The glucagon test in the diagnosis of growth hormone deficiency in children with short stature younger than 6 years

Combined growth hormone stimulation testing: Could the tests be shortened?

INTRODUCTION

Growth hormone stimulation tests (GHST) remain the cornerstone for diagnosing growth hormone deficiency (GHD), yet they can be lengthy and costly. We aimed to examine whether the combined clonidine and glucagon stimulation test (CGST) and l-dopa and glucagon stimulation test (LDGST) can be shortened without compromising the test's specificity.

MATERIAL AND METHODS

We retrospectively analyzed the baseline characteristics, auxological and laboratory data of children with short stature who had undergone a CGST and an LDGST for GHD. We compared the diagnostic accuracy for the standard test and shortened test, eliminating time points of 0 and 210 min.

RESULTS

We reviewed 830 charts (8.17 ± 2.92 years old; 56.27% males), with 431 (57.0%) children in the CGST group, and 38 (51.35%) in the LDGST group who tested negative for GHD. The peak and maximum GH levels occurred at the 60-min time point for both the CGST and LDGST. Eliminating the 0-min time point was the only time that did not affect the specificity of the CGST, with a false-positive rate of 2 (2.99%), specificity of 0.99 (0.99-0.99), and p value of 0.25. Eliminating the 0- and 210-min time points did not affect the specificity of the LDGST, with a false-positive rate of 2 (5.26%), specificity of 0.95 (0.95-0.95), and p value of 0.24.

CONCLUSIONS

We concluded that 0-min time point could be eliminated without compromising the combined GHST diagnostic value, thus resulting in cost reduction. Larger studies are needed for the combined LDGST to explore whether the 30- and 210-min time points could be eliminated, thus resulting in cost and time savings.

Diagnosis of Growth Hormone Deficiency in Children: The Efficacy of Glucagon versus Clonidine Stimulation Test

INTRODUCTION

The diagnosis of childhood growth hormone deficiency (GHD) requires a failure to respond to 2 GH stimulation tests (GHSTs) performed with different stimuli. The most commonly used tests are glucagon stimulation test (GST) and clonidine stimulation test (CST). This study assesses and compares GST and CST's diagnostic efficacy for the initial evaluation of short children.

METHODS

Retrospective, single-center, observational study of 512 short children who underwent GHST with GST first or CST first and a confirmatory test with the opposite stimulus in cases of initial GH peak <7.5 ng/mL during 2015-2018. The primary outcome measure was the efficacy of the GST first or CST first in diagnosing GHD.

RESULTS

Population characteristics include median age of 9.3 years (interquartile range 6.2, 12.1), 78.3% prepubertal, and 61% boys. Subnormal GH response in the initial test was recorded in 204 (39.8%) children: 148 (45.5%) in GST first and 56 (30%) in CST first, p < 0.001. Confirmatory tests verified GHD in 75/512 (14.6%) patients. Divergent results between the initial and confirmatory tests were more prevalent in GST first than CST first (103/148 [69.6%] vs. 26/56 [46.4%], p < 0.001) indicating a significantly lower error rate for the CST first compared to the GST first. In multivariate analysis, the only significant predictive variable for divergent results between the tests was the type of stimulation test (OR = 0.349 [95% CI 0.217, 0.562], p < 0.001).

CONCLUSIONS

Screening of GH status with CST first is more efficient than that with GST first in diagnosing GHD in short children with suspected GHD. It is suggested that performing CST first may reduce the need for a second provocative test and avoid patients' inconvenience of undergoing 2 serial tests.

Advances in differential diagnosis and management of growth hormone deficiency in children

Growth hormone (GH) deficiency (GHD) in children is defined as impaired production of GH by the pituitary gland that results in growth failure. This disease might be congenital or acquired, and occurs in isolation or in the setting of multiple pituitary hormone deficiency. Isolated GHD has an estimated prevalence of 1 patient per 4000-10,000 live births and can be due to multiple causes, some of which are yet to be determined. Establishing the correct diagnosis remains key in children with short stature, as initiating treatment with recombinant human GH can help them attain their genetically determined adult height. During the past two decades, our understanding of the benefits of continuing GH therapy throughout the transition period from childhood to adulthood has increased. Improvements in transitional care will help alleviate the consequent physical and psychological problems that can arise from adult GHD, although the consequences of a lack of hormone replacement are less severe in adults than in children. In this Review, we discuss the differential diagnosis in children with GHD, including details of clinical presentation, neuroimaging and genetic testing. Furthermore, we highlight advances and issues in the management of GHD, including details of transitional care.

Look Beyond Gluten in Short Stature with Celiac Disease - A Prospective, Interventional Study

OBJECTIVE

Short stature (SS) is a common manifestation of celiac disease (CD). After starting gluten free diet (GFD), children usually have catch-up growth (improvement in height SDS of >1 SD). However, few children in remission, even on GFD, lack catch up growth. This study was planned to assess the growth hormone (GH) axis and the prevalence of anti-pituitary antibodies in such patients.

METHODS

It was a single-centre, prospective study. Patients with CD in remission for the last 1 y, having SS and lacking catch-up growth, were included after excluding other common causes of SS. GH dynamics were studied using stimulation tests: Insulin tolerance test, clonidine stimulation test, and glucagon stimulation test. GH deficiency (GHD) was defined as non-stimulable response to 2 GH stimulation tests. Anti-pituitary antibodies were analysed in these patients using rat pituitary extract as antigen.

RESULTS

Ten patients (8 girls), with a mean age of 10 ± 2.8 y, in serological remission for CD and lacking catch-up growth, were enrolled. All had a height SDS of < -2. Fifteen age matched children with CD and adequate catch up growth served as controls. GHD was seen in 7 patients (70%), out of whom 2 received GH therapy and had an improvement in the height SDS from -2.7 to -1.4 and from -2.1 to 2.4 (over 1 y), respectively. Anti-pituitary antibodies were seen in significant titres in 55.5% of the cases and 40% of the controls.

CONCLUSIONS

Children with CD in remission but lacking catch-up growth should be evaluated for GHD.

