Once upon a time: the glucagon stimulation test in diagnosing adult GH deficiency.

PURPOSE: The clinical features of adult GH deficiency (GHD) are nonspecific, and its diagnosis is established through GH stimulation testing, which is often complex, expensive, time-consuming and may be associated with adverse side effects. Moreover, diagnosing adult GHD can be challenging due to the influence of age, gender, and body mass index on GH peak at each test. The insulin tolerance test (ITT), GHRH + arginine test, glucagon stimulation test (GST), and, more recently, testing with macimorelin are all recognized as useful in diagnosing adult GHD. To date GST is still little used, but due to the unavailability of the GHRH all over the world and the high cost of macimorelin, in the next future it will probably become the most widely used test when ITT is contraindicated. The aim of the present review is to describe the current knowledge on GST. METHODS: Narrative review. RESULTS: In the last years several studies have suggested some changes in the original GST protocol and have questioned its diagnostic accuracy when the classic GH cut-point of 3 µg/L is used, suggesting to use a lower GH cut-point to improve its sensitivity and specificity in overweight/obese patients and in those with lower pretest GHD probability. CONCLUSION: This document provides an update on the utility of GST, summarizes how to perform the test, shows which cut-points should be used in interpreting the results, and discusses its drawbacks and caveats referring to the most recent studies.

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.

New insights on diagnosis and treatment of AVP deficiency.

Arginine vasopressin deficiency (AVP-D) is one of the main entities of the polyuria-polydipsia syndrome. Its correct diagnosis and differentiation from the other two causes - AVP resistance and primary polydipsia - is crucial as this determines the further management of these patients.Over the last years, several new diagnostic tests using copeptin, the stable surrogate marker of AVP, have been introduced. Among them, hypertonic saline stimulated copeptin was confirmed to reliably and safely improve the diagnostic accuracy to diagnose AVP-D. Due to its simplicity, arginine stimulated copeptin was put forward as alternative test procedure. Glucagon-stimulated copeptin also showed promising results, while the oral growth hormone secretagogue Macimorelin failed to provide a sufficient stimulus. Interestingly, an approach using machine learning techniques also showed promising results concerning diagnostic accuracy.Once AVP-D is diagnosed, further workup is needed to evaluate its etiology. This will partly define the further treatment and management. In general, treatment of AVP-D focuses on desmopressin substitution, with oral formulations currently showing the best tolerance and safety profile. However, in addition to desmopressin substitution, recent data also showed that psychopathological factors play an important role in managing AVP-D patients.

Growth Hormone Cut-Off Post Glucagon Stimulation Test in an Indian Cohort of Overweight/Obese Hypopituitary Patients for the Diagnosis of Adult Growth Hormone Deficiency.

Obesity has been associated with reduced growth hormone (GH) secretion, which might lead to the over diagnosis of adult GH deficiency (GHD) in overweight (OW)/obese hypopituitary patients. Currently, there are no body mass index (BMI)-specific peak GH cut-offs for the glucagon stimulation test (GST) for assessing adult GHD in India, given the BMI cut-offs vary for Asians. The study's main objective was to determine a peak GH cut-off level for the diagnosis of adult GHD in overweight (OW)/obese individuals utilizing the GST. Forty OW/obese subjects were studied in two groups of 20 each. The first group included 20 OW/obese hypopituitary adults and the second group included 20 control subjects. The intervention consisted of a 3 h GST. The main outcome measured was the peak GH level on GST. The mean age of control subjects was lower (33.15 ± 7.67 v/s. 42.10 ± 13.70 years; P = 0.017) in comparison with hypopituitary adults. The mean BMI (27.93 ± 1.63 v/s. 25.81 ± 1.66 kg/m2; P < 0.001), mean IGF1 (272.81 ± 38.57 v/s. 163.75 ± 42.42; P < 0.001, and mean HOMA IR (11.8 ± 9.7 v/s. 6.02 ± 3.14; P = 0.02) was greater in OW/obese controls. The mean GH peak was significantly higher in control subjects (5.41 ± 3.59 ng/mL v/s. 1.49 ± 1.25 ng/mL; P < 0.001) compared to hypopituitary subjects. ROC curve analysis demonstrated a GH cut-off of 3.3 ng/mL with a moderate sensitivity of 70% and high specificity of 95%, with an AUC of 0.838 (P < 0.001; 95% confidence interval [CI] of 0.710-0.965) for the diagnosis of GHD in overweight/obese hypopituitary adults. This study demonstrates that a cut-off of 3.3 ng/mL would diagnose GHD in Indian overweight/obese hypopituitary adults.

