巨噬细胞移动抑制因子与脓毒症患儿肾上腺皮质功能关系的研究进展

相对性肾上腺皮质功能不全是脓毒症患儿病情恶化因素之一,目前临床诊断尚存在争议.巨噬细胞移动抑制因子能抵抗糖皮质激素的抗炎活性,在机体炎症反应中起重要作用.巨噬细胞移动抑制因子与糖皮质激素之间相互作用可能引起相对性肾上腺皮质功能不全.因此,巨噬细胞移动抑制因子可能是临床上诊断相对性肾皮质功能不全的一个重要指标.     

What is the rationale for hydrocortisone treatment in children with infection-related adrenal insufficiency and septic shock?

Recent studies show that children who die from fulminant meningococcaemia have very low cortisol:adrenocorticotrophic hormone (ACTH) ratios within the first 8 h of presentation to emergency facilities compared with survivors. This observation supports the possibility that adrenal insufficiency may contribute to rapid cardiovascular collapse in these children. In recent years, the use of hydrocortisone treatment has become increasingly popular in the care of adult and paediatric patients with septic shock. In this review, the classical adrenal insufficiency literature is presented and the existing rationale for using titrated hydrocortisone treatment (2-50 mg/kg/day) to reverse catecholamine-resistant shock in children who have absolute adrenal insufficiency (defined by peak cortisol level <18 microg/dl after ACTH challenge) or pituitary, hypothalamic or adrenal axis insufficiency is provided. In addition, the concept of relative adrenal insufficiency (basal cortisol >18 microg/dl but a peak response to ACTH <9 microg/dl) is reviewed. Although there is a good rationale supporting the use of 7 days of low-dose hydrocortisone treatment (about 5 mg/kg/day) in adults with this condition and catecholamine resistant septic shock, the paediatric literature suggests that it is prudent to conduct more studies before recommending this approach in children.     

Corticosteroid physiology and principles of therapy

The adrenal cortex secretes glucocorticoids (GC), mineralocorticoids (MC) and androgens. GC maintain homeostasis, MC regulate fluid and electrolyte balance and adrenal androgens contribute to development of secondary sexual characteristics. Pharmacologic GC therapy is frequently indicated in the pediatric age group. Besides having many important side effects, prolonged high dose systemic GC therapy has a suppressive effect on endogenous steroid production. Therefore, GC therapy should be withdrawn gradually and stopped based on assessment of hypothalamo-pituitary-adrenal (HPA) axis recovery. Patients with HPA axis suppression require physiological replacement of GC along with enhancement of doses during periods of stress. Due to its immunosuppressive effects, issues about safety and efficacy of live virus vaccines in patients receiving systemic high dose GC therapy must be borne in mind.     

Adrenal insufficiency in septic shock.

BACKGROUND: Functional adrenal insufficiency has been documented in critically ill adults. OBJECTIVE: To document the incidence of adrenal insufficiency in children with septic shock, and to evaluate its effect on catecholamine requirements, duration of intensive care, and mortality. SETTING: Sixteen-bed paediatric intensive care unit in a university hospital. METHODS: Thirty three children with septic shock were enrolled. Adrenal function was assessed by the maximum cortisol response after synthetic adrenocorticotropin stimulation (short Synacthen test). Insufficiency was defined as a post-Synacthen cortisol increment < 200 nmol/l. RESULTS: Overall mortality was 33%. The incidence of adrenal insufficiency was 52% and children with adrenal insufficiency were significantly older and tended to have higher paediatric risk of mortality scores. They also required higher dose vasopressors for haemodynamic stability. In the survivor group, those with adrenal insufficiency needed a longer period of inotropic support than those with normal function (median, 3 v 2 days), but there was no significant difference in duration of ventilation (median, 4 days for each group) or length of stay (median, 5 v 4 days). Mortality was not significantly greater in children with adrenal insufficiency than in those with adequate adrenal function (6 of 17 v 5 of 16, respectively). CONCLUSION: Adrenal insufficiency is common in children with septic shock. It is associated with an increased vasopressor requirement and duration of shock.     