Prevalence of brain MRI findings in children with nonacquired growth hormone deficiency: a systematic review and meta-analysis

PURPOSE

To verify and integrate the prevalence and phenotype of abnormalities in the sellar region in patients with growth hormone deficiency (GHD) using MRI data.

METHODS

We searched PubMed and EMBASE up to December 14, 2020. The inclusion criteria were as follows: (1) pediatric patients diagnosed with nonacquired GHD and (2) detailed data sufficient to assess the proportion of sellar and parasellar abnormalities on brain MRI scans. Finally, thirty-two studies with 39,060 children (mean or median age, 3.4-14.1 years) were included. The number and type of MRI findings from all included studies were pooled by two authors. The heterogeneity across studies was evaluated with the Q test or the inconsistency index (I²) statistic. Subgroup analyses were performed according to the type of GHD (isolated GHD [IGHD] vs. multiple pituitary hormone deficiency [MPHD]), MRI magnet, geographical region, and cutoff serum growth hormone (GH) level.

RESULTS

The pooled proportion of sellar and parasellar abnormalities was 58.0% (95% CI, 47.1-68.6%; I², 98.2%). The MPHD group showed a higher proportion of sellar and parasellar abnormalities and pituitary stalk interruption syndrome than the IGHD group (91.4% vs. 40.1%, P<0.001; 65.3% vs. 20.1%, P<0.001). The patients in studies with low peak GH levels on stimulation tests were more associated with severe MR abnormalities (cutoff GH ≤ 5 μg/l vs. cutoff GH = 10 μg/l; 72.8 % vs. 38.0%; P<0.001).

CONCLUSION

The types and incidence of MRI abnormalities of the sellar region differ significantly between the IGHD and MPHD groups.

[Comparative study of glucagon and insulin tests for diagnostics of secondary adrenal insufficiency and growth hormone deficiency in children and adolescents]

BACKGROUND

Diagnostics of growth hormone deficiency (GHD) and secondary adrenal insufficiency (SAI) is based on estimation of peak GH and cortisol concentrations in provocation tests. Russian consensus on diagnostics and treatment of hypopituitarism in children and adolescences recommends to measure GH and cortisol concentrations in every time-point of insulin test (IT). Glucagon test (GT) is discussed in literature as alternative to IT.

AIMS

To estimate the possibility to use provocation GT for diagnostics of SAI and GHD in children and adolescents.

MATERIALS AND METHODS

We investigated blood and urine cortisol levels, IT, and GT in 20 patients 6.5-17.8 years (Me 13.0 (10.4; 15.3)) after surgery and/or radiology and/or chemical therapy of head and neck tumors; remission for 0.4-7.5 years (Ме 2.1 (1.5; 5.2)).

RESULTS

With cut-off point 550 nmol/L sensitivity and specifity of IT was 100% and 60%, GT - 100% and 53% respectively. Minimal cortisol cut-off level for GT with sensitivity 100% was 500 nmol/L, maximal with specifity 100% - 400 nmol/L.Early morning cortisol levels did not exceed 250 nmol/l in 2 patients with SAI; and were above 500 nmol/l in 8 patients without SAI while primary or repeated examination.GHD was reviled by IT in all patients. Maximal GH concentrations in GT and IT did not differ significantly (p&gt;0.05) but GT results of 4 patients exceeded or met cut-off for this test (7 ng/ml).GT was characterized by less severity compared with IT.

CONCLUSIONS

For diagnostics of SAI by GT we can advise cut-off points of cortisol level 500 (sensitivity 100%, specifty 53%) and 400 nmol/L (sensitivity 80%, specifity 100%). Measuring of cortisol levels in 2-3 early morning blood samples allows to exclude or to suspect SAI in half of patients before tests. GH peaks in GT can exceed similarly data in IT that needs future investigation.

The inter - Test variability of growth hormone stimulation tests and factors affecting this variability

OBJECTIVE

To evaluate the variability of growth hormone stimulation tests results and factors affecting it in short children suspected of having growth hormone deficiency.

DESIGN

The cohort included patients with short stature suspected of having growth hormone deficiency, and who underwent a second stimulation test, after the first stimulation test was positive. Testing was done at a single center from May 2014 to October 2017. Patients' weight, height, age, sex, stimulating agents and test results were recorded.

RESULTS

The study population comprised 200 patients, 108 males and 92 females, average age 9.2 years (2.2-16.6 years). The average peak growth hormone was 5.2 μg/L and 7.8 μg/L in the first and second tests respectively and the concordance rate was 56.5%. The probability of a second positive test was increased if the peak growth hormone level in the first test was below 5 μg/L. In the second test, Clonidine and Glucagon led to higher peak growth levels than Arginine with averages of 9.02, 9.97 and 6.88 μg/L respectively. Younger children and children with higher BMI SDS only had lower peaks of growth hormone in the second test. The effect of height SDS on peak growth hormone levels was equivocal.

CONCLUSION

The reproducibility rate of GH simulation tests in our study was low. A few factors may affect the peak levels of growth hormone in the second test, the most prominent being the peak of growth hormone in the first test.

Deciphering short stature in children

Short stature is a common reason for referral to pediatric endocrinologists. Multiple factors, including genetic, prenatal, postnatal, and local environmental factors, can impair growth. The majority of children with short stature, which can be defined as a height less than 2 standard deviation score below the mean, are healthy. However, in some cases, they may have an underlying relevant disease; thus, the aim of clinical evaluation is to identify the subset of children with pathologic conditions, for example growth hormone deficiency or other hormonal abnormalities, Turner syndrome, inflammatory bowel disease, or celiac disease. Prompt identification and management of these children can prevent excessive short stature in adulthood. In addition, a thorough clinical assessment may allow evaluation of the severity of short stature and likely growth trajectory to identify the most effective interventions. Consequently, appropriate diagnosis of short stature should be performed as early as possible and personalized treatment should be started in a timely manner. An increase in knowledge and widespread availability of genetic and epigenetic testing in clinical practice in recent years has empowered the diagnostic process and appropriate treatment for short stature. Furthermore, novel treatment approaches that can be used both as diagnostic tools and as therapeutic agents have been developed. This article reviews the diagnostic approach to children with short stature, discusses the main causes of short stature in children, and reports current therapeutic approaches and possible future treatments.

