Overweight/Obese adults with pituitary disorders require lower peak growth hormone cutoff values on glucagon stimulation testing to avoid overdiagnosis of growth hormone deficiency

Pitfalls in the lab assessment of hypopituitarism

The diagnostic approach to hypopituitarism involves many disciplines. Clinical symptoms rarely are specific. Imaging techniques are helpful but cannot prove the specific functional defects. Therefore, the definitive diagnosis of pituitary insufficiency is largely based on laboratory tests. However, also laboratory methods come with inherent limitations, and it is essential for the clinician to know and recognize typical pitfalls. Most factors potentially impairing the quality of hormone measurements are introduced in the preanalytical phase, i.e. before the hormones are measured by the laboratory. For example, the timing of blood drawing with respect to circadian rhythm, stress, and medication can have an influence on hormone concentrations. During the actual analysis of the hormones, cross-reactions with molecules present in the sample presenting the same or similar epitopes than the intended analyte may affect immunoassays. Interference can also come from heterophilic or human anti-animal antibodies. Unexpected problems can also be due to popular nutritional supplements which interfere with the measurement procedures. An important example in this respect is the interference from biotin. It became only clinically visible when the use of this vitamin became popular among patients. The extreme serum concentrations reached when patients take it as a supplement can lead to incorrect measurements in immunoassays employing the biotin-streptavidin system. To some extent, hormone analyses using liquid chromatography mass spectrometry (LCMS) can overcome problems, although availability and cost-effectiveness of this method still imposes restrictions. In the post-analytical phase, appropriateness of reference intervals and cut-offs with respect to the specific analytical method used is of outmost importance. Furthermore, for interpretation, additional biological and pharmacological factors like BMI, age and concomitant diseases must be considered to avoid misinterpretation of the measured concentrations. It is important for the clinician and the laboratory to recognize when one or more laboratory values do not match the clinical picture. In an interdisciplinary approach, the search for the underlying cause should be initiated.

The influence of body composition on the response to dynamic stimulation of the endocrine pituitary-testis axis

BACKGROUND

Testosterone treatment is generally not recommended in men with obesity induced low serum testosterone. However, distinguishing this condition from overt testosterone deficiency in men with obesity where treatment should be initiated is a diagnostic challenge and tools to differentiate these conditions are scarce but could be of important clinical relevance.

OBJECTIVES

To investigate the association between body composition and dynamic responses of the pituitary-testis axis in men.

METHODS

Single-center cross-sectional study including 112 healthy men. Participants went through a full biochemical assessment of the pituitary-testis axis, and dynamic stimulatory tests of luteinizing hormone (LH) secretion (gonadotropin-releasing hormone (GnRH)-test) and testosterone secretion (choriogonadotropin (hCG)-test). A subset (N = 78) further had a DXA-scan performed.

RESULTS

A higher body mass index (BMI) was associated with lower basal serum LH (BU = -0.44, 95% CI: -0.88--0.01, p = 0.04). The GnRH-stimulated LH increase was not significantly associated with BMI (BU = -0.10, 95% CI: -0.72-0.51, p = 0.74). Furthermore, a high BMI was associated with low basal testosterone (BU -0.02, 95% CI: -0.03--0.02, p < 0.001), and free testosterone (BU -15.0, 95% CI: -19.9--10.0, p < 0.001) and men with overweight and obesity had significantly lower testosterone (9%, p = 0.003 and 24%, p < 0.001) and free testosterone (25%, p = 0.006 and 50%, p < 0.001) concentrations compared to men with normal weight. The HCG-stimulated testosterone increase was significantly less dependent on BMI compared to the influence of BMI on basal testosterone concentrations (p = 0.04 for the interaction).

CONCLUSIONS

Dynamic sex hormone responses following pituitary-testis axis stimulation were less dependent on BMI, compared to the influence of BMI on basal hormone concentrations and could potentially assist clinical decision making in patients with obesity suspected of testosterone deficiency.

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.

Impact of Childhood Cancer on Growth

Along with improvements in cancer treatment over time, the number of childhood cancer survivors has been growing. Survivors are at risk for serious medical complications, and growth impairment is among the most common. There are multiple factors that may cause impaired growth among survivors. In this article, we review the impact of cancer on growth in children and adolescents. We first provide an overview of growth disturbance among childhood cancer patients and survivors due to nonhormonal causes, including a recent understanding of the effect of targeted cancer therapies (eg, tyrosine kinase inhibitors and immune checkpoint inhibitors) on growth. Then we describe the hormonal causes of growth impairment among survivors, focusing on growth hormone deficiency, including the prevalence, risk factors, and treatment. Lastly, we briefly summarize overgrowth and tall stature in childhood cancer. It is critical to assess the linear growth of children and adolescents, especially in cancer survivors who are at risk for growth disturbance, since growth is an important measure of their health.

Growth hormone replacement in adults with cured acromegaly: Efficacy and safety

Between 2% and 60% of patients with cured acromegaly may eventually develop growth hormone deficiency. In adults, growth hormone deficiency is associated with abnormal body composition, decreased exercise capacity and quality of life, dyslipidemia, insulin resistance and increased cardiovascular risk. Similar to patients with other sellar lesions, the diagnosis of growth hormone deficiency in adults with cured acromegaly generally requires stimulation testing, with the exception of patients with very low serum insulin-like growth factor I levels and multiple additional pituitary hormone deficiencies. In adults with cured acromegaly, growth hormone replacement may have beneficial effects on body adiposity, muscle endurance, serum lipids and quality of life. Growth hormone replacement is generally well-tolerated. Arthralgias, edema, carpal tunnel syndrome and hyperglycemia may occur in patients with cured acromegaly, as is true of patients with growth hormone deficiency of other etiologies. However, there is evidence of increased cardiovascular risk in some studies of growth hormone replacement in adults with cured acromegaly. More studies are needed to fully establish the beneficial effects and elucidate the risks of growth hormone replacement in adults with cured acromegaly. Until then, growth hormone replacement can be considered in these patients on a case-by-case basis.

Mild traumatic brain injury as a cause of adult growth hormone deficiency: Diagnosis and treatment

In recent years, mild traumatic brain injury (mTBI) has been recognized as a cause of acquired growth hormone deficiency (AGHD) and is likely much more prevalent than previous estimates. There is great overlap between persistent symptoms following mTBI and those of AGHD and it is possible that these persistent symptoms of mTBI are, at least in part, due to or aggravated by AGHD. This article reviews the current literature of AGHD following mTBI, and proposes practice recommendations for the screening, diagnosis, and management of patients with AGHD following mTBI.

GHRH + arginine test and body mass index: do we need to review diagnostic criteria for GH deficiency?

INTRODUCTION

The proportion of patients with low GH response to provocative tests increases with the number of other pituitary hormone deficiencies, reason why in panhypopituitary patients GH stimulation tests may be unnecessary to diagnose GH deficiency (GHD) PURPOSE: To re-evaluate the diagnostic cut-offs of GH response to GHRH + arginine (ARG) test related to BMI, considering the patients' pituitary function as the gold standard for the diagnosis of GHD.

METHODS

The GH responses to GHRH + ARG were studied in 358 patients with history of hypothalamic-pituitary disease. GHD was defined by the presence of at least 3 other pituitary deficits (n = 223), while a preserved somatotropic function was defined by the lack of other pituitary deficits and an IGF-I SDS ≥ 0 (n = 135). The cut-off with the best sensitivity (SE) and specificity (SP), was identified for each BMI category using the ROC curve analysis. To avoid over-diagnosis of GHD we subsequently searched for the cut-offs with a SP ≥ 95%.

