The influence of insulin-induced hypoglycemia on copeptin concentrations

Plasma copeptin is a biomarker that reflects arginine vasopressin (AVP) secretion. In this study we measured copeptin during insulin tolerance test (ITT) in 65 patients referred to our department for evaluation of anterior pituitary function. Plasma for measurements of copeptin were collected at the start of the test and regurarly up to 120 minutes thereafter. Of 60 patients who developed significant hypoglycemia and were included in the analyses, 13 (22%) had corticotropic deficiency, 11 (18%) had thyreotropic deficiency, 33 (55%) had growth hormone deficiency and 4 (6%) had AVP deficieny (AVPD). Thirty-seven (62%) patients had at least one anterior pituitary deficiency. In patients without AVPD, median (range) copeptin increased from 4.5 pmol/L (1.3-33.0) to a maximum of 6.2 pmol/L (2.0-34.4; p<0.001). Baseline copeptin was similar in men and women, but maximal copeptin during ITT was higher in men. Copeptin concentrations were not affected by age, BMI, somatotropic, or corticotropic function. Copeptin concentrations were lower in patients with AVPD than patiets without AVPD, and in patients with thyrotropic deficiency, compared to patients with intact thyrotropic function, both at baseline and during ITT. In conclusion, copeptin increases significantly during insulin induced hypoglycemia but is of limited value in predicting anterior pituitary hormonal function.

Evaluation of growth hormone deficiency in women with unexplained infertility

PURPOSE

Growth hormone (GH) has been recognized to play a regulatory role in female reproduction. It has been reported that infertile GH deficient patients regained fertility after GH replacement. The frequency of GH deficiency is not established in patients diagnosed with unexplained infertility. Here, we aim to present the prevalence of GH deficieny in this patient group.

METHODS

We included patients diagnosed with unexplained infertility throughout 18 months. Insulin tolerance test (ITT) and glucagon stimulation tests (GST) were performed and insufficient response to both tests was required for the diagnosis of GH deficiency.

RESULTS

Twenty-five patients were included in the study, the mean age was 27.4 ± 4.5 years and the median duration of infertility was 60 months (min:14, max:120). Two patients were GH deficient according to GST and 14 to ITT. Two patients (8%) showed lack of response on both tests and were diagnosed with GH deficiency.

CONCLUSION

The rate of GH deficiency among women with unexplained infertility was 8% in this preliminary study. There is need for further studies with larger patient groups to verify the results.

Evaluation of the growth response of children with growth hormone deficiency according to the peak growth hormone levels in provocation tests

BACKGROUND

We aimed to evaluate the relation between the peak growth hormone (GH) levels in provocation tests and response to recombinant human GH (rhGH) therapy in patients with GH deficiency (GHD).

METHODS

This was a cross-sectional, single-center, and retrospective study. A total of 135 patients under the age of 16 years who were diagnosed with GHD through insulin tolerance tests and L-DOPA stimulation tests and who received rhGH therapy for at least 2 years in the Pediatric Endocrinology Clinic of Akdeniz University Hospital between 1997 and 2021 were included in the study.

RESULTS

The patients were divided into two groups: idiopathic GHD (group I, n = 119) and multiple pituitary hormone deficiencies or organic pathology on magnetic resonance imaging (group II, n = 16). The patients in group I were classified into three subgroups according to the peak GH values in the provocation tests (group Ia: peak GH <3 μg/L, n = 34; group Ib: peak GH between 3 and 7 μg/L, n = 71; group Ic: peak GH between 7 and 10 μg/L, n = 34). The median age was 11.5 years in group I (8.8 in group Ia, 12.1 in group Ib, 12.3 in group Ib) and 8.8 years in group II. The height standard deviation score (SDS) was -2.93 in group I (-2.85 in group Ia, -2.99 in group Ib, -2.94 in group Ic) and -3.79 in group II. The median Δheight SDS was 0.61 in group I and 1.05 in group II at the end of the first year of treatment and 0.31 in group I and 0.45 in group II at the end of the second year (p = 0.005 and p = 0.074, respectively). When the subgroups of group I were compared, height SDS, Δheight SDS, and height velocity (HV) SDS were all higher in group Ia at the end of the first year of rhGH therapy (p = 0.040, p = 0.029, and p = 0.005, respectively). The height SDS was still significantly higher in group Ia (p = 0.033) while the HV SDS and Δheight SDS were similar between the groups at the end of the second year of therapy (p = 0.164 and p = 0.522, respectively). There was a statistically significant association between the first-year HV SDS and the peak GH value in provocation tests in multiple regression analyses (p<0.001). In addition, the final model revealed that height SDS and weight SDS at the start of the treatment and the first-year HV SDS are the factors with a statistically significant effect on the second-year HV SDS (p = 0.022, p = 0.001, and p<0.001, respectively).

CONCLUSION

Our findings show that the lower the GH peak in provocation tests, the better the response to treatment. The best HV was observed in the first year of rhGH therapy, and the diagnosis should be checked in those patients who had a low first-year HV and did not have a severely low GH peak in provocation tests.

