Endocrine and neurophysiologic responses of the pituitary to insulin-induced hypoglycemia: a review

Use of overnight metyrapone test in suspected secondary adrenal insufficiency: A retrospective single centre-study

OBJECTIVE

Overnight metyrapone test (OMT) is a dynamic test used to diagnose secondary adrenal insufficiency (SAI). Data on OMT use and its safety are scarce. We aimed to describe the indications and safety of outpatient OMT and compare OMT to the cosyntropin stimulation test (CST).

DESIGN

Single-centre retrospective study of adult patients undergoing OMT between 1 April 2018 and 27 January 2023.

MEASUREMENTS

OMT-related adverse events, post-OMT diagnosis of SAI, and OMT comparison to CST.

RESULTS

OMT was performed in 114 patients (81, 71% women) at a median age of 48 (interquartile range 37-58). The pretest probability for SAI was low in 52 (46%) patients, moderate in 48 (42%) patients and high in 14 (12%) patients. Adverse events were reported in 7 (6.1%) patients and were mild except for one hospitalization. No baseline or OMT-related factors were associated with the development of adverse events. Prevalence of the OMT-based SAI diagnosis was 26 (23%) and 47 (46%) using 11-deoxycortisol cutoff <7 and <10 mcg/dL, respectively. Higher pretest probability was associated with the OMT-based diagnosis of SAI. Post-OMT 11-deoxycortisol cutoff of 10 mcg/dL was used most to diagnose SAI. Compared to the OMT-based diagnosis of SAI (11-deoxycortisol cutoff of 10 mcg/dL), the specificity of CST was 100%, but the sensitivity was only 52%.

CONCLUSIONS

OMT was well tolerated and used in patients with low and moderate pretest probability for SAI. CST can erroneously exclude patients with SAI. Thus, OMT should be considered in selected patients with normal CST.

Predictive factors for recovery from adult growth hormone deficiency after transsphenoidal surgery for nonfunctioning pituitary adenoma

OBJECTIVE

Recovery from adult growth hormone deficiency (AGHD) after transsphenoidal surgery (TSS) has not been well discussed because of the lack of examinations including pituitary provocation tests (PPTs) before and after the procedure. This study aimed to evaluate the growth hormone (GH) axis function of patients with nonfunctioning pituitary adenoma (NFPA) via pre- and postoperative PPTs. Moreover, the predictive factors for recovery from AGHD after TSS were validated to facilitate surgery for AGHD in patients with NFPA.

METHODS

In total, 276 patients (median age 60.0 years) who underwent TSS for NFPA were included in this study. PPTs were performed before and 3 months after TSS. Then, the relationships between recovery from AGHD after TSS and clinical, surgical, and hormonal factors, including peak GH level based on PPTs, were evaluated statistically.

RESULTS

In this study, 114 patients were diagnosed with preoperative AGHD. Approximately 25.4% recovered from AGHD after TSS. In contrast, among the 162 patients without preoperative AGHD, 13 (8.0%) had newly developed postoperative AGHD. The predictive factors for recovery from AGHD were younger age, female sex, initial TSS, and high peak GH level based on preoperative PPT. According to the receiver operating characteristic curve analysis, patients who were aged ≤ 62.2 years and had a peak GH level of ≥ 0.74 μg/L based on preoperative PPT were likely to recover from AGHD (sensitivity: 82.8%, specificity: 72.9%, and area under the curve: 0.8229).

CONCLUSIONS

AGHD caused by NFPA can improve after initial TSS among young patients with certain peak GH levels assessed by preoperative PPT. Whether TSS for NFPA can promote recovery from AGHD is worth considering in some patients.

High prevalence of anterior pituitary deficiencies after cranial radiation therapy for skull base meningiomas

Background

Cranial irradiation represents one of the first line treatment proposed in skull base meningiomas. While cranial irradiation is associated with a high risk of secondary hypopituitarism, few studies focused on the specific location of skull base meningiomas.

Methods

Fifty-two adults receiving photon-beam therapy for skull base meningiomas between 2003 and 2014 in our Institution were included. Anterior pituitary (ACTH, FSH, GH, LH, TSH and prolactin) as well as corresponding peripheral hormones (8 am-Cortisol, IGF-1, fT3, fT4, 17βestradiol or testosterone) were biologically screened before radiotherapy (baseline), then yearly until March 2019. The pituitary gland (PG) was delineated on CT and the mean dose delivered to it was calculated.

Results

Mean age at diagnosis was 56 +/− 14 years. Median follow-up was 7 years. Up to 60% of patients developed at least ≥2 pituitary deficiencies, 10 years after radiotherapy. Gonadotroph, thyrotroph, corticotroph and somatotroph deficiencies occurred in 37, 28, 18 and 15% of patients, respectively. Hyperprolactinemia was found in 13% of patients. None patient had only one pituitary deficiency. In the multivariate analysis, a delivered dose to the PG ≥ 50 Gy or a meningioma size ≥40 mm significantly increased the risk of developing hypopituitarism.

Conclusions

Over a long-term follow-up, cranial radiation therapy used in skull base meningiomas led to a high prevalence of hypopituitarism, further pronounced in case of tumor ≥4 cm. These results advocate for an annual and prolonged follow-up of the pituitary functions in patients with irradiated skull base meningiomas.

Anterior pituitary function in Rathke's cleft cysts versus nonfunctioning pituitary adenomas

Although Rathke's cleft cysts (RCCs) are common sellar/parasellar lesions, studies examining pituitary function in patients with nonsurgical RCC are limited. This study aimed to clarify the importance of RCCs, including small nonsurgical ones, as a cause of hypopituitarism by determining the prevalence of pituitary hormone secretion impairment and its relationship to cyst/tumor size in patients with RCC and in those with nonfunctioning pituitary adenoma (NFA). We retrospectively investigated the basal levels of each anterior pituitary hormone, its responses in the stimulation test(s), and cyst/tumor size in patients with RCC (n = 67) and NFA (n = 111) who were consecutively admitted to our hospital for endocrinological evaluation. RCCs were much smaller than NFAs (median height, 12 vs. 26 mm). The prevalence of gonadotropin, PRL, and GH secretion impairment in RCC was lower in comparison to NFA (19% vs. 44%, 34% vs. 61%, and 24% vs. 46%, respectively), whereas the prevalence of TSH and ACTH secretion impairment was comparable (21-27% and 17-24%, respectively). A significant positive relationship between cyst/tumor size and number of impaired hormones was observed in both groups, but smaller cysts could cause hormone secretion impairment in RCC. Stimulation tests suggested that most hormone secretion impairment was attributable to the interrupted hypothalamic-pituitary axis in both groups. Therefore, RCC, even small ones, can cause pituitary dysfunction. Different mechanisms may underlie hypothalamic-pituitary interruption in RCC and NFA.

Multidisciplinary protocol of preoperative and surgical management of patients with pituitary tumors candidates to pituitary surgery

The optimal planning of preoperative diagnosis, management and treatment of pituitary tumors (PT) candidates to pituitary surgery (PS) requires a multidisciplinary approach involving a team of endocrinologists, neurosurgeons, ENT, neuro-ophthalmologists and neuroradiologists with experience in pituitary diseases. Such teams improve surgical results, minimize complications and facilitate their correct treatment if occurring, and optimize the hormonal, ophthalmological and radiological preoperative and follow-up evaluation. We have developed a clinical practice protocol for patients with PT who are candidates to PS based on the most recent national and international guidelines and the relevant literature regarding PT published in the last years. The protocol has been elaborated by a multidisciplinary team of a Spanish Pituitary Tumor Center of Excellence (PTCE) that includes at least one neurosurgeon, ENT, neuroradiologist, neuro-ophthalmologist, endocrine pathologist and endocrinologist specialized in pituitary diseases. We elaborated this guideline with the aim of sharing our experience with other centers involved in the perioperative and surgical management of PT thereby facilitating the management of patients undergoing PS.

Effects of intranasal insulin as an enhancer of fear extinction: a randomized, double-blind, placebo-controlled experimental study

Fear-extinction based psychotherapy (exposure) is the most effective method for treating anxiety disorders. Notwithstanding, since some patients show impairments in the unlearning of fear and insufficient fear remission, there is a growing interest in using cognitive enhancers as adjuvants to exposure. As insulin plays a critical role in stress processes and acts as a memory enhancer, this study aimed to assess the capacity of intranasal insulin to augment fear extinction. A double-blind, placebo-controlled differential fear-conditioning paradigm was conducted in 123 healthy participants (63 females). Pictures of faces with neutral expressions were used as conditioned stimuli and electric shocks as unconditioned stimuli. The paradigm consisted of four phases presented on three consecutive days: acquisition (day 1), extinction (day 2), reinstatement and re-extinction (day 3). A single intranasal dose of insulin (160 IU) or placebo was applied on day 2, 45 min before fear extinction. Skin conductance response (SCR), fear-potentiated startle (FPS) and expectancy ratings were assessed. During extinction, the insulin group (independent of sex) showed a significantly stronger decrease in differential FPS in comparison with the placebo group. Furthermore, a sex-specific effect was found for SCR, with women in the insulin group showing a greater decrease of differential SCR both at early extinction and at late re-extinction. Our results provide first evidence that intranasal insulin facilitates fear extinction processes and is therefore a promising adjuvant for extinction-based therapies in anxiety and related disorders. Sex-specific effects should be taken into consideration in future studies.

