Depth and duration of hypoglycaemia achieved during the insulin tolerance test

A comprehensive in-vitro/in-vivo screening toolbox for the elucidation of glucose homeostasis modulating properties of plant extracts (from roots) and its bioactives

Plant extracts are increasingly recognized for their potential in modulating (postprandial) blood glucose levels. In this context, root extracts are of particular interest due to their high concentrations and often unique spectrum of plant bioactives. To identify new plant species with potential glucose-lowering activity, simple and robust methodologies are often required. For this narrative review, literature was sourced from scientific databases (primarily PubMed) in the period from June 2022 to January 2024. The regulatory targets of glucose homeostasis that could be modulated by bioactive plant compounds were used as search terms, either alone or in combination with the keyword "root extract". As a result, we present a comprehensive methodological toolbox for studying the glucose homeostasis modulating properties of plant extracts and its constituents. The described assays encompass in-vitro investigations involving enzyme inhibition (α-amylase, α-glucosidase, dipeptidyl peptidase 4), assessment of sodium-dependent glucose transporter 1 activity, and evaluation of glucose transporter 4 translocation. Furthermore, we describe a patch-clamp technique to assess the impact of extracts on KATP channels. While validating in-vitro findings in living organisms is imperative, we introduce two screenable in-vivo models (the hen's egg test and Drosophila melanogaster). Given that evaluation of the bioactivity of plant extracts in rodents and humans represents the current gold standard, we include approaches addressing this aspect. In summary, this review offers a systematic guide for screening plant extracts regarding their influence on key regulatory elements of glucose homeostasis, culminating in the assessment of their potential efficacy in-vivo. Moreover, application of the presented toolbox might contribute to further close the knowledge gap on the precise mechanisms of action of plant-derived compounds.

First results of the growth disorders related twinning programme Partners4Growth implemented at the tertiary university pediatric endocrinology clinics in Bulgaria

OBJECTIVES

Early diagnosis of childhood growth disorders, their timely and proper treatment are important for better outcomes.The aim of the present study was to assess the results of the first 18 months of the growth disorders related twinning programme "Partners4Growth" implemented at all tertiary university pediatric endocrinology clinics in Bulgaria.

METHODS

In 2019, Partners4Growth started operation at 7 centres (4 experienced and 3 twin centres) with the main aim of aligning their practices in the shortest possible time. Education of twin centres' personnel was organized, equipment and methods for growth evaluation and follow-up were standardized. The approach was tested initially at one centre. At baseline and at the 18th month a questionnaire concerning diagnosis and management of recombinant human growth hormone (rhGH) requiring disorders was applied.

RESULTS

A total of 104 new patients were diagnosed compared to 30 in the previous year. Of those, 91 started rhGH treatment - 65 (64 %) GH deficient, 12 (12 %) Turner syndrome, 7 (7 %) Prader-Willi syndrome patients, and 7 (7 %) born small for gestational age without postnatal catch-up, representing 35.8 % of all currently rhGH treated Bulgarian children. A better geographical coverage and more advanced diagnostic and management practices were achieved.

CONCLUSIONS

Partners4Growth facilitated the alignment of the tertiary pediatric endocrinology centres competences thus leading to an improved diagnosis and treatment of growth disorders as well as better patients' access. For its short existence, the Programme increased significantly the number of new patients in the difficult times of COVID-19 pandemic thus justifying its continuation.

Prevalence of refractoriness when testing growth hormone levels in children

OBJECTIVE

Late night spontaneous growth hormone (GH) pulses may influence the pituitary GH response to provocation tests. We evaluated GH response during arginine-insulin-tolerance test (AITT) after a GH peak during a short spontaneous nocturnal profile (SSNP) in children with short stature or low growth velocity.

DESIGN

Using SSNP and subsequent AITT, we examined 257 children 4-18 years old (138 (53.7%) males) recruited from three hospitals. Medical records were reviewed retrospectively. Refractory children were defined as a GH peak ≥7 μg/L during SSNP but no GH peak ≥7 μg/L during AITT.

RESULTS

In total, 201/257 children had a GH peak ≥7 μg/L at SSNP and/or AITT. Of these, 21.9% were refractory. The proportion of males (p = 0.033) and body mass index (BMI) standard deviation score (SDS) (p = 0.037) were higher in the refractory group than in children with a GH peak ≥7 μg/L during AITT. The median period between last GH peak ≥7 μg/L during SSNP and GHmax at AITT was 210 (30-390) minutes. The GHmax at AITT occurred 30 min earlier for children without a peak ≥7 μg/L during the SSNP (p = 0.004). The number of refractoriness differed somewhat between the hospitals (p = 0.025).

