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Insulin Tolerance Test Mice Interpretation

Mouse Metabolic Phenotyping Centers Mmpc Protocols

Mouse Metabolic Phenotyping Centers Mmpc Protocols

Intraperitoneal Insulin Tolerance Test Version: 1 Edited by: Fawaz G. Haj Summary: An intraperitoneal insulin tolerance test or ipITT is designed to determine determine the sensitivity of insulin-responsive tissues in the rodent. This is determined by measurement of glucose remaining in the circulation over time after a bolus ip insulin injection. Reagents and Materials: Reagent/Material Vendor Stock Number Humalin® R Eli Lilly R-100 Insulin Syringes Fisher Scientific 14-826-79 Saline Solution Fisher Scientific L97753 Easy Check Glucose test strips JRS Medical 00-101 Easy Check Glucose monitor JRS Medical Y4209 Reagent Preparation: Dilute the stock solution (100 U/ml) with saline to 0.5 U/mL (1/200 dilution) by adding 5μl stock (100 U/mL) to 995 μl 0.9% (w/v) sterile saline Protocol: 1. Fast mice for 4 h only by taking away food early in the morning (7:00am). 2. Calibrate the glucose meter according to the manufacturer’s instructions. 3. Deprive mice from water then remove approximately 5μl of blood (one drop) from the tail via a tail tip cut and transfer directly onto a glucose indicator strip. 4. Measure blood glucose immediately in a glucometer. Mouse Metabolic Phenotyping Centers MMPC Protocols 09/17/12 2 of 2 page(s) 5. 4. Give the mouse an intraperitoneal injection of insulin (0.5 U/kg) with a 27 G needle. 6. 5. Continue to take blood samples from the initial tail cut before the insulin injection and at 15, 30, 45, 60 and 120 min. 7. 6. Between each of these time points, return the mouse to its cage and monitor it every minute. NOTE: 1-The mouse is given an intraperitoneal injection with a 27G needle of insulin. Before performing the experiment, we will have to determine if the mouse strain is insulin resistant or glucose tolerant, so as to avoi Continue reading >>

Validation Of Homa-ir In A Model Of Insulin-resistance Induced By A High-fat Diet In Wistar Rats

Validation Of Homa-ir In A Model Of Insulin-resistance Induced By A High-fat Diet In Wistar Rats

Validation of HOMA-IR in a model of insulin-resistance induced by a high-fat diet in Wistar rats 1Programa de Ps-Graduao em Medicina, Cincias Mdicas, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brasil 2Grupo para o Estudo da Resistncia Insulina (GERI), Porto Alegre, RS, Brasil 3Curso de Nutrio, Departamento de Medicina Interna, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brasil 4Servio de Medicina Interna, Hospital de Clnicas de Porto Alegre (HCPA), Porto Alegre, RS, Brasil The present study aimed to validate homeostasis model assessment of insulin resistance (HOMA-IR) in relation to the insulin tolerance test (ITT) in a model of insulin-resistance in Wistar rats induced by a 19-week high-fat diet. A total of 30 male Wistar rats weighing 200-300 g were allocated into a high-fat diet group (HFD) (55% fat-enriched chow, ad lib, n = 15) and a standard-diet group (CD) standard chow, ad lib, n = 15), for 19 weeks. ITT was determined at baseline and in the 19th week. HOMA-IR was determined between the 18-19th week in three different days and the mean was considered for analysis. Area under the curve (AUC-ITT) of the blood glucose excursion along 120 minutes after intra-peritoneal insulin injection was determined and correlated with the corresponding fasting values for HOMA-IR. AUC-ITT and HOMA-IR were significantly greater after 19th week in HFD compared to CD (p < 0.001 for both). AUC-OGTT was also higher in HFD rats (p = 0.003). HOMA-IR was strongly correlated (Pearsons) with AUC-ITT r = 0.637; p < 0.0001. ROC curves of HOMA-IR and AUC-ITT showed similar sensitivity and specificity. HOMA-IR is a valid measure to determine insulin-resistance in Wistar rats. Arch Endocrinol Metab. Continue reading >>