Cortisol Levels in Glucagon Stimulation Test in Children Assessed for Short Stature: Clinical and Laboratorial Correlations

To assess total cortisol levels in children being evaluating for short stature with normal cortisol reserve and to correlate this response to clinical and laboratory data. Children assessed with glucagon test in our department were recruited in this study retrospectively. Inclusion criteria were: i) age>1 year, ii) absence of chronic illness or medication interfering with ACTH-cortisol axis, iii) GH stimulation levels>3ng/mL at least in one provocation test (glucagon or clonidine), iv) absence of multiple pituitary growth hormone deficiencies, v) normal short Synacthen test in cases of low cortisol response in glucagon test.Two hundred and thirty-seven subjects (160 males, 67.5%) with a mean age of 9.02±3.19 years, were finally included in the analysis. Cortisol peak levels but not cortisol AUC were significantly increased in females compared to males (26.83±7.31 μg/dl vs. 24.04±7.20 μg/dl). When linear correlations were studied, both cortisol peak levels and cortisol AUC were linearly but inversely correlated to age (r=-0.234, p<0.001 and r=-0.315, p<0.001, respectively). Finally, cortisol AUC was inversely correlated to weight Z-scores (r=-0.160, p=0.014). When our analysis was limited only to subjects with intact GH response (GH peak> 7 ng/mL), age was still inversely correlated to cortisol AUC (r=-0.312, p<0.001), and cortisol AUC was linearly correlated to GH AUC assessed with clonidine test (r=0.223, p=0.013). Girls, younger and thinner children exhibit higher cortisol response to glucagon test.

TIMING OF GH PEAK IN BOTH GLUCAGON AND CLONIDINE TESTS IS OF MAJOR CLINICAL IMPORTANCE

Objective: To detect a possible correlation between timing of the peak value of growth hormone (GH) during stimulatory tests (STs) and the effectiveness of treatment with recombinant human growth hormone (rhGH) in children with idiopathic GH deficiency (iGHD). Methods: We retrospectively studied 92 patients with iGHD (57 boys; mean age at diagnosis: 9.93 years). Diagnosis was confirmed by 2 different STs, glucagon stimulation test (GST), and clonidine stimulation test (CST). Auxologic parameters were recorded, while observed and predicted (according to KIGS Prediction Model) height velocity during the first year of treatment and the index of responsiveness (IoR) were calculated for the prepubertal children (n = 65). Results: Atypical GST was defined as that with peak GH value at time 0 minutes, 30 minutes, 60 minutes, or 180 minutes, whereas atypical CST was defined as that with peak timing at 0 minutes, 30 minutes, or 120 minutes. Atypical GST was detected in 18 patients (19.57%). IoR was lower in the prepubertal children with atypical GST (-1.81 ± 0.67 versus -1.34 ± 0.85; P = .051). In the CST, the 18 children who had atypical timing, had significantly lower IoR (-1.86 ± 0.66 versus -1.35 ± 0.84; P = .047). When the patients were categorized according to the number of atypical tests, significant differences in the IoR were detected (-2.09 ± 0.68 with 2 atypical STs [n = 6], -1.64 ± 0.61 with 1 atypical ST [n = 16], and -1.29 ± 0.87 with no atypical ST [n = 43], P = .045). Conclusion: The presence of atypical peak GH timing during ST may be a factor that predicts lower growth hormone velocity during the first year of rhGH treatment in prepubertal children with iGHD. Abbreviations: CST = clonidine stimulation test; GH = growth hormone; GHD = growth hormone deficiency; GST = glucagon stimulation test; iGHD = idiopathic growth hormone deficiency; IoR = index of responsiveness; rhGH = recombinant human growth hormone; SDS = standard deviation scores; ST = stimulatory test.

Growth hormone therapy in children; research and practice - A review

Short stature remains the most common reason for referral to a pediatric Endocrinologist and its management remains a challenge. One of the main controversies is the diagnosis of idiopathic short stature and the role of new technologies for genetic investigation of children with inadequate growth. Complexities in management of children with short stature includes selection of who should receive interventions such as recombinant human growth hormone, and how should this agent dose be adjusted during treatment. Should anthropometrical data be the primary determinant or should biochemical and genetic data be used to improve growth response and safety? Furthermore, what is considered a suboptimal response to growth hormone therapy and how should this be managed? Treatment of children with short stature remains a "hot" topic and more data is needed in several areas. These issues are reviewed in this paper.

Diagnosis of GH Deficiency as a Late Effect of Radiotherapy in Survivors of Childhood Cancers

BACKGROUND

Limited guidance exists for selecting a laboratory method for diagnosing GH deficiency (GHD) when it occurs as a late effect of radiotherapy in childhood cancer survivors (CCSs).

METHODS

We searched Medline, Embase, Cochrane Central Register of Controlled Trials and Database of Systematic Reviews, and Scopus for studies evaluating GHD that used IGF-1 or IGF-binding protein 3 (IGFBP-3) measurements compared with GH dynamic testing.

RESULTS

We included 15 studies [IGF-1 (8 studies) and IGFBP-3 (7 studies)] enrolling 477 patients. Comparator tests varied widely. Overall, both IGF-1 and IGFBP-3 had suboptimal diagnostic accuracy but were strongly correlated. The use of both tests simultaneously in the same cohort did not improve the diagnostic accuracy. Despite high variability in the testing protocols, dynamic tests remained the most accurate for appropriately identifying patients with GHD. The insulin tolerance test (ITT) appears to be the most accepted reference test when used alone or in combination with arginine; however, standardized testing strategies among practice groups are absent. GHRH and arginine stimulation performed almost similarly to the ITT; however, in one study GHRH with arginine stimulation had 66% sensitivity and 88% specificity compared with the ITT. Insufficient data were available to assess the accuracy of serial GH testing (nocturnal or over 24 hours).

CONCLUSION

The diagnostic accuracy of various dynamic tests for GHD in CCSs appears to follow the same patterns as those in non-CCSs. Interpreting GHRH stimulation is a challenge given the primarily hypothalamic dysfunction in CCSs. IGF-1 and IGFBP-3 perform poorly in this population.