Comparison of glucagon stimulation test and low dose ACTH test in assessing hypothalamic-pituitary-adrenal (HPA) axis in children.

INTRODUCTION: Children with a pituitary hormone deficiency are at risk for secondary adrenal insufficiency (AI). A stimulation test is usually performed for diagnosing AI, evaluating both the hypothalamic-pituitary-adrenal and growth hormone (GH)-IGF-1 axes. This single test is preferred by clinicians and is considerably more tolerable by patients. The objective of this study was to evaluate the glucagon stimulation test (GST), which is commonly used to assess both axes. Its diagnostic capability for GH deficiency is high and well accepted, however its utility for determining secondary AI has not been well established. METHODS: This retrospective study involved 120 patients under 18 years of age with short stature who had undergone both a GST and low dose ACTH stimulation test (LDACTH test). Twenty-six children who had more than 6 months elapsed between the two tests were excluded from the study. The study was conducted on patients of the Pediatric Endocrinology Department at Soroka University Hospital, a tertiary medical centre in Beer Sheva, Israel. Statistical analyses were carried out via IBM SPSS (v. 22), with a significance level determined at p < .05. RESULTS: Different cortisol cut-off values were assessed for GST and it was determined that the highest combined sensitivity and specificity yielded a cut-off point of 320 nmol/L (56% sensitivity and 83% specificity) while the currently accepted cut-off value (500 nmol/L) yielded 100% sensitivity and 6% specificity. CONCLUSION: The results of this study show that GST is not an optimal tool for diagnosing secondary AI. Therefore, clinicians using this test should interpret its results with caution.

A cross-sectional study to assess beta-cell function in individuals with recently diagnosed young-onset type 2 diabetes mellitus and its’ complications / Journal of the ASEAN Federation of Endocrine Societies

Objective@#The primary objective was to assess beta-cell function of recently-diagnosed young-onset type 2 diabetes mellitus (T2DM) individuals using basal and stimulated C-peptide levels. The secondary objective was to examine the association between C-peptide with metabolic factors and diabetes complications.@*Methodology@#A cross-sectional study was conducted for young-onset T2DM individuals aged 18-35 years with a disease duration of not more than 5 years. Plasma C-peptide was measured before and after intravenous glucagon injection. Demographic data, medical history and complications were obtained from medical records and clinical assessment. Continuous data were expressed as median and interquartile range (IQR). Categorical variables were described as frequency or percentage. Multivariable linear regression analysis was used to determine factors associated with C-peptide levels.@*Results@#113 participants with young-onset T2DM with a median (IQR) age of 29.0 (9.5) years and 24 (36) months were included in this study. The median (IQR) basal and stimulated C-peptide was 619 (655) pmol/L and 1231 (1024) pmol/L. Adequate beta-cell function was present in 78-86% of the participants based on the basal and stimulated C-peptide levels. We found hypertension, obesity and diabetic kidney disease (DKD) to be independently associated with higher C–peptide levels. In contrast, females, smokers, those on insulin therapy and with longer duration of disease had lower C–peptide levels.@*Conclusion@#Most recently diagnosed young-onset T2DM have adequate beta-cell function. Elevated C-peptide levels associated with obesity, hypertension and diabetic kidney disease suggest insulin resistance as the key driving factor for complications.

Limited Role of Endogenous Vasopressin/Copeptin in Stimulation of ACTH-Cortisol Secretion during Glucagon Stimulation Test in Humans.

