amino acid mixture (42 g) was given at 30 min. In the third study, amino acids were given, but euglycemia was maintained.

RESULTS

Plasma glucose and insulin were no different in the hypoglycemia studies with both placebo and amino acids (P > 0.2). After the amino acid mixture, plasma amino acid concentrations increased to levels observed after a mixed meal (2.4 +/- 0.13 vs. placebo study 1.7 +/- 0.1 mmol/l, P = 0.02). During clamped euglycemia, ingestion of amino acids resulted in transient increases in glucagon concentrations, which returned to basal by the end of the study. During clamped hypoglycemia, glucagon response was sustained and increased more in amino acid studies versus placebo in nondiabetic and diabetic subjects (P < 0.05), but other counter-regulatory hormones and total symptom score were not different. Beta-OH-butyrate was less suppressed after amino acids (200 +/- 15 vs. 93 +/- 9 micromol/l, P = 0.01). Among the cognitive tests administered, the following indicated less deterioration after amino acids than placebo: Trail-Making part B, PASAT (Paced Auditory Serial Addition Test) (2 s), digit span forward, Stroop colored words, and verbal memory tests for nondiabetic subjects; and Trail-Making part B, digit span backward, and Stroop color tests for diabetic subjects.

CONCLUSIONS

Oral amino acids improve cognitive function in response to hypoglycemia and enhance the response of glucagon in nondiabetic and diabetic subjects.

Fish oil attenuates adrenergic overactivity without altering glucose metabolism during an oral glucose load in haemodialysis patients

Haemodialysis patients display an increased cardiac mortality, which may be partly related to increased sympathoadrenal activity and insulin resistance. Fish oil decreases adrenal activation induced by mental stress and has an insulin sensitizing effect in healthy subjects. Whole-body glucose metabolism after oral glucose was studied in eight haemodialysis patients before and after a 3-week oral fish oil supplementation (i.e. EPA + DHA at 1·8 g/d). Plasma glucose fluxes were traced by using [6,6-2H2]glucose infusion. Substrate oxidation was determined by using indirect calorimetry. Each patient was studied in the basal state and over the 6 h following absorption of a 1 g/kg glucose load. Energy expenditure in response to glucose re-increased over the last 2 h of the experiment (P < 0·05), which coincided with an increase in plasma catecholamines, especially epinephrine (P < 0·05), strongly suggesting a sympathoadrenal overactivity. Fish oil supplementation blunted both re-increase in thermogenic response and concomitant increase in plasma epinephrine, but not in plasma norepinephrine, over the last 2 h of the experiment. Fish oil did not alter either whole-body glucose metabolism or substrate oxidation. These data show that in haemodialysis patients, fish oil attenuates adrenal overactivity induced by oral glucose but does not modulate whole-body glucose metabolism and insulin sensitivity.

Effects of controlled hypoglycaemia on cardiac repolarisation in patients with type 1 diabetes

AIMS/HYPOTHESIS

Nocturnal hypoglycaemia may contribute to sudden death in diabetic patients. However, it is not well known why hypoglycaemia makes these patients prone to death.

METHODS

We assessed the effects of controlled hypoglycaemia on cardiac repolarisation using novel electrocardiographic descriptors of T-wave and QRS complex morphology in 16 type 1 diabetic patients and eight healthy counterparts. Several electrocardiographic variables characterising repolarisation were analysed from digitised 12-lead electrocardiograms during a euglycaemic and a hypoglycaemic clamp.

RESULTS

Hypoglycaemia did not result in significant changes either in the QT interval corrected for heart rate by the nomogram method or in QT dispersion. However, the morphology of the T-wave changed significantly during hypoglycaemia. The T-wave amplitude and area in precordial leads decreased significantly in both groups (p<0.05 to p<0.001). The spatial QRS-T angle (total cosine R to T) (p<0.05) and the height and the width of the T-wave loop (p<0.05 and p<0.01, respectively) were also reduced in the diabetic patients. The changes in the repolarisation parameters did not exhibit any significant association with changes in catecholamine levels or in heart rate variability in either group.

CONCLUSIONS/INTERPRETATION

Hypoglycaemia results in distinct alterations in cardiac repolarisation, which may increase the vulnerability to arrhythmic events.