Biomarkers of GH action in children and adults

Growth hormone (GH) and IGF-I levels in serum are used as biomarkers in the diagnosis and management of GH-related disorders but have not been subject to structured validation. Auxological parameters in children and changes in body composition in adults, as well as metabolic parameters and patient related outcomes are used as clinical and surrogate endpoints. New treatment options, such as long acting GH and GH antagonists, require reevaluation of the currently used biochemical biomarkers. This article will review biomarkers, surrogate endpoints and clinical endpoints related to GH treatment in children and adults as well as in acromegaly.

The growth hormone-insulin-like growth factor-I axis in the diagnosis and treatment of growth disorders

The growth hormone (GH)-insulin-like growth factor (IGF)-I axis is a key endocrine mechanism regulating linear growth in children. While paediatricians have a good knowledge of GH secretion and assessment, understanding and use of measurements of the components of the IGF system are less current in clinical practice. The physiological function of this axis is to increase the anabolic cellular processes of protein synthesis and mitosis, and reduction of apoptosis, with each being regulated in the appropriate target tissue. Measurement of serum IGF-I and IGF-binding protein (IGFBP)-3 concentrations can complement assessment of GH status in the investigation of short stature and contribute to prediction of growth response during GH therapy. IGF-I monitoring during GH therapy also informs the clinician about adherence and provides a safety reference to avoid over-dosing during long-term management.

SERUM FREE CORTISOL DURING GLUCAGON STIMULATION TEST IN HEALTHY SHORT-STATURED CHILDREN AND ADOLESCENTS

OBJECTIVE

The total cortisol (TC) response may be measured during the glucagon stimulation test (GST) for growth hormone (GH) reserve in order to assess the integrity of the hypothalamic-pituitary-adrenal (HPA) axis. Measurements of TC are unreliable in conditions of albumin and cortisol-binding globulin (CBG) alterations (e.g., hypoproteinemia or CBG deficiency). We aimed to measure the serum free cortisol (sFC) response to the GST in children and adolescents and determine whether it could predict the GH response to glucagon stimulation.

METHODS

Infants and children with either short stature or growth attenuation who were referred for evaluation of GH reserve underwent the GST.

RESULTS

The study population consisted of 103 subjects (62 females), median age 3.9 years (range, 0.5-14). The mean basal and peak TC levels were 13.3 ± 6.7 μg/dL and 29.6 ± 8.8 μg/dL, respectively. The mean basal and peak sFC levels were 0.7 ± 0.8 μg/dL and 1.7 ± 1.1 μg/dL, respectively. There was a negative correlation between peak TC and age ( r = -0.3, P = .007) but not between peak sFC and age ( r = -0.09, P = .36). Ninety-five percent of the patients had peak TC levels >15.8 μg/dL and peak sFC levels >0.6 μg/dL.

CONCLUSION

Our results on a cohort of healthy short-statured children can serve as reference values for the sFC response during GST. Based on these results, we propose peak TC levels >15.8 μg/dL and peak sFC levels >0.6 μg/dL for defining normalcy of the HPA axis during the GST in children and adolescents.

ABBREVIATIONS

ACTH = adrenocorticotrophic hormone BMI = body mass index CBG = cortisol-binding globulin GH = growth hormone GST = glucagon stimulation test HPA = hypothalamic-pituitary-adrenal SDS = standard deviation score sFC = serum free cortisol TC = total cortisol.

Glucagon Decreases IGF-1 Bioactivity in Humans, Independently of Insulin, by Modulating Its Binding Proteins

CONTEXT

Depending on its lipolytic activity, glucagon plays a promising role in obesity treatment. Glucagon-induced growth hormone (GH) release can promote its effect on lipid metabolism, although the underlying mechanisms have not been well-defined.

OBJECTIVE

The present study highlights the glucagon effect on the GH/insulinlike growth factor 1 (IGF-1)/IGF-binding protein (IGFBP) axis in vivo and in vitro, taking into consideration insulin as a confounding factor.

MATERIALS AND METHODS

In a double-blind, placebo-controlled study, we investigated changes in GH, IGFBP, and IGF-1 bioactivity after intramuscular glucagon administration in 13 lean controls, 11 obese participants, and 13 patients with type 1 diabetes mellitus (T1DM). The effect of glucagon on the transcription factor forkhead box protein O1 (FOXO1) translocation, the transcription of GH/IGF-1 system members, and phosphorylation of protein kinase B (Akt) was further investigated in vitro.

RESULTS

Despite unchanged total IGF-1 and IGFBP-3 levels, glucagon decreased IGF-1 bioactivity in all study groups by increasing IGFBP-1 and IGFBP-2. The reduction in IGF-1 bioactivity occurred before the glucagon-induced surge in GH. In contrast to the transient increase in circulating insulin in obese and lean participants, no change was observed in those with T1DM. In vitro, glucagon dose dependently induced a substantial nuclear translocation of FOXO1 in human osteosarcoma cells and tended to increase IGFBP-1 and IGFBP-2 gene expression in mouse primary hepatocytes, despite absent Akt phosphorylation.

CONCLUSIONS

Our data point to the glucagon-induced decrease in bioactive IGF-1 levels as a mechanism through which glucagon induces GH secretion. This insulin-independent reduction is related to increased IGFBP-1 and IGFBP-2 levels, which are most likely mediated via activation of the FOXO/mTOR (mechanistic target of rapamycin) pathway.