CONCLUSIONS

Many children with short stature were refractory at testing; among them we found few clinical characteristics. Refractoriness might be influenced by some differences in procedure, but needs to be considered when evaluating GH response in children.

Preference for high-carbohydrate foods does not change for children and adolescents in insulin-induced hypoglycemia

INTRODUCTION

Hypoglycemia elicits coordinated counter-regulatory neuroendocrine responses. The extent to which this process involves an increased drive to eat, together with greater preference for foods high in carbohydrate content, is unclear. Our objective was to examine this effect in children and adolescents (age 5-19 years) without diabetes and no prior known experience of hypoglycemic episodes.

RESEARCH DESIGN AND METHODS

We administered a computerised task designed to examine preference for high-carbohydrate foods (sweet and savory) to pediatric patients (n=26) undergoing an insulin tolerance test as part of the routine clinical assessment of pituitary hormone secretory capacity. The task was completed at baseline and three time points after intravenous infusion of insulin (approximately 7, 20 and 90 min).

RESULTS

Although all patients reached insulin-induced hypoglycemia (mean venous glucose at nadir=1.9 mmol/L), there was moderate evidence of no effect on preference for high-carbohydrate foods (moderate evidence for the null hypothesis) compared with euglycemia. Patients also did not display an increase in selection of foods of high compared with low energy density. Sensitivity of the task was demonstrated by decreased preference for sweet, high-carbohydrate foods after consumption of sweet food and drink.

CONCLUSIONS

Results support the view that acute hypoglycemia does not automatically prompt the choice of high-carbohydrate foods for rapid glucose restoration, and further stresses the importance that people and families with children vulnerable to hypoglycemic episodes ensure that 'rapidly absorbed glucose rescue therapy' is always available.

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

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

CONCLUSION

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

WHAT IS KNOWN

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

WHAT IS NEW

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

A Comparison of the Blood Glucose, Growth Hormone, and Cortisol Responses to Two Doses of Insulin (0.15 U/kg vs. 0.10 U/kg) in the Insulin Tolerance Test: A Single-Centre Audit of 174 Cases

OBJECTIVE

The insulin tolerance test (ITT) is the gold standard endocrine test used to assess the integrity of the growth hormone (GH) and cortisol axes. The ITT has potential risks, and severe hypoglycaemia may necessitate intravenous glucose rescue. There is no clear consensus as to the optimal insulin dose for the ITT. Therefore, we sought to compare the standard dose (0.15 U/kg) and a low-dose ITT (0.1 U/kg).

DESIGN

Single-centre audit of ITT data (2012-2021). Patients and Measurements. Patients who underwent an ITT to assess possible GH deficiency/adrenal insufficiency were included. Glucose, GH, and cortisol were measured at baseline and 30, 45, 60, 90, and 120 minutes following I.V. insulin bolus (0.15 U/kg or 0.10 U/kg).

RESULTS

Of the ITTs performed, only 3/177 (1.7%) did not achieve adequate hypoglycaemia (≤2.2 mmol/L) with a single insulin dose. In total, 174 patients (43.5 ± 12.1 yrs, mean ± standard deviation) were included for analysis (0.15 U/kg: n = 113, 0.10 U/kg: n = 61). All 174 subjects had adequate hypoglycaemia regardless of baseline fasting blood glucose level or insulin dose. Neither nadir glucose nor glucose delta (i.e., baseline minus nadir) differed between insulin doses. Trends in both cortisol and GH responses over time were similar between groups, and a greater proportion of patients receiving the standard dose had an adequate cortisol response (77/106 (72.6%) vs. 32/60 (53.3%), p=0.01). The rates of glucose rescue did not differ in a subset of 79 patients, with on-demand glucose rescue in 4/35 (11%) for the standard dose and 2/44 (5%) for the low dose (p=0.25).

CONCLUSIONS

Our results suggest that the low-dose ITT produces comparable glucose, cortisol, and GH responses to the higher dose. Given the risks associated with hypoglycaemia, the low dose appears to be preferable to the standard dose ITT in most circumstances.