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.

Progression of Hypopituitarism and Hypothyroidism after Treatment with Pembrolizumab in a Patient with Adrenal Metastasis from Non-small-cell Lung Cancer

Pembrolizumab, or anti-programmed death receptor 1 antibody, is an immune checkpoint inhibitor that can cause immune-related adverse events. We herein report for the first time the progression of hypopituitarism and hypothyroidism after treatment with pembrolizumab in a patient with adrenal metastasis of non-small-cell lung cancer. Severe primary hypothyroidism occurred three weeks after the first administration of pembrolizumab. Four months after the discontinuation of pembrolizumab, isolated adrenocorticotropic hormone (ACTH) deficiency was noted. Corticotropin-releasing hormone and rapid ACTH tests performed repeatedly showed that the patient's pituitary and adrenal function had been gradually deteriorating. It is important to diagnose adrenal insufficiency without delay in order to prevent adrenal crisis.

Adrenal function following acute discontinuation of glucocorticoids in children with acute lymphocytic leukemia: A prospective study

Background: Children with acute lymphocytic leukemia (ALL) are enrolled in advanced treatment protocols involving high doses of glucocorticoids (GCs). Current protocols do not advocate tapering of GCs doses postinduction phase. Prolonged administration of supra-physiologic doses of GCs can induce transient suppression of the hypothalamic pituitary adrenal axis (HPA). Timely recognition of adrenal insufficiency is important in order to ensure that children at risk receive the necessary treatment and follow-up including stress coverage during illness and surgical procedures. Methods: 21 newly diagnosed patients with ALL aged 3-10 years old were prospectively enrolled in the study over a 2-year period. All enrolled patients received high doses of GCs as part of a chemotherapy treatment protocol. The HPA axis was assessed prior to the induction phase of chemotherapy and 1-2 weeks after un-tapered discontinuation of GCs. Results: All children had normal HPA axis at baseline. Postinduction 1 mcg ACTH stimulation test result was normal (cortisol > 500 nmol/L) in 75% of children and partially responsive in 25% (cortisol 300-500 nmol/L). None of the participants demonstrated clinically significant adrenal insufficiency following abrupt cessation of GCs. Conclusion: All children in our cohort had either normal or subnormal cortisol response during a low dose ACTH stimulation test 1 to 2 weeks following abrupt discontinuation of GCs, suggesting that any inhibition of the HPA axis is of short duration. We suggest that future studies investigate the timing of adrenal function recovery following GC discontinuation as well as whether tapering of the GC should be recommended.

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.

Effects of discontinuation of growth hormone replacement in adult GH-deficient patients: a cohort study and a systematic review of the literature

BACKGROUND

Recombinant human growth hormone (rhGH) replacement is advocated in adult growth hormone-deficient (GHD) patients to increase bone mass and improve lipid profile, body composition, and quality of life. The long-term effects of discontinuation of rhGh replacement are unknown.

METHODS

This cohort study and systematic review aim to evaluate the long-term metabolic effects of discontinuation of rhGh replacement in adult GHD patients, with a subgroup analyses according to age (< or > 60 years). Data on anthropometry, lipids, glucose, and bone mass density (BMD) were assessed for 3 years after discontinuation.

RESULTS

Cohort study included 64 patients who had discontinued rhGh replacement for >12 months. Fat percentage increased from 31.5±9.5% to 33.8±9.0% (mean difference 2.3, P=0.003). BMI decreased only in subjects <60 years (P=0.014). Glucose, total cholesterol, and LDL-cholesterol levels did not change; however, the percentage of patients on statins increased slightly from 39% to 44%. HDL-C concentration increased only in patients <60 years (mean difference 0.2, P=0.043). Lumbar spine BMD did not change; however, femoral neck BMD and bone turnover markers decreased in subjects <60 years (P=0.001). Systematic review included eight studies (n=166 patients) with a follow-up duration of 6-18 months. Of the Please check the edit of the sentence 'Of the eight studies "'.eight studies, three qualified as low risk of bias and five as having an intermediate risk of bias. None of the studies reported handling of statins, bisphosphonates, and glucose-lowering medication or excluded patients using these medications.

CONCLUSIONS

In this study, discontinuation of rhGh replacement resulted in metabolic changes only in patients <60 years after 3 years. Further research warrants to determine the optimal strategies for (dis)continuation of rhGh replacement in adult patients with GHD.

Diagnostic Accuracy of Perioperative Measurement of Basal Anterior Pituitary and Target Gland Hormones in Predicting Adrenal Insufficiency After Pituitary Surgery

The insulin tolerance test (ITT) is the gold standard for diagnosing adrenal insufficiency (AI) after pituitary surgery. The ITT is unpleasant for patients, requires close medical supervision and is contraindicated in several comorbidities. The aim of this study was to analyze whether tumor size, remission rate, preoperative, and early postoperative baseline hormone concentrations could serve as predictors of AI in order to increase the diagnostic accuracy of morning serum cortisol. This prospective study enrolled 70 consecutive patients with newly diagnosed pituitary adenomas. Thirty-seven patients had nonfunctioning pituitary adenomas (NPA), 28 had prolactinomas and 5 had somatotropinomas. Thyroxin (T4), thyrotropin (TSH), prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone, and insulin-like growth factor 1 (IGF-I) were measured preoperatively and on the sixth postoperative day. Serum morning cortisol was measured on the third postoperative day (CORT3) as well as the sixth postoperative day (CORT6). Tumor mass was measured preoperatively and remission was assessed 3 months after surgery. An ITT was performed 3 to 6 months postoperatively. Remission was achieved in 48% of patients and AI occurred in 51%. Remission rates and tumor type were not associated with AI. CORT3 had the best predictive value for AI (area under the curve (AUC) 0.868, sensitivity 82.4%, specificity 83.3%). Tumor size, preoperative T4, postoperative T4, and TSH were also associated with AI in a multivariate regression model. A combination of all preoperative and postoperative variables (excluding serum cortisol) had a sensitivity of 75.0% and specificity of 77.8%. The predictive power of CORT3 substantially improved by adding those variables into the model (AUC 0.921, sensitivity 94.1%, specificity 78.3%, PPV 81.9%, NPV of 92.7%). In a subgroup analysis that included only female patients with NPA, LH had exactly the same predictive value as CORT3. The addition of baseline LH to CORT3, increased sensitivity to 100.0%, specificity to 88.9%, PPV to 90.4%, and NPV to 100.0%. Besides CORT3, tumor size, thyroid hormones, and gonadotropins can serve as predictors of AI. LH in postmenopausal female patients with NPA has similar diagnostic accuracy as CORT3. Further studies are needed in order to validate the scoring system proposed by this study.

Hypothalamic-pituitary-adrenal (HPA) axis and aging

Human aging is associated with increasing frailty and morbidity which can result in significant disability. Dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis may contribute to aging-related diseases like depression, cognitive deficits, and Alzheimer's disease in some older individuals. In addition to neuro-cognitive dysfunction, it has also been associated with declining physical performance possibly due to sarcopenia. This article reviews the pathophysiology of HPA dysfunction with respect to increased basal adrenocorticotropic hormone (ACTH) and cortisol secretion, decreased glucocorticoid (GC) negative feedback at the level of the paraventricular nucleus (PVN) of the hypothalamus, hippocampus (HC), and prefrontal cortex (PFC), and flattening of diurnal pattern of cortisol release. It is possible that the increased cortisol secretion is secondary to peripheral conversion from cortisone. There is a decline in pregnolone secretion and C-19 steroids (DHEA) with aging. There is a small decrease in aldosterone with aging, but a subset of the older population have a genetic predisposition to develop hyperaldosteronism due to the increased ACTH stimulation. The understanding of the HPA axis and aging remains a complex area with conflicting studies leading to controversial interpretations.