Glucose Tolerance Test In Mice

Glucose Tolerance Test In Mice

Glucose tolerance test is a standard procedure that addresses how quickly exogenous glucose can be cleared from blood. Specifically, uptake of glucose from the blood by cells is regulated by insulin. Impairment of glucose tolerance (i.e, longer time to clear given amount of glucose) indicates problems with maintenance of glucose homeostasis (insulin resistance, carbohydrate metabolism, diabetes, etc). According to the WHO, in a standard oral glucose tolerance test (OGTT), glucose level should be below 7.8 mmol/L (140 mg/dl) at 2 h. Levels between this and 11.1 mmol/L (200 mg/dl) indicate “impaired glucose tolerance”, and any level above 11.1 mmol/L (200 mg/dl) confirms a diagnosis of diabetes. Materials and reagents Mice (~20 C57BL/6J (B6) males of 2-3 months old) 70% ethanol Beta-D(+)-glucose (Sigma-Aldrich, catalog number: G8270 ) NaCl KCl Sodium phosphate Phosphate buffered saline (PBS) (see Recipes) Equipment ACCU-CHEK comfort curve glucometer (Roche Diagnostics, catalog number: 03537536001 ) (this product has been discontinued. Any new product of ACCU-CHEK should work fine as well) Such device quantifies glucose amperometrically by measuring the current produced upon oxidation of glucose to gluconic acid by glucose oxidase, or to gluconolactone by dehydrogenase. 27 gauge needle (Single-Use Needles, supplied by VWR, BD Medical, catalog number: BD305109 ) Microvette CB300 Z serum separator (SARSTEDT, catalog number: 16.440.100 ) Acrodisc 25 mm syringe filters w/ 0.2 μM HT Tuffryn membrane (Pall Corporation, catalog number: 4192 ) Procedure Note: All the following experimental procedures that involve animals (rodents) should receive approval from IACUC or equivalent committee. Humane treatment of animals should be practiced all the time. In the Cavener lab, we us Continue reading >>

Oral Glucose Tolerance Test

Oral Glucose Tolerance Test

This assay is designed to identify genetically modified mice that exhibit alterations of metabolism associated with diabetes, obesity and cardiovascular disease. An oral glucose tolerance test (OGTT), in which the mice are challenged with a bolus of glucose and blood glucose and insulin levels are measured across a two hour time course is performed one week prior to the initiation of the HFD challenge. The mice are subjected to a seven-week HFD challenge using a Western diet. (Circulating levels of insulin, adiponectin, and cholesterol from samples taken before and after the HFD can also be measured, as well as the distribution of cholesterol in the VLDL, LDL, and HDL sub-fractions both pre and post the HFD challenge are analyzed using a polyacrylamide based system (Lipoprint).) The post HFD OGTT results are compared to those obtained before the start of the diet. The ability of genetically modified or pharmacologically treated mice to handle an oral glucose load, in combination with changes in insulin and adiponectin levels in response to the HFD, are assessed to identify genes or pharmacological agents affecting development of a diabetic or pre-diabetic state. Differences in cholesterol levels and cholesterol distribution are examined to establish if the genetic modification or the compound alters the response to the HFD. Prior to the test, the mice were fasted for 16 hours and transferred to a procedure room midway through the light phase of the Light:Dark cycle. Blood was obtained from a tail cut (by removing the distal 2 mm of the tail) and was assessed for baseline glucose levels using a One-touch Ultra 2 (Lifescan, Johnson & Johnson) glucometer. The remaining blood was processed for plasma that was later used to determine the fasting insulin levels. The mice the Continue reading >>

Insulin Tolerance Test

Insulin Tolerance Test

Glucose Test Strips - AccuChek Comfort Curve or equivalent echoMRI if the mice differ in body fat levels (see below) 0.1 U/mL humulin in PBS (make as 10uL of 100 U/mL in 10 mL, sterile filtered). This will correspond to 1 U/kg injections. If you are using a higher or lower dose of insulin, add more or less to the 10 mL of PBS, so that injections are 10 uL/g of mass. This may need to be adjusted depending on the insulin sensitivity of the mice, and this is based on a normal C57BL/6J mouse on chow. In general for insulin resistant mice, such as those >40g on a high fat diet or such, increase the dose to 2 or 2.5U/kg. In general you want the insulin to decrease blood glucose by about 60-70% in the most responsive of your too group so if your response is <20% of >70% change in blood glucose you will probably have to change your dose and retry. The insulin is diluted from Humulin R-100 and is purchased through the veterinary staff. Remove food from mice for about 6h by putting them in a fresh cage. Add do not feed tag to cages, or ideally move cage to procedure room. Try to make sure that the mice are in a quiet, undisturbed temperature controlled room with the lights on. Typically starve the mice at 8AM and aim to start injections at 2PM Prepare a 1 g/10mL solution of glucose in case some animals become hypoglyemic. Weigh mice, mark tails if necessary with different colors for rapid identification and take fasting glucose measurement via a tail clip. Prepare insulin syringes with 10 uL per g mouse weight (ie for a 30g mouse, 300 uL). At approximately 1 min intervals, inject appropriate amount of insulin into interperitoneal cavity of the mouse. Immobilize mouse and restrain tail with one hand Aim needle between the midline and the hip bone Insert syringe (do not inject) in Continue reading >>

