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.

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 as a possible predictor of residual β-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 β-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 β-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 β-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.

Effect of GLP-1 and GIP on C-peptide secretion after glucagon or mixed meal tests: Significance in assessing B-cell function in diabetes

BACKGROUND

The aim of the study was to investigate the different B-cell responses after a glucagon stimulation test (GST) versus mixed meal tolerance test (MMTT).

METHODS

We conducted GST and MMTT in 10 healthy people (aged 25-40 years) and measured C-peptide, gastric inhibitory peptide (GIP) and glucagon-like peptide-1 (GLP-1) at different time points after the administration of 1 mg i.v. glucagon for GST or a liquid mixed meal for MMTT.

RESULTS

The GST stimulated C-peptide showed a mean increase of 147.1%, whereas the mean increase of MMTT stimulated C-peptide was 99.82% (Δincrease = 47.2%). Maximum C-peptide level reached with the MMTT was greater than that obtained with the GST (C-pept max MMTT = 2.35 nmol/L vs C-pep max GST = 1.9 nmol/L). A positive and linear correlation was found between the GST incremental area under the curve C-peptide and the MMTT incremental area under the curve C-peptide (r = 0.618, P = .05). After GST, there was no increment of GIP and glucagon like peptide-1 levels compared to baseline levels. A positive and linear correlation between GIP and C-peptide levels was observed only for the MMTT (r = 0.922, P = .008) indicating that in the GST, the C-peptide response is independent of the incretin axis response.

CONCLUSIONS

Although the 2 stimulation tests may elicit a similar response in C-peptide secretion, B-cell response to MMTT depends on a functionally normal incretin axis. These results may have implications when investigating the B-cell response in people with diabetes and for studies in which stimulated C-peptide secretion is used as primary or secondary outcome for response to therapy.

Central Adrenal Insufficiency Is Not a Common Feature in CHARGE Syndrome: A Cross-Sectional Study in 2 Cohorts

OBJECTIVE

To evaluate whether central adrenal insufficiency (CAI) is present in CHARGE (Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital hypoplasia, and Ear abnormalities, including deafness) syndrome, a complex malformation disorder that includes central endocrine dysfunction.

STUDY DESIGN

Two cross-sectional studies were performed in Dutch (September 2013-February 2015) and Australian (January 2012-January 2014) CHARGE syndrome clinics. Twenty-seven Dutch and 19 Australian patients (aged 16 months-18 years) with genetically confirmed CHARGE syndrome were included. The low-dose adrenocorticotropin (ACTH) test was used to assess CAI in the Dutch cohort. A peak cortisol response less than 18.1 μg/dL (500 nmol/L) was suspected for CAI, and a glucagon stimulation test was performed for confirmation. Australian patients were screened by single measurements of ACTH and cortisol levels. If adrenal dysfunction was suspected, a standard-dose ACTH test was performed.

RESULTS

The low-dose ACTH test was performed in 23 patients (median age 8.4 [1.9-16.9] years). Seven patients showed an insufficient maximum cortisol level (10.3-17.6 μg/dL, 285-485 nmol/L), but CAI was confirmed by glucagon stimulation test in only 1 patient (maximum cortisol level 15.0 μg/dL, 415 nmol/L). In the Australian cohort, 15 patients (median age 9.1 [1.3-17.8] years) were screened, and none had CAI.

CONCLUSIONS

CAI was not common in our cohorts, and routine testing of adrenal function in children with CHARGE syndrome is not indicated.