Impaired Pituitary Axes Following Traumatic Brain Injury

Pituitary dysfunction following traumatic brain injury (TBI) is significant and rarely considered by clinicians. This topic has received much more attention in the last decade. The incidence of post TBI anterior pituitary dysfunction is around 30% acutely, and declines to around 20% by one year. Growth hormone and gonadotrophic hormones are the most common deficiencies seen after traumatic brain injury, but also the most likely to spontaneously recover. The majority of deficiencies present within the first year, but extreme delayed presentation has been reported. Information on posterior pituitary dysfunction is less reliable ranging from 3%-40% incidence but prospective data suggests a rate around 5%. The mechanism, risk factors, natural history, and long-term effect of treatment are poorly defined in the literature and limited by a lack of standardization. Post TBI pituitary dysfunction is an entity to recognize with significant clinical relevance. Secondary hypoadrenalism, hypothyroidism and central diabetes insipidus should be treated acutely while deficiencies in growth and gonadotrophic hormones should be initially observed.

Study of hypothalamic pituitary adrenal axis in patients of membranous nephropathy receiving modified Ponticelli regimen

Pulse methyl prednisolone followed by oral prednisolone and abrupt switch to chlorambucil/cyclophosphamide (Ponticelli/modified Ponticelli regimen) is used in patients with idiopathic membranous nephropathy. This therapy where steroids are stopped abruptly is unphysiologic and expected to have hypothalamic pituitary adrenal (HPA) axis suppression; however, this has not been evaluated. A total of 13 consecutive adult patients with idiopathic membranous nephropathy who had completed modified Ponticelli regimen were studied. The regimen included administration of pulse methylprednisolone 1 g for 3 days followed by oral prednisolone 0.5 mg/kg/day for 27 days followed by oral cyclophosphamide at a dose of 2 mg/kg/day for the next month. This was repeated for three courses. Patients who had received corticosteroids prior to therapy were excluded. The HPA axis was evaluated after 1 month of completing the last course of steroid therapy. The evaluation was done using a low-dose adrenocorticotropic hormone stimulation test. A single intravenous bolus dose of synacthen (1 μg) was given at 9.00 am and the serum cortisol levels were estimated by radioimmunoassay at 0, 30, and 60 min. A peak cortisol level of 550 nmol/L or higher was considered as normal. Mean baseline cortisol levels was 662.3 ± 294.6 nmol/L and peak cortisol level was 767 ± 304.4 nmol/L. A total of 6 patients (46.2%) had low basal cortisol levels, only 3 (23%) had both basal and peak cortisol levels < 550 nmol/L suggestive of HPA axis suppression. To conclude, 23% of patients had suppression of HPA axis after modified Ponticelli regimen.

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.

Different cut-off values of the insulin tolerance test, the high-dose short Synacthen test (250 μg) and the low-dose short Synacthen test (1 μg) in assessing central adrenal insufficiency

OBJECTIVE

The short Synacthen test (SST) is widely used as alternative test to the insulin tolerance test (ITT) to investigate central adrenal insufficiency (CAI), but the methodology and cut-off values of the SST are controversial. Our aim was to evaluate the cut-off value of the ITT in normal subjects and to assess the different cut-off values of the high-dose SST (250 μg, HDT) and the low-dose SST (1 μg, LDT) in subjects with suspected CAI.

SUBJECTS AND METHODS

We conducted ITTs in 208 normal subjects to establish the cut-off value for the ITT, and 28 of those subjects underwent the HDT and LDT. From 1999 to 2007, 182 patients with suspected CAI were recruited and underwent ITTs, LDTs and HDTs to establish cut-off values and compare the diagnostic accuracy between the LDT and HDT.

RESULTS

The 95th percentile of the peak cortisol level during the ITT in the normal control subjects was 14·8 μg/dl. Receiver operator characteristics (ROC) analysis revealed that the optimal cut-off values of peak cortisol in the LDT and HDT in patients with suspected CAI were 15·8 and 17·4 μg/dl, respectively. However, the cut-off values from normative data (mean - 2 SD) were 18·3 μg/dl for the LDT and 20·5 μg/dl for the HDT in normal control.

CONCLUSIONS

The optimal cut-off values of SSTs needed to be individualized according to the type of SST and tested patient population.

Neuroendocrine and sympathetic responses to an orexin receptor antagonist, SB-649868, and alprazolam following insulin-induced hypoglycemia in humans

RATIONALE

The orexin-hypocretin system is important for translating peripheral metabolic signals and central neuronal inputs to a diverse range of behaviors, from feeding, motivation and arousal, to sleep and wakefulness. Orexin signaling is thus an exciting potential therapeutic target for disorders of sleep, feeding, addiction, and stress.

OBJECTIVES/METHODS

Here, we investigated the low dose pharmacology of orexin receptor antagonist, SB-649868, on neuroendocrine, sympathetic nervous system, and behavioral responses to insulin-induced hypoglycemic stress, in 24 healthy male subjects (aged 18-45 years; BMI 19.0-25.9 kg/m(2)), using a randomized, double-blind, placebo-controlled, within-subject crossover design. Alprazolam, a licensed benzodiazepine anxiolytic, was used as a positive comparator, as it has previously been validated using the insulin tolerance test (ITT) model in humans.

RESULTS

Of the primary endpoints, ITT induced defined increases in pulse rate, plasma cortisol, and adrenocorticotropic hormone in the placebo condition, but these responses were not significantly impacted by alprazolam or SB-649868 pre-treatment. Of the secondary endpoints, ITT induced a defined increase in plasma concentrations of adrenaline, noradrenaline, growth hormone (GH), and prolactin in the placebo condition. Alprazolam pre-treatment significantly reduced the GH response to ITT (p < 0.003), the peak electromyography (p < 0.0001) and galvanic skin response (GSR, p = 0.04) to acoustic startle, the resting GSR (p = 0.01), and increased appetite following ITT (p < 0.0005). SB-649868 pre-treatment produced no significant results.

CONCLUSION

We concluded that the ITT model may be informative for assessing the effects of drugs directly acting on the neuroendocrine or sympathetic nervous systems, but could not be validated for studying low dose orexin antagonist activity.

Transphenoidal surgery without steroid replacement in patients with morning serum cortisol below 9 μg/dl (250 Nmol/l)

BACKGROUND

Adrenal insufficiency is a feared complication in patients undergoing transphenoidal surgery (TSS). Using the insulin tolerance test (ITT) for the preoperative assessment of hypothalamic-pituitary-adrenal (HPA) status is less than ideal, and the morning serum cortisol (MSC) is often used as a proxy for ITT. However, neither the ITT nor the MSC level has been validated to indicate HPA sufficiency compared to a physiological gold standard such as patients' ability to withstand transphenoidal surgery.

OBJECTIVE

To evaluate the intraoperative and postoperative course of nine patients with non-ACTH-secreting pituitary adenomas who did not receive intraoperative cortisol replacement despite having a preoperative MSC below 9 μg/dl (250 nmol/l) and to compare this with a set of patients with a preoperative MSC greater than 14.5 μg/dl (400 nmol/l) and another set of patients with MSC below 9 μg/dl (250 nmol/l) who received intraoperative cortisol administration.

METHODS

Preoperative and day 1 and day 2 postoperative MSC, intraoperative anesthetic record, vital signs, fluid balance, medications, and complications were recorded.

RESULTS

None of the patients experienced the full syndrome of adrenal insufficiency. One patient with a preoperative MSC <9 μg/dl (250 mol/l) had isolated postoperative fatigue and required cortisol replacement. No patient suffered any life-threatening complications. There were no differences among the three groups in their intraoperative or postoperative courses when compared for intraoperative hypotension, acute blood pressure drop, and administration of vasopressors.

CONCLUSION

This study suggests that TSS can be performed safely in patients with preoperative MSC less than 9 μg/dl (250 nmol/l) in closely monitored settings without intraoperative cortisol administration. Further studies are warranted.

The use of an early postoperative CRH test to assess adrenal function after transsphenoidal surgery for pituitary adenomas

Transsphenoidal surgery (TS) is the treatment of choice for many pituitary tumors. Because TS may cause pituitary insufficiency in some of these patients, early postoperative assessment of pituitary function is essential for appropriate endocrine management. The aim of our study was to evaluate the clinical relevance of the CRH-stimulation test in assessing postoperative pituitary-adrenal function. We performed a retrospective analysis of 144 patients treated by TS between January 1990 and November 2009, in whom a CRH-test and a second stimulation test was performed to assess adrenal function during follow-up. Patients with Cushing's disease were excluded. Hydrocortisone substitution was started if peak cortisol levels were <550 nmol/L. The cortisol response was insufficient in 42(29%) and sufficient in 102 patients at the postoperative CRH-test. Thirteen of 42(30%) demonstrated a normal cortisol response during a second cortisol stimulation test. In 75 of the 102 patients with a sufficient response to CRH repeat testing revealed an insufficient cortisol response in 14 patients (14%). All but one had concomitant pituitary hormone deficits. There were no cases of adrenal crises during follow-up. Additional pituitary insufficiency was significantly more present (P < 0.001) in the group of patients with an abnormal response to CRH directly after surgery. In this study a substitution strategy of hydrocortisone guided by the postoperative cortisol response to CRH appeared safe and did not result in any case of adrenal crises. However, the early postoperative CRH-test does not reliably predict adrenal function after TS for pituitary adenomas in all patients and retesting is mandatory.