Evaluation of field-testing protocols to diagnose insulin dysregulation in ponies using a Bayesian approach

Field tests and their association with laminitis have not been evaluated in large cohorts. The objectives of this study were to evaluate the performance of basal insulin (BI), the oral sugar test (OST) and the insulin tolerance test (ITT) to diagnose ID and investigate their association with laminitis. Insulin dysregulation status was determined in 146 ponies using BI (insulin concentration >20 µIU/mL), an OST (insulin concentration >65 µIU/mL at 60 or 90 min after oral administration of 0.45 mL/kg corn syrup) and an ITT (< 50% reduction in glucose concentration 30 min after intravenous administration of 0.1 IU/kg insulin). Laminitis was identified using modified-Obel scores. A Bayesian approach was used to define the characteristics of the tests and receiver operating characteristic curves were used to assess their association with laminitis. All tests were well tolerated and laminitis was diagnosed in 9% of ponies. Insulin dysregulation was diagnosed in 15% of ponies using BI, 38% using the OST and 54% using the ITT with 11% of ponies positive for all three tests. The sensitivities and specificities of BI, the OST and the ITT to diagnose ID were 0.52 (95% confidence interval [CI], 0.35-0.79) and 0.97 (95% CI, 0.91 - 1.00), 0.84 (95% CI, 0.70 - 0.94) and 0.60 (95% CI, 0.49 - 0.71), and 0.85 (95% CI, 0.68-0.96) and 0.88 (95% CI, 0.75 - 0.97), respectively. Only BI and the OST were associated with laminitis (P = 0.003 and 0.015, respectively).

Clinical characteristics of patients with unexplainable hypothalamic disorder diagnosed by the corticotropin-releasing hormone challenge test: a retrospective study

BACKGROUND

The corticotropin-releasing hormone (CRH) challenge test can distinguish the disorders of the hypothalamus from those of the pituitary. However, the pathophysiology of hypothalamic disorder (HD) has not been fully understood. This study aimed to elucidate the clinical characteristics of patients with unexplainable HD, diagnosed by the CRH challenge test.

METHODS

We retrospectively reviewed patients who underwent the CRH challenge test. Patients were categorized into four groups as follows: patients with peak serum cortisol ≥18 μg/dL were assigned to the normal response (NR) group (n = 18), among patients with peak serum cortisol < 18 μg/dL and peak adrenocorticotropic hormone (ACTH) increase ≥two-fold, patients without obvious background pathology were assigned to the unexplainable-HD group (n = 18), whereas patients with obvious background pathology were assigned to the explainable-HD group (n = 38), and patients with peak serum cortisol < 18 μg/dL and peak ACTH increase <two-fold were assigned to the pituitary disorder (PD) group (n = 15). Inter-group comparisons were performed based on clinical characteristics.

RESULTS

In the CRH challenge test, the peak plasma ACTH levels were significantly lower in the unexplainable-HD group than in the NR group, despite more than two-fold increase compared to basal levels. The increase in serum cortisol was significantly higher in the unexplainable-HD group than in the explainable-HD and PD groups. Although patients in the unexplainable-HD group showed a clear ACTH response in the insulin tolerance test, some patients had peak serum cortisol levels of < 18 μg/dL. Furthermore, attenuated diurnal variations and low normal levels of urinary free cortisol were observed. Most patients in the unexplainable-HD group were young women with chronic fatigue. However, supplementation with oral hydrocortisone at physiological doses reduced fatigue only in some patients.

CONCLUSIONS

Patients with unexplainable HD diagnosed by the CRH challenge test had hypothalamic-pituitary-adrenal (HPA) axis dysfunction and some patients had mild central adrenal insufficiency. Hydrocortisone supplementation reduced fatigue only in some patients, suggesting that HPA axis dysfunction may be a physiological adaptation. Further investigation of these patients may help elucidate the pathophysiology of myalgic encephalitis/chronic fatigue syndrome.

Is the fear from insulin tolerance test in the evaluation of short stature justified?

Among growth hormone (GH) provocative tests, insulin tolerance test (ITT) is considered a valuable test in children with short stature to diagnose GH deficiency. However, many pediatric endocrinologists are reluctant to perform it. We conducted a nationwide survey among all the pediatric endocrine clinics' heads in Israel regarding their position on this issue. We found that the number of endocrine units performing ITT is almost nil. Sense of fear from severe hypoglycemia was a dominating cause for not performing ITT. We review the pros and cons of performing ITT versus other tests, especially glucagon test. Glucagon tolerance test is not considered the test of choice by some endocrinologists but recommended by others including in Israel. We also note the influence of a widely cited report published in 1992 (many times inaccurately) on endocrinologists' views.

CONCLUSION

A nationwide survey in Israel revealed a high rate of reluctance to perform ITT. The rationale behind this attitude was a sense of fear of performing the test by many endocrinologists. We discuss the preferences for choosing GH stimulation tests and the pros and cons of alternatives to ITT. The fear of not performing ITT was not always justified.

WHAT IS KNOWN

• ITT test is considered a gold standard in the evaluation of short stature to diagnose GH deficiency by many endocrinologists.

WHAT IS NEW

• High reluctance rate found in Israel to perform ITT, prompted us to evaluate the attitudes of pediatric endocrinologists around the world showing conflicting ideas. • The role of a single paper sometimes misquoted also contributed to these conflicting results.