Copeptin is a stable part of a vasopressin precursor that closely mirrors arginine vasopressin (AVP) secretion. It is known that AVP/copeptin is also released in response to nonosmotic stimuli, such as stress evoked during anterior pituitary dynamic testing. In order to examine the role of AVP in challenging the hypothalamo-pituitary-adrenal axis, we assessed adrenocorticotropic hormone (ACTH), cortisol, copeptin and growth hormone (GH) during a glucagon stimulation test (GST) in 10 patients with satisfactory initial cortisol concentrations (mean ± SD: 20.34 ± 5.10 µg/dL) and failure to show any further cortisol increment on stimulation. For comparison, we measured copeptin in two subjects during an insulin tolerance test (ITT). During GST, there was an increase in copeptin (p = 0.02, average individual increase of 98%, range 10% to 321%). There was a robust increase in GH (p = 0.002, average increase 3300%), a decline in cortisol (p = 0.02, average decline 21.8%) and a fall in ACTH (p = 0.06). The relative increase in copeptin during ITT (176% and 52.2%) overlapped with increments observed during GST; however, here there was an increase in cortisol (20.45→24.26 µg/dL and 4.23→29.29 µg/dL, respectively). There was a moderate correlation between copeptin and GH concentrations (r = 0.4235, p = 0.0007). These results confirm that AVP is not crucial for ACTH-cortisol stimulation, though it might be an important factor in GH secretion.

Safety Assessment and Potential Risks of the Glucagon Stimulation Test in the Diagnosis of Secondary Adrenal Insufficiency.

BACKGROUND: Although it takes more time, the Glucagon Stimulation Test (GST) is a reliable measure for assessing growth hormone (GH) and Adrenocorticotropic Hormone (ACTH) secretion. The GST is considered to be a safe test; however, it still has mild side effects and potential risks. OBJECTIVES: The objective of this study was to analyze the side effects of the GST while testing adrenal-insufficient patients. METHODS: This was a prospective study in which GST was performed in eighty-one patients (44 men, 37 women, mean age: 35.83A9.62 years) with the pituitary disorder. The GST consisted of an intramuscular injection of 1 mg of glucagon. Blood samples were collected at baseline, and 30, 60, 90, 120, 150, 180, and 210 min after glucagon injection for cortisol measurements. All patients were asked to report side effects associated with this test. RESULTS: The mean peak blood glucose level under GST was 9.01A.03 mmol/L, and the mean glycemic nadir was 4.34A.75 mmol/L most frequently found during the 30th minute (p <10-3). During the test, 35 subjects (43.2%) had side effects with a mean age of 42.89 A19.75 years. Frequent side effects included: nausea (29.62%), vomiting (27.16%), abdominal cramps (18.51%) and hunger (13.58%). All patients tolerated the test until the end. Adverse effects were significantly more prevalent in patients older than 50 years (p=0.012). CONCLUSIONS: The GST is a reliable alternative to assess the hypothalamic pituitary adrenal axis but should be cautiously used especially in the elderly, despite minor side effects.

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.

Reducing adverse events associated with the glucagon stimulation test for the assessment of growth hormone deficiency in adults with a high prevalence of pituitary hormone deficiencies.

DESIGN: A retrospective review of the adverse events (AEs) in 78 patients during the glucagon stimulation test (GST) for the assessment of growth hormone deficiency (GHD) before and after protocol amendments which aimed to reduce AEs in a group of patients with a high prevalence of pituitary hormone deficiencies. PATIENTS: Based on our observations of frequent AEs during the standard GST protocol in an initial 25 patients (cohort 1), a modified protocol was introduced to include the routine administration of 20 mg of hydrocortisone pre-GST in a subsequent 53 patients (cohort 2). Post hoc analysis of the effect of glucocorticoid dosing pre-GST on AEs was examined in those receiving <20 mg hydrocortisone (group A, n = 19) vs ≥20 mg hydrocortisone (group B, n = 59). MEASUREMENTS: AEs including hypotension, hypoglycaemia and nausea/vomiting. RESULTS: Of the 78 patients undergoing the GST, 79% had ≥2 hormone deficiencies. Rates of AEs were 41% vs 30% for hypotension, 60% vs 28% for hypoglycaemia (p < .05) and 20% vs 13% for nausea/vomiting in cohort 1 compared with cohort 2, respectively. Post hoc analysis revealed lower rates of AEs in those receiving ≥20 mg hydrocortisone (group B) compared to those receiving <20 mg due to a reduction in hypoglycaemic events (82% vs 26%, p < .001) and hypotension (50% vs 27%, p = .05). Similar numbers of patients in group A and group B met criteria for GHD. CONCLUSIONS: In patients with a high prevalence of pituitary deficiencies, a modified GST protocol of additional stress dose glucocorticoid attenuated the frequency of AEs without appearing to compromise the performance of the GST.