Short Stature Diagnosis and Referral

The "360° GH in Europe" meeting, which examined various aspects of GH diseases, was held in Lisbon, Portugal, in June 2016. The Merck KGaA (Germany) funded meeting comprised three sessions entitled "Short Stature Diagnosis and Referral," "Optimizing Patient Management," and "Managing Transition." Each session had three speaker presentations, followed by a discussion period, and is reported as a manuscript, authored by the speakers. The first session examined current processes of diagnosis and referral by endocrine specialists for pediatric patients with short stature. Requirements for referral vary widely, by country and by patient characteristics such as age. A balance must be made to ensure eligible patients get referred while healthcare systems are not over-burdened by excessive referrals. Late referral and diagnosis of non-GH deficiency conditions can result in increased morbidity and mortality. The consequent delays in making a diagnosis may compromise the effectiveness of GH treatment. Algorithms for growth monitoring and evaluation of skeletal disproportions can improve identification of non-GH deficiency conditions. Performance and validation of guidelines for diagnosis of GH deficiency have not been sufficiently tested. Provocative tests for investigation of GH deficiency remain equivocal, with insufficient information on variations due to patient characteristics, and cutoff values for definition differ not only by country but also by the assay used. When referring and diagnosing causes of short stature in pediatric patients, clinicians need to rely on many factors, but the most essential is clinical experience.

Classical and non-classical causes of GH deficiency in the paediatric age

Growth hormone deficiency (GHD) may result from a failure of hypothalamic GHRH production or release, from congenital disorders of pituitary development, or from central nervous system insults including tumors, surgery, trauma, radiation or infiltration from inflammatory diseases. Idiopathic, isolated GHD is the most common sporadic form of hypopituitarism. GHD may also occur in combination with other pituitary hormone deficiencies, and is often referred to as hypopituitarism, combined pituitary hormone deficiency (CPHD), multiple pituitary hormone deficiency (MPHD) or panhypopituitarism. Children without any identifiable cause of their GHD are commonly labeled as having idiopathic hypopituitarism. MRI imaging is the technique of choice in the diagnosis of children with hypopituitarism. Marked differences in MRI pituitary gland morphology suggest different etiologies of GHD and different prognoses. Pituitary stalk agenesis and ectopic posterior pituitary (EPP) are specific markers of permanent GHD, and patients with these MRI findings show a different clinical and endocrine outcome compared to those with normal pituitary anatomy or hypoplastic pituitary alone. Furthermore, the classic triad of ectopic posterior pituitary gland, pituitary stalk hypoplasia/agenesis, and anterior pituitary gland hypoplasia is generally associated with permanent GHD. T2 DRIVE images aid in the identification of pituitary stalk without the use of contrast medium administration. Future developments in imaging techniques will undoubtedly reveal additional insights. Mutations in a number of genes encoding transcription factors - such as HESX1, SOX2, SOX3, LHX3, LHX4, PROP1, POU1F1, PITX, GLI3, GLI2, OTX2, ARNT2, IGSF1, FGF8, FGFR1, PROKR2, PROK2, CHD7, WDR11, NFKB2, PAX6, TCF7L1, IFT72, GPR161 and CDON - have been associated with pituitary dysfunction and abnormal pituitary gland development; the correlation of genetic mutations to endocrine and MRI phenotypes has improved our knowledge of pituitary development and management of patients with hypopituitarism, both in terms of possible genetic counseling, and of early diagnosis of evolving anterior pituitary hormone deficiencies.

Diagnosis of growth hormone deficiency in the paediatric and transitional age

Growth hormone deficiency is a rare cause of childhood short stature, but one for which treatment exists in the form of recombinant human growth hormone. A diagnosis of growth hormone deficiency is made based on auxology, biochemistry and imaging. Although no diagnostic gold standard exists, growth hormone provocation tests are considered the mainstay of diagnostic investigations. However, these must be interpreted with caution in view of issues with variability and reproducibility, as well as the limited evidence-base for cut-off values used to distinguish growth hormone deficient and non-growth hormone deficient subjects. In addition, nutritional and pubertal status can affect results, with no consensus on the role of priming with sex steroid hormones. Difficulties with assays exist both for growth hormone as well as insulin-like growth factor-1. Pituitary magnetic resonance imaging is a useful diagnostic, and possibly prognostic, aid. Although genetic testing is not routine, the discovery of more relevant mutations makes it an increasingly important investigation. Children with growth hormone deficiency are retested biochemically on completion of growth, to assess whether they remain so into adulthood.

Brain Magnetic Resonance Imaging as First-Line Investigation for Growth Hormone Deficiency Diagnosis in Early Childhood

BACKGROUND/AIMS

The diagnosis of growth hormone (GH) deficiency (GHD) in infancy and early childhood is not straightforward. GH stimulation tests are unsafe and unreliable in infants, and normative data are lacking. This study aims to investigate whether brain magnetic resonance imaging (MRI) may replace GH stimulation tests in the diagnosis of GHD in children younger than 4 years.

METHODS

We examined a retrospective cohort, with longitudinal follow-up, of 68 children consecutively diagnosed with GHD before the age of 4 years. The prevalence of hypothalamic-pituitary (HP) alterations at MRI and the associations with age and either isolated GHD (IGHD) or multiple pituitary hormone deficiency (MPHD) were assessed.

RESULTS

The prevalences of IGHD and MPHD were 54.4 and 45.6%, respectively. In the first group, brain MRI showed abnormalities in 83.8%: isolated pituitary hypoplasia in 48.7% and complex defects in 35.1%. In patients with MPHD, MRI showed complex alterations in 100%. All children younger than 24 months showed HP MRI abnormalities, regardless of the diagnosis. Complex defects were found in 94% of patients younger than 12 months and in 75% of patients between 13 and 24 months.

CONCLUSION

Our data suggest that brain MRI may represent the first-line investigation for diagnosing GHD in infancy and early childhood.

Revised GH and cortisol cut-points for the glucagon stimulation test in the evaluation of GH and hypothalamic-pituitary-adrenal axes in adults: results from a prospective randomized multicenter study

CONTEXT

Recent studies suggest using lower GH cut-points for the glucagon stimulation test (GST) in diagnosing adult GH deficiency (GHD), especially in obese patients. There are limited data on evaluating GH and hypothalamic-pituitary-adrenal (HPA) axes using weight-based dosing for the GST.

OBJECTIVE

To define GH and cortisol cut-points to diagnose adult GHD and secondary adrenal insufficiency (SAI) using the GST, and to compare fixed-dose (FD: 1 or 1.5 mg in patients >90 kg) with weight-based dosing (WB: 0.03 mg/kg). Response to the insulin tolerance test (ITT) was considered the gold standard, using GH and cortisol cut-points of ≥3 ng/ml and ≥18 µg/dL, respectively.

