Diagnosis of ACTH deficiency. Comparison of overnight metyrapone test to either low-dose or high-dose ACTH test

Current Screening Strategies for the Diagnosis of Adrenal Insufficiency in Children

Adrenal insufficiency can arise from a primary adrenal disorder, secondary to adrenocorticotropic hormone deficiency, or by suppression of hypothalamic-pituitary-adrenal axis due to exogenous glucocorticoids. Diagnosis of adrenal insufficiency is usually delayed because the initial presentation is often subtle and nonspecific. Clinician awareness and recognition is crucial for timely diagnosis to avoid adrenal crisis. Current screening strategies for the diagnosis of adrenal insufficiency in children in various clinical situations are discussed in this review.

Development and Resolution of Secondary Adrenal Insufficiency after an Intra-Articular Steroid Injection

Corticosteroid injections are commonly indicated in inflammatory conditions involving the soft tissues, tendon sheaths, bursae, and joints. Local corticosteroids carry a lower risk of complications than systemic corticosteroid but may be systemically absorbed and subsequently suppress the hypothalamic-pituitary-adrenal (HPA) axis. This can cause secondary adrenal insufficiency (SAI) as well as iatrogenic Cushing's syndrome. We report a 78-year-old female who presented with nonspecific gastrointestinal symptoms after a recent intra-articular steroid injection in her shoulder. She had hyponatremia, low morning cortisol, and failed to respond to high-dose cosyntropin. Further workup revealed the underlying cause to be SAI. Follow-up testing revealed a recovery of HPA responsiveness within 2 weeks of her initial diagnosis. Conclusion. Our case highlights how the hypothalamic-pituitary axis (HPA) can be suppressed with intra-articular steroids. The threshold to test corticosteroid users for adrenal insufficiency should be low in clinical practice, especially for those patients with nonspecific symptoms after steroid injections. Once diagnosed, temporary treatment with steroids may be required.

Glucocorticoid induced adrenal insufficiency

Synthetic glucocorticoids are widely used for their anti-inflammatory and immunosuppressive actions. A possible unwanted effect of glucocorticoid treatment is suppression of the hypothalamic-pituitary-adrenal axis, which can lead to adrenal insufficiency. Factors affecting the risk of glucocorticoid induced adrenal insufficiency (GI-AI) include the duration of glucocorticoid therapy, mode of administration, glucocorticoid dose and potency, concomitant drugs that interfere with glucocorticoid metabolism, and individual susceptibility. Patients with exogenous glucocorticoid use may develop features of Cushing's syndrome and, subsequently, glucocorticoid withdrawal syndrome when the treatment is tapered down. Symptoms of glucocorticoid withdrawal can overlap with those of the underlying disorder, as well as of GI-AI. A careful approach to the glucocorticoid taper and appropriate patient counseling are needed to assure a successful taper. Glucocorticoid therapy should not be completely stopped until recovery of adrenal function is achieved. In this review, we discuss the factors affecting the risk of GI-AI, propose a regimen for the glucocorticoid taper, and make suggestions for assessment of adrenal function recovery. We also describe current gaps in the management of patients with GI-AI and make suggestions for an approach to the glucocorticoid withdrawal syndrome, chronic management of glucocorticoid therapy, and education on GI-AI for patients and providers.

Different Potent Glucocorticoids, Different Routes of Exposure but the Same Result: Iatrogenic Cushing’s Syndrome and Adrenal Insufficiency

OBJECTIVE

Potent glucocorticoids (GC) cause iatrogenic Cushing’s syndrome (ICS) due to suppression of hypothalamo-pituitary-adrenal (HPA) axis and may progress to adrenal insufficiency (AI). The aim was to review the clinical and laboratory findings of patients with ICS and to investigate other serious side effects.

METHODS

The possibility of AI was investigated by low-dose adrenocorticotrophic hormone test. Hydrocortisone was started in patients with adrenal failure.

RESULTS

Fourteen patients (five boys) with ages ranging from 0.19 to 11.89 years were included. The duration of GC exposure ranged from 1 to 72 months. Ten patients were prescribed topical GC and the rest had oral exposure. Moon face and abdominal obesity were detected in all patients. At presentation, 12 of 14 had AI and two infants had hypercalcemia and nephrocalcinosis. Of 11 patients, ultrasonography revealed hepatosteatosis in five. A cream for diaper dermatitis was used in one infant and the active ingredient was listed as panthenol. However, blood and urine steroid analyses revealed that all endogenous steroids were suppressed. Median (range) time to normalization of HPA axis function was 60 (30-780) days.