Investigation of the Hypothalamo-pituitary-adrenal (HPA) axis: a contemporary synthesis

The hypothalamo-pituitary-adrenal (HPA) axis is one of the main components of the stress system. Maintenance of normal physiological events, which include stress responses to internal or external stimuli in the body, depends on appropriate HPA axis function. In the case of severe cortisol deficiency, especially when there is a triggering factor, the patient may develop a life-threatening adrenal crisis which may result in death unless early diagnosis and adequate treatment are carried out. The maintenance of normal physiology and survival depend upon a sufficient level of cortisol in the circulation. Life-long glucocorticoid replacement therapy, in most cases meeting but not exceeding the need of the patient, is essential for normal life expectancy and maintenance of the quality of life. To enable this, the initial step should be the correct diagnosis of adrenal insufficiency (AI) which requires careful evaluation of the HPA axis, a highly dynamic endocrine system. The diagnosis of AI in patients with frank manifestations is not challenging. These patients do not need dynamic tests, and basal cortisol is usually enough to give a correct diagnosis. However, most cases of secondary adrenal insufficiency (SAI) take place in a gray zone when clinical manifestations are mild. In this situation, more complicated methods that can simulate the response of the HPA axis to a major stress are required. Numerous studies in the assessment of HPA axis have been published in the world literature. In this review, the tests used in the diagnosis of secondary AI or in the investigation of suspected HPA axis insufficiency are discussed in detail, and in the light of this, various recommendations are made.

Strain-based and sex-biased differences in adrenal and pancreatic gene expression between KK/HlJ and C57BL/6 J mice

Background

The ever-increasing prevalence of diabetes and associated comorbidities serves to highlight the necessity of biologically relevant small-animal models to investigate its etiology, pathology and treatment. Although the C57BL/6 J model is amongst the most widely used mouse model due to its susceptibility to diet-induced obesity (DIO), there are a number of limitations namely [1] that unambiguous fasting hyperglycemia can only be achieved via dietary manipulation and/or chemical ablation of the pancreatic beta cells. [2] Heterogeneity in the obesogenic effects of hypercaloric feeding has been noted, together with sex-dependent differences, with males being more responsive. The KK mouse strain has been used to study aspects of the metabolic syndrome and prediabetes. We recently conducted a study which characterized the differences in male and female glucocentric parameters between the KK/HlJ and C57BL/6 J strains as well as diabetes-related behavioral differences (Inglis et al. 2019). In the present study, we further characterize these models by examining strain- and sex-dependent differences in pancreatic and adrenal gene expression using Affymetrix microarray together with endocrine-associated serum analysis.

Results

In addition to strain-associated differences in insulin tolerance, we found significant elevations in KK/HlJ mouse serum leptin, insulin and aldosterone. Additionally, glucagon and corticosterone were elevated in female mice of both strains. Using 2-factor ANOVA and a significance level set at 0.05, we identified 10,269 pancreatic and 10,338 adrenal genes with an intensity cut-off of ≥2.0 for all 4 experimental groups. In the pancreas, gene expression upregulated in the KK/HlJ strain related to increased insulin secretory granule biofunction and pancreatic hyperplasia, whereas ontology of upregulated adrenal differentially expressed genes (DEGs) related to cell signaling and neurotransmission. We established a network of functionally related DEGs commonly upregulated in both endocrine tissues of KK/HlJ mice which included the genes coding for endocrine secretory vesicle biogenesis and regulation: PCSK2, PCSK1N, SCG5, PTPRN, CHGB and APLP1. We also identified genes with sex-biased expression common to both strains and tissues including the paternally expressed imprint gene neuronatin.

Conclusion

Our novel results have further characterized the commonalities and diversities of pancreatic and adrenal gene expression between the KK/HlJ and C57BL/6 J strains as well as differences in serum markers of endocrine physiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07495-4.

The Cut-off Limits of Growth Hormone Response to the Insulin Tolerance Test Related to Body Mass Index for the Diagnosis of Adult Growth Hormone Deficiency

INTRODUCTION

The diagnosis of growth hormone deficiency (GHD) in adults is based on a reduced GH response to provocative tests, such as the insulin tolerance test (ITT) and the GH-releasing hormone (GHRH) + arginine (ARG) test. However, the cut-off limits of peak GH response in lean subjects are not reliable in obese patients; this is noteworthy since adult GHD is often associated with obesity. To date, there are no ITT cut-offs related to body mass index (BMI).

OBJECTIVE

We aimed to evaluate the diagnostic cut-offs of GH response to the ITT in the function of BMI.

METHODS

The GH response to the ITT was studied in 106 patients with a history of hypothalamic-pituitary disease, a mean age of 48.2 ± 12.4 years, and a mean BMI of 26.8 ± 6.1 kg/m2). Patients were divided into lean, overweight, and obese groups according to their BMI. The lack of GH response to GHRH + ARG test was considered the gold standard for the diagnosis of GHD. The best GH cut-off in the ITT, defined as the one with the best sensitivity (SE) and specificity (SP), was identified using receiver-operating characteristics curve (ROC) analysis.

RESULTS

The best GH cut-off in the ITT was 3.5 μg/L in lean subjects (SE 82.1%; SP 85.7%), 1.3 μg/L in overweight subjects (SE 74.1%; SP 85.7%), and 2.2 μg/L in obese subjects (SE 90.0%; SP 50.0%). The diagnostic accuracy was 97.2, 76.5, and 76.7%, respectively.