RESULTS

The best GH cut-off was 8.0 μg/l (SE 95%, SP 100%) in lean, 7.0 μg/l (SE 97.3%, SP 82.8%) in overweight, and 2.8 μg/l (SE 84.3%, SP 91.7%) in obese subjects. The cut-off with a SP ≥ 95% was 2.6 μg/l (SE 68.5%, SP 96.6%) in overweight and 1.75 μg/l (SE 70.0%, SP 97.2%) in obese subjects.

CONCLUSIONS

This is the first study that evaluates the diagnostic cut-offs of GH response to GHRH + ARG related to BMI using a clinical definition of GHD as gold standard. Our results suggest that with this new approach, the GHRH + ARG cut-offs should be revised to avoid GHD over-diagnosis.

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.

IGF-1 is positively associated with BMI in patients with acromegaly

PURPOSE

Acromegaly is a disorder characterized by IGF-1 excess due to autonomous GH secretion. In individuals without acromegaly, IGF-1 is not only influenced by GH secretion but is also sensitive to other factors including nutritional status, as evidenced by the inverted U-shaped association between BMI and IGF-1; in low-weight individuals (BMI < 18.5 kg/m²) and those who are obese, IGF-1 levels may be frankly low. It is not known if this same relationship between BMI and IGF-1 is also observed in acromegaly.

METHODS

Retrospective study including patients who underwent resection of a pituitary adenoma (n = 197) for either acromegaly (n = 32) or a nonfunctioning adenoma (NFPA, n = 165) at a large academic medical center between 1/1/2015 and 5/31/2021.

RESULTS

Median BMI in acromegaly was 30.8 kg/m² (range 20.9-42.6 kg/m²). Percent upper limit of normal (%ULN) IGF-1 was 228.2% [159.0, 271.4] in acromegaly versus 32.2% [18.5, 50] in NFPA (p < 0.0001). There was a significant positive association between BMI and %ULN IGF-1 (R = 0.35, p < 0.05) in acromegaly. In contrast, there was no association between BMI and %ULN IGF-1 in the NFPA group as a whole (p = 0.22), but a significant inverse association between BMI and %ULN IGF-1 in NFPA patients with a BMI ≥ 35 kg/m² (rho =  - 0.39, p = 0.02).

CONCLUSION

In contrast to individuals without acromegaly, BMI is significantly and positively associated with IGF-1 in acromegaly across the weight spectrum. Future studies are needed to determine if obese patients with acromegaly experience more significant symptoms related to their disease, or if patients with a low BMI may require different diagnostic criteria.

ENDOCRINE OBESITY: Pituitary dysfunction in obesity

Obesity, the growing pandemic of the 21st century, is associated with multiple organ dysfunction, either by a direct increase in fatty organ content or by indirect modifications related to general metabolic changes driven by a specific increase in biologic products. The pituitary gland is not protected against such a situation. Different hypothalamic-pituitary axes experience functional modifications initially oriented to an adaptive situation that, with years of obesity, turn to maladaptive dynamics that contribute to perpetuating obesity and specific symptoms of their hormonal nature. This paper reviews the recent knowledge on obesity-related pituitary dysfunction and its pathogenic mechanisms and discusses potential therapeutic actions aimed at contributing to ameliorating the complex treatment of severe cases of obesity.

Impact of GH administration on skeletal endpoints in adults with overweight/obesity

OBJECTIVE

Overweight/obesity is associated with relative growth hormone (GH) deficiency and increased fracture risk. We hypothesized that GH administration would improve bone endpoints in individuals with overweight/obesity.

DESIGN

An 18-month, randomized, double-blind, placebo-controlled study of GH, followed by 6-month observation.

METHODS

In this study, 77 adults (53% men), aged 18-65 years, BMI ≥ 25 kg/m2, and BMD T- or Z-score ≤ -1.0 were randomized to daily subcutaneous GH or placebo, targeting IGF1 in the upper quartile of the age-appropriate normal range. Forty-nine completed 18 months. DXA, volumetric quantitative CT, and high-resolution peripheral quantitative CT were performed.

RESULTS

Pre-treatment mean age (48 ± 12 years), BMI (33.1 ± 5.7 kg/m2), and BMD were similar between groups. P1NP, osteocalcin, and CTX increased (P < 0.005) and visceral adipose tissue decreased (P = 0.04) at 18 months in the GH vs placebo group. Hip and radius aBMD, spine and tibial vBMD, tibial cortical thickness, and radial and tibial failure load decreased in the GH vs placebo group (P < 0.05). Between 18 and 24 months (post-treatment observation period), radius aBMD and tibia cortical thickness increased in the GH vs placebo group. At 24 months, there were no differences between the GH and placebo groups in bone density, structure, or strength compared to baseline.

CONCLUSIONS

GH administration for 18 months increased bone turnover in adults with overweight/obesity. It also decreased some measures of BMD, bone microarchitecture, and bone strength, which all returned to pre-treatment levels 6 months post-therapy. Whether GH administration increases BMD with longer treatment duration, or after mineralization of an expanded remodeling space post-treatment, requires further investigation.

Safety of growth hormone replacement in survivors of cancer and intracranial and pituitary tumours: a consensus statement

Growth hormone (GH) has been used for over 35 years, and its safety and efficacy has been studied extensively. Experimental studies showing the permissive role of GH/insulin-like growth factor 1 (IGF-I) in carcinogenesis have raised concerns regarding the safety of GH replacement in children and adults who have received treatment for cancer and those with intracranial and pituitary tumours. A consensus statement was produced to guide decision-making on GH replacement in children and adult survivors of cancer, in those treated for intracranial and pituitary tumours and in patients with increased cancer risk. With the support of the European Society of Endocrinology, the Growth Hormone Research Society convened a Workshop, where 55 international key opinion leaders representing 10 professional societies were invited to participate. This consensus statement utilized: (1) a critical review paper produced before the Workshop, (2) five plenary talks, (3) evidence-based comments from four breakout groups, and (4) discussions during report-back sessions. Current evidence reviewed from the proceedings from the Workshop does not support an association between GH replacement and primary tumour or cancer recurrence. The effect of GH replacement on secondary neoplasia risk is minor compared to host- and tumour treatment-related factors. There is no evidence for an association between GH replacement and increased mortality from cancer amongst GH-deficient childhood cancer survivors. Patients with pituitary tumour or craniopharyngioma remnants receiving GH replacement do not need to be treated or monitored differently than those not receiving GH. GH replacement might be considered in GH-deficient adult cancer survivors in remission after careful individual risk/benefit analysis. In children with cancer predisposition syndromes, GH treatment is generally contraindicated but may be considered cautiously in select patients.

Towards Understanding the Direct and Indirect Actions of Growth Hormone in Controlling Hepatocyte Carbohydrate and Lipid Metabolism

Growth hormone (GH) is critical for achieving normal structural growth. In addition, GH plays an important role in regulating metabolic function. GH acts through its GH receptor (GHR) to modulate the production and function of insulin-like growth factor 1 (IGF1) and insulin. GH, IGF1, and insulin act on multiple tissues to coordinate metabolic control in a context-specific manner. This review will specifically focus on our current understanding of the direct and indirect actions of GH to control liver (hepatocyte) carbohydrate and lipid metabolism in the context of normal fasting (sleep) and feeding (wake) cycles and in response to prolonged nutrient deprivation and excess. Caveats and challenges related to the model systems used and areas that require further investigation towards a clearer understanding of the role GH plays in metabolic health and disease are discussed.