CONCLUSION

The majority (85%) of patients had life-threatening AI and two patients had hypercalcemia. These results highlight the serious side-effects of inappropriate use of potent GCs, especially in infants. The recovery of the HPA axis in children might take as long as three years. Parents should be informed regarding the possibility of some products containing unlisted synthetic GC and to be aware of their side effects.

Evidence Limitations in Determining Sexually Dimorphic Outcomes in Pediatric Post-Traumatic Hypopituitarism and the Path Forward

Neuroendocrine dysfunction can occur as a consequence of traumatic brain injury (TBI), and disruptions to the hypothalamic-pituitary axis can be especially consequential to children. The purpose of our review is to summarize current literature relevant to studying sex differences in pediatric post-traumatic hypopituitarism (PTHP). Our understanding of incidence, time course, and impact is constrained by studies which are primarily small, are disadvantaged by significant methodological challenges, and have investigated limited temporal windows. Because hormonal changes underpin the basis of growth and development, the timing of injury and PTHP testing with respect to pubertal stage gains particular importance. Reciprocal relationships among neuroendocrine function, TBI, adverse childhood events, and physiological, psychological and cognitive sequelae are underconsidered influencers of sexually dimorphic outcomes. In light of the tremendous heterogeneity in this body of literature, we conclude with the common path upon which we must collectively arrive in order to make progress in understanding PTHP.

Pediatric Adrenal Insufficiency: Diagnosis, Management, and New Therapies

Adrenal insufficiency may result from a wide variety of congenital or acquired disorders of hypothalamus, pituitary, or adrenal cortex. Destruction or dysfunction of the adrenal cortex is the cause of primary adrenal insufficiency, while secondary adrenal insufficiency is a result of pituitary or hypothalamic disease. Timely diagnosis and clinical management of adrenal insufficiency are critical to prevent morbidity and mortality. This review summarizes the etiologies, presentation, and diagnosis of adrenal insufficiency utilizing different dynamic hormone testing and describes current treatment recommendations and new therapies.

The diagnosis and treatment of adrenal insufficiency during childhood and adolescence

The diagnosis and treatment of adrenal insufficiency in childhood and adolescence poses a number of challenges. Clinical features of chronic adrenal insufficiency are vague and non-specific, and mimic many other causes of chronic ill health. A range of diagnostic tests are available for the assessment of adrenal function, all of which have advantages and disadvantages. Cortisol responses to these tests may vary with age and between genders. Knowledge of normal cortisol levels during health and ill health in childhood is also limited, and the cortisol replacement therapies available in clinical practice enable only crude mimicry of physiological patterns of cortisol secretion. An awareness of the limitations of diagnostic tests and treatments is important, and critical clinical assessment, integrating clinical and biochemical data, is essential for the diagnosis and treatment of children with suspected adrenal insufficiency. The aim of this review is to draw on data from clinical studies to inform a pragmatic approach to the child presenting with symptoms of chronic adrenal insufficiency. Clinical features of primary and secondary adrenal insufficiency, and syndromes associated with these diagnoses are described. Factors to consider when selecting a diagnostic test of adrenal function and interpretation of test results are considered. Finally, the limitations of cortisol replacement therapy are also discussed.

A systematic review and meta-analysis of Synacthen tests for assessing hypothalamic-pituitary-adrenal insufficiency in children

BACKGROUND

The diagnostic value of tests used in assessing hypothalamic-pituitary-adrenal axis (HPA) in children remains controversial.

DESIGN

A systematic review and meta-analysis with receiver-operated-characteristic curve was undertaken to assess the diagnostic values of conventional standard dose 250 μg tetracosactrin (ACTH), short Synacthen test (SSST) and/or low-dose Synacthen test (LDSST) in the assessment of HPA insufficiency in children. Studies eligible for inclusion were any study that compared the use of the LDSST and/or SSST in the assessment of central adrenal insufficiency in children compared with reference standard test.

RESULTS

There were no randomised trials found. SSST resulted in higher specificity and positive likelihood ratio than LDSST. The LDSST had a higher sensitivity (86% vs 61%) but a lower specificity (88% vs 99%) than the SSST, but there was high heterogeneity from the LDSST studies with various doses of Synacthen used.

CONCLUSIONS

Lack of standardisation of assays and protocols with regard to timing, frequency and dose has resulted in diagnostic inaccuracies. There is no clear evidence to indicate that LDSST is superior to SSST in the assessment of HPA axis in children. The choice of either SSST or LDSST should be individualised based on clinical judgement for each patient. This systematic review has identified the need for a well-designed, adequately powered, randomised controlled trial on the use of diagnostic tests used in assessing HPA axis in children.

Central adrenal insufficiency could not be confirmed by measurement of basal serum DHEAS levels in pubertal children

BACKGROUND

Central adrenal insufficiency (CAI) is due to a decrease of CRH and/or ACTH secretion. ACTH-dependent dehydroepiandrosterone sulphate (DHEAS) has been postulated as a possible marker of adrenal function in adult patients.