CONCLUSIONS

Our data show that the ITT represents a reliable diagnostic tool for the diagnosis of adult GHD in lean subjects if an appropriate cut-off limit is assumed. Overweight and obesity strongly reduce the GH response to the ITT, GH BMI-related cut-off limits, and the diagnostic reliability of the test.

Morning Serum Cortisol Level Predicts Central Adrenal Insufficiency Diagnosed by Insulin Tolerance Test

INTRODUCTION

According to guidelines, a morning serum cortisol level <83 nmol/L is diagnostic for central adrenal insufficiency (CAI), a value >414 nmol/L excludes CAI, while values between 83 and 414 nmol/L require stimulation tests. However, there are no currently reliable data on morning serum cortisol for prediction of cortisol response to insulin tolerance test (ITT).

OBJECTIVE

Using the receiver-operating characteristic curve analysis, the purpose of this study was to detect the morning serum cortisol cutoff with a specificity (SP) or a sensitivity (SE) above 95% that identify those patients who should not be tested with ITT.

METHODS

We included 141 adult patients (83 males) aged 42.7 ± 12.3 (mean ± standard deviation) years old. Based on the serum cortisol response to ITT, patients have been divided into 2 groups: subjects with CAI (peak serum cortisol <500 nmol/L; 65 patients) and subjects with preserved adrenocortical function (peak cortisol >500 nmol/L; 76 patients).

RESULTS

The best morning cortisol cutoff, in terms of SE (87.7%) and SP (46.1%), was ≤323.3 nmol/L. The cutoff of morning serum cortisol concentration that best predicted a deficient response to ITT was ≤126.4 nmol/L (SE 13.8%, SP 98.7%). The cutoff of morning serum cortisol concentration that best predicted a normal response to ITT was >444.7 nmol/L (SE 96.9%, SP 14.5%).

CONCLUSIONS

This is the first study that identifies a morning serum cortisol cutoff that best predict the response to ITT in order to simplify the diagnostic process in patients with suspected CAI. A new diagnostic flow-chart for CAI is proposed.

Strain and sex-based glucocentric & behavioral differences between KK/HlJ and C57BL/6J mice

INTRODUCTION

Small-animal models are the most widely used preclinical model for studying the etiology, pathology and treatment of diabetes, prediabetes and diabetic comorbidities. Diabetic patients are burdened with higher rates of depression, anxiety and cognitive decline due to inadequate control of blood glucose levels, vascular damage and aberrant CNS insulin signaling. The C57BL/6J model is amongst the most widely used mouse model due to its susceptibility to diet-induced obesity (DIO). This strain has also been well-characterized in behavioral research studies. However the C57BL/6J model has a number of limitations: [1] overt fasting hyperglycemia can only be induced by dietary manipulation and/or chemical ablation of the pancreatic beta cells. [2] There is heterogeneity in the obesogenic response to hypercaloric feeding as well as sex-dependent differences, with males being more responsive. The KK inbred strain has been used to study aspects of the metabolic syndrome and prediabetes due to inherent glucose intolerance, hyperinsulinemia and insulin resistance. However KK/HlJ mice are less well-characterized and there have been fewer behavioral studies reported. The aim of this study was to examine differences in male and female glucocentric parameters between KK/HlJ and C57BL/6J mice, and to compare their performance in a variety of standard behavioral tests relating to general, anxiogenic and cognitive paradigms.

METHODS

Strain differences in male and female KK/HlJ and C57BL/6J mouse adiposity, glucose and insulin parameters were studied together with group differences in standard Open Field, Object Recognition, Elevated Plus Maze, Light-Dark Transition, Porsolt test, Marble Burying, Social Recognition and Morris Water Maze tests. Correlations between behavioral variables were analyzed.

RESULTS AND CONCLUSION

In addition to being uniformly larger, hyperinsulinemic and more insulin intolerant than C57BL/6J mice, we observed marked strain and sex-differences in KK/HlJ behavior. KK/HlJ mice exhibited less locomotor and vertical exploratory behavior in comparison to C57BL/6J, whereas object exploration and novel object discrimination were superior in KK/HlJ mice. Female KK/HlJ mice were faster swimmers, whereas the males exhibited greater spatial cognition and place-learning during the MWM test.

Insulin Tolerance Test under Anaesthesia to Measure Tissue-specific Insulin-stimulated Glucose Disposal

Insulin resistance is a pathophysiological state defined by impaired responses to insulin and is a risk factor for several metabolic diseases, most notably type 2 diabetes. Insulin resistance occurs in insulin target tissues including liver, adipose and skeletal muscle. Methods such as insulin tolerance tests and hyperinsulinaemic-euglycaemic clamps permit assessment of insulin responses in specific tissues and allow the study of the progression and causes of insulin resistance. Here we detail a protocol for assessing insulin action in adipose and muscle tissues in anesthetized mice administered with insulin intravenously.