Impact of body mass index on growth hormone stimulation tests in children and adolescents: a systematic review and meta-analysis

Peak stimulated growth hormone (GH) levels are known to decrease with increasing body mass index (BMI), possibly leading to overdiagnosis of GH deficiency (GHD) in children with overweight and obesity. However, current guidelines do not guide how to interpret the peak GH values of these children. This systematic review and meta-analysis aimed to study the effect of the BMI standard deviation score (SDS) on stimulated peak GH values in children, to identify potential moderators of this association, and to quantify the extent to which peak GH values in children with obesity are decreased. This systematic review was performed by the PRISMA guidelines. Medline, Embase, Cochrane, Web of Science, and Google Scholar databases were searched for studies reporting the impact of weight status on peak GH in children. Where possible, individual participant data was extracted and/or obtained from authors. Quality and risk of bias were evaluated using the Scottish Intercollegiate Guidelines Network (SIGN) checklists. The primary outcome was the association between peak GH values and BMI SDS. The pooled correlation coefficient r, 95% confidence interval (CI), and heterogeneity statistic I² were calculated under a multilevel, random-effects model. In addition, exploratory moderator analyses and meta-regressions were performed to investigate the effects of sex, pubertal status, presence of syndromic obesity, mean age and mean BMI SDS on the study level. For the individual participant dataset, linear mixed-models regression analysis was performed with BMI SDS as the predictor and ln(peak GH) as the outcome, accounting for the different studies and GH stimulation agents used. In total, 58 studies were included, providing data on n = 5135 children (576 with individual participant data). Thirty-six (62%) studies had high, 19 (33%) medium, and 3 (5%) low risks of bias. Across all studies, a pooled r of -0.32 (95% CI -0.41 to -0.23, n = 2434 patients from k = 29 subcohorts, I² = 75.2%) was found. In meta-regressions, larger proportions of males included were associated with weaker negative correlations (p = 0.04). Pubertal status, presence of syndromic obesity, mean age, and mean BMI SDS did not moderate the pooled r (all p > 0.05). Individual participant data analysis revealed a beta of -0.123 (95% CI -0.160 to -0.086, p < 0.0001), i.e. per one-point increase in BMI SDS, peak GH decreases by 11.6% (95% CI 8.3-14.8%). To our knowledge, this is the first systematic review and meta-analysis to investigate the impact of BMI SDS on peak GH values in children. It showed a significant negative relationship. Importantly, this relationship was already present in the normal range of BMI SDS and could lead to overdiagnosis of GHD in children with overweight and obesity. With the ever-rising prevalence of pediatric obesity, there is a need for BMI (SDS)-specific cutoff values for GH stimulation tests in children. Based on the evidence from this meta-analysis, we suggest the following weight status-adjusted cutoffs for GH stimulation tests that have cutoffs for children with normal weight of 5, 7, 10, and 20 µg/L: for overweight children: 4.6, 6.5, 9.3, and 18.6 µg/L; and for children with obesity: 4.3, 6.0, 8.6, and 17.3 µg/L.

Experience of a Pituitary Clinic for US Military Veterans With Traumatic Brain Injury

Context

Traumatic brain injury (TBI) is considered the "signature" injury of veterans returning from wartime conflicts in Iraq and Afghanistan. While moderate/severe TBI is associated with pituitary dysfunction, this association has not been well established in the military setting and in mild TBI (mTBI). Screening for pituitary dysfunction resulting from TBI in veteran populations is inconsistent across Veterans Affairs (VA) institutions, and such dysfunction often goes unrecognized and untreated.

Objective

This work aims to report the experience of a pituitary clinic in screening for and diagnosis of pituitary dysfunction.

Methods

A retrospective analysis was conducted in a US tertiary care center of veterans referred to the VA Puget Sound Healthcare System pituitary clinic with a history of TBI at least 12 months prior. Main outcome measures included demographics, medical history, symptom burden, baseline hormonal evaluation, brain imaging, and provocative testing for adrenal insufficiency (AI) and adult-onset growth hormone deficiency (AGHD).

Results

Fatigue, cognitive/memory problems, insomnia, and posttraumatic stress disorder were reported in at least two-thirds of the 58 patients evaluated. Twenty-two (37.9%) were diagnosed with at least one pituitary hormone deficiency, including 13 (22.4%) AI, 12 (20.7%) AGHD, 2 (3.4%) secondary hypogonadism, and 5 (8.6%) hyperprolactinemia diagnoses; there were no cases of thyrotropin deficiency.

Conclusion

A high prevalence of chronic AI and AGHD was observed among veterans with TBI. Prospective, larger studies are needed to confirm these results and determine the effects of hormone replacement on long-term outcomes in this setting.

Growth hormone deficiency in adults with Cushing's disease

Growth hormone deficiency (GHD) generally occurs in patients with Cushing's disease (CD) as a consequence of cortisol excess. Mass effect may contribute to the development of GHD in the minority of patients with CD due to corticotroph macroadenomas. Patients with CD in remission are at considerable risk of GH deficiency as a consequence of pituitary surgery or radiation therapy. The purpose of the present review is to summarize data on GH deficiency in adults with CD. Untreated GH deficiency is associated with increased visceral adiposity, decreased lean mass, bone mass, and exercise capacity, impaired linear growth (in children), dyslipidemia, insulin resistance and impaired quality of life. Evaluation and treatment of GHD should be considered in patients with CD in remission. Serum insulin-like growth factor I (IGF-I) can be helpful in the diagnosis of GHD among patients with multiple additional pituitary hormone deficiencies. The diagnosis of GHD generally requires dynamic testing, including insulin, glucagon or macimorelin stimulation. Growth hormone replacement may improve body composition, bone density, linear growth (in children), exercise capacity, dyslipidemia and quality of life. While generally safe, GH replacement requires careful monitoring to assure effectiveness and tolerance in treated patients.

Current concepts of the diagnosis of adult growth hormone deficiency

In adults, growth hormone (GH) deficiency is associated with increased visceral adiposity, decreased lean body mass, bone mineral density and exercise capacity, dyslipidemia, insulin resistance, increased cardiometabolic and fracture risk, and impaired quality of life. The aim of the present article is to review the diagnosis of GH deficiency in adults. To avoid overdiagnosis of GH deficiency, it is critical to evaluate only patients at risk for pituitary dysfunction, including those who have had sellar masses, pituitary surgery, radiation therapy, traumatic brain injury, subarachnoid hemorrhage or childhood onset GH deficiency. Evaluation for GH deficiency should be undertaken after testing and replacement of other pituitary hormone deficits. Since GH secretion is pulsatile, measuring serum GH levels randomly is not helpful in establishing the diagnosis of GH deficiency. Serum insulin-like growth factor I (IGF-I) levels lack substantial diurnal variation but also lack sufficient sensitivity and specificity in the diagnosis of GH deficiency in adults. However, adults with multiple (≥3) additional pituitary hormone deficiencies, risk factors for hypopituitarism and low serum IGF-I levels are very likely to be GH deficient. In most cases, the diagnosis of GH deficiency requires stimulation testing. These tests involve the administration of a pharmacologic agent that normally stimulates GH release from pituitary somatotrophs, including insulin, glucagon, growth hormone releasing hormone-arginine or macimorelin, followed by sampling of serum specimens at regular intervals for GH assay. Patients with a peak GH level that is below a predetermined cutpoint are classified as GH deficient. A systematic approach to the diagnosis of GH deficiency is essential in order to accurately identify adults who may benefit from GH replacement.

Clinical, Diagnostic, and Therapeutic Aspects of Growth Hormone Deficiency During the Transition Period: Review of the Literature

The role of growth hormone (GH) during childhood and adulthood is well established. Once final stature is reached, GH continues to act during the transition, the period between adolescence and adulthood in which most somatic and psychological development is obtained. The achievement of peak bone mass represents the most relevant aspect of GH action during the transition period; however, equally clear is its influence on body composition and metabolic profile and, probably, in the achievement of a complete gonadal and sexual maturation. Despite this, there are still some aspects that often make clinical practice difficult and uncertain, in particular in evaluating a possible persistence of GH deficiency once final stature has been reached. It is also essential to identify which subjects should undergo re-testing and, possibly, replacement therapy, and the definition of unambiguous criteria for therapeutic success. Moreover, even during the transition phase, the relationship between GH substitution therapy and cancer survival is of considerable interest. In view of the above, the aim of this paper is to clarify these relevant issues through a detailed analysis of the literature, with particular attention to the clinical, diagnostic and therapeutic aspects.