Depth and duration of hypoglycaemia achieved during the insulin tolerance test

CONTEXT

The insulin tolerance test (ITT) is the gold standard for assessment of the pituitary adrenal axis but its use is limited because of concerns relating to the risk of hypoglycaemia.

OBJECTIVE

This study examined the depth and duration of hypoglycaemia achieved during the test in a large cohort of patients.

DESIGN

Two hundred and twenty ITTs were performed from 2005 to 2010.

SETTING

A 1200-bed University Teaching Hospital.

PATIENTS

Two hundred and twenty ITTs were carried out in patients with suspected or known pituitary disorders.

INTERVENTIONS

Intravenous insulin was administered to achieve nadir plasma glucose (NPG) of 2.2 mmol/l (39.6 mg/dl). Blood chemistry to show the cortisol and GH response to hypoglycaemic stress was measured.

MAIN OUTCOME MEASURES

Predictors of depth and duration of hypoglycaemia, adverse events and within-subject variability of nadir glucose, peak cortisol and peak GH were studied.

RESULTS

Thirty percent of the cohort achieved a nadir glucose of <2.0 mmol/l (36 mg/dl) that lasted for 60 min or more. The NPG correlated positively with fasting plasma glucose (FPG; r=0:56; P<0.0005), insulin dose (r=0.27; P<0.0005) and weight (r=0.21; P<0.004). The within subject variability of nadir glucose was 15.2%, peak cortisol was 11.7% and peak GH was 6.4%. The factors determining nadir blood glucose were FPG (b=0.56, P<0.0005, 20% contribution) and weight (b=0.14, P<0.05, 2% contribution). The five patients with adverse events had NPG and insulin dose comparable with the rest of the population.

CONCLUSIONS

The hypoglycaemia achieved during the ITT is much lower than the target required. However, adverse events are few and do not relate to the depth of hypoglycaemia.

Diagnosing growth hormone deficiency in adults

Adult growth hormone (GH) deficiency is a recognised syndrome associated with adverse phenotypic, metabolic, and quality-of-life features which improve in many patients when GH is substituted. The appropriate selection of patients at risk of growth hormone deficiency (GHD) is the crucial first step in arriving at a correct diagnosis. Although multiple diagnostic modalities are available including a 24-hour serum GH profile, stimulated GH levels, and insulin-like growth factor-1 (IGF-1) levels, the use of dynamic tests for GH reserves is required in most cases. This paper discusses the utility and drawbacks of the various testing modalities with reference to international guidelines. Regardless of the test chosen, clinical pitfalls including age and obesity must be taken into account. In addition, there is considerable analytical variation in the biochemical measurements of GH and IGF-1 which must be considered before making a diagnosis of GHD in adulthood.

Glucoreceptors located in the brain mediate NPY release induced by hypoglycemia in normal men

The NPY secretory pattern after an insulin tolerance test (ITT) (0.15 IU/kg body weight) was evaluated in 8 normal men. They were infused with normal saline (control test), glucose or fructose. Insulin-induced hypoglycemia produced a significant increment in serum NPY in the control test. The infusion of fructose was unable to change the NPY secretory pattern during insulin-induced hypoglycemia. In contrast, the NPY increase during ITT was completely abolished when the concomitant infusion of glucose prevented insulin-induced hypoglycemia. These results exclude a direct role of hyperinsulinemia in the mechanism underlying the stimulation of NPY secretion during ITT. Furthermore, since glucose but not fructose crosses the blood-brain-barrier (BBB), the NPY increase during ITT appears to be generated by low glucose concentrations at the level of glucosensitive areas located inside the brain.

The comparison of low and standard dose ACTH and glucagon stimulation tests in the evaluation of hypothalamo-pituitary-adrenal axis in healthy adults

Evaluation of the HPA axis is still a challenge; due to different sensitivities and stimulation efficiencies of dynamic tests, lack of standard assays for cortisol measurement and lack of data regarding the effects of age and gender on the results of the HPA axis evaluation with different dynamic tests. This study was performed to compare 1 μg ACTH, 250 μg ACTH and glucagon tests in the evaluation of HPA axis. The study was carried out on 55 healthy individuals (28 men, 27 women). 10-12 volunteers were included from every decades between 20 and 70 years. Low dose short synacthen test (1 μg ACTH), standard dose short synacthen test (250 μg ACTH) and glucagon tests were performed consecutively. The mean peak cortisol response to standard dose ACTH stimulation test was found to be significantly higher than the low dose ACTH and glucagon stimulation tests. The mean peak cortisol responses to low dose ACTH and the glucagon stimulation tests were not significantly different. The mean peak cortisol responses did not differ significantly between different age or sex groups. The lowest peak cortisol responses obtained after low dose ACTH and glucagon stimulation tests were 12.5 and 9.1 μg/dl respectively in the volunteers who all had cortisol responses higher than 20 μg/dl after standard dose ACTH stimulation test. The lowest cortisol responses obtained during 250 μg ACTH, 1 μg ACTH and glucagon stimulation tests were found to be 20.1, 12.5 and 9.1 μg/dl in a known group of healthy people. So the consideration of appropriate hormonal cut-off levels for each test seems reasonable. The age, sex and body mass indeces were not shown to affect the cortisol response to dynamic stimulation tests.

Can basal cortisol measurement be an alternative to the insulin tolerance test in the assessment of the hypothalamic-pituitary-adrenal axis before and after pituitary surgery?

BACKGROUND

The aims of this study were to evaluate the validity of preoperative basal serum cortisol levels measured in predicting preoperative adrenal insufficiency and also the validity of basal serum cortisol levels and early postoperative insulin tolerance test (ITT) in predicting postoperative adrenal insufficiency.

METHODS

The study was prospectively designed and included 64 patients who underwent pituitary surgery for conditions other than Cushing's disease. An ITT was performed preoperatively, on the 6th postoperative day and at the 1st postoperative month. Basal serum cortisol levels were measured on the 2nd, 3rd, 4th, 5th, and 6th postoperative days.

RESULTS

Patients with a preoperative basal cortisol level of <165 nmol/l (6 microg/dl) showed insufficient cortisol response and those with levels higher than 500 nmol/l (18 microg/dl) had sufficient cortisol response to the preoperative ITT. The positive predictive value of the ITT performed on the 6th postoperative day was 69.7%, and the negative predictive value in predicting adrenal insufficiency at the 1st postoperative month was 58%. Patients were considered to have an insufficient cortisol response to ITT at the 1st postoperative month if their basal cortisol levels were <193 nmol/l (7 microg/dl) or 220 nmol/l (8 microg/dl) or 193 nmol/l (7 microg/dl) or 165 nmol/l (6 microg/dl) or 83 nmol/l (3 microg/dl) on the 2nd-6th postoperative days respectively.

CONCLUSION

Serum basal cortisol levels may be used as the first-line test in the assessment of the hypothalamic-pituitary-adrenal axis both preoperatively and postoperatively. Dynamic testing should be limited to the patients with indeterminate basal cortisol levels.

Factors determining inadequate hypoglycaemia during insulin tolerance testing (ITT) after pituitary surgery

BACKGROUND

Some patients fail to achieve adequate hypoglycaemia following a standard dose of intravenous insulin during the insulin tolerance test (ITT). Persistent acromegaly or Cushing's disease may contribute to inadequate hypoglycaemia. Aim To identify factors that predict failure to achieve adequate hypoglycaemia during an ITT after pituitary surgery.

METHODS

We reviewed consecutive ITTs performed over a 10-year period in 76 patients following pituitary surgery. Analyses were performed to determine if body mass index (BMI), fasting blood glucose (FBG), cortisol, GH status or underlying diagnosis influenced the outcome.

RESULTS

Adequate hypoglycaemia (blood glucose < 2.2 mmol/l) was not achieved in 33 patients (Group 1) following a standard dose of neutral insulin (0.1 units/kg); 43 patients (Group 2) achieved adequate hypoglycaemia. Group 1 had significantly higher BMI, FBG, baseline cortisol and peak cortisol concentrations than Group 2. Peak GH response was not different. Multiple regression analysis showed that FBG was the only independent predictor of adequate hypoglycaemia. An insulin dose of 0.2 units/kg achieved adequate hypoglycaemia in 80% of patients with FBG >or= 5.5 mmol/l. In patients with acromegaly or Cushing's disease, failure to achieve adequate hypoglycaemia was associated with persistent disease.