Revisiting peak serum cortisol response to insulin-induced hypoglycemia in children

PURPOSE

To evaluate factors that could potentially affect the hypothalamic-pituitary adrenal (HPA) axis response to insulin-induced hypoglycemia in children without history or symptoms of adrenal insufficiency and to propose a cut-off value to define a normal response in this population.

METHODS

Exploratory single-center study involving 78 children that prospectively underwent insulin tolerance test (ITT) for suspected growth hormone (GH) deficiency.

METHODS

Glucose, cortisol, GH, adrenocorticotrophic hormone (ACTH), epinephrine and norepinephrine levels were measured at baseline and after insulin-induced hypoglycemia. Serum cortisol was measured using Access automated immunoassay.

RESULTS

Mean (range) basal morning serum cortisol of 8 (2.2-19.5) µg/dL/222 (61-542) nmol/L increased after hypoglycemia to 20.5 (14.6-29.5) µg/dL/570 nmol/L (405-819) nmol/L. Peak serum cortisol levels of 14.6 µg/dL (405 nmol/L) and 15.4 µg/dL (428 nmol/L) corresponded to the 2.5th and 5th percentiles, respectively. Peak serum cortisol correlated with peak plasma epinephrine (r = 0.367; P = 0.0014) but did not correlate with age, BMI-SD or peak serum GH. Children with intact and abnormal GH responses presented similar mean peak serum cortisol levels (20.0 vs. 20.6 µg/dL/555 vs. 572 nmol/L; P = 0.21).

CONCLUSION

Our data indicate that the current cut-off to define normal HPA axis response in children after insulin-induced hypoglycemia warrants reevaluation to avoid over-diagnosis of adrenal insufficiency. Our results suggest that peak serum cortisol levels ≥ 15.4 µg/dL (428 nmol/L) in children undergoing ITT might represent a normal cortisol response to stress, regardless of age, BMI or GH secretory capacity.

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

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

Copeptin response to hypoglycemic stress is linked to prolactin activation in children

PURPOSE

The physiological role of arginine vasopressin (AVP) in the acute stress response in humans and especially in children is unclear. The aim of this study was to explore the interaction between copeptin, a well-established surrogate marker of AVP release, and anterior pituitary hormone activation in response to acute hypoglycemic stress in children and adolescents.

METHODS

We conducted an exploratory single center study involving 77 children and adolescents undergoing insulin-induced hypoglycemia. Blood levels of copeptin, ACTH, cortisol, GH, prolactin, interleukin-6 (IL-6), adrenaline and noradrenaline were determined at baseline and after insulin-induced hypoglycemia.

RESULTS

Basal plasma levels of copeptin (median: 5.2 pmol/L) increased significantly after hypoglycemia (median 9.7 pmol/L; P < 0.0001). Subjects with insufficient HPA axis response or severe GH deficiency had lower hypoglycemia-induced copeptin increase (median: 2.3 pmol/L) compared with individuals with intact pituitary response (median: 5.2 pmol/L, P = 0.02). Copeptin increase correlated significantly with the maximal increase of ACTH (r_s = 0.30; P = 0.010), cortisol (r_s = 0.33; P = 0.003), prolactin (r_s = 0.25; P = 0.03), IL-6 (r_s = 0.35; P = 0.008) and with BMI-SDS (r_s = - 0.28, P = 0.01). In multivariate regression analysis, prolactin increase was the only independent variable associated with copeptin increase (P = 0.0004).

CONCLUSION

Our data indicate that: (1) hypoglycemic stress elicits a marked copeptin response in children and adolescents, pointing out its role as an acute stress marker in this population; (2) stress-induced AVP/copeptin release is associated with anterior pituitary activation, mainly a prolactin response.

Interleukin-6 response to insulin-induced hypoglycemia is associated with hypothalamic-pituitary-adrenal axis activation

Increased plasma levels of interleukin-6 (IL-6) in response to acute hypoglycemia have been well documented. Aiming to study the interaction between IL-6 and counter-regulatory hormones during hypoglycemic stress we conducted an exploratory single center study involving 26 adult patients undergoing insulin tolerance test. Insulin-induced hypoglycemia elicited a significant dynamic response of IL-6, adrenaline, noradrenaline, GH, prolactin, ACTH and serum and salivary cortisol (P < 0.001 for all variables). Patients with insufficient HPA axis response had lower hypoglycemia-induced IL-6 increase (median: 0.88 pg/mL) compared with individuals with intact HPA axis response (2.03 pg/mL, P = 0.007). IL-6 maximal increase correlated with the maximal increase of serum cortisol (rs = 0.48; P = 0.013), salivary cortisol (rs = 0.66; P = 0.012), plasma ACTH (rs = 0.48; P = 0.013) and with the increase in procedure-related symptoms of anxiety and hypoglycemia (rs = 0.57; P = 0.003). In conclusion, hypoglycemic stress-induced IL-6 increase is associated with activation of the HPA axis, suggesting that IL-6 response to hypoglycemic stress may be regarded as part of the counter-regulatory response, possibly contributing to the maintenance of glucose homeostasis.