Sensitivity and specificity of the macimorelin test for diagnosis of AGHD

OBJECTIVE

The macimorelin test is approved for the diagnosis of adult growth hormone deficiency (AGHD) based on its efficacy vs the insulin tolerance test (ITT). Macimorelin has a significant advantage over ITT in avoiding hypoglycemia. Analyses were conducted to determine whether macimorelin performance is affected by age, BMI, or sex, and evaluate its performance vs ITT over a range of GH cutpoints.

DESIGN

Post hoc analyses of data from a previous randomized phase 3 study included participants aged 18-66 years with BMI <37 kg/m2 and high (Group A), intermediate (Group B), or low (Group C) likelihood for AGHD based on pituitary history, and matched controls (Group D).

METHODS

Probability of AGHD was estimated using unadjusted, age-adjusted, BMI-adjusted, and sex-adjusted logistic models. Area under the curve (AUC) of the estimated receiver operating characteristic (ROC) curve (range, 0-1; 1 = perfect) was compared for adjusted vs unadjusted models. Separate analyses evaluated agreement, sensitivity, and specificity for macimorelin and ITT using cutpoints of 2.8, 4.0, 5.1, and 6.5 ng/mL.

RESULTS

For participants in Group A (n = 41) and Group D (n = 29), unadjusted, age-adjusted, BMI-adjusted, and sex-adjusted models had ROC AUCs (95% CIs) of 0.9924 (0.9807-1), 0.9924 (0.9807-1), 0.9916 (0.9786-1), and 0.9950 (0.9861-1), respectively.

CONCLUSIONS

Macimorelin performance was not meaningfully affected by age, BMI, or sex, indicating robustness for AGHD diagnosis. Of the 4 GH cutpoints evaluated, the cutpoint of 5.1 ng/mL provided maximal specificity (96%) and high sensitivity (92%) and was in good overall agreement with the ITT at the same cutpoint (87%).

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

INTRODUCTION

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Development and Internal Validation of a Predictive Model for Adult GH Deficiency Prior to Stimulation Tests

BACKGROUND

The diagnosis of adult GH deficiency (GHD) relies on a reduced GH response to provocative tests. Their diagnostic accuracy, however, is not perfect, and a reliable estimation of pre-test GHD probability could be helpful for a better interpretation of their results.

METHODS

Eighty patients showing concordant GH response to two provocative tests, i.e. the insulin tolerance test and the GHRH + arginine test, were enrolled. Data on IGF-I values and on the presence/absence of other pituitary deficits were collected and integrated for the estimation of GHD probability prior to stimulation tests.

RESULTS

An independent statistically significant association with the diagnosis of GHD was found both for IGF-I SDS (OR 0.34, 95%-CI 0.18-0.65, p=0.001) and for the presence of other pituitary deficits (OR 6.55, 95%-CI 2.06-20.83, p=0.001). A low (<25%) pre-test GHD probability could be predicted when IGF-I SDS > +0.91 in the presence of other pituitary deficits or IGF-I SDS > -0.52 in the absence of other pituitary deficits. A high (>75%) pre-test GHD probability could be predicted when IGF-I SDS < -0.82 in the presence of other pituitary deficits or IGF-I SDS < -2.26 in the absence of other pituitary deficits.

CONCLUSION

This is the first study that proposes a quantitative estimation of GHD probability prior to stimulation tests. Our risk class stratification represents a simple tool that could be adopted for a Bayesian interpretation of stimulation test results, selecting patients who may benefit from a second stimulation test and possibly reducing the risk of wrong GHD diagnosis.

[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.

GH deficiency in cancer survivors in the transition age: diagnosis and therapy

BACKGROUND

Survival rates among childhood cancer survivors (CCSs) have significantly risen in the last 40 years due to substantial improvements in treatment protocols. However, this improvement has brought with it serious late effects that frequently involve the endocrine system. Of the endocrine disorders, GH deficiency (GHD) is the most common among CCSs as a consequence of a history of cancers, surgery, and/or radiotherapy involving the hypothalamo-pituitary region.

METHODS

A comprehensive search of English language articles regardless of age was conducted in the MEDLINE database between December 2018 and October 2019. We selected all studies on GH therapy in CCSs during the transition age regarding the most challenging topics: when to retest; which diagnostic tests and cut-offs to use; when to start GH replacement therapy (GHRT); what GH dose to use; safety; quality of life, compliance and adherence to GHRT; interactions between GH and other hormonal replacement treatments.

RESULTS

In the present review, we provide an overview of the current clinical management of challenges in GHD in cancer survivors in the transition age.

CONCLUSIONS

Endocrine dysfunction among CCSs has a high prevalence in the transition age and increase with time. Many endocrine disorders, including GHD, are often not diagnosed or under-diagnosed, probably due to the lack of specialized centers for the long-term follow-up. Therefore, it is crucial that transition specialized clinics should be increased in terms of number and specific skills in order to manage endocrine disorders in adolescence, a delicate and complex period of life. A multidisciplinary approach, also including psychological counseling, is essential in the follow-up and management of these patients in order to minimize their disabilities and maximize their quality of life.

Diagnosis and Treatment of Growth Hormone Deficiency: A Position Statement from Korean Endocrine Society and Korean Society of Pediatric Endocrinology

Growth hormone (GH) deficiency is caused by congenital or acquired causes and occurs in childhood or adulthood. GH replacement therapy brings benefits to body composition, exercise capacity, skeletal health, cardiovascular outcomes, and quality of life. Before initiating GH replacement, GH deficiency should be confirmed through proper stimulation tests, and in cases with proven genetic causes or structural lesions, repeated GH stimulation testing is not necessary. The dosing regimen of GH replacement therapy should be individualized, with the goal of minimizing side effects and maximizing clinical improvements. The Korean Endocrine Society and the Korean Society of Pediatric Endocrinology have developed a position statement on the diagnosis and treatment of GH deficiency. This position statement is based on a systematic review of evidence and expert opinions.

Traumatic brain injuries induced pituitary dysfunction: a call for algorithms

Traumatic brain injury affects many people each year, resulting in a serious burden of devastating health consequences. Motor-vehicle and work-related accidents, falls, assaults, as well as sport activities are the most common causes of traumatic brain injuries. Consequently, they may lead to permanent or transient pituitary insufficiency that causes adverse changes in body composition, worrisome metabolic function, reduced bone density, and a significant decrease in one's quality of life. The prevalence of post-traumatic hypopituitarism is difficult to determine, and the exact mechanisms lying behind it remain unclear. Several probable hypotheses have been suggested. The diagnosis of pituitary dysfunction is very challenging both due to the common occurrence of brain injuries, the subtle character of clinical manifestations, the variable course of the disease, as well as the lack of proper diagnostic algorithms. Insufficiency of somatotropic axis is the most common abnormality, followed by presence of hypogonadism, hypothyroidism, hypocortisolism, and diabetes insipidus. The purpose of this review is to summarize the current state of knowledge about post-traumatic hypopituitarism. Moreover, based on available data and on our own clinical experience, we suggest an algorithm for the evaluation of post-traumatic hypopituitarism. In addition, well-designed studies are needed to further investigate the pathophysiology, epidemiology, and timing of pituitary dysfunction after a traumatic brain injury with the purpose of establishing appropriate standards of care.

Growth hormone replacement in adults: Real-world data from two large studies in US and Europe

OBJECTIVE

This report describes the effectiveness and safety of growth hormone replacement in 3180 adult patients with growth hormone deficiency followed-up for 0.0-12.2 years in two completed, complementary, non-interventional, multicentre studies, NordiNet® International Outcome Study (IOS) (NCT00960128) and the American Norditropin® Studies: Web-Enabled Research (ANSWER) Program (NCT01009905).