CONCLUSION

FBG is an important determinant of the dose of insulin required to achieve adequate hypoglycaemia during an ITT in patients after pituitary surgery. A standard insulin dose of 0.1 U/kg is insufficient for adequate hypoglycaemia in patients with FBG > 5.5 mmol/l. Adequate response to a standard dose of insulin suggests a likelihood of cure of acromegaly or Cushing's disease after pituitary surgery.

Stimulus-response paradigm for characterizing the loss of resilience in homeostatic regulation associated with frailty

Frailty is a state of health signified by an increased vulnerability to adverse health outcomes in the face of stressors (e.g. infection). There is emerging consensus that research on both the theory and measurement of frailty must focus on the dynamic interactions within and across systems underlying the frailty syndrome. In this paper, we propose a dynamical systems modeling approach, based on the stimulus-response experimental paradigm, to propel future advances in the study of frailty. Our proposal is novel in that it provides a quantitative framework to operationalize and test the core notion underlying frailty that it signifies a loss of resilience in homeostatic regulation. The proposed framework offers many important benefits, including (a) insights into whether and how homeostatic regulation differs between frail and non-frail older adults, (b) identification of critical regulatory systems, if they exist, that could function as sentinel systems for screening and early detection of frailty, (c) establishment of the value of provocative tests that can provide maximal information on the integrity of systems identified in (b), and (d) evaluation and unification of diverse empirical descriptions of frailty by providing a mathematical framework anchored in quantifying the loss of resilience, an essential property of frailty.

Hypothalamus-pituitary-adrenal axis evaluation in patients with hypothalamo-pituitary disorders: comparison of different provocative tests

BACKGROUND

The insulin tolerance test (ITT) is the gold standard test to evaluate hypothalamic-pituitary-adrenal (HPA) axis in suspected ACTH insufficiency. When contraindicated, alternative tests have been proposed such as metyrapone and ACTH stimulation test. 250 microg ACTH is a supramaximal dose and unreliable in this setting. The diagnostic reliability of 1.0 microg ACTH test is controversial and very low doses have been proposed.

DESIGN

In 31 patients with hypothalamo-pituitary disorders and normal basal cortisol, we compared the diagnostic sensitivity, specificity and accuracy of metyrapone [metyrapone test (MET) 30 mg/kg p.o.], high (HDT, 250 microg i.v.), low (LDT, 1.0 microg i.v.) and very-low (VLDT, 0.06 microg i.v.) dose ACTH tests. Receiver operator curve (ROC) analysis was applied with ITT as reference test.

RESULTS

MET approached the best pairs of values for highest sensitivity (71.4% and 64.3%) and highest specificity (100% and 82.4%) using ACTH and 11-deoxycortisol (11-DOC) cut-off of 17.3 pmol/l and 144.3 nmol/l. Either HDT or LDT sensitivity approached 71.4% with a specificity of 82.4% or 73.3% with a specificity of 80% for cortisol cut-off of 582.1 or 477.3 nmol/l. VLDT approached the highest sensitivity (57.1%) and highest specificity (88.2%) for a cortisol cut-off of 364.2 nmol/l.

CONCLUSION

Neither MET nor ACTH test can be considered completely reliable for the diagnosis of secondary hypoadrenalism, when compared with ITT that remains the best test. Either MET or ACTH stimulation test, at both high and low dose, show an overall similar reliability, provided that appropriated cut-off values were considered; testing with very low ACTH doses seems to be misleading.

Adrenal axis function after high-dose steroid therapy for childhood acute lymphoblastic leukemia

BACKGROUND

A 4-week course of high-dose glucocorticoids may cause prolonged adrenal suppression even after a 9-day tapering phase. In this study, adrenal function and signs and symptoms of adrenal insufficiency were prospectively assessed in children with acute lymphoblastic leukemia (ALL) after induction treatment including high-dose prednisone (PDN) or dexamethasone (DXM).

PROCEDURES

Sixty-four children with ALL, treated according to the AIEOP ALL 2000 Study protocol, underwent low dose ACTH (LD-ACTH) stimulation 24 hr after the last tapered steroid dose. In those with impaired cortisol response, additional LD ACTH tests were performed every 1-2 weeks until cortisol levels normalized. Signs and symptoms of adrenal insufficiency were recorded during the observation period.

RESULTS

All patients had normal basal cortisol values at diagnosis. Twenty-four hours after last glucocorticoid dose, morning cortisol was reduced in 40/64 (62.5%) patients. LD-ACTH testing showed adrenal suppression in 52/64 (81.5%) patients. At the following ACTH test 7-14 days later, morning cortisol values were reduced in 8/52 (15.4%) patients and response to the test was impaired in 12/52 (23%). Adrenal function completely recovered in all patients within 10 weeks. No difference was found between patients treated with PDN or DXM. Almost 35% of children with impaired cortisol values at the first test developed signs or symptoms of adrenal insufficiency. One child developed a severe adrenal crisis during adrenal suppression.

CONCLUSIONS

High-dose glucocorticoid therapy in ALL children may cause prolonged adrenal suppression and related clinical symptoms. Laboratory monitoring of cortisol levels and steroid coverage during stress episodes may be indicated.

Corticotrope hypersecretion coupled with cortisol hypo-responsiveness to stimuli is present in patients with autoimmune endocrine diseases: evidence for subclinical primary hypoadrenalism?

OBJECTIVE

In autoimmune polyglandular syndrome types 1, 2, and 4 primary adrenal insufficiency is present, but its diagnosis is often late. We investigated the function of the hypothalamic-pituitary-adrenal axis in a group of patients with autoimmune diseases (AP) without any symptoms and signs of hypoadrenalism.

DESIGN

In 10 AP and 12 normal subjects (NS), we studied cortisol (F), aldosterone (A), and DHEA responses to 0.06 microg adrenocorticotropin (ACTH) (1-24) followed by 250 microg, ACTH and F responses to human corticotropin-releasing hormone (hCRH; 100 microg) and insulin tolerance test (ITT) (0.1 UI/kg).

RESULTS

Basal F, A, DHEA, as well as urinary free cortisol and plasma renin activity levels in AP and NS were similar, whereas ACTH levels in AP were higher (P<0.05) than in NS. NS showed F, A, and DHEA response to both consecutive ACTH doses. In AP, the F, A, and DHEA responses to 250 microg ACTH were similar to those in NS, whereas the 0.06 microg ACTH dose did not elicit any significant response. The ACTH responses to hCRH and ITT in AP were higher (P<0.05) than in NS. The F response to hCRH in AP was lower (P<0.05) than in NS, whereas the F response to ITT in AP did not significantly differ from NS.

CONCLUSIONS

Enhancement of both basal and stimulated corticotrope secretion coupled with reduced adrenal sensitivity to low ACTH dose is present in AP patients without symptoms and signs of hypoadrenalism. This functional picture suggests that normal adrenal secretion is maintained due to corticotrope hyperfunction, suggesting the existence of some subclinical primary hypoadrenalism.

Hypothalamic-pituitary dysfunction after irradiation of nonpituitary brain tumors in adults

CONTEXT

Hypothalamic-pituitary (HP) dysfunction is common in children treated with cranial radiotherapy (RT) for brain tumors, but there is little known about the risk of HP dysfunction in adults treated with RT for primary nonpituitary brain tumors.

OBJECTIVE

The objective was to study the frequency of HP dysfunction in adults after RT for nonpituitary brain tumors.

METHOD

We studied 56 adult patients who received external beam RT for primary nonpituitary brain tumors at time intervals of 12-150 months after RT. The control group consisted of 20 RT-naive patients with primary brain tumors. GH and adrenal axes were assessed using the insulin tolerance test or the glucagon stimulation test. Gonadotroph, thyrotroph, and lactotroph function were assessed using baseline blood measurements. The biological effective dose (BED) to the HP axis was calculated in the RT patients.

RESULTS

Hypopituitarism was present in 41% of patients. The frequency of GH, ACTH, gonadotropin, and TSH deficiencies, and hyperprolactinemia was 32, 21, 27, 9, and 32%, respectively. Any degree of hypopituitarism and GH deficiency was significantly associated with longer time interval from RT and greater BED. However, gonadotropin deficiency and hyperprolactinemia were only related to BED, whereas ACTH deficiency was only significantly associated with the time interval from RT. One RT-naive patient was GH deficient.

CONCLUSION

Adult patients treated with cranial irradiation for primary nonpituitary brain tumors are at high risk of hypopituitarism, which is time and dose dependent. Long-term surveillance and periodic evaluation are needed. We recommend that adult late effect clinics, similar to those for children, should be established.