Occult sporadic insulinoma: localization and surgical strategy

Insulinomas continue to pose a diagnostic challenge to physicians, surgeons and radiologists alike. Most are intrapancreatic, benign and solitary. Biochemical diagnosis is obtained and imaging techniques to localize lesions continue to evolve. Surgical resection is the treatment of choice. Despite all efforts, an occult insulinoma (occult insulinoma refers to a biochemically proven tumor with indeterminate anatomical site before operation) may still be encountered. New localization preoperative techniques decreases occult cases and the knowledge of the site of the mass before surgery allows to determine whether enucleation of the tumor or pancreatic resection is likely to be required and whether the tumor is amenable to removal via a laparoscopic approach. In absence of preoperative localization and intraoperative detection of an insulinoma, blind pancreatic resection is not recommended.

Hypoglycemia, brain energetics, and hypoglycemic neuronal death

Hypoglycemia is a common and serious problem among diabetic patients receiving treatment with insulin or other glucose-lowering drugs. Moderate hypoglycemia impairs neurological function, and severe hypoglycemia leads to death of selectively vulnerable neurons. Recent advances have shed new light on the underlying processes that cause neuronal death in hypoglycemia and the factors that may render specific neuronal populations especially vulnerable to hypoglycemia. In addition to its clinical importance, the pathophysiology of hypoglycemia is an indicator of the unique bioenergetic properties of the central nervous system, in particular the metabolic coupling of neuronal and astrocyte metabolism. This review will focus on relationships between bioenergetics and brain dysfunction in hypoglycemia, the neuronal cell death program triggered by hypoglycemia, and the role of astrocytes in these processes.

Endogenous hyperinsulinemic hypoglycemia: diagnostic strategies, predictive features of malignancy and long-term survival

Diagnostic strategies, malignancy predictors and long-term survival were retrospectively evaluated in patients with hyperinsulinemic hypoglycemia (64 insulinomas). Lower median glycemia was 30 (range 20-53) mg/dl [1.6 (1.1-2.9) mmol/l] with concurrent insulin of 48 (13.2-217) microU/ml and 15 (2-46) microU/ml measured by radioimmunoassay (RIA) and immunofluorimetric assay (IFMA), respectively. All patients with insulinomas had a positive prolonged fast within 48 h. Sensitivity of localization methods was: ultrasonography (US) 23%, computed tomography (CT) 28%, magnetic resonance imaging (MRI) 65%, endoscopic US 75%, arteriography 38%, portal venous sampling 67%, selective arterial calcium stimulation 67%, intraoperative US 94% and palpation 92%. Nine patients (14%) had malignant insulinomas. Age at diagnosis (mean+/-SD, 53.8+/-19 vs 39.4+/-16.3 yr; p=0.03), insulin (1372+/-730 vs 785+/-659% (percentage of the method's diagnostic cut-off; 6 and 3 microU/ml for RIA and IFMA, respectively; p=0.007) and C-peptide levels (9.8+/-2.9 vs 3.9+/-2.8 ng/ml (3.2+/-0.9 vs 1.3+/-0.9 nmol/l; p=0.006), and tumor size (6.2+/-4.1 vs 1.5+/-0.6 cm; p=0.0002) were increased in malignant insulinomas. C-peptide level above 6.1 ng/ml (2.0 nmol/l) had a 100% sensitivity and 96% specificity, and tumor size above 2.6 cm yielded a sensitivity of 88% and specificity of 100% in predicting malignancy. Survival of patients with malignant insulinomas was significantly impaired (16 vs 100% at 5 yr; p=0.0000001). The diagnosis of insulinoma can be made within 48 h of fasting. The association between intraoperative US and palpation evidenced the tumor in 95% of the patients. C-peptide and tumor size were reliable malignancy predictors.

The management of insulinoma

BACKGROUND

Insulinomas are rare tumours. Their clinical presentation, localization techniques and operative management were reviewed.

METHODS

An electronic search of the Medline, Embase and Cochrane databases was undertaken for articles published between January 1966 and June 2005 on the history, presentation, clinical evaluation, use of imaging techniques for tumour localization and operative management of insulinoma.

RESULTS AND CONCLUSION

Most insulinomas are intrapancreatic, benign and solitary. Biochemical diagnosis is obtained during a supervised 72-h fast. Non-invasive preoperative imaging techniques to localize lesions continue to evolve. Intraoperative ultrasonography can be combined with other preoperative imaging modalities to improve tumour detection. Surgical resection is the treatment of choice. In the absence of preoperative localization and intraoperative detection of an insulinoma, blind pancreatic resection is not recommended.