DESIGN

In both studies, Norditropin® (somatropin; Novo Nordisk A/S, Denmark) was administered at the discretion of the treating physician and according to routine practice. We present data on baseline characteristics, growth hormone dose, safety data and change from baseline in waist circumference, body mass index and bioimpedance (NordiNet® IOS only).

RESULTS

Mean (SD) baseline characteristics (effectiveness analysis set) in NordiNet® IOS (n = 971) and ANSWER (n = 304): females, 45%; 69%; mean growth hormone dose (mg/day) (female, 0.338 [0.177]; male, 0.289 [0.157]); (female, 0.501 [0.313]; male, 0.505 [0.351]). Most patients had BMI ≥25 kg/m². Median (P10,P90) exposure (females, 3.5 [0.42,11.0]; 1.6 [3.2; 0.3,8.6]; males, 4.1 [0.33,10.8]; 2.3 [2.9; 0.0,7.5] years). Mean (SD) change from baseline for waist circumference (-0.46 [6.38] cm [n = 403], BMI (0.30 [3.30] kg/m² [n = 857]) and bioimpedance (-17.4 (59.19) ohm [n = 239]) were associated with growth hormone dose (waist/bioimpedance) and duration of follow-up (BMI/bioimpedance). No new safety signals were observed among patients in the full analysis set (NordiNet® IOS, n = 2321; ANSWER, n = 859).

CONCLUSIONS

Long-term growth hormone replacement is associated with an improvement in body composition. The accumulated data from >10 years of follow-up support the long-term effectiveness and safety of growth hormone replacement as prescribed in clinical practice.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY GUIDELINES FOR MANAGEMENT OF GROWTH HORMONE DEFICIENCY IN ADULTS AND PATIENTS TRANSITIONING FROM PEDIATRIC TO ADULT CARE

Objective: The development of these guidelines is sponsored by the American Association of Clinical Endocrinologists (AACE) Board of Directors and American College of Endocrinology (ACE) Board of Trustees and adheres with published AACE protocols for the standardized production of clinical practice guidelines (CPG). Methods: Recommendations are based on diligent reviews of clinical evidence with transparent incorporation of subjective factors, according to established AACE/ACE guidelines for guidelines protocols. Results: The Executive Summary of this 2019 updated guideline contains 58 numbered recommendations: 12 are Grade A (21%), 19 are Grade B (33%), 21 are Grade C (36%), and 6 are Grade D (10%). These detailed, evidence-based recommendations allow for nuance-based clinical decision-making that addresses multiple aspects of real-world care of patients. The evidence base presented in the subsequent Appendix provides relevant supporting information for the Executive Summary recommendations. This update contains 357 citations of which 51 (14%) are evidence level (EL) 1 (strong), 168 (47%) are EL 2 (intermediate), 61 (17%) are EL 3 (weak), and 77 (22%) are EL 4 (no clinical evidence). Conclusion: This CPG is a practical tool that practicing endocrinologists and regulatory bodies can refer to regarding the identification, diagnosis, and treatment of adults and patients transitioning from pediatric to adult-care services with growth hormone deficiency (GHD). It provides guidelines on assessment, screening, diagnostic testing, and treatment recommendations for a range of individuals with various causes of adult GHD. The recommendations emphasize the importance of considering testing patients with a reasonable level of clinical suspicion of GHD using appropriate growth hormone (GH) cut-points for various GH-stimulation tests to accurately diagnose adult GHD, and to exercise caution interpreting serum GH and insulin-like growth factor-1 (IGF-1) levels, as various GH and IGF-1 assays are used to support treatment decisions. The intention to treat often requires sound clinical judgment and careful assessment of the benefits and risks specific to each individual patient. Unapproved uses of GH, long-term safety, and the current status of long-acting GH preparations are also discussed in this document. LAY ABSTRACT This updated guideline provides evidence-based recommendations regarding the identification, screening, assessment, diagnosis, and treatment for a range of individuals with various causes of adult growth-hormone deficiency (GHD) and patients with childhood-onset GHD transitioning to adult care. The update summarizes the most current knowledge about the accuracy of available GH-stimulation tests, safety of recombinant human GH (rhGH) replacement, unapproved uses of rhGH related to sports and aging, and new developments such as long-acting GH preparations that use a variety of technologies to prolong GH action. Recommendations offer a framework for physicians to manage patients with GHD effectively during transition to adult care and adulthood. Establishing a correct diagnosis is essential before consideration of replacement therapy with rhGH. Since the diagnosis of GHD in adults can be challenging, GH-stimulation tests are recommended based on individual patient circumstances and use of appropriate GH cut-points. Available GH-stimulation tests are discussed regarding variability, accuracy, reproducibility, safety, and contraindications, among other factors. The regimen for starting and maintaining rhGH treatment now uses individualized dose adjustments, which has improved effectiveness and reduced reported side effects, dependent on age, gender, body mass index, and various other individual characteristics. With careful dosing of rhGH replacement, many features of adult GHD are reversible and side effects of therapy can be minimized. Scientific studies have consistently shown rhGH therapy to be beneficial for adults with GHD, including improvements in body composition and quality of life, and have demonstrated the safety of short- and long-term rhGH replacement. Abbreviations: AACE = American Association of Clinical Endocrinologists; ACE = American College of Endocrinology; AHSG = alpha-2-HS-glycoprotein; AO-GHD = adult-onset growth hormone deficiency; ARG = arginine; BEL = best evidence level; BMD = bone mineral density; BMI = body mass index; CI = confidence interval; CO-GHD = childhood-onset growth hormone deficiency; CPG = clinical practice guideline; CRP = C-reactive protein; DM = diabetes mellitus; DXA = dual-energy X-ray absorptiometry; EL = evidence level; FDA = Food and Drug Administration; FD-GST = fixed-dose glucagon stimulation test; GeNeSIS = Genetics and Neuroendocrinology of Short Stature International Study; GH = growth hormone; GHD = growth hormone deficiency; GHRH = growth hormone-releasing hormone; GST = glucagon stimulation test; HDL = high-density lipoprotein; HypoCCS = Hypopituitary Control and Complications Study; IGF-1 = insulin-like growth factor-1; IGFBP = insulin-like growth factor-binding protein; IGHD = isolated growth hormone deficiency; ITT = insulin tolerance test; KIMS = Kabi International Metabolic Surveillance; LAGH = long-acting growth hormone; LDL = low-density lipoprotein; LIF = leukemia inhibitory factor; MPHD = multiple pituitary hormone deficiencies; MRI = magnetic resonance imaging; P-III-NP = procollagen type-III amino-terminal pro-peptide; PHD = pituitary hormone deficiencies; QoL = quality of life; rhGH = recombinant human growth hormone; ROC = receiver operating characteristic; RR = relative risk; SAH = subarachnoid hemorrhage; SDS = standard deviation score; SIR = standardized incidence ratio; SN = secondary neoplasms; T3 = triiodothyronine; TBI = traumatic brain injury; VDBP = vitamin D-binding protein; WADA = World Anti-Doping Agency; WB-GST = weight-based glucagon stimulation test.

Impact of BMI on peak growth hormone responses to provocative tests and therapeutic outcome in children with growth hormone deficiency

This study investigated the relationship between peak stimulated growth hormone (GH) and body mass index (BMI), as well as the impact of BMI on therapeutic response in patients with GH deficiency (GHD). A total of 460 patients were enrolled in the study. The patients were divided into four groups as per the etiology and peak GH values: idiopathic (n = 439), organic (n = 21), complete (n = 114), and partial (n = 325) GHD groups. Subsequently, they were classified as normal, overweight, or obese based on their BMI. There was no difference in BMI between complete and partial GHD. A significant negative relationship between peak GH and BMI were found. Moreover, obese GHD children had a considerably better therapeutic response in height increase and BMI decrease during 2 years of GH treatment compared to non-obese children with GHD. There was no difference between peak GH and type of GH stimulation test (GHST), except the clonidine test, which showed a much lower peak GH in obese GHD children. In conclusion, BMI had a negative impact on peak GH response, and therapeutic outcome was more favorable in the obese group. Despite no difference in GH response by type of GHST, the degree of obesity differentially affected the results.