Glucagon stimulation test to assess growth hormone status in Prader-Willi syndrome.

PURPOSE: Growth hormone deficiency (GHD) must be confirmed before starting treatment in adults with Prader-Willi syndrome (PWS). Most studies use the growth-hormone-releasing hormone plus arginine (GHRH-arginine) test. No data are available on the glucagon stimulation test (GST) in PWS. We compared the utility of fixed-dose (1 mg) GST versus GHRH-arginine test in diagnosing GHD. METHODS: Adults and late adolescents with PWS underwent both tests on separate days. In the GHRH-arginine test, GHD was defined according to body mass index. In the GST, two cutoffs were analyzed: peak GH concentration < 3 ng/mL and < 1 ng/mL. For analyses, patients were divided into two groups according to body weight (≤ 90 kg and > 90 kg). RESULTS: We analyzed 34 patients: 22 weighing ≤ 90 kg and 12 weighing > 90 kg. In patients weighing ≤ 90 kg, the two tests were concordant in 16 (72.72%) patients (k = 0.476, p = 0.009 with GST cutoff < 3 ng/mL, and k = 0.450, p = 0.035 with GST cutoff < 1 ng/mL). In patients weighing > 90 kg, the two tests were not concordant with GST cutoff < 3 ng/mL, but were concordant in 11 (91.6%) patients (k = 0.833, p = 0.003) with GST cutoff < 1 ng/mL. GH peaks on the two tests correlated (r = 0.725, p = 0.008). CONCLUSION: Fixed-dose (1 mg) GST using a peak GH cutoff of < 3 ng/mL or < 1 ng/mL promises to be useful for screening for GHD in adults and late adolescents with PWS. However, in those weighing > 90 kg, the < 1 ng/mL cutoff seems better. Larger studies are necessary to establish definitive glucagon doses and cutoffs, especially in extremely obese patients.

Glucagon stimulation test as a possible predictor of residual ß-cell function.

BACKGROUND: We aimed to investigate the significance of the C-peptide levels on a glucagon stimulation test (GST) conducted soon after diagnosis as a predictive marker for residual ß-cell function over time in Japanese children with type 1 diabetes (TD1). METHODS: We retrospectively enrolled 65 Japanese children (25 male, 40 female; age <16 years) with new-onset TD1. A GST was conducted within 1 month of diagnosis, when glucose toxicity improved. One- to 2-h postprandial serum C-peptide values were measured at 0, 3, 6, 12, 24, 36, 60, and 120 months after diagnosis. RESULTS: Receiver operating characteristic analysis showed that the cutoff values of peak serum C-peptide levels used to predict the complete destruction of ß-cells at 3, 6, and 12 months after diagnosis were all 0.20 ng/mL (area under the curve [AUC] 0.867, 95% confidence interval [CI] 0.745-0.990; AUC 0.774, 95% CI 0.634-0.914; and AUC 0.804, 95% CI 0.695-0.914, respectively); the values at 24, 36, and 60 months were 0.69 ng/mL (AUC 0.828, 95% CI 0.721-0.936), 0.60 ng/mL (AUC 0.777, 95% CI 0.636-0.918), and 0.70 ng/mL (AUC 0.848, 95% CI 0.715-0.982), respectively. On multivariate analysis, peak serum C-peptide level on a GST, diabetic ketoacidosis, age, and HbA1c level at diagnosis were associated with residual ß-cell function over time. CONCLUSIONS: Peak serum C-peptide levels on a GST conducted soon after diagnosis in Japanese children with TD1 could predict the time to decrease in postprandial serum C-peptide values to < 0.20 ng/mL.