Cortisol cut-points for the glucagon stimulation test in the evaluation of hypothalamic pituitary adrenal axis

Diagnosis of adrenal insufficiency requires evaluation by dynamic stimulation tests. The insulin tolerance test (ITT) is accepted as the gold-standard test for the evaluation of hypothalamo-pituitary-adrenal (HPA) axis but the test is unpleasant and dangerous. Although it takes more time, glucagon stimulation test (GST) is a good alternative to ITT. The primary aim of this study was to compare the ITT and GSTs in the evaluation of HPA axe in patients with pituitary disorders. We conducted a prospective study in which ITT and GST were performed within 7 days in 81 patients. Serum cortisol was measured. We divided our population in Group 1 (G1): Adrenal Insufficiency (Peak cortisol under ITT <200 ng/mL) and Group 2 (G2): normal response (Peak cortisol under ITT >200 ng/mL). Receiver-operating characteristic (ROC) analysis was performed to identify the thresholds for GST. The mean peak of cortisol under GST was not significantly different from that obtained after ITT in the whole cohort (182.67 ± 89.07 ng/mL vs. 179.75 ± 79.01 ng/mL), and it was significantly reduced in patients of G1 (p < 10^-3). ROC curve analysis showed that the best diagnostic accuracy was obtained with a peak cortisol cut-off to GST of 167 ng/mL (sensitivity, 89%; specificity, 79%). Using this cut-off, 86.4% of the patients were correctly classified. In our prospective series, GST is a potential accurate and safe alternative test for the assessment HPA. Test-specific cut-offs should be applied to avoid misinterpretation.

Androst-5-ene-3β,7α/β,17β-triols, their plasma levels and dependence on the hypothalamic-pituitary-adrenal axis

Androst-5-ene-triols are metabolites of dehydroepiandrosterone, the most abundant steroid hormone in human circulation. Many observations in rodents have demonstrated the anti-inflammatory and immune modulating activity of 7β-hydroxy-androst-5-enes, and on the basis of these experiments androst-5-ene-3β,7β,17β-triol is considered as a potential agent in the treatment of autoimmune diseases. In contrast to the fairly abundant information on the levels and effects of androst-5-ene-triols in experimental animals and of their the pharmacological perspective, little is known about androst-5-ene-3β,7α/β,17β-triols circulating in human blood, their regulation by the hypothalamo-pituitary-adrenal axis, or their daily concentration variability. Here we provide some data on androst-5-ene-3β,7α/β,17β-triol concentrations under various conditions in men and women.

Algorithm for Screening of Adrenal Function in Stable Patients with Cirrhosis

INTRODUCTION AND AIMS

Adrenal insufficiency (AI) is common in patients with cirrhosis. We aimed to assess the presence of AI in stable patients with cirrhosis using the gold-standard insulin tolerance test (ITT) and to propose an algorithm for screening AI in these patients.

MATERIAL AND METHODS

We studied 40 stable patients with cirrhosis. We determined the basal total (BTC) and peak cortisol (PTC) levels. Using the ITT, we defined AI as a serum PTC < 18 μg/dL at 30 min after insulin-induced hypoglycemia. We assessed the diagnostic accuracy of BTC in different stages of liver disease to discriminate between those with NAF and AI.

RESULTS

Of the 40 patients, 24 (60%) presented with AI. Child-Pugh and MELD scores differed between the NAF and AI groups (Child-Pugh: NAF 7.2 ± 1.7 vs. AI 8.8 ± 2.4, p = 0.024 and MELD: NAF 9.9 ± 2.5 vs. AI 14.9 ± 6.3, p = 0.001). The BTC level was lower in patients with AI than in those with NAF (7.2 ± 2.4 vs. 12.5 ± 5.2, p < 0.001). A BTC value ≤ 10.0 μg/dL had a 96% sensitivity (negative predictive value: 90%) for identifying AI. This cutoff value (BTC ≤ 10.0 μg/dL) provided 100% specificity (positive predictive value: 100%) in patients with advanced liver disease (Child-Pugh ≥ 9 or MELD ≥ 12).

CONCLUSION

An algorithm including the use of BTC and the severity of liver disease may be a useful and simple method for assessing adrenal function in stable patients with cirrhosis.

sustained efficacy of Liraglutide on glycemic control in type 2 diabetes patients: A prospective real-world setting study

AIMS

Less than half of type 2 diabetes patients treated with Glucagon-Like Peptide 1 (GLP-1) analogs displays good glycemic control, according to real life studies. Predictive markers of inefficacy/efficacy are therefore needed. The effectiveness of Liraglutide in terms of glycemic control and weight loss was then evaluated according to putative predictive parameters.

METHODS

80 type 2 diabetes patients treated with Liraglutide were included in this prospective study. An Insulin Tolerance test (ITT) was performed at baseline to calculate velocity of C-Peptide decrease (C-peptide T½). Several clinical and biological parameters including HbA_1c and weight were assessed at baseline and after 12, 24, 52 and 104 weeks of treatment.

RESULTS

HbA_1c decrease over the follow-up period was highly associated with C-peptide T½. A mean fall of 0.7% of HbA1c (7.7 mmol/mol) was predicted with 82% sensitivity and 80% specificity by C-peptide T½. In patients with rapid response during ITT (C-peptide T½ < 120 min), a HbA1c decrease of 1.5% (16.5 mmol/mol) was constantly found (p = .002) all over the follow-up. HbA1c remained unmodified for the rest of the patients (p = .34) compared to baseline. HbA_1c evolution was not predicted by diabetes duration. Weight loss was predicted only by low baseline C-peptide plasma level.