The frequency and the diagnosis of pituitary dysfunction after traumatic brain injury

PURPOSE

Clinical research studies over the last 15 years have reported a significant burden of hypopituitarism in survivors of traumatic brain injury (TBI). However, debate still exists about the true prevalence of hypopituitarism after head injury.

METHODS

We have reviewed the literature describing the frequency of post-traumatic hypopituitarism and discuss the factors which may explain the variable frequency of the reported deficits in clinical studies including research methodology and the natural history of the disease.

RESULTS

Pituitary hormone perturbations in the acute phase following injury are frequent but are difficult to attribute to traumatic pituitary damage due to physiological hormonal changes in acute illness, the confounding effect of medications, other co-morbidities and lack of appropriate control subjects. Nevertheless, a small number of studies have emphasised the clinical importance of acute, dynamic disturbance of the hypothalamic-pituitary-adrenal axis. There is a much larger evidence base examining the frequency of hypopituitarism in the chronic, recovery phase following head injury. These studies report a very broad prevalence of long-term pituitary hormone dysfunction in survivors of TBI. However, systematic review suggests the prevalence to be between 27 and 31%.

CONCLUSION

Survivors of head injury are at risk of pituitary hormone dysfunction and we suggest an approach to the diagnosis of post-traumatic hypopituitarism in routine clinical practice.

Hypothalamic-Pituitary and Growth Disorders in Survivors of Childhood Cancer: An Endocrine Society Clinical Practice Guideline

OBJECTIVE

To formulate clinical practice guidelines for the endocrine treatment of hypothalamic-pituitary and growth disorders in survivors of childhood cancer.

PARTICIPANTS

An Endocrine Society-appointed guideline writing committee of six medical experts and a methodologist.

CONCLUSIONS

Due to remarkable improvements in childhood cancer treatment and supportive care during the past several decades, 5-year survival rates for childhood cancer currently are >80%. However, by virtue of their disease and its treatments, childhood cancer survivors are at increased risk for a wide range of serious health conditions, including disorders of the endocrine system. Recent data indicate that 40% to 50% of survivors will develop an endocrine disorder during their lifetime. Risk factors for endocrine complications include both host (e.g., age, sex) and treatment factors (e.g., radiation). Radiation exposure to key endocrine organs (e.g., hypothalamus, pituitary, thyroid, and gonads) places cancer survivors at the highest risk of developing an endocrine abnormality over time; these endocrinopathies can develop decades following cancer treatment, underscoring the importance of lifelong surveillance. The following guideline addresses the diagnosis and treatment of hypothalamic-pituitary and growth disorders commonly encountered in childhood cancer survivors.

The effect of growth hormone on bioactive IGF in overweight/obese women

OBJECTIVE

Overweight/obesity is characterized by decreased growth hormone (GH) secretion whereas circulating IGF-I levels are less severely reduced. Yet, the activity of the circulating IGF-system appears to be normal in overweight/obese subjects, as estimated by the ability of serum to activate the IGF-I receptor in vitro (bioactive IGF). We hypothesized that preservation of bioactive IGF in overweight/obese women is regulated by an insulin-mediated suppression of IGF-binding protein-1 (IGFBP-1) and IGFBP-2, and by suppression of IGFBP-3, mediated by low GH. We additionally hypothesized that increases in bioactive IGF would drive changes in body composition with low-dose GH administration.

DESIGN

Cross-sectional analysis and 3-month interim analysis of a 6-month randomized, placebo-controlled study of GH administration in 50 overweight/obese women without diabetes mellitus. Bioactive IGF (kinase receptor activation assay) and body composition (DXA) were measured.

RESULTS

Prior to treatment, IGFBP-3 (r = -0.33, p = 0.02), but neither IGFBP-1 nor IGFBP-2, associated inversely with bioactive IGF. In multivariate analysis, lower IGFBP-3 correlated with lower peak stimulated GH (r = 0.45, p = 0.05) and higher insulin sensitivity (r = -0.74, p = 0.003). GH administration resulted in an increase in mean serum IGF-I concentrations (144 ± 56 to 269 ± 66 μg/L, p < 0.0001) and bioactive IGF (1.29 ± 0.39 to 2.60 ± 1.12 μg/L, p < 0.0001). The treatment-related increase in bioactive IGF, but not total IGF-I concentration, predicted an increase in lean mass (r = 0.31, p = 0.03) and decrease in total adipose tissue/BMI (r = -0.43, p = 0.003).

CONCLUSIONS

Our data suggest that in overweight/obesity, insulin sensitivity and GH have opposing effects on IGF bioactivity through effects on IGFBP-3. Furthermore, increases in bioactive IGF, rather than IGF-I concentration, predicted GH administration-related body composition changes.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00131378.

The prevalence of growth hormone deficiency in survivors of subarachnoid haemorrhage: results from a large single centre study

OBJECTIVE

The variation in reported prevalence of growth hormone deficiency (GHD) post subarachnoid haemorrhage (SAH) is mainly due to methodological heterogeneity. We report on the prevalence of GHD in a large cohort of patients following SAH, when dynamic and confirmatory pituitary hormone testing methods are systematically employed.

DESIGN

In this cross-sectional study, pituitary function was assessed in 100 patients following SAH. Baseline pituitary hormonal profile measurement and glucagon stimulation testing (GST) was carried out in all patients. Isolated GHD was confirmed with an Arginine stimulation test and ACTH deficiency was confirmed with a short synacthen test.

RESULTS

The prevalence of hypopituitarism in our cohort was 19% and the prevalence of GHD was 14%. There was no association between GHD and the clinical or radiological severity of SAH at presentation, treatment modality, age, or occurrence of vasospasm. There were statistically significant differences in terms of Glasgow Outcome Scale (GOS; p = 0.03) between patients diagnosed with GHD and those without. Significant inverse correlations between GH peak on GST with body mass index (BMI) and waist hip ratio (WHR) was also noted (p < 0.0001 and p < 0.0001 respectively).

CONCLUSION

Using the current testing protocol, the prevalence of GHD detected in our cohort was 14%. It is unclear if the BMI and WHR difference observed is truly due to GHD or confounded by the endocrine tests used in this protocol. There is possibly an association between the development of GHD and worse GOS score. Routine endocrine screening of all SAH survivors with dynamic tests is time consuming and may subject many patients to unnecessary side-effects. Furthermore the degree of clinical benefit derived from growth hormone replacement in this patient group, remains unclear. Increased understanding of the most appropriate testing methodology in this patient group and more importantly which SAH survivors would derive most benefit from GHD screening is required.

Update on GH therapy in adults

Over the last three decades, short- and long-term observational studies, clinical trials, systematic reviews, and meta-analyses have provided relevant information on the efficacy and safety of growth hormone (GH) replacement therapy in adults with GH deficiency (AGHD). The knowledge acquired during this time has been compiled into different guidelines that offer clinicians an evidence-based, practical approach for the management of AGHD. There are, however, still open questions in some key areas in which recommendations are supported by only moderate or weak evidence. In the last recent years, the development of long-acting GH preparations has created new therapeutic possibilities by decreasing injection frequency, improving adherence and thereby potentially maximizing clinical outcomes. The aims of this review are to advance our understanding on the diagnosis and treatment of AGHD and to present an update and future perspectives on the use of long-acting GH preparations.