Is biochemical hypoglycemia necessary during an insulin tolerance test?

Objective The insulin tolerance test (ITT) has been accepted as the gold standard test for assessing the integrity of the growth hormone (GH) - insulin-like growth factor (IGF-1) axis and the hypothalamic-pituitary-adrenal (HPA) axis. The goal of the test is to achieve clinical and biochemical hypoglycemia at a blood glucose level ≤ 40 mg/dL to effectively and correctly assess the HPA and GH-IGF-1 axes. In this study, the GH and cortisol responses of patients who achieved and failed to achieve biochemical hypoglycemia during an ITT were compared. Subjects and methods One hundred thirty-five patients with pituitary disorders were included in the study. Samples for blood glucose levels were obtained after clear symptoms of clinical hypoglycemia developed. The patients were enrolled in the hypoglycemic and nonhypoglycemic groups according to whether their plasma glucose level ≤ 40 mg/dL or > 40 mg/dL during an ITT, and the groups were compared in terms of their GH and cortisol responses. Results The mean age, body mass index and waist circumference of the two patient groups were found to be similar. The mean blood glucose level was significantly lower in the hypoglycemic group than in the nonhypoglycemic group (19.3 and 52.0 mg/dL, respectively). When the two groups were compared in terms of peak cortisol and GH responses, no statistically significant differences were found. Conclusion The data presented suggest that clinically symptomatic hypoglycemia is as effective as biochemically confirmed hypoglycemia during an ITT. Arch Endocrinol Metab. 2020;64(1):82-8.

The Optimized Calculation Method for Insulin Dosage in an Insulin Tolerance Test (ITT): A Randomized Parallel Control Study

Objective: To explore the most suitable calculation method for insulin dosage in an insulin tolerance test (ITT) and to evaluate the clinical application value of the optimization coefficient (γ). Methods: In this study, 140 adult patients with congenital growth hormone deficiency (GHD) or acquired hypopituitarism were randomized into the following two groups: the conventional group (n = 70) and the optimized group (n = 70). Oral glucose tolerance tests (OGTTs), insulin release tests (IRTs), and ITTs were conducted. For ITTs, insulin doses were the product of body weight (kg) and related coefficient (0.15 IU/kg for the control group and γ IU/kg for the optimized group, respectively). Notably, γ was defined as -0.034 + 0.000176 × AUC_INS + 0.009846 × BMI, which was based on our previous study. Results: In the ITTs, the rate of achieving adequate hypoglycemia with a single insulin dose was significantly higher for the optimized group compared with the conventional group (92.9 vs. 60.0%, P < 0.001). The optimized group required higher initial doses of insulin (0.23 IU/kg). Meanwhile, the two groups did not differ significantly in their nadir blood glucose (1.9 vs. 1.9 mmol/L, P = 0.828). Conclusion: This study confirmed that the proposed optimized calculation method for insulin dosage in ITTs led to more efficient hypoglycemia achievement, without increasing the incidence of serious adverse events.

Fall in thyroid stimulating hormone (TSH) may be an early marker of ipilimumab-induced hypophysitis

PURPOSE

Hypophysitis develops in up to 19% of melanoma patients treated with ipilimumab, a cytotoxic T-lymphocyte antigen-4 antibody. Early detection may avert life-threatening hypopituitarism. We aimed to assess the incidence of ipilimumab-induced hypophysitis (IH) at a quaternary melanoma referral centre, and to determine whether cortisol or thyroid stimulating hormone (TSH) monitoring could predict IH onset.

METHODS

We performed a retrospective cohort study of ipilimumab-treated patients at a quaternary melanoma referral centre in Australia. The inclusion criteria were patients with metastatic or unresectable melanoma treated with ipilimumab monotherapy, and cortisol and TSH measurements prior to ≥ 2 infusions. The main outcomes were IH incidence and TSH and cortisol patterns in patients who did and did not develop IH.