CONCLUSIONS

This study suggests ITT as an efficient test to discriminate non-response from long-term efficacy before initiating Liraglutide. ITT could therefore help avoiding "try and see" prescription pattern by using a more precise and patient-centered strategy in order to reduce inertia in adapting treatment and so reduce subsequent complications.

Hormonal response to a non-exercise stress test in athletes with overtraining syndrome: results from the Endocrine and metabolic Responses on Overtraining Syndrome (EROS) - EROS-STRESS

OBJECTIVES

Overtraining syndrome (OTS) leads to worsened sports performance and fatigue. The pathophysiology of OTS has not been entirely elucidated, and there is a lack of accurate markers for its diagnosis. Changes in hormonal responses implicated in OTS were stimulated by exercise, which has limited their interpretation. Hence, we aimed to evaluate growth hormone (GH) and prolactin responses to a gold-standard and exercise-independent stimulation test, the insulin tolerance test (ITT).

DESIGN

Volunteers were recruited and divided into OTS-affected athletes (OTS), healthy athletes (ATL), and healthy non-active subjects (NCS) groups, after general and specific inclusion and exclusion criteria.

METHODS

We evaluated the responses of growth hormone (GH) and prolactin to the ITT, and compared between groups.

RESULTS

A total of 51 subjects were included (OTS, n=14, ATL, n=25, and NCS, n=12). OTS disclosed significantly lower basal levels of GH (p=0.003) and prolactin (p=0.048), and GH (p=0.001) and prolactin (p<0.001) responses to ITT (p=0.001), compared to ATL, but similar to NCS. OTS showed a later rise in GH levels in response to hypoglycemia, compared to ATL, but not to NCS. We suggest cutoffs for GH and prolactin levels to aid in the diagnosis of OTS.

CONCLUSIONS

OTS-affected athletes show reduced GH and prolactin basal levels and responses to a non-exercise stress test compared to healthy athletes, but not to sedentary subjects.

Sexual dimorphism in the glucose homeostasis phenotype of the Aromatase Knockout (ArKO) mice

We investigated the effects of estrogens on glucose homeostasis using the Aromatase Knockout (ArKO) mouse, which is unable to convert androgens into estrogens. The ArKO mouse is a model of total estrogen ablation which develops symptoms of metabolic syndrome. To determine the development and progression of whole body state of insulin resistance of ArKO mice, comprehensive whole body tolerance tests were performed on WT, ArKO and estrogen administrated mice at 3 and 12 months of age. The absence of estrogens in the male ArKO mice leads to hepatic insulin resistance, glucose and pyruvate intolerance from 3 to 12 months with consistent improvement upon estrogen treatment. Estrogen absence in the female ArKO mice leads to glucose intolerance without pyruvate intolerance or insulin resistance. The replacement of estrogens in the female WT and ArKO mice exhibited both insulin sensitizing and resistance effects depending on age and dosage. In conclusion, this study presents information on the sexually dimorphic roles of estrogens on glucose homeostasis regulation.

Factors associated with an inadequate hypoglycemia in the insulin tolerance test in Japanese patients with suspected or proven hypopituitarism

We attempted to identify the predictors of an inadequate hypoglycemia in insulin tolerance test (ITT), defined as a blood glucose level higher than 2.8 mmol/L after insulin injection, in Japanese patients with suspected or proven hypopituitarism. A total of 78 patients who had undergone ITT were divided into adequate and inadequate hypoglycemia groups. The relationships between the subjects' clinical parameters and inadequate hypoglycemia in ITT were analyzed. Stepwise logistic regression analysis identified high systolic blood pressure (SBP) and high homeostasis model assessment of insulin resistance (HOMA-IR) as being independent factors associated with inadequate hypoglycemia in ITT. Receiver operating characteristic (ROC) curve analysis revealed the cutoff value for inadequate hypoglycemia was 109 mmHg for SBP and 1.4 for HOMA-IR. The areas under ROC curve for SBP and HOMA-IR were 0.72 and 0.86, respectively. We confirmed that high values of SBP and HOMA-IR were associated with inadequate hypoglycemia in ITT, regardless of the degree of reduction of pituitary hormone levels. Furthermore, the strongest predictor of inadequate hypoglycemia was obtained by using the cutoff value of HOMA-IR. Our results suggest that HOMA-IR is a useful pre-screening tool for ITT in these populations.

A Comparison of Salivary Steroid Levels during Diagnostic Tests for Adrenal Insufficiency

Numerous diagnostic tests are used to evaluate the hypothalamic-pituitary-adrenal axis (HPA axis). The gold standard is still considered the insulin tolerance test (ITT), but this test has many limitations. Current guidelines therefore recommend the Synacthen test first when an HPA axis insufficiency is suspected. However, the dose of Synacthen that is diagnostically most accurate and sensitive is still a matter of debate. We investigated 15 healthy men with mean/median age 27.4/26 (SD±4.8) years, and mean/median BMI (body mass index) 25.38/24.82 (SD±3.2) kg/m2. All subjects underwent 4 dynamic tests of the HPA axis, specifically 1 μg, 10 μg, and 250 μg Synacthen (ACTH) tests and an ITT. Salivary cortisol, cortisone, pregnenolone, and DHEA (dehydroepiandrosterone) were analysed using liquid chromatography-tandem mass spectrometry. During the ITT maximum salivary cortisol levels over 12.5 nmol/l were found at 60 minutes. Maximum cortisol levels in all of the Synacthen tests were higher than this; however, demonstrating that sufficient stimulation of the adrenal glands was achieved. Cortisone reacted similarly as cortisol, i.e. we did not find any change in the ratio of cortisol to cortisone. Pregnenolone and DHEA were higher during the ITT, and their peaks preceded the cortisol peak. There was no increase of pregnenolone or DHEA in any of the Synacthen tests. We demonstrate that the 10 μg Synacthen dose is sufficient stimulus for testing the HPA axis and is also a safe and cost-effective alternative. This dose also largely eliminates both false negative and false positive results.