Hepatic lipid metabolism and non-alcoholic fatty liver disease in aging

Aging is associated with dysregulation of glucose and lipid metabolism. Various factors that contribute to the dysregulation include both modifiable (e.g. obesity, insulin resistance) and non-modifiable risk factors (age-associated physiologic changes). Although there is no linear relationship between aging and prevalence of non-alcoholic fatty liver disease, current data strongly suggests that advanced age leads to more severe histological changes and poorer clinical outcomes. Hepatic lipid accumulation could lead to significant hepatic and systemic consequences including steatohepatitis, cirrhosis, impairment of systemic glucose metabolism and metabolic syndrome, thereby contributing to age-related diseases. Insulin, leptin and adiponectin are key regulators of the various physiologic processes that regulate hepatic lipid metabolism. Recent advances have expanded our understanding in this field, highlighting the role of novel mediators such as FGF 21, and mitochondria derived peptides. In this review, we will summarize the mediators of hepatic lipid metabolism and how they are altered in aging.

Oral glucose-stimulated growth hormone (GH) test in adult GH deficiency patients and controls: Potential utility of a novel test

CONTEXT

The diagnosis of adult GH deficiency requires confirmation with a GH stimulation test. Oral glucose (OG) administration affects GH secretion, initially decreasing and subsequently stimulating GH secretion.

OBJECTIVE

The aim of this study was to investigate the diagnostic efficacy and safety of a long OG test (LOGT) as a stimulus of GH secretion for the diagnosis of adult GH deficiency (AGHD).

DESIGN

Prospective experimental cross-sectional study.

SETTINGS

The study was conducted at the Endocrinology department of the University Hospital of a Coruña, Spain.

PARTICIPANTS AND METHODS

We included 60 (40 women) AGHD patients (15) and controls (45) paired 1:3, of similar age, sex and BMI. The area under the curve (AUC) and peak were calculated for GH. The Mann-Whitney test was used to compare the different groups. ROC curve analyses were used. p-Values<0.05 were considered as statistically significant.

INTERVENTIONS

The intervention consisted of orally administering 75g oral glucose administration; GH was obtained every 30min for a total of 300min.

MAIN OUTCOME MEASUREMENT

Peak GH area under receiver operating characteristic curve (ROC-AUC) following LOGT.

RESULTS

Peak GH (μg/L) levels were lower in the AGHD patients (0.26±0.09) than in the controls (4.00±0.45), p<0.001. After LOGT, with the ROC plot analysis the best peak GH cut-point was 1.0μg/L, with 100% sensitivity, 78% specificity, ROC-AUC of 0.9089 and 81.82% accuracy. There were no relevant adverse events during any of the LOGT.

CONCLUSIONS

The LOGT could be a cheap, safe, convenient and effective test for the diagnosis of AGHD.

Growth hormone and cortisol secretion in the elderly evaluated using the glucagon stimulation test

OBJECTIVES

The glucagon stimulation test is a reliable alternative test to assess growth hormone and cortisol secretion, but has not been widely used in the elderly population. The aim of this study was to evaluate growth hormone and cortisol secretion using the glucagon stimulation test in an elderly population without known hypothalamic-pituitary disease and to correlate growth hormone and cortisol peaks with age (less than or greater than 80 years) and body mass index.

METHODS

Forty-two subjects (67-88 years) from the geriatric ambulatory unit were submitted and 41 subjects completed the glucagon stimulation test.

RESULTS

Median growth hormone peak was 5.99 μg/L and median cortisol peak was 21.6 μg/dL. Growth hormone peak was >3 µg/L in 73.2%, and cortisol peak was >18 µg/dL in 65.8% of patients. There was a statistically significant positive correlation between the growth hormone peak and the cortisol peak. The cortisol peak was significantly different between subjects stratified by growth hormone peak of < or >3 μg/L (15.7 and 21.8 μg/dL, respectively). There was a statistically significant difference in cortisol peak according to age < or > 80 years (22.4 and 18.5 µg/dL, respectively). Considering lower cut-offs recently proposed for growth hormone peak (1.0 μg/L for overweight subjects) and cortisol peak (9.1 μg/dL), only two patients had a growth hormone peak below this value, and all patients had preserved cortisol secretion.

CONCLUSIONS

We did find a positive correlation between growth hormone and cortisol peaks in the glucagon stimulation test in the elderly, confirming the capacity of the glucagon stimulation test to stimulate both axes. According to the new proposed cut-points for growth hormone and cortisol, we had 95% of normal growth hormone and 100% of normal cortisol responses.

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.

Growth Hormone Control of Hepatic Lipid Metabolism

In humans, low levels of growth hormone (GH) and its mediator, IGF-1, associate with hepatic lipid accumulation. In mice, congenital liver-specific ablation of the GH receptor (GHR) results in reductions in circulating IGF-1 and hepatic steatosis, associated with systemic insulin resistance. Due to the intricate relationship between GH and IGF-1, the relative contribution of each hormone to the development of hepatic steatosis is unclear. Our goal was to dissect the mechanisms by which hepatic GH resistance leads to steatosis and overall insulin resistance, independent of IGF-1. We have generated a combined mouse model with liver-specific ablation of GHR in which we restored liver IGF-1 expression via the hepatic IGF-1 transgene. We found that liver GHR ablation leads to increases in lipid uptake, de novo lipogenesis, hyperinsulinemia, and hyperglycemia accompanied with severe insulin resistance and increased body adiposity and serum lipids. Restoration of IGF-1 improved overall insulin sensitivity and lipid profile in serum and reduced body adiposity, but was insufficient to protect against steatosis-induced hepatic inflammation or oxidative stress. We conclude that the impaired metabolism in states of GH resistance results from direct actions of GH on lipid uptake and de novo lipogenesis, whereas its actions on extrahepatic tissues are mediated by IGF-1.

Hypopituitarism

Hypopituitarism refers to deficiency of one or more hormones produced by the anterior pituitary or released from the posterior pituitary. Hypopituitarism is associated with excess mortality, a key risk factor being cortisol deficiency due to adrenocorticotropic hormone (ACTH) deficiency. Onset can be acute or insidious, and the most common cause in adulthood is a pituitary adenoma, or treatment with pituitary surgery or radiotherapy. Hypopituitarism is diagnosed based on baseline blood sampling for thyroid stimulating hormone, gonadotropin, and prolactin deficiencies, whereas for ACTH, growth hormone, and antidiuretic hormone deficiency dynamic stimulation tests are usually needed. Repeated pituitary function assessment at regular intervals is needed for diagnosis of the predictable but slowly evolving forms of hypopituitarism. Replacement treatment exists in the form of thyroxine, hydrocortisone, sex steroids, growth hormone, and desmopressin. If onset is acute, cortisol deficiency should be replaced first. Modifications in replacement treatment are needed during the transition from paediatric to adult endocrine care, and during pregnancy.

[Hypopituitarism following traumatic brain injury: diagnostic and therapeutic issues]

Traumatic Brain Injury (TBI) is a well-known public health problem worldwide and is a leading cause of death and disability, particularly in young adults. Besides neurological and psychiatric issues, pituitary dysfunction can also occur after TBI, in the acute or chronic phase. The exact prevalence of post-traumatic hypopituitarism is difficult to assess due to the wide heterogeneity of published studies and bias in interpretation of hormonal test results in this specific population. Predictive factors for hypopituitarism have been proposed and are helpful for the screening. The pathophysiology of pituitary dysfunction after TBI is not well understood but the vascular hypothesis is privileged. Activation of pituitary stem/progenitor cells is probably involved in the recovery of pituitary functions. Those cells also play a role in the induction of pituitary tumors, highlighting their crucial place in pituitary conditions. This review updates the current data related to anterior pituitary dysfunction after TBI and discusses the bias and difficulties encountered in its diagnosis.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY DISEASE STATE CLINICAL REVIEW: A NEUROENDOCRINE APPROACH TO PATIENTS WITH TRAUMATIC BRAIN INJURY

OBJECTIVE

Traumatic brain injury (TBI) is now recognized as a major public health concern in the United States and is associated with substantial morbidity and mortality in both children and adults. Several lines of evidence indicate that TBI-induced hypopituitarism is not infrequent in TBI survivors and may contribute to the burden of illness in this population. The goal of this article is to review the published data and propose an approach for the neuroendocrine evaluation and management of these patients.