RESULTS

Of 78 ipilimumab-treated patients, 46 met the study criteria and 9/46 (20%) developed IH at a median duration of 13.0 weeks (range 7.7-18.1) following ipilimumab initiation. All patients whose TSH fell ≥ 80% compared to baseline developed IH, and, in 5/9 patients with IH, TSH fell prior to cortisol fall and IH diagnosis. Pre-cycle-4 TSH was significantly lower in those who developed IH (0.31 vs. 1.73 mIU/L, P = 0.006). TSH fall was detected at a median time of 9.2 (range 7.7-16.4) weeks after commencing ipilimumab, and a median of 3.6 (range of - 1.4 to 9.7) weeks before IH diagnosis. There was no difference in TSH between the groups before cycles 1-3 or in cortisol before cycles 1-4.

CONCLUSIONS

TSH fall ≥ 80% may be an early marker of IH. Serial TSH measurement during ipilimumab therapy may be an inexpensive tool to expedite IH diagnosis.

Acute Hypoglycemia in Healthy Humans Impairs Insulin-Stimulated Glucose Uptake and Glycogen Synthase in Skeletal Muscle: A Randomized Clinical Study

Hypoglycemia is the leading limiting factor in glycemic management of insulin-treated diabetes. Skeletal muscle is the predominant site of insulin-mediated glucose disposal. Our study used a crossover design to test to what extent insulin-induced hypoglycemia affects glucose uptake in skeletal muscle and whether hypoglycemia counterregulation modulates insulin and catecholamine signaling and glycogen synthase activity in skeletal muscle. Nine healthy volunteers were examined on three randomized study days: 1) hyperinsulinemic hypoglycemia (bolus insulin), 2) hyperinsulinemic euglycemia (bolus insulin and glucose infusion), and 3) saline control with skeletal muscle biopsies taken just before, 30 min after, and 75 min after insulin/saline injection. During hypoglycemia, glucose levels reached a nadir of ∼2.0 mmol/L, and epinephrine rose to ∼900 pg/mL. Hypoglycemia impaired insulin-stimulated glucose disposal and glucose clearance in skeletal muscle, whereas insulin signaling in glucose transport was unaffected by hypoglycemia. Insulin-stimulated glycogen synthase activity was completely ablated during hyperinsulinemic hypoglycemia, and catecholamine signaling via cAMP-dependent protein kinase and phosphorylation of inhibiting sites on glycogen synthase all increased.

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

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

A comparison of low-dose ACTH, glucagon stimulation and insulin tolerance test in patients with pituitary disorders

CONTEXT

Diagnosis of secondary adrenal insufficiency and GH deficiency requires evaluation by dynamic stimulation tests in most cases. Although insulin tolerance test (ITT) is accepted as the gold-standard test for the evaluation of both hypothalamo-pituitary-adrenal (HPA) and (GH)-IGF-1 axes, the test is cumbersome. In clinical practice, low-dose adrenocorticotrophic hormone (ACTH) stimulation test is a sensitive, safe and easily applicable alternative to ITT. Although it takes more time, glucagon stimulation test (GST) is also a good alternative to ITT and can evaluate both axes.

OBJECTIVE

The primary aim of this study was to compare the ITT, low-dose ACTH and GSTs in the evaluation of HPA and GH-IGF-1 axes in patients with pituitary disorders and to evaluate the repeatability of all three tests.

DESIGN

ITT, low-dose ACTH and GSTs were performed in all 129 patients, and the tests were repeated in 66 of these patients.

SETTING

Erciyes University Medical School, Department of Endocrinology.

PATIENTS OR OTHER PARTICIPANTS

One hundred and twenty-nine adult patients (76 women, 53 men) with pituitary disorder were included in the study.

MAIN OUTCOME MEASURE(S)

The cortisol and GH responses of patients to dynamic tests.

RESULTS

Peak cortisol levels obtained during ITT were significantly lower than the values obtained during both low-dose ACTH and GSTs. Peak cortisol levels obtained during the GST were lower than those found during the low dose ACTH stimulation test. Peak GH responses were found to be higher in GST than in ITT. All three tests had good reproducibility.

CONCLUSIONS

Any of 3 tests can be used in the evaluation of the HPA axis and either GST or the ITT can be used in the evaluation of the GH-IGF-1 axis but cut-off levels for the insufficiency of HPA or GH-IGF-1 axis should be individualized for each test.