DESIGN

28 Patients with hypothalamic-pituitary disease and 1-2 (n = 14) or ≥3 (n = 14) pituitary hormone deficiencies, and 14 control subjects matched for age, sex, estrogen status and body mass index (BMI) underwent the ITT, FD- and WB-GST in random order.

RESULTS

Age, sex ratio and BMI were comparable between the three groups. The best GH cut-point for diagnosis of GHD was 1.0 (92 % sensitivity, 100 % specificity) and 2.0 ng/mL (96 % sensitivity and 100 % specificity) for FD- and WB-GST, respectively. Age negatively correlated with peak GH during FD-GST (r = -0.32, P = 0.04), but not WB-GST. The best cortisol cut-point for diagnosis of SAI was 8.8 µg/dL (92 % sensitivity, 100 % specificity) and 11.2 µg/dL (92 % sensitivity and 100 % specificity) for FD-GST and WB-GST, respectively. Nausea was the most common side effect, and one patient had a seizure during the FD-GST.

CONCLUSION

The GST correctly classified GHD using GH cut-points of 1 ng/ml for FD-GST and 2 ng/ml for WB-GST, hence using 3 ng/ml as the GH cut-point will misclassify some GH-sufficient adults. The GST may also be an acceptable alternative to the ITT for evaluating the HPA axis utilizing cortisol cut-points of 9 µg/dL for FD-GST and 11 µg/dL for WB-GST.

Pegvisomant-primed glucagon stimulation test in assessing GH reserve and GH/IGF kinetics in adults suspected of GH deficiency

PURPOSE

The accuracy of the glucagon stimulation test(GST) in diagnosing adult GH deficiency (GHD) has recently been questioned. Because pegvisomant (PegV)increases endogenous GH secretion, we hypothesized that priming PegV to the GST (PegV-GST) 72 h beforehand would improve the diagnostic accuracy of this test. This pilot study aimed to prospectively compare PegV-GST to two other diagnostic tests for adult GHD.

METHODS

Adults suspected of GHD underwent PegVGST,GST and insulin tolerance test (ITT) in random order.Growth hormone levels (measured by a PegV insensitive assay) during PegV-GST, GST and ITT were compared,and acute effects of PegV on GH/IGF kinetics were assessed.

RESULTS

Ten subjects with hypothalamic-pituitary disease and 1–4 pituitary hormone deficiencies were studied. Basal and peak GH levels with the PegV-GST were comparable to those of the GST and ITT. The five subjects that failed the GST and ITT were the same subjects that failed the PegVGST,using the peak GH cut point of<3 ng/mL for this test. After PegV priming, basal GH and GH binding protein(GHBP) increased (both P<0.01) and total IGF-I and bioactive IGF decreased (both P<0.05), whereas IGF-II and IGFBPs -1, -2 and -3 were unchanged compared to pre-PegV priming. Serum PegV levels correlated positively with basal GH, peak GH, IGFBP-1 and IGFBP-2 levels, and negatively with D bioactive IGF and DGHBP (all P<0.05).

CONCLUSION

Single dose PegV administration in adults suspected of GHD increased basal GH and GHBP, with concomitant rapid fall in IGF-I levels and bioactive IGF. PegV priming did not appear to improve the diagnostic accuracy of the GST. Further studies involving larger subject numbers are needed to verify the clinical utility of PegV-GST in evaluating adult GHD.

Controversies in the diagnosis and management of growth hormone deficiency in childhood and adolescence

Growth hormone deficiency (GHD) is a rare but important cause of short stature in childhood with a prevalence of 1 in 4000. The diagnosis is currently based on an assessment of auxology along with supporting evidence from biochemical and neuroradiological studies. There are significant controversies in the diagnosis and management of GHD. Growth hormone (GH) stimulation tests continue to play a key role in GHD diagnosis but the measured GH concentration can vary significantly with stimulation test and GH assay used, creating difficulties for diagnostic accuracy. Such issues along with the use of adjunct biochemical markers such as IGF-I and IGFBP-3 for the diagnosis of GHD, will be discussed in this review. Additionally, the treatment of GHD remains a source of much debate; there is no consensus on the best mechanism for determining the starting dose of GH in patients with GHD. Weight and prediction based models will be discussed along with different mechanisms for dose adjustment during treatment (auxology or IGF-I targeting approaches). At the end of growth and childhood treatment, many subjects diagnosed with isolated GHD re-test normal. It is not clear if this represents a form of transient GHD or a false positive diagnosis during childhood. Given the difficulties inherent in the diagnosis of GHD, an early reassessment of the diagnosis in those who respond poorly to GH is to be recommended.

Evaluation of the hypothalamic-pituitary-adrenal axis and its relationship with central respiratory dysfunction in children with Prader-Willi syndrome

BACKGROUND

Children with Prader-Willi Syndrome (PWS) have been considered at risk for central adrenal insufficiency (CAI). Hypothalamic dysregulation has been proposed as a common mechanism underlying both stress-induced CAI and central respiratory dysfunction during sleep.

OBJECTIVE

To evaluate CAI and sleep-related breathing disorders in PWS children.

PATIENTS AND METHODS

Retrospective study of cortisol response following either insulin tolerance test (ITT) or glucagon test (GT) in 20 PWS children, and comparison with 33 non- Growth Hormone deficient (GHD) controls. Correlation between sleep related breathing disorders and cortisol response in 11 PWS children who received both investigations.

RESULTS

In PWS children, the cortisol peak value showed a significant, inverse correlation with age (Kendall's τ = -0.411; p = 0.012). A similar though non-significant correlation was present between cortisol increase and age (τ = -0.232; p = 0.16). Similar correlations were found in controls. In only 1 of 20 PWS children (5 %), ITT was suggestive of CAI. Four patients had an elevated central apnea index but they all exhibited a normal cortisol response. No relationship was found between peak cortisol or cortisol increase and central apnea index (respectively p = 0.94 and p = 0.14) or the other studied polysomnography (PSG) parameters.

CONCLUSIONS

CAI assessed by ITT/GT is rare in PWS children. Our data do not support a link between CAI and central respiratory dysregulation.