Mouse Models of Type 2 Diabetes Mellitus in Drug Discovery

Type 2 diabetes is a fast-growing epidemic in industrialized countries, associated with obesity, lack of physical exercise, aging, family history, and ethnic background. Diagnostic criteria are elevated fasting or postprandial blood glucose levels, a consequence of insulin resistance. Early intervention can help patients to revert the progression of the disease together with lifestyle changes or monotherapy. Systemic glucose toxicity can have devastating effects leading to pancreatic beta cell failure, blindness, nephropathy, and neuropathy, progressing to limb ulceration or even amputation. Existing treatments have numerous side effects and demonstrate variability in individual patient responsiveness. However, several emerging areas of discovery research are showing promises with the development of novel classes of antidiabetic drugs.The mouse has proven to be a reliable model for discovering and validating new treatments for type 2 diabetes mellitus. We review here commonly used methods to measure endpoints relevant to glucose metabolism which show good translatability to the diagnostic of type 2 diabetes in humans: baseline fasting glucose and insulin, glucose tolerance test, insulin sensitivity index, and body type composition. Improvements on these clinical values are essential for the progression of a novel potential therapeutic molecule through a preclinical and clinical pipeline.

Can a glucagon stimulation test characterized by lower GH cut-off value be used for the diagnosis of growth hormone deficiency in adults?

OBJECTIVE

The aim of this study was to assess diagnostic values of insulin tolerance test (ITT), glucagon stimulation test (GST), and insulin like growth factor-I (IGF-I) level, to find optimal GH cut-off values for GST, and to evaluate efficiencies of patient age, gender, body-mass index (BMI), and additional pituitary hormone deficiencies (PHDs) in the diagnosis of growth hormone deficiency (GHD).

STUDY DESIGN

This retrospective study involved 216 patients with a pituitary disease and 26 healthy controls. Age, gender, BMI, medical histories, and hormonal data including baseline and stimulated hormone values were evaluated. Three cut-off values for peak GH responses to stimulation tests were evaluated: (a) 3.00 µg/L on ITT, (b) 3.00 µg/L on GST, and (c) 1.07 µg/L on GST.

RESULTS

According to the ITT, GST with 3.00 µg/L cut-off, and GST with 1.07 µg/L cut-off, GHD was present in 86.1, 74.5, and 54.2 % patients, respectively. Patient age, BMI, and number of PHDs, but not gender, were found to be correlated with IGF-I and peak GH concentrations. All patients with an IGF-I concentration ≤95 ng/ml or ≥3 PHD had GHD. None of the patients with adequate GH response to the GST with 1.07 µg/L cut-off, but blunted responses to ITT and GST with 3.00 µg/L cut-off, had ≥3 PHDs. 12 out of 26 (46.2 %) healthy subjects failed the GST with 3.00 µg/L cut-off, but not with 1.07 µg/L cut-off.

CONCLUSIONS

Patient age, IGF-I, BMI, and number of PHDs are efficient factors associated with the diagnosis of GHD. A 4 h GST with a diagnostic GH threshold of 1.07 µg/L seems to be a good diagnostic method for GHD.

Prenatal tolbutamide treatment alters plasma glucose and insulin concentrations and negatively affects the postnatal performance of chickens

To examine the relationship of insulin and glucose, broiler embryos were subjected to acute or prolonged hypoglycemia during the late embryonic phase by, respectively, injecting once (at embryonic day [ED] 16 or 17) or on 3 consecutive days (ED 16, 17, and 18) with tolbutamide (80 μg/g embryo weight), a substance that stimulates insulin secretion from the pancreas. After 1 tolbutamide injection, a prolonged (32 h) decrease of plasma glucose and a profound acute increase in plasma insulin were observed. The 3 consecutive tolbutamide injections induced hypoglycemia for 4 days (from ED 16 to ED 19). The postnatal performance after 3 consecutive tolbutamide injections in broiler embryos was also investigated. Body weight was lower in tolbutamide-treated chickens from hatch to 42 d compared with sham (P = 0.001) and control (P < 0.001) chickens. Feed intake was lower in the tolbutamide group from hatch to 42 d as compared with sham (P = 0.007) and control (P = 0.017) animals. In addition, at 42 d, plasma glucose concentrations, after an insulin injection challenge (50 μg/kg body weight), were higher in tolbutamide-treated chickens compared with the sham and the control group as were their basal glucose levels (P value of group effect <0.001). In conclusion, tolbutamide treatment during the late embryonic development in broilers resulted in prolonged hypoglycemia in this period and negatively influenced the posthatch performance.