Amelioration Of Insulin Resistance In Streptozotocin Diabetic Mice By Transgenic Overexpression Of Glut4 Driven By An Adipose-specific Promoter

Amelioration Of Insulin Resistance In Streptozotocin Diabetic Mice By Transgenic Overexpression Of Glut4 Driven By An Adipose-specific Promoter

In diabetic rodents and humans, glucose transporter 4 (GLUT4) expression is suppressed in adipocytes in association with insulin resistance. Transgenic mice overexpressing GLUT4 selectively in fat have enhanced glucose disposal in vivo and massively increased glucose transport in adipocytes. To determine whether overexpression can be maintained in diabetes and whether it can prevent insulin resistance, we rendered wild-type and transgenic mice diabetic with streptozotocin. After 1214 days, blood glucose was more than 21.4 mm and plasma insulin was 1.06 ng/ml or less in both diabetic groups in the fed state. Body weight was reduced and gonadal fat pad weight and adipocyte size were 5275% smaller in both nontransgenic and transgenic diabetic mice, compared with nondiabetic. Basal and maximally-stimulated rates of lipolysis were similar in adipocytes from nontransgenic and transgenic mice, but the ED50 for isoproterenol stimulation was 50% lower in transgenic mice. There was no difference in the sensitivity to insulin to inhibit lipolysis. In adipocytes of nontransgenic diabetic mice, GLUT4 protein was reduced 34%, with a 46% reduction in insulin stimulated glucose transport. In contrast, in adipocytes of transgenic diabetic mice, GLUT4 remained 21-fold overexpressed, resulting in 21-fold increased basal and 10-fold increased insulin stimulated glucose transport. Injection of insulin (0.7 mU/g BW) resulted in a 35% decrease in blood glucose in transgenic diabetic mice (P < 0.05), with no effect in nontransgenic diabetic mice. Thus, high-level overexpression of GLUT4 driven by a fat specific promoter can be maintained with insulinopenic diabetes, even when fat cell metabolism is markedly altered. Overexpression of GLUT4 in adipocytes prevents insulin resistant glucose tran Continue reading >>

Methods And Models For Metabolic Assessment In Mice

Methods And Models For Metabolic Assessment In Mice

Journal of Diabetes Research Volume 2013 (2013), Article ID 986906, 8 pages 1Metabolic Unit, ISIB CNR, 35127 Padova, Italy 2Department of Medicine, Lund University, 221 84 Lund, Sweden Academic Editor: Daisuke Koya Copyright © 2013 G. Pacini et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The development of new therapies for the treatment of type 2 diabetes requires robust, reproducible and well validated in vivo experimental systems. Mice provide the most ideal animal model for studies of potential therapies. Unlike larger animals, mice have a short gestational period, are genetically similar, often give birth to many offspring at once and can be housed as multiple groups in a single cage. The mouse model has been extensively metabolically characterized using different tests. This report summarizes how these tests can be executed and how arising data are analyzed to confidently determine changes in insulin resistance and insulin secretion with high reproducibility. The main tests for metabolic assessment in the mouse reviewed here are the glucose clamp, the intravenous and the oral glucose tolerance tests. For all these experiments, including some commonly adopted variants, we describe: (i) their performance; (ii) their advantages and limitations; (iii) the empirical formulas and mathematical models implemented for the analysis of the data arising from the experimental procedures to obtain reliable measurements of peripheral insulin sensitivity and beta cell function. Finally, a list of previous applications of these methods and analytical techniques is provided to better comprehend their use a Continue reading >>

Could Insulin Induce A Blood Glucose Level Increase In Insulin Tolerance Tests For Mice?

Could Insulin Induce A Blood Glucose Level Increase In Insulin Tolerance Tests For Mice?