Hypothalamic‐pituitary‐adrenal axis suppression in asthmatic children on inhaled corticosteroids: Part 1. Which test should be used?

The effect of inhaled corticosteroids (ICS) on the hypothalamic-pituitary-adrenal axis (HPA) has been regarded as a 'benign physiological response'. A recent survey suggests that adrenal crisis might be more common in asthmatic children on ICS than previously thought. The clinical features of adrenal insufficiency are non-specific and can easily be missed. Accurate biochemical assessment of the axis is therefore mandatory. A review of the literature determined that all basal adrenal function tests, including plasma cortisol profiles, cannot identify which children can respond to stress. There is no evidence to suggests that the degree of the physiological adjustment of the HPA to ICS predicts clinically significant HPA suppression. Only gold standard adrenal function tests can assess the integrity of the whole axis. Of the two available tests, the correctly performed overnight metyrapone test (with ACTH levels) is safe and better by far. The use of cortisol profiles should only be used to demonstrate differences in systemic activity of various ICS and delivery devices. Regulatory bodies should insist on trials that evaluate the HPA with a gold standard adrenal function test before it is declared safe and allowed to be marketed. A re-analysis of studies that have utilized gold standard adrenal function tests only might identify the lowest safe dose and duration of ICS.     

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??Adrenal insufficiency??AI?? is an uncommon clinical disorder that arises from an inadequate basal or stress level of plasma cortisol. The clinical findings of primary adrenal insufficiency??PAI?? are associated with deficient synthesis or release of glucocorticoids and frequent deficiency of mineralocorticoids. The presentation of adrenal insufficiency may be insidious and difficult to recognize??so it is important to diagnose adrenal insufficiency properly??for an unrecognized or untreated disorder sometimes might be fatal. Once suspected??the exact underlying diagnosis needs to be confirmed by a stepwise diagnostic approach??with an open eye for other differential diagnostic possibilities. The definite diagnosis should be supported by laboratory evaluation on the function of adrenocortical and HPA axis.     

Antenatal glucocorticoids and programming of the developing CNS

Glucocorticoids (GCs) are essential for many aspects of normal brain development. However, there is growing evidence from a number of species that exposure of the fetal brain to excess GC, at critical stages of development, can have life-long effects on behavior and neuroendocrine function. The hypothalamo-pituitary-adrenal axis, which is central to the integration of the individual's endocrine and behavioral response to stress, appears highly sensitive to excess GC exposure during development. A number of animal studies have shown that exposure to synthetic GCs in utero results in adult offspring that exhibit hyperactivity of the hypothalamo-pituitary-adrenal axis. This will have a long-term impact on health, inasmuch as increased life-long exposure to endogenous GC has been linked to the premature onset of diseases associated with aging. The mechanisms involved in the permanent programming of hypothalamo-pituitary-adrenal function and behavior are not well understood. Synthetic GCs are used extensively to promote pulmonary maturation in fetuses at risk of being delivered before term. Therefore, it is important that we understand the potential long-term consequences of prenatal GC exposure on brain development as well as the underlying mechanisms involved. This review will explore the current state of knowledge in this rapidly expanding field.     

Development of the hypothalamic-pituitary-adrenal axis in the fetus and preterm infant

The development of the hypothalamic-pituitary-adrenal (HPA) axis in the human fetus is a complex process. The feto-placental unit may be responsible for important maturational processes in vital organ systems in the fetus. A late gestational cortisol surge may be important in fetal maturation, particularly maturation of the lungs. Several striking differences exist between the function of the HPA axis in the fetus and in adults, such as a relative deficiency of 3beta-hydroxysteroid dehydrogenase in the fetal adrenal cortex. With the transition from intrauterine to extra-uterine life several changes occur in the function of the HPA axis. In infants born before term, the function of the HPA axis may still be immature at both the central and adrenal level. This immaturity of the HPA axis may be important in the development of neonatal morbidity. The present review describes the development of the HPA axis in the fetus and in preterm infants and discusses the possible role of HPA immaturity in the development of neonatal morbidity.     