Does priming with sex steroids improve the diagnosis of normal growth hormone secretion in short children?

INTRODUCTION

There is still controversy for priming with sex steroid before growth hormone (GH) testing.

OBJECTIVE

We studied GH response to stimulation in 92 children >9 years with idiopathic short stature (height standard deviation score [HtSDS]-2). They were divided randomly into two groups. Children in Group 1 (n = 50) were primed with premarin in girls and testosterone in boys and those in Group 2 were not primed (n = 42). All children were tested using standard clonidine test and their serum insulin-like growth factor-I concentration (IGF-I). Additionally the growth and GH-IGF-I data of the two groups of children were compared with those for 32 short children (HtSDS <-2) below the age 9 years who were non-primed before GH testing (Group 3).

RESULTS

Neither GH peak response to provocation nor IGF-I concentrations differed between the two groups with and without priming.

DISCUSSION

Taking a cut-level of 7 ng/ml for normal GH response to clonidine, priming with sex steroids did not significantly increase the percentage of patients with normal GH response (52%) versus nonpriming (47%). IGF-I level did not show any significant difference among the two studied groups >9 years. The peak GH response to clonidine provocation test did not differ before (n = 42) versus after 9 years (n = 32) of age.

CONCLUSIONS

In this randomized study priming with sex steroids before GH testing did not significantly increase the yield of diagnosing short patients with normal GH secretion. In addition, GH response to provocation did not vary significantly between young (<9 years) and old (>9 years) short children.

Clonidine and glucagon stimulation for testing growth hormone secretion in children and adolescents: can we make it with fewer samples?

BACKGROUND

Our aim was to retrospectively evaluate the possibility to reduce the number of GH analyses during clonidine and glucagon tests without compromising accuracy.

SUBJECTS AND METHODS

Two hundred and forty-five tests were performed in a total of 188 children and adolescents with a mean age of 9.93 ± 2.88 yr in a single center during the last 5 yr.

RESULTS

Ninety-one out of 158 (57.59%) clonidine tests and 47/87 (54.02%) glucagon tests had at least one sample >10 μg/l (negative). For clonidine tests, not measuring GH at 30 min would have resulted in only one negative test missed (0.63% false positive result), whereas not measuring GH both at 0 and 30 min would have increased the false positive percentage to 2.53%. Ending clonidine tests at 90 min would have resulted in 7 negative tests missed (4.43% false positive results). For glucagon tests, more than half of the tests peaked at 120 min (56.32%). Skipping sampling at 0, 60 and 180 min provided a false positive rate of 5.75%.

CONCLUSIONS

For clonidine tests we can omit blood sampling at time points 0 and 30 min without significantly compromising accuracy.

Clinical characteristics, timing of peak responses and safety aspects of two dosing regimens of the glucagon stimulation test in evaluating growth hormone and cortisol secretion in adults

Weight-based (WB: 0.03 mg/kg) and fixed dose (FD: 1-1.5 mg) regimens of the glucagon stimulation test (GST) have been used to evaluate GH and cortisol secretion in children and adults, respectively. However, experience of the WB regimen in assessing GH and cortisol secretion in adults are limited. We describe a multicenter experience using WB and FD regimens in evaluating GH and cortisol secretion in adults suspected of GH deficiency and central adrenal insufficiency. Retrospective case series of GSTs (n = 515) performed at five tertiary centers. Peak and nadir glucose, and peak GH and peak cortisol responses occurred later with WB (mean dose: 2.77 mg) compared to FD (mean dose: 1.20 mg) regimens. Main side-effects were nausea and vomiting, particularly in younger females. Nausea was comparable but vomiting was more frequent in the WB regimen (WB: 10.0 % vs FD: 2.4 %; P < 0.05). Peak and nadir glucose, ΔGH, and peak and Δcortisol were higher in the WB regimen. In both regimens, age correlated negatively with peak cortisol levels, and body mass index (BMI), fasting, peak and nadir glucose correlated negatively with peak GH levels. WB and FD regimens can induce adult GH and cortisol secretion, but peak responses occur later in the WB regimen. Both regimens are relatively safe, and vomiting was more prevalent in the WB regimen. As age, BMI, and glucose tolerance negatively correlated with peak GH and cortisol levels, the WB regimen may be more effective than the FD regimen in older overweight glucose intolerant patients.

Magnetic resonance imaging of CNS in 15,043 children with GH deficiency in KIGS (Pfizer International Growth Database)

OBJECTIVES

Neuroimaging has become an essential part of the diagnostic process in children with GH deficiency (GHD). The aim of the study was to document the frequency of neuroanatomical abnormalities in a very large cohort of children with GHD and to relate these findings to patient clinical characteristics.

DESIGN AND METHODS

Results of magnetic resonance imaging (MRI) were reported in 15,043 of 43,725 children with non-acquired GHD (idiopathic, neurosecretory dysfunction (NSD) and known congenital cause) who were enrolled in KIGS (Pfizer International Growth Database) between 1987 and 2011. Clinical characteristics of patients before GH treatment with normal MRI (idiopathic GHD (IGHD) and NSD) were compared with those of patients with abnormal pituitaries (hypoplasia, empty sella (ES), HME (hypoplastic anterior pituitary, missing pituitary stalk and ectopic posterior pituitary)).

RESULTS

Abnormal MRIs were found in 4032 (26.8%) children, within which ES (N=1178 (7.8%)) and HME (N=1019 (6.8%)) were the most frequent findings. In 2361 children diagnosed as IGHD or NSD before MRI examination, anatomical abnormalities ((pituitary hypoplasia: n=974); (HME: n=459)) were documented. Patients with anatomical abnormalities had more severe characteristics of GHD: normal MRI < pituitary hypoplasia < ES < HME.

CONCLUSIONS

GHD is associated with a great variety of neuroanatomical abnormalities as identified by MRI. The investigation and evaluation of MRI need to be conducted in a structured mode. There is an association between anatomical and functional abnormalities of the pituitary.