Etiologies of acute hypoglycemia in a Taiwanese Hospital Emergency Department

The etiologies of acute hypoglycemia (< 2.8 mmol/L) in adult emergency patients were assessed to provide more proper and prompt management. There were 228 hypoglycemic patients (112 women and 116 men, ranging in age from 22 to 93 years, mean = 69.6 years) identified for the study. These patients had hypoglycemia mainly due to excessive use of sulfonylureas or insulin. There was a diabetic history in 182 patients (79.83%). Other primary etiologies of acute hypoglycemia were sepsis in 13 (5.70%), and extensive liver disease in 13 (5.70%). This study indicates that good diabetic control can dramatically decrease the number of episodes of acute hypoglycemia in Taiwan. For acute hypoglycemic patients without a diabetic history, the possibility of sepsis or extensive liver disease is a problem in Taiwan.

Feeding and neuroendocrine responses after recurrent insulin-induced hypoglycemia

Prior exposure to hypoglycemia impairs neuroendocrine counterregulatory responses (CRR) during subsequent hypoglycemia. Defective CRR to hypoglycemia is a component of the clinical syndrome hypoglycemia-associated autonomic failure (HAAF). Hypoglycemia also potently stimulates food intake, an important behavioral CRR. Because the increased feeding response to hypoglycemia is behavioral and not hormonal, we hypothesized that it may be regulated differently with recurrent bouts of hypoglycemia. To test this hypothesis, we simultaneously evaluated neuroendocrine CRR and food intake in rats experiencing one or three episodes of insulin-induced hypoglycemia. As expected, recurrent hypoglycemia significantly reduced neuroendocrine hypoglycemic CRR. Epinephrine (E), norepinephrine (NE) and glucagon responses 120 min after insulin injection were significantly reduced in recurrent hypoglycemic rats, relative to rats experiencing hypoglycemia for the first time. Despite these neuroendocrine impairments, food intake was significantly elevated above baseline saline intake whether rats were experiencing a first (hypoglycemia: 3.4+/-0.4 g vs. saline: 0.94+/-0.3 g, P<0.05) or third hypoglycemic episode (hypoglycemia: 3.8+/-0.3 g vs. saline: 1.2+/-0.3 g, P<0.05). These findings demonstrate that food intake elicited in response to hypoglycemia is not impaired as a result of recurrent hypoglycemia. Thus, neuroendocrine and behavioral (stimulation of food intake) CRR are differentially regulated by recurrent hypoglycemia experience.

Adult spontaneous hypoglycaemia

Spontaneous hypoglycaemia is not a diagnosis, but a manifestation of a disease process. It is important to recognize spontaneous hypoglycaemia, as treatment may be preventative or curative. It is equally important to avoid mislabelling healthy individuals as having hypoglycaemia as this may have a negative impact on the quality of life and use of scarce health-care resources.

Effects of sustained insulin-induced hypoglycemia on cardiovascular autonomic regulation in type 1 diabetes

Effects of hypoglycemia on cardiac autonomic regulation may contribute to the occurrence of adverse cardiac events. This study assessed the effects of sustained hyperinsulinemic hypoglycemia on cardiovascular autonomic regulation in type 1 diabetic patients and their nondiabetic counterparts. The study consisted of 16 type 1 diabetic patients and 8 age-matched healthy control subjects who underwent euglycemic and hypoglycemic clamp procedures in a random order. Heart rate variability was measured from continuous electrocardiogram recordings by time and frequency domain methods, along with Poincare plot analysis during both a hyperinsulinemic-euglycemic and hypoglycemic clamp at three different glucose levels (4.5-5.5, 3.0-3.5, and 2.0-2.5 mmol/l). Controlled hypoglycemia resulted in an increase of supine heart rate in both the diabetic patients (from 72 +/- 9 to 80 +/- 11 bpm, P < 0.01) and the control subjects (from 59 +/- 5 to 65 +/- 5 bpm, P < 0.05) and progressive reductions of the high-frequency spectral component and beat-to-beat heart rate variability (SD1; P < 0.05 in the diabetic patients and P < 0.01 in control subjects). No significant changes in heart rate variability occurred during the euglycemic clamp. We conclude that hypoglycemia results in a reduction of cardiac vagal outflow in both diabetic and nondiabetic subjects. Altered autonomic regulation may contribute to the occurrence of cardiac events during hypoglycemia.