METHODS

To identify pertinent articles, electronic literature searches were conducted using the following keywords: "traumatic brain injury," "pituitary," "hypopituitarism," "growth hormone deficiency," "hypogonadism," "hypoadrenalism," and "hypothyroidism." Relevant articles were identified and considered for inclusion in the present article.

RESULTS

TBI-induced hypopituitarism appears to be more common in patients with severe TBI. However, patients with mild TBI or those with repeated, sports-, or blast-related TBI are also at risk for hypopituitarism. Deficiencies of growth hormone and gonadotropins appear to be most common and have been associated with increased morbidity in this population. A systematic approach is advised in order to establish the presence of pituitary hormone deficiencies and implement appropriate replacement therapies.

CONCLUSION

The presence of traumatic hypopituitarism should be considered during the acute phase as well as during the rehabilitation phase of patients with TBI. All patients with moderate to severe TBI require evaluation of pituitary function. In addition, symptomatic patients with mild TBI and impaired quality of life are at risk for hypopituitarism and should be offered neuroendocrine testing.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY DISEASE STATE CLINICAL REVIEW: UPDATE ON GROWTH HORMONE STIMULATION TESTING AND PROPOSED REVISED CUT-POINT FOR THE GLUCAGON STIMULATION TEST IN THE DIAGNOSIS OF ADULT GROWTH HORMONE DEFICIENCY

OBJECTIVE

The clinical features of adult GH deficiency (GHD) are nonspecific, and GH stimulation testing is often required to confirm the diagnosis. However, diagnosing adult GHD can be challenging due to the episodic and pulsatile GH secretion, concurrently modified by age, gender, and body mass index (BMI).

METHODS

PubMed searches were conducted to identify published data since 2009 on GH stimulation tests used to diagnose adult GHD. Relevant articles in English language were identified and considered for inclusion in the present document.

RESULTS

Testing for confirmation of adult GHD should only be considered if there is a high pretest probability, and the intent to treat if the diagnosis is confirmed. The insulin tolerance test (ITT) and glucagon stimulation test (GST) are the two main tests used in the United States. While the ITT has been accepted as the gold-standard test, its safety concerns hamper wider use. Previously, the GH-releasing hormone-arginine test, and more recently the GST, are accepted alternatives to the ITT. However, several recent studies have questioned the diagnostic accuracy of the GST when the GH cut-point of 3 μg/L is used and have suggested that a lower GH cut-point of 1 μg/L improved the sensitivity and specificity of this test in overweight/obese patients and in those with glucose intolerance.

CONCLUSION

Until a potent, safe, and reliable test becomes available, the GST should remain as the alternative to the ITT in the United States. In order to reduce over-diagnosing adult GHD in overweight/obese patients with the GST, we propose utilizing a lower GH cut-point of 1 μg/L in these subjects. However, this lower GH cut-point still needs further evaluation for diagnostic accuracy in larger patient populations with varying BMIs and degrees of glucose tolerance.

ABBREVIATIONS

AACE = American Association of Clinical Endocrinologists BMI = body mass index GH = growth hormone GHD = GH deficiency GHRH = GH-releasing hormone GHS = GH secretagogue GST = glucagon stimulation test IGF = insulin-like growth factor IGFBP-3 = IGF-binding protein 3 ITT = insulin tolerance test ROC = receiver operating characteristic WB-GST = weight-based GST.

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.

Copeptin under glucagon stimulation

Stimulation of growth hormone (GH) and adrenocorticotropic hormone (ACTH) secretion by glucagon is a standard procedure to assess pituitary dysfunction but the pathomechanism of glucagon action remains unclear. As arginine vasopressin (AVP) may act on the release of both, GH and ACTH, we tested here the role of AVP in GST by measuring a stable precursor fragment, copeptin, which is stoichiometrically secreted with AVP in a 1:1 ratio. ACTH, cortisol, GH, and copeptin were measured at 0, 60, 90, 120, 150, and 180 min during GST in 79 subjects: healthy controls (Group 1, n = 32), subjects with pituitary disease, but with adequate cortisol and GH responses during GST (Group 2, n = 29), and those with overt hypopituitarism (Group 3, n = 18). Copeptin concentrations significantly increased over baseline 150 and 180 min following glucagon stimulation in controls and patients with intact pituitary function but not in hypopituitarism. Copeptin concentrations were stimulated over time and the maximal increment correlated with ACTH, while correlations between copeptin and GH were weaker. Interestingly, copeptin as well as GH secretion was significantly attenuated when comparing subjects within the highest to those in the lowest BMI quartile (p < 0.05). Copeptin is significantly released following glucagon stimulation. As this release is BMI-dependent, the time-dependent relation between copeptin and GH may be obscured, whereas the close relation to ACTH suggests that AVP/copeptin release might be linked to the activation of the adrenal axis.

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.

Effects of gender, body weight, and blood glucose dynamics on the growth hormone response to the glucagon stimulation test in patients with pituitary disease

OBJECTIVE

Body weight blunts the growth hormone (GH) response to provocative stimuli. The appropriate GH cut-off to confirm GH deficiency in obese and overweight patients undergoing the glucagon stimulation test (GST) has recently been questioned. We hypothesized that the peak GH would be inversely related to the nadir blood glucose (BG) after glucagon and that this may be a mechanism influencing peak GH in overweight patients. This retrospective study examined effects of gender, body weight, and BG dynamics on GH response to GST in patients evaluated in our Pituitary Center.

DESIGN

Adult patients who underwent GST from September 2009-2014 were included. Continuous variable comparisons were analyzed using the Mann-Whitney U-test and categorical data by Fisher's Exact Test. Spearman correlation was used to determine associations between continuous variables.

RESULTS

42 patients (N=28, 66.7% female) had sufficient data for analysis. Obese patients (N=26) had a reduced GH response, summarized as GH area under the curve (AUC) (p=0.03 vs. non-obese patients) and higher BG during GST, summarized as AUC (p<0.01 vs. non-obese patients). Obese women (N=19), in particular, stimulated lower (p=0.03 vs. non-obese women) and had a higher nadir BG (p=0.03 vs. non-obese women). While weight correlated with extent (rs=0.35; p=0.02) and timing (rs=0.31; p=0.05) of nadir BG reached, there was no significant correlation between BG dynamics and the GH response in the total population (N=42). Ten patients (7 with pan anterior hypopituitarism, defined as 3 anterior pituitary deficiencies) had a peak GH≤0.1ng/mL during GST. When these subjects with a negligible peak GH response were excluded from the analysis, weight was associated with GH AUC (rs=-0.45; p=0.01), peak GH response (rs=-0.42; p=0.02) and nadir BG (rs=0.48; p<0.01). Furthermore, the nadir BG achieved during GST was inversely related to GH AUC (rs=-0.38; p=0.03) and peak GH (rs=-0.37; p=0.04) such that patients (N=32) with higher nadir BG had lower peak GH in response to glucagon.

CONCLUSIONS

Obese patients, particularly women, do not respond as robustly to glucagon stimulation. These data suggest that there exists an altered BG profile during GST in obese individuals, and that a less robust hypoglycemic stimulus may contribute to an impaired GH response. We suggest measuring BG levels during glucagon stimulation testing to assist with clinical interpretation of GH dynamics. The diagnostic accuracy of the GST in patients with known disorders in glucose metabolism and those taking anti-diabetic medications deserves further study.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSIONS

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