AIMS

To evaluate the usefulness of basal serum DHEAS determination to diagnose CAI in pubertal patients with a suspected diagnosis of CAI.

METHODS

Ninety-four pubertal patients suspected of having CAI were divided into two groups according to sufficient (group 1) or insufficient (group 2) low-dose ACTH test serum cortisol response. Concordance with low (<2.5th percentile) or normal (≥2.5th percentile) basal serum DHEAS levels for age and sex, respectively, was analysed.

RESULTS

Fifty patients (53.2%) in group 1 and 44 (46.8%) in group 2 were included. The median value of serum DHEAS levels in group 2 (0.7 µmol/l, interquartile range 0.44-1.49) was significantly lower than in group 1 (2.13 µmol/l, interquartile range 0.87-3.5; p < 0.03). Nevertheless, serum basal DHEAS levels as a diagnostic marker of CAI showed 39% sensitivity and 80% specificity.

CONCLUSION

In pubertal patients, basal serum DHEAS levels do not seem to be a useful tool to diagnose either sufficiency or insufficiency of secondary adrenal function.

Hypopituitarism in pediatric survivors of inflicted traumatic brain injury

Endocrine dysfunction is common after accidental traumatic brain injury (TBI). Prevalence of endocrine dysfunction after inflicted traumatic brain injury (iTBI) is not known. The aim of this study was to examine endocrinopathy in children after moderate-to-severe iTBI. Children with previous iTBI (n=14) were evaluated for growth/endocrine dysfunction, including anthropometric measurements and hormonal evaluation (nocturnal growth hormone [GH], thyrotropin surge, morning and low-dose adrenocorticotropin stimulated cortisol, insulin-like growth factor 1, IGF-binding protein 3, free thyroxine, prolactin [PRL], and serum/urine osmolality). Analysis used Fisher's exact test and Wilcoxon's rank-sum test, as appropriate. Eighty-six percent of subjects had endocrine dysfunction with at least one abnormality, whereas 50% had two or more abnormalities, significantly increased compared to an estimated 2.5% with endocrine abnormality in the general population (p<0.001). Elevated prolactin was common (64%), followed by abnormal thyroid function (33%), short stature (29%), and low GH peak (17%). High prolactin was common in subjects with other endocrine abnormalities. Two were treated with thyroid hormone and 2 may require GH therapy. In conclusion, children with a history of iTBI show high risk for endocrine dysfunction, including elevated PRL and growth abnormalities. This effect of iTBI has not been well described in the literature. Larger, multi-center, prospective studies would provide more data to determine the extent of endocrine dysfunction in iTBI. We recommend that any child with a history of iTBI be followed closely for growth velocity and pubertal changes. If growth velocity is slow, PRL level and a full endocrine evaluation should be performed.

Lack of sensitivity of the 1-μg low-dose ACTH stimulation test in a paediatric population with suboptimal cortisol responses to insulin-induced hypoglycaemia

CONTEXT

The insulin-tolerance test (ITT) is the gold standard for evaluation of the hypothalamic-pituitary-adrenal (HPA) axis. The low-dose ACTH stimulation test is increasingly used for evaluation of secondary adrenal insufficiency as several studies performed in adults have demonstrated high sensitivity and specificity when compared to the ITT. Whether the ACTH stimulation test demonstrates similar sensitivity in a paediatric and adolescent population compared with the gold standard is unclear.

OBJECTIVE

To compare the sensitivity of the low-dose (1-μg) Synacthen(™) test (LDSST) and the gold-standard ITT in a paediatric and adolescent population.

DESIGN AND PATIENTS

A retrospective review of 42 consecutive LDSSTs in children and adolescents with suboptimal cortisol responses (peak <500 nm) on ITT.

RESULTS

Thirty-one patients (74%) had an adequate cortisol response to low-dose Synacthen(™) (sensitivity 26%). Patients had a higher cortisol increment with the LDSST than ITT (median Δ cortisol 294 vs 168 nm, P < 0.0001) and correspondingly a higher cortisol peak (median peak cortisol 572 vs 396 nm, P < 0.0001). Patients who had a suboptimal peak cortisol both on ITT and on LDSST had a lower baseline cortisol on ITT (median 178 vs 227 nm, P = 0.04). Peak cortisol on ITT was significantly higher in patients who had a subsequent normal LDSST than those that did not (median 417 vs 300 nm, P = 0.0005).

CONCLUSIONS

The 1-μg LDSST lacks sensitivity in detection of secondary adrenal insufficiency in children when compared to the gold-standard ITT.