Hypoglycaemia causes degeneration of large myelinated nerve fibres in the vagus nerve of insulin-treated diabetic BB/Wor rats

The aim of this study was to find out whether dysglycaemia causes neuropathy in the vagus nerve of insulin-treated diabetic BB/Wor rats. Specimens were collected from the left vagus nerve proximal and distal to the level of recurrent laryngeal branch and from the recurrent branch itself in control rats and diabetic BB/Wor rats subjected to hyper- or hypoglycaemia. Myelinated and unmyelinated axons were counted and myelinated axon diameters were measured by electron microscopy. In controls, the vagus nerve proximal to the recurrent branch exhibited three regions in terms of fibre composition: part A was mainly composed of large myelinated axons, part B contained small myelinated and unmyelinated axons, and part C contained mainly unmyelinated axons. The distal level resembled part C at the proximal level and the recurrent branch resembled parts A and B. In hyperglycaemic rats, a normal picture was found at the proximal and distal levels of the vagus nerve and in the recurrent branch. In hypoglycaemic rats, signs of past and ongoing degeneration and regeneration of large myelinated axons were found at the proximal and distal levels and in the recurrent branch. We conclude that hypoglycaemia elicits degenerative alterations in large myelinated axons in the vagus and recurrent laryngeal nerves in diabetic BB/Wor rats. The absence of signs of neuropathy in unmyelinated and small myelinated axons suggests that the sensory and autonomic components of the nerve are less affected. In contrast, the hyperglycaemic rats examined here did not show obvious degenerative alterations.

Current Therapeutic Options for Treating Primary Hyperhidrosis

Severe hyperhidrosis can cause extreme embarrassment that may lead to social and professional isolation. Therapeutic strategies to hyperhidrosis should employ the least invasive treatment that provides effective symptom control. The treatment options available for control of hyperhidrosis, non-surgical or surgical, differ in their invasiveness and efficacy. Mechanisms of action of antiperspirants, iontophoresis, cholinergic inhibitor drugs, botulinum toxin, and surgical sympathectomy are reviewed. There is little published evidence in the form of comparative randomised trials to support the use of one treatment over another. However, authors have tended to recommend those therapies that are available to their speciality. Specific therapies should be tailored to the patient's symptoms to gain maximum symptomatic improvement with minimum invasiveness and side-effects. To achieve this, the full range of treatment options should be available to, or accessible by the consulting doctor in order for the patient to have a meaningful choice.

Leptin administration to normal rats does not alter catecholamine responsiveness to insulin-induced hypoglycemia

We previously showed, through direct neural recording in conscious rats, that hypoglycemia increases adrenal sympathetic nerve activity (SNA) both acutely and 24 hours following the second of 2 daily antecedent hypoglycemic episodes. Nonetheless, antecedent hypoglycemia impaired catecholamine responsiveness to subsequent acute hypoglycemia. Here we hypothesized that antecedent, nonhypoglycemic adrenal sympathetic stimulation by leptin would impair acute adrenal catecholamine responsiveness to subsequent hypoglycemia. We also hypothesized that acute leptin administration (after 2 days of antecedent hypoglycemia) would enhance adrenal SNA and thereby enhance catecholamine responsiveness to concurrent hypoglycemia. Leptin or saline was administered to normal rats in repeated subcutaneous injections for 2 days prior to acute insulin-induced hypoglycemia. In contrast to our hypothesis, antecedent leptin did not change catecholamine responsiveness or glycemic change in response to subsequent acute insulin administration. In additional studies, intravenous leptin or saline was acutely administered beginning 1 hour before insulin-induced hypoglycemia. All rats had been exposed to antecedent hypoglycemia. In these experiments, acute leptin did not alter catecholamine responses to insulin or glycemic change during or after termination of insulin. We conclude that antecedent nonhypoglycemic sympathetic stimulation by leptin does not alter subsequent catecholamine or glycemic responses to insulin. Moreover, concurrent leptin does not enhance catecholamine responses to insulin in rats exposed to antecedent hypoglycemia.