Evaluation of hypothalamic-pituitary-adrenal axis suppression by low-dose (0.5 microg) and standard-dose (250 microg) adrenocorticotropic hormone (ACTH) tests in asthmatic children treated with inhaled corticosteroid

The aim of this study was to compare the results of low-dose (LDT) and standard-dose (SDT) ACTH tests in the assessment of adrenal function in 30 asthmatic children (mean age 9.35 +/- 1.9 years, 19 boys) who were treated with budesonide Turbohaler at conventional 400 microg or 600 microg daily doses for 8 weeks by a prospective, randomized, and open parallel study. Budesonide did not lead to any significant suppression of the hypothalamic-pituitary-adrenal (HPA) axis in either treatment group. However, when individual patient values were examined at the end point, peak cortisol concentrations after LDT were below 2 SDs of the pretreatment values in four patients (13.3%). Also, the increment in cortisol values was <200 nmol/l in all four patients. Decreased 24-hour urinary free cortisol excretion provided further evidence for HPA axis suppression in these patients. Two of these four poor responders to LDT showed normal stimulation with SDT. In conclusion, even with moderate doses and short-term use, adrenal suppression may occur in certain susceptible patients. The low-dose ACTH test is more reliable than SDT for the evaluation of such patients.     

Diagnosis and management of pediatric adrenal insufficiency

Background

Adrenal insufficiency (AI) is a wellknown cause of potentially life-threatening disorders. Defects at each level of the hypothalamic-pituitary-adrenal axis can impair adrenal function, leading to varying degrees of glucocorticoid (GC) deficiency. Iatrogenic AI induced by exogenous GCs is the most common cause of AI. The criteria for the diagnosis and management of iatrogenic AI, neonatal AI, and critical illness-related corticosteroid insufficiency (CIRCI) are not clear.

Data sources

We reviewed the recent original publications and classical data from the literature, as well as the clinical, diagnostic and management strategies of pediatric AI.

Results

Practical points in the diagnosis and management of AI with an emphasis on iatrogenic AI, neonatal AI, and CIRCI are provided. Given the lack of sensitive and practical biochemical tests for diagnosis of subtle AI, GC treatment has to be tailored to highly suggestive clinical symptoms and signs. Treatment of adrenal crisis is well standardized and patients almost invariably respond well to therapy. It is mainly the delay in treatment that is responsible for mortality in adrenal crisis.

Conclusions

Education of patients and health care professionals is mandatory for timely interventions for patients with adrenal crisis.

     

Duration of adrenal insufficiency during treatment for childhood acute lymphoblastic leukemia

Children with acute lymphoblastic leukemia (ALL) recive high doses of glucocorticosteroid as part of their treatment. This may lead to suppression of the hypothalamic-pituitary-adrenal axis, acute adrenal insufficiency, and ultimately to life-threatening conditions. This study explores the adrenal function in 96 children with ALL treated according to common protocols. After cessation of induction glucocorticosteroid therapy, they received hydrocortisone substitution therapy (10 mg/m/24 h) until an adrenocorticotropic hormone test (250 μg tetracosatide) showed a sufficient adrenal response [plasma (p)-cortisol ≥500 nM]. At the first adrenocorticotropic hormone test, 67% of the patients had adrenal insufficiency. When including these patients in a multivariate model, not adjusting for risk factors, the mean elapsed time between end of induction therapy and adrenal sufficiency was 8.5 months (95% confidence interval: 6.3;10.7). Low 0-minute p-cortisol (P=0.02) and low rise in p-cortisol (P<0.0001) at first test caused a longer time of adrenal insufficiency. In addition, patients with B-cell precursor leukemia reached adrenal sufficiency later than those with T-cell leukemia (P=0.067). As adrenal insufficiency is frequent in children treated for ALL and as they often experience infections and other stressors, the adrenal response should be determined and hydrocortisone substitution therapy should be considered during such episodes in patients with adrenal insufficiency.     

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. Pediatr Blood Cancer 2008;50:537–541. © 2007 Wiley‐Liss, Inc.     