Postradiation therapy hypopituitarism

The increasing use of radiation treatment for head and neck cancers and other tumors, including pituitary adenomas, from the mid-20th Century onwards led to the recognition that pituitary function may be affected - often leading to some degree of pituitary insufficiency. Our knowledge is mostly based on observational or retrospective rather than randomized prospective studies. The various axes may be impacted at the hypothalamic or pituitary levels, or both. Some axes - the somatotropic and gonadotropic - appear to be especially vulnerable to radiation damage and may be affected quite early, whereas posterior pituitary function is rarely affected. Increased use of stereotactic radiosurgery, which focuses the radiation dose on the abnormal tissue, may be expected to reduce the impact on normal pituitary function, but such studies that are available are, as yet, relatively short term. Prospective studies of the effect of stereotactic radiosurgery on pituitary function would be valuable.

The low-dose ACTH test does not identify mild insufficiency of the hypothalamnic-pituitary-adrenal axis in children with inadequate stress response

OBJECTIVE

To investigate retrospectively the sensitivity of published cortisol cut-off points of the low-dose ACTH test (LDAT) in children with proven mild hypothalamic-pituitary-adrenal (HPA) axis insufficiency.

PATIENTS AND METHODS

The HPA axis of 11 pediatric patients (age range: 5.5-14.5 yr) with established mild HPA axis insufficiency was reinvestigated with the LDAT. The sensitivity of the LDAT was calculated on the basis of published stimulated cortisol cut-off points.

RESULTS

The LDAT showed both a significantly higher cortisol peak and a greater cortisol rise compared with the ITT (both P < 0.01). The LDAT yielded a low sensitivity of 9-55% using published cortisol cut-off points as references.

CONCLUSION

Using published cortisol cut-off points, the LDAT showed a poor sensitivity to detect mild HPA axis insufficiency. We cannot recommend the use of the LDAT as a screening test of HPA axis impairment in such children.

A prospective multicenter study of adrenal function in critically ill children

RATIONALE

Adrenal insufficiency is a clinical condition associated with fluid- and catecholamine-resistant hypotension.

OBJECTIVES

The objectives of this study were to determine the prevalence of adrenal insufficiency, risk factors and potential mechanisms for its development, and its association with clinically important outcomes in critically ill children.

METHODS

A prospective, cohort study was conducted from 2005 to 2008 in seven tertiary-care, pediatric intensive care units in Canada on patients up to 17 years of age with existing vascular access. Adrenocorticotropic hormone stimulation tests (1 microg) were performed and adrenocorticotropic hormone levels measured in all participants.

MEASUREMENTS AND MAIN RESULTS

A total of 381 patients had adrenal testing on admission. The prevalence of adrenal insufficiency was 30.2% (95% confidence interval, 25.9-35.1). Patients with adrenal insufficiency had higher baseline cortisol levels (28.6 microg/dl vs. 16.7 microg/dl, P < 0.001) and were significantly older (11.5 yr vs. 2.3 yr, P < 0.001) than those without adrenal insufficiency. Adrenal insufficiency was associated with an increased need for catecholamines (P < 0.001) and more fluid boluses (P = 0.026). The sensitivity and specificity of the low-dose adrenocorticotropic hormone stimulation test were 100% and 84%, respectively.

CONCLUSIONS

Adrenal insufficiency occurs in many disease conditions in critically ill children and is associated with an increased use of catecholamines and fluid boluses. It is likely multifactorial in etiology and is associated with high baseline cortisol levels. Further research is necessary to determine which of these critically ill children are truly cortisol deficient before any treatment recommendations can be made.

Pitfalls in the diagnosis of central adrenal insufficiency in children

The diagnosis of central adrenal insufficiency relies heavily on laboratory testing of cortisol levels in the systemic circulation. The lack of cortisol assay standardization challenges the reliability of dynamic tests of the hypothalamic-pituitary adrenal axis. Although the insulin-induced hypoglycemia or metyrapone tests remain the accepted standards for evaluating central adrenal insufficiency in children their associated risks and inconvenience make them unattractive for routine use. Corticotropin testing is an effective first step to evaluate for chronic central adrenal insufficiency for children older than 2 years who are ambulatory, have normal sleep-wake cycle and normal serum protein levels. The low-dose (1 microg) corticotropin test may be superior to standard-dose (250 mcg) for patients with suspected hypothalamic-pituitary disease.