Pembrolizumab-induced fulminant type 1 diabetes with C-peptide persistence at first referral.

SUMMARY: A 72-year-old man with no history of diabetes was referred to our department due to hyperglycemia during pembrolizumab treatment for non-small-cell lung carcinoma. His blood glucose level was 209 mg/dL, but he was not in a state of ketosis or ketoacidosis. Serum C-peptide levels persisted at first, but gradually decreased, and 18 days later, he was admitted to our hospital with diabetic ketoacidosis (DKA). The patient was diagnosed with fulminant type 1 diabetes (FT1D) induced by pembrolizumab. According to the literature, the insulin secretion capacity of a patient with type 1 diabetes (T1D) induced by anti-programmed cell death-1 (anti-PD-1) antibody is depleted in approximately 2 to 3 weeks, which is longer than that of typical FT1D. Patients with hyperglycemia and C-peptide persistence should be considered for hospitalization or frequent outpatient visits with insulin treatment because these could indicate the onset of life-threatening FT1D induced by anti-PD-1 antibodies. Based on the clinical course of this patient and the literature, we suggest monitoring anti-PD-1 antibody-related T1D. LEARNING POINTS: Immune checkpoint inhibitors, such as anti-PD-1 antibodies, are increasingly used as anticancer drugs. Anti-PD-1 antibodies can cause immune-related adverse events, including T1D. FT1D, a novel subtype of T1D, is characterized by the abrupt onset of hyperglycemia with ketoacidosis, a relatively low glycated hemoglobin level and depletion of C-peptide level at onset. In patients being treated with anti-PD-1 antibody, hyperglycemia with C-peptide level persistence should be monitored through regular blood tests. Because of C-peptide persistence and mild hyperglycemia, it is possible to miss a diagnosis of life-threatening FT1D induced by anti-PD-1 antibody. In particular, in patients who have no history of diabetes, hyperglycemia without DKA is likely to be the very beginning of anti-PD-1 antibody-induced T1D. Therefore, such patients must be considered for either hospitalization or frequent outpatient visits with insulin injections and self-monitoring of blood glucose.

Relationship between glucose variability evaluated by continuous glucose monitoring and clinical factors, including glucagon-stimulated insulin secretion in patients with type 2 diabetes.

AIMS: To evaluate the clinical factors affecting daily and day-to-day glucose variability by using continuous glucose monitoring. METHODS: We performed a cross-sectional analysis of patients with type 2 diabetes mellitus (T2DM) who underwent a glucagon stimulation test (GST) with 72 h of continuous glucose monitoring. Daily glucose variability was evaluated by mean amplitude of glycemic excursions [MAGE], percentage coefficient of variation for glucose (%CV), and day-to-day glucose variability (mean of daily differences [MODD]) by using continuous glucose monitoring. Correlations of clinical factors, including insulin secretion ability by the GST with MAGE, %CV, and MODD, were analyzed. RESULTS: In 83 T2DM with insulin therapy, age and hemoglobin A1c (HbA1c) correlated with MAGE and %CV, fasting plasma glucose with MAGE and MODD, and increment of C-peptide immunoreactivity (ΔCPR) by GST correlated inversely with MAGE, %CV, and MODD. In 126 T2DM without insulin therapy, age, diastolic blood pressure, and triglycerides correlated with MODD, HbA1c with MAGE and MODD, and ΔCPR inversely correlated with %CV. Use of α-glucosidase inhibitors inversely correlated with %CV, whereas that of sulfonylurea was associated with MAGE and %CV. CONCLUSIONS: These results suggest that ΔCPR correlated with stability of glycemic control, whereas poorly controlled diabetes is associated with increase in glucose variability. α-glucosidase inhibitors may be superior to sulfonylureas in reducing the glucose variability in T2DM.