The natural history of post-traumatic hypopituitarism: implications for assessment and treatment

PURPOSE

Hypopituitarism has been reported in up to half of long-term survivors of traumatic brain injury. We attempted to define the natural history of post-traumatic hypopituitarism to devise guidelines for the optimal timing of patients' assessment and hormone replacement.

SUBJECTS AND METHODS

Fifty consecutive patients with severe or moderate head trauma were enrolled in a prospective study of pituitary function during the acute phase, at 6 months, and at 12 months after injury. Growth hormone and adrenocorticotropin hormone reserves were assessed using the glucagon stimulation test. Baseline serum concentrations of other anterior pituitary hormones were measured. Results were compared with normative data obtained from matched healthy controls.

RESULTS

Nine patients (18%) had growth hormone deficiency in the acute phase; at 6 months, 5 patients recovered function and 2 new deficiencies were detected; at 12 months, 1 patient recovered, leaving 5 patients (10%) with growth hormone deficiency. Eight patients (16%) showed subnormal cortisol response in the acute phase; at 6 months, 4 patients had recovered and 5 new deficiencies were detected; all 9 patients had persistent abnormalities at 2 months. Forty patients (80%) had gonadotropin deficiency in the acute phase, of whom 29 (73%) recovered by 6 months and 34 (85%) recovered by 12 months. Thyrotropin deficiency was present in 1 patient in the acute phase, who recovered by 6 months; 1 new case was diagnosed at 6 months, which persisted at 12 months.

CONCLUSION

After traumatic brain injury, early neuroendocrine abnormalities are sometimes transient, whereas late abnormalities present during the course of rehabilitation. A follow-up strategy with periodic evaluation is a necessary part of the optimal care for patients with traumatic brain injury.

Decreased cortisol response to insulin induced hypoglycaemia in asthmatics treated with inhaled fluticasone propionate

AIMS

To assess adrenal function in asthmatic children treated with inhaled fluticasone propionate for up to 16 weeks.

METHODS

Children with asthma and bronchial hyperresponsiveness to inhaled methacholine were treated with inhaled fluticasone 250-750 microg/day via Volumatic spacer. The insulin tolerance test (ITT) was performed to assess adrenal function.

RESULTS

Eighteen asthmatic patients (10 boys, 8 girls), aged 7-17 years received inhaled fluticasone therapy at a median dose of 477 microg/m2 per day for 5-16 weeks. Adrenal suppression, defined as 60 minute serum cortisol less than 500 nmol/l, was found in 9 of 18 children. Following the ITT, the median basal and 60 minute serum cortisol concentrations of the suppressed group were 135.0 and 350.0 nmol/l, respectively; the corresponding values for the unsuppressed group were 242.2 and 564.7 nmol/l. Repeat ITT in the suppressed group 2-3 months after discontinuation of fluticasone revealed that all patients had a 60 minute serum cortisol greater than 500 nmol/l.

CONCLUSION

After therapy for asthma with inhaled fluticasone at approximately 500 microg daily for up to 16 weeks, half the children had evidence of adrenal suppression.

Conventional glucocorticoid replacement overtreats adult hypopituitary patients with partial ACTH deficiency

BACKGROUND

Glucocorticoid therapy is associated with potentially serious side-effects, but there is no information available regarding glucocorticoid requirement in adult hypopituitary patients with partial ACTH deficiency.

SUBJECTS

Ten male adult hypopituitary patients with partial ACTH deficiency, baseline plasma cortisol > 200 nmol/l but a peak stimulated cortisol < 500 nmol/l and 10 matched healthy male control volunteers participated.

DESIGN

Patients were assigned, in a random order, to a cross-over protocol of treatment for 1 week with full dose hydrocortisone (10 mg twice daily), half-dose hydrocortisone (5 mg twice daily), or no treatment. All patients completed all three of the treatment limbs.

MEASUREMENTS

Following each treatment schedule, patients underwent an 11-h cortisol day curve (CDC), and the results were compared with those from the 10 control volunteers on no glucocorticoid treatment.

RESULTS

The integrated CDC values were significantly higher in patients taking a full dose of hydrocortisone compared to controls (P < 0.001). There was no significant difference in the integrated CDC between patients on half-dose (P = 0.37) or no hydrocortisone treatment (P = 0.13), compared to control subjects. Peak postabsorption cortisol values were higher in patients receiving full-dose hydrocortisone treatment compared to controls (P < 0.001). There was no significant difference in plasma sodium concentration, blood pressure or corticosteroid-binding globulin between patients on any treatment schedule and controls.

CONCLUSION

Adult patients with pituitary disease and partial ACTH deficiency have a cortisol secretory pattern comparable to that of healthy controls. Conventional full-dose replacement with 10 mg twice daily of hydrocortisone produces hypercortisolaemia, whereas half-dose produces a CDC that is not statistically different from that of healthy controls. The results suggest that current conventional glucocorticoid replacement overtreats patients with partial ACTH deficiency under normal unstressed physiological conditions.

Associations between neuroendocrine responses to the Insulin Tolerance Test and patient characteristics in chronic fatigue syndrome

OBJECTIVE

Subtle dysregulations of the hypothalamic-pituitary-adrenal (HPA) axis have been proposed as an underlying pathophysiological mechanism in chronic fatigue syndrome (CFS). This study attempted to assess the relationship between patient characteristics and HPA axis functioning using a neuroendocrine challenge test.

METHOD

A test battery designed to assess different dimensions of CFS was given to 18 CFS patients and 17 controls. To evaluate the integrity of the HPA axis, the Insulin Tolerance Test (ITT), a centrally acting neuroendocrine challenge test, was performed on patients and controls. ACTH, salivary free cortisol and total plasma cortisol levels were assessed as a measure of the HPA axis stress response. Correlations of patient characteristics were calculated with integrated responses for all endocrine parameters.

RESULTS

CFS patients had a significantly reduced area under the ACTH response curve (AUC) in the ITT. The AUC was significantly associated with the duration of CFS symptoms (r = -.592, P = .005) and the severity of fatigue symptomatology (r = -.41, P = .045). In addition, duration of CFS was correlated with the severity of fatigue symptoms (r = .38, P = .045). Similar associations were not observed for cortisol parameters.

CONCLUSION

It has been postulated that neuroendocrine dysregulations observed in CFS are of an acquired nature. The results of a strong association between the integrated ACTH response and the duration of CFS emphasizes the need to consider factors known to be risk factors for the chronicity of CFS symptoms, such as profound inactivity, deconditioning and sleep abnormalities, as possible candidates for secondary causes of neuroendocrine dysregulations in CFS.

Alprazolam (a benzodiazepine activating GABA receptor) reduces the neuroendocrine responses to insulin-induced hypoglycaemia in humans

OBJECTIVE

Alprazolam (ALP), a benzodiazepine-activating GABAergic receptor, possesses clear centrally mediated inhibitory effects on ACTH and cortisol secretion that could reflect an inhibitory influence on CRH- and/or AVP-secreting neurones. An inhibitory effect of ALP on catecholamine release has also been shown while its effect on GH secretion is unclear. To further clarify the neuroendocrine actions of ALP, we studied the ALP effects on the neurohormonal responses to hypoglycaemia in a group of normal subjects.

DESIGN

In eight normal subjects [four women and four men, 22-34 years old, body mass index (BMI) 20-25 kg/m2] the ACTH, cortisol, GH, adrenaline (A) and noradrenaline (NA) responses to insulin-induced hypoglycaemia [ITT, 0.1 UI/kg regular insulin intravenously (i.v.) at 0 min] preceded by placebo or ALP (0.02 mg/kg orally at -90 min) were studied in two sessions at least 10 days apart.

MEASUREMENTS

Blood samples were taken basely at -90 and 0 min and every 15 min up to +120 min. ACTH, cortisol, GH, A and NA level were assayed at each time point in both sessions.

RESULTS

All subjects experienced hypoglycaemia (plasma glucose levels below 2.2 mmol/l). After placebo ITT induced clear-cut increases in ACTH (peak vs. baseline, mean +/- SEM: 27.9 +/- 3.9 vs. 7.1 +/- 1.5 pmol/l), cortisol (438.1 +/- 32.0 vs. 237.7 +/- 19.3 nmol/l) and GH (38.1 +/- 9.7 vs. 5.7 +/- 2.0 micro g/l) levels (P < 0.05). Marked increase in A (6627.2 +/- 116.7 vs. 263.7 +/- 71.4 pmol/l) and NA (3.8 +/- 1.5 vs. 1.6 +/- 1.0 nmol/l) levels were also recorded (P < 0.05). Pretreatment with ALP significantly inhibited the ACTH peak response to ITT (17.8 +/- 5.0 pmol/l, P < 0.05), while the cortisol response showed a non significant reduction (342.1 +/- 38.7 nmol/l). ALP also significantly reduced the GH (21.7 +/- 4.7 micro g/l, P < 0.02) and A (3828.0 +/- 1400.7 pmol/l, P < 0.02) responses to ITT. On the contrary, ALP lowered basal NA levels (P < 0.05) but did not significantly affect its response to ITT (2.2 +/- 1.2 nmol/l). Glucose changes induced by ITT were not modified by ALP.