Adrenal insufficiency in pediatric critical illness: controversies regarding its prevalence, pathogenesis, definition and management

Proper functioning of the hypothalamic–pituitary–adrenal axis is necessary for normal homeostasis in children and especially under conditions of stress, such as critical illness. Disturbances of this axis have been classified collectively under the heading of adrenal insufficiency. Although the majority of literature has focused on children with septic shock, more recent evidence suggests that adrenal insufficiency occurs in a much broader group of critically ill children. Its etiology in pediatric critical illness remains unclear but is most likely multifactorial. Several studies have suggested possible diagnostic criteria for adrenal insufficiency in pediatric critical illness; however, to date none of these biochemical definitions have been validated. Similarly, current management of this condition in children remains based primarily on an empiric, best-practice approach. Future large-scale studies are needed to elucidate the prevalence, pathogenesis, definition, diagnosis and management of this condition.

Low-dose adrenocorticotropic hormone stimulation testing in term infants

BACKGROUND

Low-dose adrenocorticotropic hormone (ACTH) stimulation testing is a commonly accepted way to evaluate adrenal function in children. However, there are no published data on the use of this test in term infants less than 12 months of age outside the newborn period.

METHODS

We identified 14 infants at our center who were full term and had one or more ACTH tests at less than 12 months of age to evaluate for secondary adrenal insufficiency (AI). We retrospectively assessed peak cortisol response in these infants to determine whether a cut-off of 20 microg/dl is appropriate to distinguish normal from abnormal adrenal function in this age group.

RESULTS

Five infants had peak cortisol > or =20 microg/dl on their first ACTH test and had a clinical picture consistent with normal adrenal function. Nine infants had peak cortisol <20 microg/dl on their first ACTH test. When retested later in infancy, four of these patients achieved peak cortisol > or =20 microg/dl.

CONCLUSIONS

In term infants, the low-dose ACTH stimulation test is useful for demonstrating normal adrenal function but is of limited value in diagnosing secondary AI. For infants with peak cortisol <20 microg/dl, clinical observation and repeat ACTH testing later in infancy clarified diagnosis.

Use of the low-dose corticotropin stimulation test for the monitoring of children with asthma treated with inhaled corticosteroids

OBJECTIVE

Subnormal hypothalamic-pituitary-adrenal (HPA) function and rare cases of adrenal crisis have been reported in asthmatic children treated with inhaled corticosteroids. We investigated subnormal HPA activity and followed up affected patients until recovery of normal HPA functions.

STUDY DESIGN

100 children with persistent asthma underwent low-dose corticotropin testing, with the administration of 1 microg of 1-24 ACTH intravenously. Treatments were beclomethasone dipropionate as a metered-dose inhaler, n = 14, budesonide as a dry-powder inhaler, n = 16, fluticasone propionate as a metered-dose inhaler n = 31 or a dry-powder inhaler n = 39. The mean commercially labelled dose was 520 +/- 29 microg/day (mean +/- SEM, range: 160-1,000) and the equipotent dose (which compares the efficiency of these drugs for treating asthma and their responsibility for systemic effects) was 890 +/- 55 microg/day (range: 200-2,000).

RESULTS

The mean stimulated cortisol level +/- SEM (and range) of the patient was 482 +/- 12 (148-801), and that of 40 age-matched controls was 580 +/- 12.5 (439-726), (SD = 79). The result was subnormal (more than 2 SD below the mean of the controls) in28 of the 100 patients. One-four stepwise decreases of 10-100% in the daily equipotent doses received by the patients with abnormal low-dose corticotropin testing results led to normal results in subsequent low-dose corticotropin testing in 27 retested patients. The mean time interval between two tests was 5 months (range: 2-6 months) and the mean period required for normalization of the test was 13 months (range: 2-21). Only one case of asthma exacerbation and no adrenal crisis were observed over these periods.

CONCLUSIONS

Decreasing daily equipotent doses led to recovery of normal HPA function without asthma exacerbation. Thus, a revision of the doses of inhaled corticosteroids used in asthmatic children with a progressive decrease to the consensus-recommended doses should decrease the systemic effects of inhaled corticosteroids, while minimizing the risk of asthma exacerbation.

Relationship between Cortisol Increment and Basal Cortisol: Implications for the Low-Dose Short Adrenocorticotropic Hormone Stimulation Test

Background: We analyzed the low-dose (1 μg) rapid adrenocorticotropic hormone test (LDST) in 17 patients with a normal hypothalamic-pituitary-adrenal axis to determine reference intervals for the LDST on the basis of poststimulation cortisol increments.

Methods: We analyzed test results for 17 patients (14 females and 3 males; age range, 18–46 years) who had received a 2-mL aliquot of low-dose (1 μg) adrenocorticotropic hormone prepared from one 250-μg vial of Synacthen diluted in 500 mL of sterile normal saline solution. Sampling took place at 0, 20, 30, and 60 min post stimulation. The cortisol increment was plotted against basal cortisol.