C-Peptide Area Under the Curve at Glucagon Stimulation Test Predicts Glucose Improvements by GLP-1 Receptor Analogue: A Retrospective Observational Study.

INTRODUCTION: Despite the widespread use of glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1ras) to improve glycemic regulation, with a low risk of hypoglycemia and weight reduction, their effectiveness varies among individuals. This study aimed to identify predictors of the efficacy of GLP-1ra on Hemoglobin A1c (HbA1c) in patients with insulin-independent diabetes. METHODS: In total, 58 patients with insulin-independent diabetes were included. Patients were included if their ß-cell function was evaluated via a glucagon stimulation test (GST) before the introduction of GLP-1ra therapy. ß-Cell function-related indices, such as the C-peptide index (CPI), increments in C-peptide immunoreactivity (CPR) after glucagon stimulation (ΔCPR), and the area under the CPR curve (CPR-AUC) during the GST, were evaluated. HbA1c and body weight (BW) were measured at 6 and 12 months after the initiation of GLP-1ra. RESULTS: A univariate regression analysis revealed a significant correlation between CPR-AUC and changes in HbA1c at 6 months and with changes in BW at 6 and 12 months. A multivariate regression analysis revealed that CPR-AUC was significantly correlated with changes in HbA1c at 6 months. A receiver-operating characteristic analysis revealed that 21.9 ng/ml·min CPR-AUC was the optimal cut-off value to predict an HbA1c level < 7%, i.e., 53 mmol/mol. CONCLUSION: Residual ß-cell function, as assessed via CPR-AUC in the GST, is an effective predictor of the efficacy of GLP-1ras.

Capturing residual beta cell function in type 1 diabetes.

Since the 1970s, C-peptide has been used as a surrogate marker for monitoring the progression of type 1 and type 2 diabetes and to determine the effects of interventions designed to preserve or improve residual beta cell function. C-peptide measurement is a well-established surrogate of residual beta cell activity and of clinical significance as it is associated with HbA1c, risk for microvascular complications and the incidence of hyperglycaemia in longitudinal studies. Measurement of C-peptide after a mixed meal tolerance test is considered the gold standard of measuring beta cell function in type 1 diabetes, but the method is laborious and inconvenient. In this issue of Diabetologia, Wentworth et al ( https://doi.org/10.1007/s00125-018-4722-z ) report an algorithm for estimating C-peptide (CPEST) based on six routine clinical measures. These do not include stimulated C-peptide measurement and outperform other prevailing algorithms for estimating residual beta cell function. Going forward it is very likely that this new algorithm will serve as a simple measure of beta cell function in routine practice and as a more acceptable primary outcome measure in future trials of disease-modifying therapies.

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.

Normal meal tolerance test is preferable to the glucagon stimulation test in patients with type 2 diabetes that are not in a hyperglycemic state: Comparison with the change of C-peptide immunoreactivity.

AIMS/INTRODUCTION: The aim of the present study was to evaluate the properties of the glucagon stimulation test (GST) and the normal meal tolerance test (NMTT) in patients with type 2 diabetes. MATERIALS AND METHODS: We enrolled 142 patients with type 2 diabetes, and carried out a GST and a NMTT. We carried out the NMTT using a calorie-controlled meal based on an intake of 30 kcal/kg ideal bodyweight/day. We calculated the change in C-peptide immunoreactivity (ΔCPR) by subtracting fasting CPR from the CPR 6 min after the 1-mg glucagon injection (GST) or 120 min after the meal (NMTT). RESULTS: Mean ΔCPR for the GST was 2.0 ng/mL, and for the NMTT was 3.1 ng/mL. A total of 104 patients had greater ΔCPR in the NMTT than the GST, and the mean ΔCPR was significantly greater in the NMTT than the GST (P < 0.05). To exclude any influence of antidiabetic drugs, we examined 42 individuals not taking antidiabetic agents, and found the mean ΔCPR was significantly greater in the NMTT than the GST (GST 2.4 ng/mL, NMTT 4.3 ng/mL; P < 0.05). To consider the influence of glucose toxicity, we carried out receiver operating characteristic analyses with fasting plasma glucose and glycated hemoglobin. The optimal cut-off levels predicting GST ΔCPR to be larger than NMTT ΔCPR were fasting plasma glucose 147 mg/dL and glycated hemoglobin 9.0% (fasting plasma glucose: sensitivity 0.64, specificity 0.76, area under the curve 0.73; glycated hemoglobin: sensitivity 0.56, specificity 0.71, area under the curve 0.66). CONCLUSIONS: The NMTT is a reliable insulin secretion test in patients with type 2 diabetes, except for those in a hyperglycemic state.