CONCLUSIONS

This study shows that GABAergic activation by alprazolam significantly inhibits the neuroendocrine and adrenomedullary responses to hypoglycaemia.

Sensitivity and specificity of six tests for the diagnosis of adult GH deficiency

Although the use of the insulin tolerance test (ITT) for the diagnosis of adult GH deficiency is well established, diagnostic peak GH cut-points for other commonly used GH stimulation tests are less clearly established. Despite that fact, the majority of patients in the United States who are evaluated for GH deficiency do not undergo insulin tolerance testing. The aim of this study was to evaluate the relative utility of six different methods of testing for adult GH deficiency currently used in practice in the United States and to develop diagnostic cut-points for each of these tests. Thirty-nine patients (26 male, 13 female) with adult-onset hypothalamic-pituitary disease and multiple pituitary hormone deficiencies were studied in comparison with age-, sex-, estrogen status-, and body mass index-matched control subjects (n = 34; 20 male, 14 female). A third group of patients (n = 21) with adult-onset hypothalamic-pituitary disease and no more than one additional pituitary hormone deficiency was also studied. The primary end-point was peak serum GH response to five GH stimulation tests administered in random order at five separate visits: ITT, arginine (ARG), levodopa (L-DOPA), ARG plus L-DOPA, and ARG plus GHRH. Serum IGF-I concentrations were also measured on two occasions. For purposes of analysis, patients with multiple pituitary hormone deficiencies were assumed to be GH deficient. Three diagnostic cut-points were calculated for each test to provide optimal separation of multiple pituitary hormone deficient and control subjects according to three criteria: 1) to minimize misclassification of control subjects and deficient patients (balance between high sensitivity and high specificity); 2) to provide 95% sensitivity for GH deficiency; and 3) to provide 95% specificity for GH deficiency. The greatest diagnostic accuracy occurred with the ITT and the ARG plus GHRH test, although patients preferred the latter (P = 0.001). Using peak serum GH cut-points of 5.1 microg/liter for the ITT and 4.1 microg/liter for the ARG plus GHRH test, high sensitivity (96 and 95%, respectively) and specificity (92 and 91%, respectively) for GH deficiency were achieved. To obtain 95% specificity, the peak serum GH cut-points were lower at 3.3 microg/liter and 1.5 microg/liter for the ITT and ARG plus GHRH test, respectively. There was substantial overlap between patients and control subjects for the ARG plus L-DOPA, ARG, and L-DOPA tests, but test-specific cut-points could be defined for all three tests to provide 95% sensitivity for GH deficiency (peak GH cut-points: 1.5, 1.4 and 0.64 microg/liter, respectively). However, 95% specificity could be achieved with the ARG plus L-DOPA and ARG tests only with very low peak GH cut-points (0.25 and 0.21 microg/liter, respectively) and not at all with the L-DOPA test. Although serum IGF-I levels provided less diagnostic discrimination than all five GH stimulation tests, a value below 77.2 microg/liter was 95% specific for GH deficiency. In conclusion, the diagnosis of adult GH deficiency can be made without performing an ITT, provided that test-specific cut-points are used. The ARG plus GHRH test represents an excellent alternative to the ITT for the diagnosis of GH deficiency in adults.

Steroids and the surgical patient

In patients undergoing surgery, a thorough history is important to obtain, including use of any steroid therapy within the previous year. If there is a history of steroid use, and if time permits, testing of the HPA axis should be performed. If adrenal unresponsiveness is documented or if clinical suspicion of [table: see text] adrenal insufficiency is high (without testing), a stress dose of steroids should be administered during the perioperative period to prevent an adrenal crisis.

Hypothalamo-pituitary-adrenal axis dysfunction in chronic fatigue syndrome, and the effects of low-dose hydrocortisone therapy

These neuroendocrine studies were part of a series of studies testing the hypotheses that 1) there may be reduced activity of the hypothalamic-pituitary-adrenal axis in chronic fatigue syndrome and 2) low-dose augmentation with hydrocortisone therapy would improve the core symptoms. We measured ACTH and cortisol responses to human CRH, the insulin stress test, and D-fenfluramine in 37 medication-free patients with CDC-defined chronic fatigue syndrome but no comorbid psychiatric disorders and 28 healthy controls. We also measured 24-h urinary free cortisol in both groups. All patients (n = 37) had a pituitary challenge test (human CRH) and a hypothalamic challenge test [either the insulin stress test (n = 16) or D-fenfluramine (n = 21)]. Baseline cortisol concentrations were significantly raised in the chronic fatigue syndrome group for the human CRH test only. Baseline ACTH concentrations did not differ between groups for any test. ACTH responses to human CRH, the insulin stress test, and D- fenfluramine were similar for patient and control groups. Cortisol responses to the insulin stress test did not differ between groups, but there was a trend for cortisol responses both to human CRH and D-fenfluramine to be lower in the chronic fatigue syndrome group. These differences were significant when ACTH responses were controlled. Urinary free cortisol levels were lower in the chronic fatigue syndrome group compared with the healthy group. These results indicate that ACTH responses to pituitary and hypothalamic challenges are intact in chronic fatigue syndrome and do not support previous findings of reduced central responses in hypothalamic-pituitary-adrenal axis function or the hypothesis of abnormal CRH secretion in chronic fatigue syndrome. These data further suggest that the hypocortisolism found in chronic fatigue syndrome may be secondary to reduced adrenal gland output. Thirty-two patients were treated with a low-dose hydrocortisone regime in a double-blind, placebo-controlled cross-over design, with 28 days on each treatment. They underwent repeated 24-h urinary free cortisol collections, a human CRH test, and an insulin stress test after both active and placebo arms of treatment. Looking at all subjects, 24-h urinary free cortisol was higher after active compared with placebo treatments, but 0900-h cortisol levels and the ACTH and cortisol responses to human CRH and the insulin stress test did not differ. However, a differential effect was seen in those patients who responded to active treatment (defined as a reduction in fatigue score to the median population level or less). In this group, there was a significant increase in the cortisol response to human CRH, which reversed the previously observed blunted responses seen in these patients. We conclude that the improvement in fatigue seen in some patients with chronic fatigue syndrome during hydrocortisone treatment is accompanied by a reversal of the blunted cortisol responses to human CRH.

Stressor specificity of central neuroendocrine responses: implications for stress-related disorders

Despite the fact that many research articles have been written about stress and stress-related diseases, no scientifically accepted definition of stress exists. Selye introduced and popularized stress as a medical and scientific idea. He did not deny the existence of stressor-specific response patterns; however, he emphasized that such responses did not constitute stress, only the shared nonspecific component. In this review we focus mainly on the similarities and differences between the neuroendocrine responses (especially the sympathoadrenal and the sympathoneuronal systems and the hypothalamo-pituitary-adrenocortical axis) among various stressors and a strategy for testing Selye's doctrine of nonspecificity. In our experiments, we used five different stressors: immobilization, hemorrhage, cold exposure, pain, or hypoglycemia. With the exception of immobilization stress, these stressors also differed in their intensities. Our results showed marked heterogeneity of neuroendocrine responses to various stressors and that each stressor has a neurochemical "signature." By examining changes of Fos immunoreactivity in various brain regions upon exposure to different stressors, we also attempted to map central stressor-specific neuroendocrine pathways. We believe the existence of stressor-specific pathways and circuits is a clear step forward in the study of the pathogenesis of stress-related disorders and their proper treatment. Finally, we define stress as a state of threatened homeostasis (physical or perceived treat to homeostasis). During stress, an adaptive compensatory specific response of the organism is activated to sustain homeostasis. The adaptive response reflects the activation of specific central circuits and is genetically and constitutionally programmed and constantly modulated by environmental factors.

Psychoneuroendocrinological contributions to the etiology of depression, posttraumatic stress disorder, and stress-related bodily disorders: the role of the hypothalamus-pituitary-adrenal axis

Following the assumption that stressors play an important part in the etiology and maintenance of psychiatric disorders, it is necessary to evaluate parameters reflecting stress-related physiological reactions. Results from these examinations may help to deepen the insight into the etiology of psychiatric disorders and to elucidate diagnostic uncertainties. One of the best-known stress-related endocrine reactions is the hormonal release of the hypothalamic-pituitary-adrenal (HPA) axis. Dysregulations of this axis are associated with several psychiatric disorders. Profound hyperactivity of the HPA-axis has been found in melancholic depression, alcoholism, and eating disorders. In contrast, posttraumatic stress disorder, stress-related bodily disorders like idiopathic pain syndromes, and chronic fatigue syndrome seem to be associated with diminished HPA activity (lowered activity of the adrenal gland). Hypotheses referring to (a) the psychophysiological meaning and (b) the development of these alterations are discussed.