Extracellular glucose in rat ventromedial hypothalamus during acute and recurrent hypoglycemia

The activity of neurons in the ventromedial hypothalamus (VMH) important for initiating compensatory responses to hypoglycemia is influenced by ambient glucose concentration. In the present study, we used in vivo microdialysis to evaluate interstitial glucose concentrations in rat VMH under various glycemic conditions. Using the zero-net-flux method, steady-state glucose concentration in the VMH was approximately 20% of blood glucose (approximately 1.4 mmol/l) in fed rats but approximately 14% of blood glucose (approximately 0.7 mmol/l) in overnight-fasted rats. During moderate hypoglycemia VMH glucose declined in parallel with blood glucose; however, VMH glucose decreased to a greater degree than blood glucose during a more severe hypoglycemic episode, falling to 10 +/- 1.2% of blood levels (P < 0.01). To determine whether VMH glucose concentrations were influenced by recurrent episodes of hypoglycemia a second zero-net-flux study was conducted. Steady-state glucose concentrations in the VMH were approximately 20% lower after three episodes of recurrent hypoglycemia, a value 17.8 +/- 0.8% of blood glucose, although the relative change in VMH glucose levels during the first and fourth hypoglycemic episodes were similar. From these results, we conclude that interstitial glucose concentrations in the VMH are not maintained at a constant level and are more dynamic than previously proposed.

Norepinephrine and epinephrine-deficient mice are hyperinsulinemic and have lower blood glucose

Norepinephrine (NE) and epinephrine (Epi) help maintain normal blood glucose levels by stimulating glucagon release, glycogenolysis, and food consumption, and by inhibiting insulin release. The absence of NE and Epi in dopamine beta-hydroxylase-null (Dbh-/-) mice results in chronically low blood glucose levels, an impaired glucagon response to hypoglycemia, and elevated insulin levels. Nevertheless, Dbh-/- mice have normal glycogen levels and degrade it normally during a fast. Dbh-/- mice defend blood glucose levels better than controls in an insulin tolerance test but have increased sensitivity to glucose-stimulated insulin secretion and respond normally in a glucose tolerance test. Pharmacological evidence indicates that the hyperinsulinemia results from lack of alpha2-adrenoreceptor stimulation and increased parasympathetic tone. Dbh-/- mice eat normally after challenges with modest levels of insulin or 2-deoxyglucose but fail to eat under more extreme conditions when control mice still do. We suggest that the primary difference in Dbh-/- mice is chronic hyperinsulinemia associated with an altered glucose set point. However, these animals compensate for NE/Epi-mediated glycogenolysis and feeding.

Best practice No 173: clinical and laboratory investigation of adult spontaneous hypoglycaemia

Adult spontaneous hypoglycaemia is not a diagnosis per se but a manifestation of a disease. Although rare, it is important to identify spontaneous hypoglycaemia and its causes because treatment may be preventative or curative. Hypoglycaemia can occur as an epiphenomenon in many serious diseases. It is sufficient to recognise the disease's association with hypoglycaemia and then take appropriate action to prevent the recurrence of hypoglycaemia. In investigating apparently healthy individuals, common pitfalls to avoid are: failure to recognise subacute neuroglycopenia clinically; failure to document hypoglycaemia adequately during symptoms; failure to measure pancreatic hormones, counter-regulatory hormones, and ketones in hypoglycaemic samples; failure to recognise pre-analytical and analytical limitations of laboratory assays; and failure to abandon obsolete and inappropriate investigations. Providing these caveats are met, appropriate laboratory and radiological investigations will almost always uncover the cause of spontaneous hypoglycaemia.

Association of hypoglycemia and cardiac ischemia: a study based on continuous monitoring

OBJECTIVE

In some studies intensive diabetes treatment in patients with type 2 diabetes may be associated with increased cardiovascular events. It is not clear whether these events are related to hypoglycemic episodes. To determine whether episodes of hypoglycemia were more likely to be associated with cardiac ischemia than normoglycemia or hyperglycemia, we carried out a study in 21 patients with coronary artery disease (CAD) and type 2 diabetes treated with insulin who had good glycemic control.

RESEARCH DESIGN AND METHODS

We carried out 72-h continuous glucose monitoring along with simultaneous cardiac Holter monitoring for ischemia. Patients also recorded symptoms of cardiac ischemia (chest pain) and symptoms of hypoglycemia.