促肾上腺皮质激素应用于原发性肾病综合征频复发及激素依赖患儿疗效及安全性初探

目的 探讨促肾上腺皮质激素（ACTH）治疗原发性肾病综合征（PNS）频复发或激素依赖患儿的疗效和安全性。方法 以符合PNS频复发或激素依赖患儿为ACTH组,每月给予ACTH缓慢静滴 3~5 d,并逐渐激素减量至停药;以激素维持治疗PNS患儿为对照组。观察治疗前与治疗后3、6和12个月两组激素剂量、复发次数、肾上腺皮质功能及不良反应。结果 2010年9~12月ACTH组纳入14例,对照组纳入6例。①ACTH组12/14例均能顺利将激素减量至停药,无复发;2例因感染尿蛋白波动,感染控制后尿蛋白仍阳性,激素加量至尿蛋白转阴后减量,继续ACTH冲击,其中1例因感染后再次复发,停用ACTH改用他克莫司。ACTH组13例进入分析。②ACTH组治疗后3、6和12个月激素剂量与治疗前差异有统计学意义（P<0.05）;对照组治疗后3、6和12个月激素剂量与治疗前差异无统计学意义（P>0.05）;ACTH组与对照组治疗后6、12个月激素剂量差异有统计学意义（P<0.05）。③治疗前ACTH组和对照组均存在肾上腺皮质功能低下,ACTH组13例在治疗3、6和12个月分别有9、11和13例肾上腺皮质功能恢复正常;对照组6例12个月治疗期间均表现为肾上腺皮质功能低下。④ACTH组观察到腰部皮疹和心率加快各1例。⑤ACTH组治疗后6、12个月身高与治疗前差异有统计学意义,对照组治疗前后身高差异无统计学意义（P＞0.05）。ACTH组治疗前后体重差异无统计学意义,对照组治疗后6、12个月体重与治疗前差异有统计学意义（P<0.05）。⑥ACTH组和对照组治疗前后骨密度差异均无统计学意义（P＞0.05）。结论 ACTH治疗PNS频复发或激素依赖患儿有一定疗效,可避免长期激素治疗的不良反应,值得进一步探讨。     

Monitoring growth in asthmatic children treated with high dose inhaled glucocorticoids does not predict adrenal suppression.

AIMS: To determine whether routine outpatient monitoring of growth predicts adrenal suppression in prepubertal children treated with high dose inhaled glucocorticoid. METHODS: Observational study of 35 prepubertal children (aged 4-10 years) treated with at least 1000 microg/day of inhaled budesonide or equivalent potency glucocorticoid for at least six months. Main outcome measures were: changes in HtSDS over 6 and 12 month periods preceding adrenal function testing, and increment and peak cortisol after stimulation by low dose tetracosactrin test. Adrenal suppression was defined as a peak cortisol < or =500 nmol/l. RESULTS: The areas under the receiver operator characteristic curves for a decrease in HtSDS as a predictor of adrenal insufficiency 6 and 12 months prior to adrenal testing were 0.50 (SE 0.10) and 0.59 (SE 0.10). Prediction values of an HtSDS change of -0.5 for adrenal insufficiency at 12 months prior to testing were: sensitivity 13%, specificity 95%, and positive likelihood ratio of 2.4. Peak cortisol reached correlated poorly with change in HtSDS (rho = 0.23, p = 0.19 at 6 months; rho = 0.33, p = 0.06 at 12 months). CONCLUSIONS: Monitoring growth does not enable prediction of which children treated with high dose inhaled glucocorticoids are at risk of potentially serious adrenal suppression. Both growth and adrenal function should be monitored in patients on high dose inhaled glucocorticoids. Further research is required to determine the optimal frequency of monitoring adrenal function.     