Results: We observed a marked interdependence of the basal cortisol concentration with the increase in cortisol concentration. The relationship was inverse and linear with the best fit observed at 30 min post stimulation. The lower 95% prediction limit for basal cortisol at the zero increment was 400 nmol/L with a mean concentration of 600 nmol/L.

Conclusions: We propose that a peak cortisol concentration &lt;400 nmol/L is a sufficient single criterion for abnormal adrenal function as assessed by the LDST. Concentrations of 400–600 nmol/L are in the gray area, and those &gt;600 nmol/L confirm normal adrenal function. Repeat analyses with larger sample sizes are warranted to confirm these observations.

Growth, bone mineral accretion, and adrenal function in glucocorticoid-treated infants with hemangiomas-- a retrospective study

Hemangiomas, common proliferative vascular tumors, can grow rapidly in the first months of life. Although therapy with high-dose oral glucocorticoids is standard for lesions that threaten vital functions or are disfiguring, little is known about the endocrine consequences of this treatment. Using retrospective data, we examined growth velocity, changes in bone mineral density, and adrenal function in infants with hemangiomas treated with systemic glucocorticoids. Treatment consisted of oral prednisolone 2 to 4 mg/kg/day or dexamethasone 1 mg/kg/day. Mean growth velocity Z score on glucocorticoid therapy was -1.41 standard deviations in 13 patients. In four infants with adequate follow-up, growth velocity increased to +1.90 standard deviations after glucocorticoid treatment (Delta growth velocity +3.31 standard deviations). Mean lumbar spine bone mineral density Z score was -2.46 standard deviations before glucocorticoid treatment and -1.08 standard deviations at the end of treatment in six infants. Adrenal function after glucocorticoid therapy was assessed by low-dose adrenocorticotropic hormone stimulation test in 10 infants. Eight had a normal cortisol response, and one had a borderline response. One infant, who had been treated with dexamethasone, had an abnormal test result. In conclusion, systemic glucocorticoid treatment in infants with hemangiomas slowed linear growth, but "catch-up" growth was observed after treatment ceased. Glucocorticoids did not affect bone mineralization adversely. Only 1 of 10 glucocorticoid-treated infants had clear evidence of adrenal insufficiency after therapy was stopped.

Stimulation of the hypothalamic-pituitary-adrenal axis with the opioid antagonist nalmefene

Nalmefene Stimulation of the HPA Axis.

BACKGROUND

The Hypothalamic-pituitary-adrenal (HPA) axis plays a vital role in the body's response to stress. The traditional gold standard for evaluating the HPA axis, the insulin hypoglycemia test (IHT), has several known limitations, and a second test, the standard ACTH stimulation test, can detect severe deficiencies of cortisol, but often misses mild or early cases. Therefore, a better test for the evaluation of the HPA axis is needed. This study evaluated the opiate antagonist nalmefene as a stimulation test of the HPA axis.

METHODS

25 healthy subjects were studied, 9 women and 16 men, mean age 30.4 yr. (range 21-55), and mean BMI 24.1 kg/m2 (range 18.6-34.2). Subjects received one of 3 doses of intravenously administered nalmefene: 2 mg (n = 6), 6 mg (n = 12), or 10 mg (n = 7). Serum cortisol and plasma ACTH were measured before and serially over two hours after the administration of nalmefene.

RESULTS

ACTH and cortisol levels rose significantly and similarly after the 10 mg dose and the 6 mg dose. After the 10 mg dose, mean peak ACTH was 82.4 +/- 22.6 pg/ml and mean peak cortisol was 25.2 +/- 1.8 microg/dl. After the 6 mg dose, mean peak ACTH was 70.3 +/- 7.7 pg/ml and mean peak cortisol was 24.7 +/- 1.7 microg/dl. Cortisol levels rose above 18 microg/dl in all subjects receiving 10 mg of nalmefene, and in all but two of the subjects receiving 6 mg of nalmefene. Side effects to nalmefene were of greater duration and intensity in the subjects receiving 10 mg of nalmefene vs. those receiving 6 or 2 mg. These included most notably fatigue, lightheadedness, nausea and vomiting.

CONCLUSIONS

Of the nalmefene doses we studied, 6 mg achieved the best combination of stimulation of ACTH and cortisol and fewest side effects. If further studies show a concordance between nalmefene and IHT, nalmefene testing could be used to assess the HPA axis in patients at risk for dysfunction of this axis.