RESULTS

Satisfactory continuous glucose monitoring system recordings were obtained in 19 patients. We recorded 54 episodes of hypoglycemia (blood glucose <70 mg/dl; 26 of these were symptomatic) and 59 episodes of hyperglycemia (blood glucose >200 mg/dl; none symptomatic). Of the 54 episodes of hypoglycemia, 10 were associated with symptoms of chest pain, during 4 of which electrocardiographic abnormalities were documented. In contrast, only 1 episode of chest pain occurred during 59 episodes of hyperglycemia. No chest pain or electrocardiographic abnormalities occurred when the blood glucose was within the normal range. The difference between the frequency of ischemia during hypoglycemia and the frequency during both hyperglycemia and normoglycemia was statistically significant (P < 0.01). There were 50 episodes during which the blood glucose changed by >100 mg over a 60-min period, and ischemic symptoms occurred during 9 of these episodes (P < 0.01 compared with stable normoglycemia or hyperglycemia).

CONCLUSIONS

Hypoglycemia is more likely to be associated with cardiac ischemia and symptoms than normoglycemia and hyperglycemia, and it is particularly common in patients who experience considerable swings in blood glucose. These data may be important in the institution of insulin treatment and attempting near-normal glycemia in patients with known CAD. Further research is needed to determine strategies to prevent ischemia associated with hypoglycemia.

A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women

Claims about the merits or risks of carbohydrate (CHO) vs. protein for weight loss diets are extensive, yet the ideal ratio of dietary carbohydrate to protein for adult health and weight management remains unknown. This study examined the efficacy of two weight loss diets with modified CHO/protein ratios to change body composition and blood lipids in adult women. Women (n = 24; 45 to 56 y old) with body mass indices >26 kg/m(2) were assigned to either a CHO Group consuming a diet with a CHO/protein ratio of 3.5 (68 g protein/d) or a Protein Group with a ratio of 1.4 (125 g protein/d). Diets were isoenergetic, providing 7100 kJ/d, and similar amounts of fat ( approximately 50 g/d). After consuming the diets for 10 wk, the CHO Group lost 6.96 +/- 1.36 kg body weight and the Protein Group lost 7.53 +/- 1.44 kg. Weight loss in the Protein Group was partitioned to a significantly higher loss of fat/lean (6.3 +/- 1.2 g/g) compared with the CHO Group (3.8 +/- 0.9). Both groups had significant reductions in serum cholesterol ( approximately 10%), whereas the Protein Group also had significant reductions in triacylglycerols (TAG) (21%) and the ratio of TAG/HDL cholesterol (23%). Women in the CHO Group had higher insulin responses to meals and postprandial hypoglycemia, whereas women in the Protein Group reported greater satiety. This study demonstrates that increasing the proportion of protein to carbohydrate in the diet of adult women has positive effects on body composition, blood lipids, glucose homeostasis and satiety during weight loss.

Inactivation of the PVN during hypoglycemia partially simulates hypoglycemia-associated autonomic failure

The anatomic connections of the paraventricular nucleus of the hypothalamus (PVN) are such that it is ideally situated to modulate and/or control autonomic responses to a variety of stressors, including hypoglycemia. In our experimental model of hypoglycemia-associated autonomic failure (HAAF), a syndrome in which the counterregulatory response to hypoglycemia is partially compromised via unknown mechanisms, activation of the PVN is blunted (15). We hypothesized that this blunted PVN activation during HAAF may be sufficient to cause the impaired counterregulatory response. To test this hypothesis, we anesthetized the PVN with lidocaine during insulin-induced hypoglycemia in rats and measured counterregulatory hormone levels. PVN inactivation decreased indexes of the sympathoadrenal response (plasma epinephrine and norepinephrine) and the hypothalamic-pituitary axis response (ACTH). Inactivation decreased the peak epinephrine response to hypoglycemia by almost half (-42 +/- 6% from control; P = 0.04) and the peak norepinephrine response by 34 +/- 5% (P = 0.01). The peak plasma ACTH levels attained were suppressed by 35 +/- 6% (P = 0.02). Adrenal corticosterone and pancreatic glucagon responses were not impaired. This pattern of neuroendocrine response is unlike that previously seen with our HAAF model. Control infusions of lidocaine >or=1 mm anterior or posterior to the PVN did not simulate this neuroendocrine pattern. Thus it appears that decreased PVN activation, as occurs with HAAF, may be involved in specific components of HAAF (i.e., blunting the sympathoadrenal and hypothalamic-pituitary-adrenocortical axis response), but not in others (i.e., blunting the glucagon response).