Normally, the blood glucose level goes down at 15 min after insulin injection in insulin tolerance test. However, when I did an insulin tolerance test, I observed that blood glucose levels increased 15 min after insulin injection (0.75u/kg) in my experimental group mice, and slightly decreased 30 min after insulin injection. One mouse in the experimental group that received more insulin (20% more than standard) has more higher blood glucose level than other mice in experimental group. Blood glucose level in control group mice dramatically decreased 15 min after the insulin injection. My question is whether it is possible that insulin could enhance blood glucose level in some conditions which is opposite to our common sense. Continue reading >>

Jci -increased Glucose Tolerance And Reduced Adiposity In The Absence Of Fasting Hypoglycemia In Mice With Liver-specific Gs Deficiency

Jci -increased Glucose Tolerance And Reduced Adiposity In The Absence Of Fasting Hypoglycemia In Mice With Liver-specific Gs Deficiency

The G protein Gs is essential for hormone-stimulated cAMP generation and is an important metabolic regulator. We investigated the role of liver Gs-signaling pathways by developing mice with liver-specific Gs deficiency (LGsKO mice). LGsKO mice had increased liver weight and glycogen content and reduced adiposity, whereas survival, body weight, food intake, and metabolic rates at ambient temperature were unaffected. LGsKO mice had increased glucose tolerance with both increased glucose-stimulated insulin secretion and increased insulin sensitivity in liver and muscle. Fed LGsKO mice were hypoglycemic and hypoinsulinemic, with low expression of hepatic gluconeogenic enzymes and PPAR coactivator1. However, LGsKO mice maintained normal fasting glucose and insulin levels, probably due to prolonged breakdown of glycogen stores and possibly increased extrahepatic gluconeogenesis. Lipid metabolism was unaffected in fed LGsKO mice, but fasted LGsKO mice had increased lipogenic and reduced lipid oxidation gene expression in liver and increased serum triglyceride and FFA levels. LGsKO mice had very high serum glucagon and glucagon-like peptide1 levels and pancreatic cell hyperplasia, probably secondary to hepatic glucagon resistance and/or chronic hypoglycemia. Our results define novel roles for hepatic Gs-signaling pathways in glucose and lipid regulation, which may prove useful in designing new therapeutic targets for diabetes and obesity. Glucose production and utilization are regulated by a complex hormonal system that keeps serum glucose levels in a narrow range. Insulin stimulates glucose uptake, glycolysis, and glycogen synthesis and inhibits gluconeogenesis ( 1 ). These actions are counteracted by various hormones, including glucagon, epinephrine, growth hormone, and gluc Continue reading >>

Impaired Glucose Tolerance And Predisposition To The Fasted State In Liver Glycogen Synthase Knock-out Mice*

Impaired Glucose Tolerance And Predisposition To The Fasted State In Liver Glycogen Synthase Knock-out Mice*

Conversion to glycogen is a major fate of ingested glucose in the body. A rate-limiting enzyme in the synthesis of glycogen is glycogen synthase encoded by two genes, GYS1, expressed in muscle and other tissues, and GYS2, primarily expressed in liver (liver glycogen synthase). Defects in GYS2 cause the inherited monogenic disease glycogen storage disease 0. We have generated mice with a liver-specific disruption of the Gys2 gene (liver glycogen synthase knock-out (LGSKO) mice), using Lox-P/Cre technology. Conditional mice carrying floxed Gys2 were crossed with mice expressing Cre recombinase under the albumin promoter. The resulting LGSKO mice are viable, develop liver glycogen synthase deficiency, and have a 95% reduction in fed liver glycogen content. They have mild hypoglycemia but dispose glucose less well in a glucose tolerance test. Fed, LGSKO mice also have a reduced capacity for exhaustive exercise compared with mice carrying floxed alleles, but the difference disappears after an overnight fast. Upon fasting, LGSKO mice reach within 4 h decreased blood glucose levels attained by control floxed mice only after 24 h of food deprivation. The LGSKO mice maintain this low blood glucose for at least 24 h. Basal gluconeogenesis is increased in LGSKO mice, and insulin suppression of endogenous glucose production is impaired as assessed by euglycemic-hyperinsulinemic clamp. This observation correlates with an increase in the liver gluconeogenic enzyme phosphoenolpyruvate carboxykinase expression and activity. This mouse model mimics the pathophysiology of glycogen storage disease 0 patients and highlights the importance of liver glycogen stores in whole body glucose homeostasis. After ingestion of a meal, glucose is cleared from the bloodstream primarily by conversion t Continue reading >>