Hypothalamic-pituitary-adrenal axis suppression in asthmatic children on inhaled corticosteroids (Part 2) – the risk as determined by gold standard adrenal function tests: A systematic review

The evidence for hypothalamic-pituitary-adrenal axis (HPA) suppression by inhaled corticosteroids (ICS) was found to be conflicting. Reviewers have not distinguished between gold standard and basal adrenal function tests. The utility of the latter is limited by physiological and pathological variability as well as by methodological concerns. The risk of HPA suppression in asthmatic children and adolescents treated with ICS, as determined by gold standard adrenal function tests, needs to be established. A systematic review of the literature from January 1973 to July 2005 was performed. The Medline and Cochrane databases were searched, the reference lists of retrieved articles were inspected and pharmaceutical companies were approached. Randomized-controlled trials, cohort and case-control studies designed to detect HPA suppression caused by ICS, diagnosed by the insulin tolerance test (ITT) or the metyrapone test, performed on asthmatics of all ages not on oral steroids, were included and assessed for methodological quality. Of the 22 identified studies only four met the criteria for inclusion. All of these were published before 1988 and only one was methodologically sound. The cohort study showed that the baseline risk for HPA suppression is 0% while the absolute risk is 100% in asthmatic children treated with a beclomethasone dipropionate metered dose inhaler at a dose of 250-600 mug/m(2)/day for 6-42 months. As suggested by other observations these results could be generalized to other ICS. They may be of clinical significance especially if children are subjected to stress. Further research is needed to establish the cumulative dose for all ICS at which HPA suppression will be precipitated. Guidelines for future trials are suggested.     

Adrenal insufficiency in septic shock

BACKGROUND—Functional adrenal insufficiency has been documented in critically ill adults.OBJECTIVE—To document the incidence of adrenal insufficiency in children with septic shock, and to evaluate its effect on catecholamine requirements, duration of intensive care, and mortality.SETTING—Sixteen-bed paediatric intensive care unit in a university hospital.METHODS—Thirty three children with septic shock were enrolled. Adrenal function was assessed by the maximum cortisol response after synthetic adrenocorticotropin stimulation (short Synacthen test). Insufficiency was defined as a post-Synacthen cortisol increment < 200 nmol/l.RESULTS—Overall mortality was 33%. The incidence of adrenal insufficiency was 52% and children with adrenal insufficiency were significantly older and tended to have higher paediatric risk of mortality scores. They also required higher dose vasopressors for haemodynamic stability. In the survivor group, those with adrenal insufficiency needed a longer period of inotropic support than those with normal function (median, 3 v 2 days), but there was no significant difference in duration of ventilation (median, 4 days for each group) or length of stay (median, 5 v 4 days). Mortality was not significantly greater in children with adrenal insufficiency than in those with adequate adrenal function (6 of 17 v 5 of 16,respectively).CONCLUSION—Adrenal insufficiency is common in children with septic shock. It is associated with an increased vasopressor requirement and duration of shock.     

Impaired adrenal function after glucocorticoid therapy in children with acute lymphoblastic leukemia

BACKGROUND: Glucocorticoids are commonly used in the treatment of childhood acute lymphoblastic leukemia (ALL). The purpose of this study was to assess the incidence of adrenal insufficiency and the time for children with ALL to recover after treatment with the glucorticoids prednisolone or dexamethasone. PROCEDURE: Seventeen children, 2-15 years, with ALL were studied after receiving prednisolone (60 mg/m(2)/day, n = 10) for 5 weeks during remission induction therapy or dexamethasone (10 mg/m(2)/day, n = 7) for 3 weeks during reinduction therapy. Both drugs were tapered over 9 days. The adrenal function was assessed by an ACTH stimulation test within 2 weeks after discontinuing glucocorticoid therapy. In case of adrenal insufficiency, the ACTH test was repeated at 3-5 weeks interval, and patients were put on hydrocortisone substitution therapy. RESULTS: Three out of ten patients had a normal adrenal function within the first 2 weeks after prednisolone therapy. Another three patients recovered within 7 weeks, whereas the remaining four patients still showed adrenal insufficiency at the end of follow-up after 2.5-4 months. For dexamethasone, two out of seven patients showed a normal adrenal function within the first 2 weeks. Of the remaining patients, two recovered within 7 weeks, whereas three patients still had a demonstrated adrenal insufficiency at the end of follow-up after 4-8 months. CONCLUSIONS: Adrenal insufficiency occurs and may persist for several months in children with ALL after treatment with high doses of prednisolone or dexamethasone.     