Endocrine consequences of brain irradiation

Cranial radiation is routinely used to manage pituitary tumours, craniopharyngiomas, primary brain tumours, tumours of the head and neck and, in the past, for the prophylaxis of intracranial disease in patients with acute lymphoblastic leukaemia. If the hypothalamic-pituitary axis falls within the radiation fields, the patient is at risk of developing hypopituitarism. The effect of radiation is determined by the dose and the time that has elapsed since treatment. Classically, growth hormone (GH) is the most sensitive of the anterior pituitary hormones to irradiation, followed by gonadotrophins, adrenocorticotrophic hormone (ACTH) and thyroid-stimulating hormone (TSH). Low-dose irradiation in prepubertal children can initially cause early or precocious puberty and subsequently gonadotrophin deficiency. Higher doses may cause gonadotrophin deficiency and pubertal delay. The ACTH and TSH axes are relatively resistant to the effects of irradiation, but minor abnormalities may occur. Patients who receive cranial irradiation that affects the hypothalamic-pituitary axis remain at risk of developing multiple hormone deficiencies for many years and require long-term follow-up by an endocrinologist.

Endocrinological outcome of different treatment options in children with craniopharyngioma: a retrospective analysis of 66 cases

Craniopharyngioma is one of the leading causes of hypothalamic-pituitary dysfunction in childhood, caused either by the tumor itself or the consequences of treatment. Tumor management in terms of recurrence rate, quality of life and complications is still controversial. Sixty-six patients with craniopharyngioma at pediatric age were reviewed for symptoms, signs, types of treatment, recurrence rates, complications, and endocrinological outcome. The majority of symptoms was related to the neurological system. Complaints only affecting the endocrinological system were seen in 6% of patients. The most frequent complaints were headache and vomiting (74.2%). The main endocrinological complaints were polyuria and polydipsia (15%), and lassitude (10.6%). Although short stature was a symptom in 9.1% of patients, it was a finding in 39.7% of patients. Plain skull X-rays raised the suspicion of intracranial tumor in more than 90% of children with craniopharyngioma. Recurrence rates were independent of the extent of tumor removal (total or subtotal). The frequency of endocrine dysfunction increased significantly after treatment. The most frequent hypothalamic-pituitary dysfunction was growth hormone deficiency (100%) and gonadotropin deficiency (80%). Hypothyroidism was diagnosed in 74% of patients. The frequency of hypothalamic-pituitary dysfunction was not affected by the extent of tumor removal. Radiotherapy did not increase the frequency of endocrine dysfunctions further. In conclusion, growth follow-up in childhood seems to be an important indicator of craniopharyngioma in early diagnosis. Radiotherapy and extent of tumor removal - either total or subtotal - did not influence endocrine outcome.

Critical issues in endocrinology

Endocrine emergencies are commonly encountered in the ICU. This article focuses on several important endocrine emergencies, including diabetic hyperglycemic states, adrenal insufficiency, myxedema coma, thyroid storm, and pituitary apoplexy. Other endocrine issues that are related to intensive care, such as intensive insulin therapy, relative adrenal insufficiency, and thyroid function test abnormalities are also covered in detail.

Significance of Low-Dose and Standard-Dose ACTH Tests Compared to Overnight Metyrapone Test in the Diagnosis of Adrenal Insufficiency in Childhood

OBJECTIVE

To discover the value of low-dose (LDAT) and standard-dose ACTH tests (SDAT) as compared with the metyrapone test in the diagnosis of secondary adrenal insufficiency.

PATIENTS AND METHODS

LDAT (0.5 microg/m2), SDAT (250 microg/m2) and overnight metyrapone (30 mg/kg) tests were carried out in 29 patients with suspected adrenal insufficiency. LDAT and SDAT were also performed in 36 control subjects.

RESULTS

18 of 29 patients were grouped in the adrenal-sufficient (AS) group and 11 of 29 patients in the adrenal-deficient (AD) group according to the metyrapone test results. The control group had significantly higher cortisol responses than the AS and AD groups during LDAT. The control group had similar cortisol responses to the AS group but higher cortisol responses than the AD group during SDAT. The AS group was divided into 2 subgroups: AS patients with multiple pituitary hormone deficiencies (AS-multiple) and AS patients with idiopathic growth hormone deficiencies (AS-isolated). The AS-multiple group had statistically lower cortisol responses than the control group during LDAT. Receiver-operating characteristics analysis revealed that the cortisol cutoff value in LDAT was 19.8 microg/dl (100% sensitivity, 89% specificity) and 30.4 microg/dl in SDAT (82% sensitivity, 78% specificity).

CONCLUSION

LDAT is capable of identifying patients with adrenal insufficiency more effectively than SDAT. The cortisol cutoff value in LDAT was calculated as 19.8 microg/dl with 100% sensitivity. AS patients with multiple pituitary hormone deficiencies had lower cortisol responses to LDAT than the control group implying that these patients might have a lower cortisol secretory capacity than healthy subjects.