Quantifying the risk of hypoglycaemia in children undergoing the glucagon stimulation test

OBJECTIVE

The low-dose (15-30 μg/kg) glucagon stimulation test (GST) is assumed to be associated with fewer episodes of low blood glucose (BG). We aimed to quantify the risk of hypoglycaemia in children undergoing the low-dose GST to evaluate their growth hormone status.

DESIGN AND PATIENTS

Blood glucose fluctuations during the GST in 80 children (median age 8·7 years, 45 boys, 66 prepubertal) who received a median 20·5 μg/kg of intramuscular glucagon were reviewed.

MEASUREMENTS

The rate of (i) hypoglycaemia (BG < 3·3 mm), (ii) falling BG trend at the end of the GST (lower BG at 180 min than at 120 min), (iii) hypoglycaemia and falling BG trend at the end of the GST, and (iv) at-risk patients (those with at least one of the three risks measures).

RESULTS

Twenty-seven of the 80 children had hypoglycaemia during the GST. Twenty-six children showed a falling BG trend at the end of the GST and were significantly younger than the other 54 children with a rising BG trend [5·1 (3·1-10·4) years vs 9·6 (5·4-11·8) years, P = 0·02]. Eight children had both a falling BG trend and hypoglycaemia at end of the test. Forty-four children were at-risk patients, and the odds ratio of being an at-risk patient in those <8 years old was 2·63 (95% CI 1·06-6·57, P = 0·04).

CONCLUSIONS

Hypoglycaemia is not uncommon during the low-dose GST. Young children, especially those <8 years old, are particularly at risk. BG monitoring should be considered essential from a safety perspective.

Update in growth hormone therapy of children

Although recombinant human GH (rhGH) has been available since 1985, there are several questions related to its use that remain unanswered. The Entrez-PubMed search engine was used to conduct a review of publications appearing since 2007 that address growth and GH treatment. Recent publications related to the diagnosis of GH deficiency, genetics of growth, the use of rhGH in different genetic conditions, in idiopathic short stature, and in puberty, and strategies to adjust rhGH dose were reviewed. New studies investigating the genetics of growth and the response to rhGH therapy in different groups are helping in the understanding of the physiology of normal growth. Although in most children treated with rhGH there is a short-term benefit, the clinical relevance of the benefits after long-term treatment in some conditions remains unclear. The challenges are to define milder forms of GH deficiency and to assess the relevance of the benefits, if any, caused by rhGH in different patient populations and the best therapeutic approach for these patients. Well-designed long-term studies using anthropometric, genetic, and laboratory data that will also assess long-term quality of life benefits are needed to help clinicians select patients to initiate treatment with rhGH and to adjust treatment to improve outcome.

Pituitary function at long-term follow-up of childhood traumatic brain injury

Pituitary dysfunction is a recognized sequela of traumatic brain injury (TBI), occurring in 10-83% of adult patients, but there are few data on the prevalence or natural history in childhood. Our objective was to determine pituitary function in children and young adults at least 4 years after TBI requiring pediatric intensive care unit (PICU) admission. The effects of TBI and hypopituitarism on height, adiposity, and quality of life (QOL) were also evaluated. Unselected patients discharged from the regional PICU with TBI (age < 18 years at injury) from 1999-2004 were recruited. Blood and urine samples were collected for baseline pituitary function testing. Height and weight were measured. Adiposity was assessed by mid-upper arm and waist circumferences, and body fat percentage estimation using four-site skinfold thickness and bioelectrical impedance. Auxology and adiposity data were compared to local age- and sex-matched healthy control data. QOL questionnaires (PedsQL 4.0 and QOL-AGHDA) were completed. Twenty subjects (median age 16.7 years, range 9.2-23.3 years, 13 male) of 127 who were eligible agreed to participate at a median of 6.8 years (range 4.2-10.3 years) since TBI. Markers of injury were higher in those recruited than those who were not. Biochemical evidence of hypopituitarism was identified in only one case, possibly related to comorbid pre-existing attention deficit-hyperactivity disorder. Height, weight, and adiposity were similar to healthy controls. Poor QOL was seen in patients with chronic functional deficits or comorbidities. Overall, pituitary dysfunction was less prevalent than in previous studies in adults and children. The results of this study do not support the use of routine endocrine evaluation of children following TBI.

The accuracy of the glucagon test compared to the insulin tolerance test in the diagnosis of adrenal insufficiency in young children with growth hormone deficiency

CONTEXT

The accuracy of the glucagon test in the diagnosis of central adrenal insufficiency in young children has not yet been definitively established.

OBJECTIVE

The aim of this study was to investigate the diagnostic accuracy of the glucagon test as an alternative to the insulin tolerance test (ITT) in children with GH deficiency under 6 yr of age.

DESIGN AND SETTING

This was a prospective study conducted in two Pediatric Endocrinology Centers.

PATIENTS AND METHODS

Forty-eight children (median age, 4.2 yr) with GH deficiency confirmed by a peak GH to ITT and arginine less than 10 microg/liter were enrolled: 24 with normal hypothalamic-pituitary anatomy, seven with isolated anterior pituitary hypoplasia, and 17 with structural hypothalamic-pituitary abnormalities at magnetic resonance imaging. Twelve subjects had central adrenal insufficiency defined by a peak cortisol response of less than 20 microg/dl to ITT. All children underwent a glucagon stimulation test with blood sampling for cortisol and glucose (time 0 to 180 min) after the im administration of 30 microg/kg of glucagon.

RESULTS

The mean peak cortisol after glucagon was not significantly different from that obtained after ITT in the whole cohort (25.9 vs. 26.0 microg/dl; P = 0.908), and it was significantly reduced in patients with structural hypothalamic-pituitary abnormalities (P < 0.001). Receiver operating characteristic curve analysis showed that the best diagnostic accuracy was obtained with a peak cortisol cutoff to glucagon of 14.6 microg/dl (sensitivity, 66.67%; specificity, 100%; area under the curve = 0.91; 95% confidence interval, 0.82-0.99). Using this cutoff, 91.67% of the patients were correctly classified.

CONCLUSIONS

This study shows that glucagon is an accurate and safe diagnostic test for adrenal function in young children who are at risk for adrenal insufficiency.