Desacyl ghrelin is influenced by changes in insulin concentration during an insulin tolerance test

OBJECTIVE

Ghrelin, a gut-brain peptide, regulates energy homeostasis and glucose metabolism and is present in acylated and nonacylated form in the circulation. Although desacyl ghrelin (DAG), the predominant form of ghrelin, is associated with insulin sensitivity and improved metabolic state, not much is known about its direct regulation by insulin. We aimed to assess changes in DAG in response to the rapid increase in insulin concentration during an insulin tolerance test (ITT) in normal weight and obese subjects.

DESIGN

We performed an observational single center study. An ITT was assessed in eight subjects (four males), median age of 29.9 years (range 19.6-42.0). DAG concentrations were measured at 20, 40, 60 and 90 min after insulin infusion. Homeostatic Model Assessment (HOMA) was calculated from fasting insulin and glucose. Body mass index (BMI) and waist circumference were assessed.

RESULTS

Three subjects were obese (BMI ≥ 30 kg/m(2)), one subject was overweight (BMI = 25-30 kg/m(2)) and four subjects had normal weight (BMI = 18.5-25 kg/m(2)). Median DAG decreased after insulin infusion (90 pg/mL, p = 0.028), especially in normal weight subjects. Baseline DAG was lower in subjects with higher BMI (ρ = -0.76, p = 0.028) and higher fasting insulin (ρ = -0.76, p = 0.030). DAG changes correlated with fasting insulin levels (ρ = -0.85, p = 0.007), HOMA (ρ = -0.86, p = 0.007), BMI (ρ = -0.83, p = 0.010) and waist circumference (ρ = -0.93, p < 0.001).

CONCLUSION

DAG levels rapidly decreased in response to insulin administration in normal subjects, but not in insulin-resistant obese who are in a state of relative DAG deficiency.

Usefulness of the insulin tolerance test in patients with type 2 diabetes receiving insulin therapy

Aims/Introduction

To establish the validity of the plasma glucose disappearance rate (KITT), derived from an insulin‐tolerance test (ITT), for evaluating the insulin sensitivity of patients with type 2 diabetes after insulin therapy.

Materials and Methods

In the first arm of the study, 19 patients with poorly controlled diabetes were treated with insulin and underwent an ITT and a euglycemic clamp test (clamp‐IR). The relationship between the insulin resistance index, as assessed by both the clamp‐IR and KITT tests, was examined. In the second arm of the study, the relationships between KITT values and various clinical parameters were investigated in 135 patients with poorly controlled diabetes, after achieving glycemic control with insulin.

Results

In study 1, a close correlation between KITT and the average glucose infusion rate during the last 30 min of the standard clamp‐IR test (M‐value) was noted (P < 0.001). In study 2, body mass index (P = 0.0011), waist circumference (P = 0.0004), visceral fat area (P = 0.0011) and the log‐transformed homeostasis model assessment of insulin resistance value (P = 0.0003) were negatively correlated with the log‐transformed KITT. High‐density lipoprotein cholesterol (P = 0.0183), low‐density lipoprotein cholesterol (P = 0.0121) and adiponectin (P = 0.0384) levels were positively correlated with the log‐transformed KITT.

Conclusions

The ITT is a valid and useful test for evaluating the insulin sensitivity of patients with diabetes, even after treatment with insulin.

A search for variables predicting cortisol response to low-dose corticotropin stimulation following supraphysiological doses of glucocorticoids

OBJECTIVES

To determine which biological or clinical variables may predict cortisol response to low-dose adrenocorticotropic hormone (ACTH) stimulation following supraphysiological doses of glucocorticoids in children.

STUDY DESIGN

This retrospective study included all patients who underwent ACTH testing (1 μg) between October 2008 and June 2010 at the Sainte-Justine University Hospital Center, Montreal, after supraphysiological doses of glucocorticoids.

RESULTS

Data from 103 patients (median age, 8.0 years; range, 0.6-18.5 years; 57 girls) were analyzed, revealing growth deceleration in 37% and excessive weight gain in 33%. Reasons for glucocorticoid treatment included asthma (n = 30) and hematologic (n = 22), dermatologic (n = 19), rheumatologic (n = 16), and miscellaneous (n = 16) disorders. The following information was recorded: duration of glucocorticoid treatment (median, 374 days; range, 5-4226 days); duration of physiological hydrocortisone replacement (median, 118 days; range, 0-1089 days); maximum daily (median, 200 mg/m(2)/day; range, 12-3750 mg/m(2)/day) and cumulative (median, 16 728 mg/m(2); range, 82-178 209 mg/m(2)) doses, in hydrocortisone equivalents; and interval since the last dose (median, 43 days; range, 1-1584 days). Sixty-two patients (58%) exhibited a normal response (ie, peak cortisol >500 nmol/L) to ACTH stimulation. Peak cortisol level was not related to sex, prior morning cortisol level, duration of treatment, or cumulative glucocorticoid dose; 28% of the patients with normal baseline cortisol levels nevertheless demonstrated a subnormal response to ACTH.

CONCLUSION

Given the absence of clinical or biological predictors of the cortisol response to ACTH after suppressive doses of glucocorticoids, physicians have only 2 options: (1) empirically advocate glucocorticoid stress coverage during 18 months after cessation of high-dose glucocorticoid treatment; or (2) perform serial ACTH testing in all such patients until a normal peak cortisol level is attained.