An update on the diagnosis of growth hormone deficiency.

Growth hormone deficiency (GHD) is an endocrine disorder, which may be either isolated or associated with other pituitary hormone deficiencies. In children, short stature is a useful clinical marker for GHD. In contrast, symptomatology is not always so obvious in adults, and the existing methods of testing might be inaccurate and imprecise, especially in the lack of a suggestive clinical profile. Since the quality of life of patients diagnosed with GHD could also be significantly affected, in both children and adults, a correct and accurate diagnosis is therefore tremendously important to select those patients that can benefit from the GH treatment. In general, the endocrine diseases are challenging in terms of diagnosis, the simple measurement of the basal level of hormones is not sufficient for distinguishing between the physiological and pathological conditions. Traditionally, several stimulation tests have been considered by professional clinical guidelines, such as insulin tolerance test (ITT), GHRH-arginine stimulation test and the glucagon stimulation test, and all of them have both advantages and limitations. More recently (December 2017), FDA approved a growth hormone secretagogue receptor agonist, macimorelin, for the diagnosis of adults with GHD. The obvious advantage for macimorelin is the simple oral administration and the high level of agreement with the insulin tolerance test for those patients with organic disease and low levels of insulin-like growth factor (IGF-I). However, the safety profile and the diagnostic value was not yet established for the pediatric population and for those adults with extreme or morbid obesity. In addition, administration of macimorelin with drugs that prolong QT interval and CYP3A4 inducers should be avoided. Genetic screening could obviously bring a great insight in the GHD pathology. However, it remains an open question if it would be also cost effective to include it in the routine evaluation of the patients with GHD. Although major progresses have been made in this area, genetic testing continues to be difficult to access, mostly because of its high costs, especially in the low-income and middle-income countries.

Assessing the adrenal axis by the glucagon stimulation test in children with idiopathic growth hormone deficiency.

Approximately 30% of children with idiopathic growth hormone deficiency (IGHD) also suffer from other pituitary hormone deficien-cies. Of children with IGHD, approximately 10% are unable to generate appropriate ACTH levels in response to stress. This study was prospectively designed to test the integrity of the adrenal axis in patients with an established diagnosis of IGHD using the glucagon stimulation test (GST). The study population comprised 39 patients with established childhood-onset IGHD. The diagnosis of GHD was established on the basis of failure of GH to increase over 10 ng/ml after two stimulation tests. The GST was performed by intra-muscular injection of 1 mg glucagon. The criteria followed to define adrenal deficiency was cortisol less than 167 ng/l in response to GST. The mean peak blood glucose level was 8.64 ±1.71 mmol/l. Analysing the cohort using the cut-off of 167 ng/ml to define adrenal insufficiency under GST, there were 25.64% of children diagnosed: 20% among males and 35.7% among females. Subjects with GH and ACTH deficiency had a mean peak GH of 2.07 ±1.79 ng/ml - significantly lower than GH peak of children with IGHD alone (p < 0,001). The frequency of children with combined somatotroph and corticotroph deficiencies with a GH peak < 3 ng/ml was 21% (p < 0,001). The current study identified a prevalence of adrenal insufficiency of 25.64%, which could predict greater risk for children if untreated, especially because a substantial proportion of patients do not present clinical symptoms.