Pharmacologic treatment of the critically ill patient with diabetes

The pharmacologic approach to the management of DKA and HHNS involves the use of insulin, fluids, and electrolytes. Essential to the successful treatment of DKA and HHNS is a carefully planned post-intensive-care transition period. This period is based on the understanding that insulin therapy is never interrupted in patients with type 1 diabetes and the transition to insulin and/or oral hypoglycemic therapy in type 2 patients is strategically planned. The use of acute adjuvant insulin-glucose therapy in acute coronary syndromes and cardiac surgeries can result in decrease in overall morbidity and mortality in patients with diabetes. Ultimately, however, the major approaches to the treatment of diabetes is primary prevention of diabetes itself and the secondary prevention of complications through vigorous glucose control.

PVN activation is suppressed by repeated hypoglycemia but not antecedent corticosterone in the rat

The mechanism(s) underlying hypoglycemia-associated autonomic failure (HAAF) are unknown. To test the hypothesis that the activation of brain regions involved in the counterregulatory response to hypoglycemia is blunted with HAAF, rats were studied in a 2-day protocol. Neuroendocrine responses and brain activation (c-Fos immunoreactivity) were measured during day 2 insulin-induced hypoglycemia (0.5 U insulin x 100 g body x wt(-1) x h(-1) iv for 2 h) after day 1 hypoglycemia (Hypo-Hypo) or vehicle. Hypo-Hypo animals demonstrated HAAF with blunted epinephrine, glucagon, and corticosterone (Cort) responses and decreased activation of the medial hypothalamus [the paraventricular (PVN), dorsomedial (DMH), and arcuate (Arc) nuclei]. To evaluate whether increases in day 1 Cort were responsible for the decreased hypothalamic activation, Cort was infused intracerebroventricularly (72 microg) on day 1 and the response to day 2 hypoglycemia was measured. Intracerebroventricular Cort infusion failed to alter the neuroendocrine response to day 2 hypoglycemia, despite elevating both central nervous system and peripheral Cort levels. However, day 1 Cort blunted responses in two of the same hypothalamic regions as Hypo-Hypo (the DMH and Arc) but not in the PVN. These results suggest that decreased activation of the PVN may be important in the development of HAAF and that antecedent exposure to elevated levels of Cort is not always sufficient to produce HAAF.

The insulin hypoglycemia test: hypoglycemic criteria and reproducibility

The insulin hypoglycemia test (IHT) is widely regarded as the "gold standard" for dynamic stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. This study aimed to investigate the temporal relationship between a rapid decrease in plasma glucose and the corresponding rise in plasma adenocorticotropic hormone (ACTH), and to assess the reproducibility of hormone responses to hypoglycemia in normal humans. Ten normal subjects underwent IHTs, using an insulin dose of 0.15 U/kg. Of these, eight had a second IHT (IHT2) and three went on to a third test (IHT3). Plasma ACTH and cortisol were measured at 15-min intervals and, additionally, in four IHT2s and the three IHT3s, ACTH was measured at 2.5- or 5-min intervals. Mean glucose nadirs and mean ACTH and cortisol responses were not significantly different between IHT1, IHT2 and IHT3. Combined data from all 21 tests showed the magnitude of the cortisol responses, but not the ACTH responses, correlated significantly with the depth and duration of hypoglycemia. All subjects achieved glucose concentrations of of < or = 1.6 mmol/l before any detectable rise in ACTH occurred. In the seven tests performed with frequent sampling, an ACTH rise never preceded the glucose nadir, but occurred at the nadir, or up to 15 min after. On repeat testing, peak ACTH levels varied markedly within individuals, whereas peak cortisol levels were more reproducible (mean coefficient of variation 7%). In conclusion, hypoglycemia of < or = 1.6 mmol/l was sufficient to cause stimulation of the HPA axis in all 21 IHTs conducted in normal subjects. Nonetheless, our data cannot reveal whether higher glucose nadirs would stimulate increased HPA axis activity in all subjects. Overall, the cortisol response to hypoglycemia is more reproducible than the ACTH response but, in an individual subject, the difference in peak cortisol between two IHTs may exceed 100 nmol/l.