Standard Operating Procedures For Describing And Performing Metabolic Tests Of Glucose Homeostasis In Mice

Standard Operating Procedures For Describing And Performing Metabolic Tests Of Glucose Homeostasis In Mice

Standard operating procedures for describing and performing metabolic tests of glucose homeostasis in mice 1Vanderbilt-NIH Mouse Metabolic Phenotyping Center, Nashville, TN 37232, USA 2Sanford-Burnham Medical Research Institute at Lake Nona, Orlando, FL 32827, USA 1Vanderbilt-NIH Mouse Metabolic Phenotyping Center, Nashville, TN 37232, USA 2Sanford-Burnham Medical Research Institute at Lake Nona, Orlando, FL 32827, USA 3Yale-NIH Mouse Metabolic Phenotyping Center, New Haven, CT 06520, USA 4University of Washington-NIH Mouse Metabolic Phenotyping Center, Seattle, WA 98109, USA 5University of Cincinnati-NIH Mouse Metabolic Phenotyping Center, Cincinnati, OH 45267, USA 6Case Western Reserve University-NIH Mouse Metabolic Phenotyping Center, Cleveland, OH 44106, USA *Author for correspondence ( [email protected] ) This article has been cited by other articles in PMC. The Mouse Metabolic Phenotyping Center (MMPC) Consortium was established to address the need to characterize the growing number of mouse models of metabolic diseases, particularly diabetes and obesity. A goal of the MMPC Consortium is to propose standard methods for assessing metabolic phenotypes in mice. In this article, we discuss issues pertaining to the design and performance of various tests of glucose metabolism. We also propose guidelines for the description of methods, presentation of data and interpretation of results. The recommendations presented in this article are based on the experience of the MMPC Consortium and other investigators. The miniaturization of metabolic techniques for use in the mouse has resulted in important advances in our understanding of the pathophysiology of diabetes and its associated complications. An important goal of the Mouse Metabolic Phenotyping Center (MMPC) Co Continue reading >>

Assessment Of Methods And Indexes Of Insulin Sensitivity

Assessment Of Methods And Indexes Of Insulin Sensitivity

Insulin resistance contributes to the pathophysiology of diabetes and is a hallmark of obesity, metabolic syndrome, and many cardiovascular diseases. Therefore, quantifying insulin sensitivity/resistance in humans and animal models is of great importance. Various methods are used to assess insulin sensitivity both in individuals and in study populations. Validity, reproducibility, cost, and degree of subject burden are important factors for both clinicians and researchers to consider when weighing the merits of a particular method. Some methods rely on steady-state analysis of glucose and insulin, whereas others rely on dynamic testing. Each of these methods has distinct advantages and limitations. Thus, optimal choice and employment of a specific method depend on the nature of the studies being performed. Established direct methods for measuring insulin sensitivity in vivo are relatively complex. Finally, simple surrogate indexes for insulin sensitivity/resistance are available that are derived from blood insulin and glucose concentrations under fasting conditions (steady state) or in the postprandial state (dynamic). This article highlight merits, limitations, and appropriate use of current in vivo measures of insulin sensitivity/resistance and presents the advantages and disadvantages of each. A resistência à insulina contribui para a fisiopatologia da diabetes e é uma característica marcante da obesidade, da síndrome metabólica, e de doenças cardiovasculares. Assim, quantificar a sensibilidade à insulina vs resistência à insulina em humanos e em modelos animais é de grande importância. Existem vários métodos para avaliar a sensibilidade à insulina, tanto em indivíduos, como em populações de estudo. A validade, reprodutibilidade, custo e envolviment Continue reading >>