The insulin hypoglycemia test: hypoglycemic criteria and reproducibility

The insulin hypoglycemia test (IHT) is widely regarded as the "gold standard" for dynamic stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. This study aimed to investigate the temporal relationship between a rapid decrease in plasma glucose and the corresponding rise in plasma adenocorticotropic hormone (ACTH), and to assess the reproducibility of hormone responses to hypoglycemia in normal humans. Ten normal subjects underwent IHTs, using an insulin dose of 0.15 U/kg. Of these, eight had a second IHT (IHT2) and three went on to a third test (IHT3). Plasma ACTH and cortisol were measured at 15-min intervals and, additionally, in four IHT2s and the three IHT3s, ACTH was measured at 2.5- or 5-min intervals. Mean glucose nadirs and mean ACTH and cortisol responses were not significantly different between IHT1, IHT2 and IHT3. Combined data from all 21 tests showed the magnitude of the cortisol responses, but not the ACTH responses, correlated significantly with the depth and duration of hypoglycemia. All subjects achieved glucose concentrations of of < or = 1.6 mmol/l before any detectable rise in ACTH occurred. In the seven tests performed with frequent sampling, an ACTH rise never preceded the glucose nadir, but occurred at the nadir, or up to 15 min after. On repeat testing, peak ACTH levels varied markedly within individuals, whereas peak cortisol levels were more reproducible (mean coefficient of variation 7%). In conclusion, hypoglycemia of < or = 1.6 mmol/l was sufficient to cause stimulation of the HPA axis in all 21 IHTs conducted in normal subjects. Nonetheless, our data cannot reveal whether higher glucose nadirs would stimulate increased HPA axis activity in all subjects. Overall, the cortisol response to hypoglycemia is more reproducible than the ACTH response but, in an individual subject, the difference in peak cortisol between two IHTs may exceed 100 nmol/l.

Contribution of excitatory amino acids to hypoglycemic counter-regulation

We determined the contribution of central N-methyl-D-aspartate (NMDA) receptor activation to the neuro-endocrine counter-regulatory response to insulin-induced hypoglycemia. Glucose kinetics, gluconeogenic substrate balance and counter-regulatory hormonal responses were determined in two groups of conscious dogs fitted with chronic vascular catheters and intracerebroventricular (i.c.v.) cannula. Peripheral insulin infusion (5 mU/kg per min for 3 h) decreased plasma glucose levels 40% and increased the rate of glucose appearance (R(a)) 2-fold. This was associated with significant increases in net hepatic uptake of glycerol and lactate, without any change in the net hepatic uptake of alanine. i.c.v. pretreatment with MK-801, an NMDA receptor antagonist, blunted (50%) the rise in glucose R(a) as well as the increase in the net hepatic uptake of glycerol and lactate. Hypoglycemia increased plasma cortisol (3-fold to 14.3+/-1 mg/dl) and epinephrine levels (14-fold to 3811+/-172 pg/ml), and this stress response was attenuated (30% and 60%, respectively) by MK-801 pretreatment. In controls, MK-801 did not alter the increase in norepinephrine or glucagon elicited by hypoglycemia. These results indicate that during hypoglycemia, central excitatory amino acids contribute to the modulation of the glucoregulatory response through activation of NMDA receptors, resulting in stimulation of the sympathoadrenal and hypothalamic-pituitary adrenal axis. This mechanism appears to play an important role in the sustained elevation in hepatic glucose production during hypoglycemia.

Reproducibility of the insulin tolerance test (ITT) for assessment of growth hormone and cortisol secretion in normal and hypopituitary adult men

OBJECTIVE

The within subject variability of the insulin tolerance test (ITT) for assessment of growth hormone (GH) status and cortisol reserve has rarely been examined, particularly in patients with hypopituitarism. This becomes important when biochemical criteria are used to determine which adults with hypopituitarism should receive GH and/or cortisol replacement. In the present study we assessed the reproducibility of GH and cortisol responses in repeated ITTs. Baseline insulin-like growth factor 1 (IGF-1) levels were also assessed for reproducibility on each occasion.

DESIGN AND PATIENTS

Three consecutive ITTs were performed in seven normal adult men (ages 22-27 years) and two ITTs in 11 men with hypopituitarism and suspected GH deficiency (ages 23-48 years).

MEASUREMENTS

Serum GH and IGF-1 were measured by immunoradiometric and cortisol by immunofluorimetric assays.

RESULTS

In normal men group peak GH responses did not differ between the three tests. There was no correlation between individual peak values. The within subject peak GH variability was between 4.6 and 59.3%, and the overall variability in 21 tests was 35%. The lowest peak GH concentration was 70 mU/l (27 microg/l). All hypopituitary men had severe GH deficiency (all peak GH concentrations < 4 mU/l (1.5 microg/l) in both tests). There was a highly significant correlation between individual peak GH values (r = 0.95, P < 0.0001). Basal IGF-1-values in normal and hypopituitary men were highly correlated between tests (r = 0.98, P < 0.0001). The overall within subject variability of IGF-1-values was 11.9% in normal and 22.7% in hypopituitary men. In normal men group peak cortisol responses were not different between the three tests. There was a good correlation between individual peak cortisol responses in the three ITTs. The within subject peak cortisol variability (median 8.3%; range 0.7-21.5%) was significantly less than that of GH (P < 0.03) in two of three test comparisons. In hypopituitary men the within subject peak cortisol variability (median 41.6%; range 3.5-92.7%) was significantly greater (P < 0.001) than in normal men. All patients were correctly classified as cortisol deficient or normal in both ITTs.

CONCLUSION

The cortisol response to repeated hypoglycaemia is very reproducible in normal men but the GH response is less so. In hypopituitary men the reproducibility of the GH response is good while that of the cortisol response is poor. However, a single ITT did not misclassify hypopituitary patients who are severely GH and/or ACTH deficient and was therefore adequate for clinical decisions regarding GH and/or cortisol replacement. Nevertheless, it remains possible that a single ITT could misclassify some hypopituitary patients with partial GH or ACTH deficiency.

Low plasma lecithin:cholesterol acyltransferase and lipid transfer protein activities in growth hormone deficient and acromegalic men: role in altered high density lipoproteins

Growth hormone (GH) deficiency and acromegaly may be associated with increased cardiovascular risk. Little is known about alterations in high density lipoproteins (HDL) in these conditions. Lecithin:cholesterol acyl transferase (LCAT) has the ability to esterify free cholesterol (FC) in HDL. Cholesteryl ester transfer protein (CETP) is able to transfer cholesteryl esters (CE) from HDL to very low and low density lipoproteins (VLDL and LDL). During phospholipid transfer protein (PLTP)-mediated HDL remodelling, small pre beta-HDL particles are generated which serve as acceptors for cellular cholesterol and provide the initial LCAT-substrate. We documented plasma lipids, LCAT, CETP and PLTP activity levels as well as plasma cholesterol esterification (EST) and cholesteryl ester transfer (CET) in 12 adult men with acquired GH deficiency, 12 acromegalic men and 24 healthy male subjects. All GH deficient and acromegalic patients received conventional hormonal replacement therapy if necessary. VLDL + LDL cholesterol and plasma triglycerides were higher in GH deficient (P < 0.01 and P < 0.05) and acromegalic patients (P < 0.05 and P < 0.01) than in healthy subjects. HDL cholesterol and HDL CE were lower (P < 0.05 for both) and the HDL FC/CE ratio was higher (P < 0.01) in these patient groups compared to healthy subjects. Plasma LCAT, CETP and PLTP activity levels were lower in acromegalic patients (P < 0.01 for all) and CETP activity was lower in GH deficient patients (P < 0.01) compared to healthy subjects. Plasma EST and CET were decreased in both acromegalic (P < 0.01 for both) and GH deficient patients (P < 0.05 for both). Multiple regression analysis demonstrated independent negative relationships of plasma insulin-like growth factor I with plasma LCAT (P = 0.0001), CETP (P = 0.009) and PLTP activity levels (P = 0.021). Plasma LCAT (P = 0.0001) and CETP activity (P = 0.0001) were also negatively associated with (substitution therapy for) adrenal insufficiency. In conclusion, GH deficient and acromegalic patients show abnormalities in HDL, consistent with impaired LCAT action. Decreases in plasma EST and CET in such patients, as well as a low PLTP activity in acromegaly suggest that reverse cholesterol transport may be impaired, contributing to increased cardiovascular risk.