Preirradiation endocrinopathies in pediatric brain tumor patients determined by dynamic tests of endocrine function

PURPOSE

To prospectively evaluate pediatric patients with localized primary brain tumors for evidence of endocrinopathy before radiotherapy (RT).

METHODS AND MATERIALS

Seventy-five pediatric patients were evaluated with the arginine tolerance test and L-dopa test for growth hormone secretory capacity and activity; thyroid-stimulating hormone surge and thyrotropin-releasing hormone stimulation test for the hypothalamic-thyroid axis; the 1-microg adrenocorticotropin hormone (ACTH) and metyrapone test for ACTH reserve; and, depending on age, a gonadotropin-releasing hormone stimulation test to determine gonadotropin response. The study included 38 male and 37 female patients, age 1-21 years with ependymoma (n = 35), World Health Organization (WHO) Grade I-II astrocytoma (n = 18), WHO Grade III-IV astrocytoma (n = 10), craniopharyngioma (n = 7), optic pathway tumor (n = 4), and germinoma (n = 1). Seven patients receiving dexamethasone at the time of the evaluation were excluded from the final analysis.

RESULTS

Of 68 assessable patient, 45 (66%) had evidence of endocrinopathy before RT, including 15 of 32 patients (47%) with posterior fossa tumors. Of the 45 patients, 38% had growth hormone deficiency, 43% had thyroid-stimulating hormone secretion abnormality, 22% had an abnormality in ACTH reserve, and 13% had an abnormality in age-dependent gonadotropin secretion.

CONCLUSION

The incidence of pre-RT endocrinopathy in pediatric brain tumor patients is high, including patients with tumors not adjacent to the hypothalamic-pituitary unit. These data suggest an overestimation in the incidence of radiation-induced endocrinopathy. Baseline endocrine function should be determined for brain tumor patients before therapy. The potential for radiation-induced endocrinopathy alone cannot be used as an argument for alternatives to RT for most patients. Pre-RT endocrinopathy may be an early indicator of central nervous system damage that will influence the functional outcome unrelated to RT.

Adrenocorticotropin stimulation tests in patients with hypothalamic-pituitary disease: low dose, standard high dose and 8-h infusion tests

OBJECTIVES

Low doses of ACTH [1-24] (0.1, 0.5 and 1.0 microg per 1.73 m2) may provide a more physiological level of adrenal stimulation than the standard 250 microg test, but not all studies have concluded that the 1.0 microg is a more sensitive screening test for central hypoadrenalism. Eight-hour infusions of high dose ACTH [1-24] have also been suggested as a means of assessing the adrenals' capacity for sustained cortisol secretion. In this study, we compared the diagnostic accuracy of three low dose ACTH tests (LDTs) and the 8-h infusion with the standard 250 microg test (HDT) and the insulin hypoglycaemia test (IHT) in patients with hypothalamic-pituitary disease.

SUBJECTS AND DESIGN

Three groups of subjects were studied. A healthy control group (group 1, n = 9) and 33 patients with known hypothalamic or pituitary disease who were divided into group 2 (n = 12, underwent IHT) and group 3 (n = 21, IHT contraindicated). Six different tests were performed: a standard IHT (0.15 U/kg soluble insulin); a 60-minute 250 microg HDT; three different LDTs using 0.1 microg, 0.5 microg and 1.0 microg (all per 1.73 m2); and an 8-h infusion test (250 microg ACTH [1-24] at a constant rate over 8 h).

RESULTS

Nine out of the 12 patients in group 2 failed the IHT. Three out of 12 patients from group 2 who clearly passed the IHT, also passed all the ACTH [1-24] stimulation tests. Seven of the 9 patients who failed the IHT, failed by a clear margin (peak cortisol < 85% of the lowest normal). Two of the 7 also failed all the ACTH [1-24] tests. Five of the 7 patients had discordant results, four passed the 0.1 LDT, one (out of four) passed the 0.5 LDT, none (out of three) passed the 1.0 LDT, two passed the HDT and three passed the 8-h test. Two patients were regarded as borderline fails in the IHT. Both passed the ACTH [1-24] tests, although one was a borderline pass in the 8-h test. Only five out of the 21 patients in group 3 showed discordance between the HDT and the LDTs. One patient passed the HDT and failed the 0.1 LDT, four patients failed the HDT but passed some of the different LDTS.

CONCLUSIONS

We conclude that in the diagnosis of central hypoadrenalism, ACTH [1-24] stimulation tests may give misleading results compared to the IHT. The use of low bolus doses of ACTH [1-24] (1.0, 0.5 or 0.1 microg) or a high dose prolonged infusion does not greatly improve the sensitivity of ACTH [1-24] testing. Dynamic tests that provide a central stimulus remain preferable in the assessment of patients with suspected ACTH deficiency.