Melior Discovery: Insulin Tolerance Test

Melior Discovery: Insulin Tolerance Test

The Insulin Tolerance Test (ITT) is designed to determine the sensitivity of insulin receptors in tissue by measuring blood glucose levels before and after insulin administration.This is a standard test to determine the diabetic status in humans and experimental animals. This test is used to assess the efficacy of insulin-like compounds and pharmacological agents that can modify insulin responsiveness. The graph above illustrates the difference in response to an insulin challenge (ITT) in insulin-depleted (streptozotocin-treated) mice administered insulin, insulin+MLR-1023 or MLR-1023 alone. This study shows that MLR-1023 significantly extended the duration and magnitude of the insulin response. Data are mean SEM, *p<0.05, ***p<0.001 compared to vehicle. MLR-1023 is a potential "next-generation" insulin sensitizer that works independently of a PPAR mechanism. This compound improves glycemic control by directly and selectively activating the enzyme Lyn kinase. Lyn kinase has been previously shown to modulate the insulin-signaling pathway. MLR-1023 is the first described specific and direct activator of Lyn kinase that elicits glycemic control activity through potentiation of insulin activity. For more information on MLR-1023, please visitour sister site, Melior Pharmaceuticals . In addition to MLR-1023 studies, Melior routinely performs ITT studies in mice fed a "Western diet" that is designed to approximate the "typical" human diet of North Americaand Europe. The "Western diet" contains greater than five times more fat than the normal diet. In this study, mice were fasted four hours prior to study commencement. Insulin tolerance test. A baseline glucose measurement was evaluated one hour prior to dosing. At time 0 minutes, mice received either insulin or vehicle (no in Continue reading >>

Insulin Resistance And Diabetes In Humans And Mice

Insulin Resistance And Diabetes In Humans And Mice

Clinical, biochemical and genetic features of diabetic individuals with defects in HMGA1 expression are reported in Table 1 . Patient 1 (ref. 10), a nonobese 45-year-old Italian man with the usual features of type 2 diabetes, came to medical attention because of his fasting hyperglycemia and hyperinsulinemia. Patient 2 (ref. 11), an 11-year-old Japanese boy, was diagnosed with type 2 diabetes at age 6 and had the male form of type A insulin resistance with acanthosis nigricans. Patient 3, an 11-year-old Italian girl with type A insulin resistance, came to medical attention because of hyperinsulinemia. At that time, she was noted to be diabetic (2 h glucose, 202 mg/dl), although she did not have fasting hyperglycemia. She had acanthosis nigricans, hyperandrogenism and obesity. Her mother (patient 4), aged 35 years and with a history of hypertension, presented with hirsutism, acanthosis nigricans and obesity. She had hyperinsulinemia and diabetes (2 h glucose, 206 mg/dl), without fasting hyperglycemia. To cast light on the mechanisms underlying decreased HMGA1 protein expression in these individuals, we carried out genomic Southern blot hybridization and dosage analysis of the HMGA1 gene (Figure 1a). No major gene rearrangements or reductions were found in patients 1 and 2. In contrast, a 50% reduction in the dosage of the HMGA1 gene was found in peripheral blood lymphocytes and cultured lymphoblasts from patients 3 and 4, and this result is consistent with the loss of one allele (hemizygous deletion) of HMGA1 from chromosome 6p21, as documented by fluorescence in situ hybridization (FISH; Figure 1b). In both subjects, the mutation in the HMGA1 gene segregated with the disease. A heterozygous single-nucleotide deletion was found in exon 8 (a G deletion at position 895 in Continue reading >>

Insulin Tolerance Test

Insulin Tolerance Test

An insulin tolerance test (ITT) is a medical diagnostic procedure during which insulin is injected into a patient's vein, after which blood glucose is measured at regular intervals. This procedure is performed to assess pituitary function, adrenal function, and sometimes for other purposes. An ITT is usually ordered and interpreted by endocrinologists. Insulin injections are intended to induce extreme hypoglycemia below 2.2 mmol/l (40 mg/dl). Patient must have symptomatic neuroglycopenia to trigger counter-regulatory cascade. Glucose levels below 2.2 nmol/L are insufficient absent symptoms. The brain must register low glucose levels. In response, adrenocorticotropic hormone (ACTH) and growth hormone (GH) are released as a part of the stress mechanism. ACTH elevation causes the adrenal cortex to release cortisol. Normally, both cortisol and GH serve as counterregulatory hormones, opposing the action of insulin, i.e. acting against the hypoglycemia.[1] Thus ITT is considered to be the gold standard for assessing the integrity of the hypothalamic–pituitary–adrenal axis. Sometimes ITT is performed to assess the peak adrenal capacity, e.g. before surgery. It is assumed that the ability to respond to insulin induced hypoglycemia translates into appropriate cortisol rise in the stressful event of acute illness or major surgery.[2] This test is potentially very dangerous and must be undertaken with great care, because it can iatrogenically induce the equivalent of a diabetic coma. A health professional must attend it at all times. Other provocation tests which cause much less release of growth hormone include the use of glucagon, arginine and clonidine. Side effects[edit] Side effects include sweating, palpitations, loss of consciousness and rarely convulsions due to severe Continue reading >>

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