Monitoring growth in asthmatic children treated with high dose inhaled glucocorticoids does not predict adrenal suppression

Aims: To determine whether routine outpatient monitoring of growth predicts adrenal suppression in prepubertal children treated with high dose inhaled glucocorticoid. Methods: Observational study of 35 prepubertal children (aged 4–10 years) treated with at least 1000 µg/day of inhaled budesonide or equivalent potency glucocorticoid for at least six months. Main outcome measures were: changes in HtSDS over 6 and 12 month periods preceding adrenal function testing, and increment and peak cortisol after stimulation by low dose tetracosactrin test. Adrenal suppression was defined as a peak cortisol ⩽500 nmol/l. Results: The areas under the receiver operator characteristic curves for a decrease in HtSDS as a predictor of adrenal insufficiency 6 and 12 months prior to adrenal testing were 0.50 (SE 0.10) and 0.59 (SE 0.10). Prediction values of an HtSDS change of –0.5 for adrenal insufficiency at 12 months prior to testing were: sensitivity 13%, specificity 95%, and positive likelihood ratio of 2.4. Peak cortisol reached correlated poorly with change in HtSDS (ρ = 0.23, p = 0.19 at 6 months; ρ = 0.33, p = 0.06 at 12 months). Conclusions: Monitoring growth does not enable prediction of which children treated with high dose inhaled glucocorticoids are at risk of potentially serious adrenal suppression. Both growth and adrenal function should be monitored in patients on high dose inhaled glucocorticoids. Further research is required to determine the optimal frequency of monitoring adrenal function.     

Hypothalamo-pituitary-adrenal axis integrity after cranial irradiation for childhood posterior fossa tumours

BACKGROUND: The evolution of anterior pituitary deficits after treatment for pituitary tumours has been largely attributed to local irradiation, but may be influenced as much by tumour mass or surgery. Other than growth hormone (GH) insufficiency, the late endocrinopathies after survival from non-central brain tumours have been little documented. The aim of this study was to investigate the hypothalamic-pituitary-adrenal (HPA) axis in long-term survivors of cranial irradiation for childhood posterior fossa tumours. PROCEDURE: We studied long-term data in patients treated prepubertally for posterior fossa brain tumours and systematically referred by radiation oncologists for growth and pubertal monitoring to the London Centre for Paediatric Endocrinology over the last 25 years. They must have undergone HPA axis assessment twice, first prepubertally at documentation of growth failure, and second at completion of growth and puberty. Data on sixteen patients (12 males, 4 females; median age: 5.7 years, range: 2.5-8.8 years), who had undergone excision surgery with high dose cranial irradiation and/or chemotherapy for childhood posterior fossa tumours, were examined. Patients were followed for a median of 11.0 (range: 6.8-21.4) years after radiotherapy. HPA axis assessment was undertaken with the insulin-induced hypoglycaemia test (ITT). Basal thyroid, cortisol and gonadal function tests were undertaken annually throughout the follow-up period and any deficits replaced. RESULTS: At each ITT, all patients mounted an inadequate GH response. By the end of the follow-up period all patients remained severely GH deficient, two (12.5%) had partial ACTH insufficiency, one (6.3%) had secondary hypothyroidism but none were gonadotropin deficient or hyperprolactinaemic. CONCLUSIONS: Unlike the severe, evolving multiple pituitary deficits after treatment of pituitary or central tumours in adults, these findings in children with posterior fossa tumours suggest that, with the exception of GH, neurotoxicity due to irradiation per se is associated with a low prevalence of anterior pituitary hormone deficiencies, even at a long follow-up. Since the children in this study were selected for assessment on the basis of growth failure, the high prevalence of GH insufficiency at first testing is to be expected; however, the early onset (within 1-3 years of irradiation) and permanence we have identified supports the view that GH is the most sensitive hormone to radiation injury.