Effect of acute and antecedent hypoglycemia on sympathetic neural activity and catecholamine responsiveness in normal rats

Adrenergic responsiveness to acute hypoglycemia is impaired after prior episodes of hypoglycemia. Although circulating epinephrine responses are blunted, associated alterations in adrenal sympathetic nerve activity (SNA) have not been reported. We examined adrenal nerve traffic in normal conscious rats exposed to acute insulin-induced hypoglycemia compared with insulin with (clamped) euglycemia. We also examined adrenal SNA and catecholamine responses to insulin-induced hypoglycemia in normal conscious rats after two antecedent episodes of hypoglycemia (days -2 and -1) compared with prior episodes of sham treatment. Acute insulin-induced hypoglycemia increased adrenal sympathetic nerve traffic compared with insulin administration with clamped euglycemia (165 +/- 12 vs. 118 +/- 21 spikes/s [P < 0.05]; or to 138 +/- 8 vs. 114 +/- 10% of baseline [P < 0.05]). In additional experiments, 2 days of antecedent hypoglycemia (days -2 and -1) compared with sham treatment significantly enhanced baseline adrenal SNA measured immediately before subsequent acute hypoglycemia on day 0 (180 +/- 11 vs. 130 +/- 12 spikes/s, respectively; P < 0.005) and during subsequent acute hypoglycemia (229 +/- 17 vs. 171 +/- 16 spikes/s; P < 0.05). However, antecedent hypoglycemia resulted in a nonsignificant reduction in hypoglycemic responsiveness of adrenal SNA when expressed as percent increase over baseline (127 +/- 5% vs. 140 +/- 14% of baseline). Antecedent hypoglycemia, compared with sham treatment, resulted in diminished epinephrine responsiveness to subsequent hypoglycemia. Norepinephrine responses to hypoglycemia were not significantly altered by antecedent hypoglycemia. In summary, prior hypoglycemia in normal rats increased adrenal sympathetic tone, but impaired epinephrine responsiveness to acute hypoglycemia. Hence, these data raise the intriguing possibility that increased sympathetic tone resulting from antecedent hypoglycemia downregulates subsequent epinephrine responsiveness to hypoglycemia. Alternatively, it is possible that the decrease in epinephrine responsiveness after antecedent hypoglycemia could be the result of reduced adrenal sympathetic nerve responsiveness.

Forty-eight-hour fast: the diagnostic test for insulinoma

Insulinoma causes fasting hypoglycemia due to inappropriate insulin secretion. Its diagnosis is based on demonstrating Whipple's triad during a supervised 72-h fast. For 75 yr, the 72-h fast has been the cornerstone for the diagnosis; however, it has never been critically assessed using newer assays for insulin, C peptide, and proinsulin. Thus, the aim of the current study is to assess the need for a full 72-h fast for the diagnosis of insulinoma. Patients with suspected hypoglycemia with documented glucose concentrations below 45 mg/dL were admitted to the NIH. Data obtained during the supervised fast of patients with pathologically proven insulinoma over a 30-yr period (1970-2000) were reviewed. We identified 127 patients with insulinoma. The average age of patients was 42.7 +/- 15.9 yr, with a predominance of females (62%). 107 patients had a benign tumor, 20 had malignant insulinoma, and 15 patients had multiple endocrine neoplasia type 1. The fast was terminated due to hypoglycemia in 44 patients (42.5%) by 12 h, 85 patients (66.9%) by 24 h, and 120 (94.5%) by 48 h. Seven patients fasted beyond 48 h despite subtle neuroglycopenic symptoms and glucose and insulin concentrations diagnostic of insulinoma. Immunoreactive proinsulin was elevated at the beginning of the fast in 90% of 42 patients. Proinsulin in noninsulinoma, in contrast to insulinoma, patients is usually suppressible; therefore, samples taken in the suppressed state have the greatest diagnostic value. We conclude that with the current available insulin and proinsulin assays, the diagnosis of insulinoma can be made within 48 h. Thus, the 48-h fast should replace the 72-h fast in textbooks and hospital protocols as the new diagnostic standard.

High-glycemic index foods, hunger, and obesity: is there a connection?

The relative importance of different dietary causes of obesity remains controversial. This review examines whether consumption of high-glycemic index (GI) carbohydrates may be a contributing factor. Although data from long-term studies are lacking, short-term investigations indicate that consumption of high-GI carbohydrates may increase hunger and promote overeating relative to consumption of items with a lower GI. As long-term research on GI and weight regulation accumulates, consumption of whole grain and lower GI cereals instead of highly refined cereals is a dietary change that may help prevent overeating and is consistent with current dietary guidelines.