Pituitary-adrenal suppression and recovery in preterm very low birth weight infants after dexamethasone treatment for bronchopulmonary dysplasia

Predicting iatrogenic adrenal insufficiency in neonates exposed to prolonged steroid courses: do cortisol levels help?

OBJECTIVE

To determine whether random cortisol levels obtained in neonates to assess for secondary adrenal insufficiency (AI) after prolonged steroid exposure are predictive of central AI.

STUDY DESIGN

Data were collected on neonates born 2017-2022 who received ≥10 consecutive days of systemic steroids and had cortisol measured thereafter. Data were then collected on whether those neonates developed signs of AI or had a failed adrenocorticotropic hormone (ACTH) stimulation test.

RESULTS

Of the 71 cortisol levels (in 67 neonates) that were analyzed, there was no difference in cortisol levels between neonates who developed AI (median cortisol level of 6.5 mcg/dl) and those who did not (median of 9.2 mcg/dl), or between those who failed their ACTH stimulation test or passed it, using Wilcoxon ranked sum tests.

CONCLUSION

These findings demonstrate that cortisol levels may not be helpful in identifying AI in neonates exposed to prolonged steroids.

Effects of amoxicillin exposure at different stages, doses and courses of pregnancy on adrenal development in fetal mice

Pregnant women are usually treated with amoxicillin before cesarean section to prevent infection. This study aimed to investigate the effects of amoxicillin exposure on fetal adrenal development at different stages, doses and courses of pregnancy. We found prenatal amoxicillin exposure (PAmE) could cause adrenal developmental toxicity in both male and female fetal mice in a stage, dose and course-dependent manner, among which the third trimester, high dose and multiple courses of PAmE could significantly reduce the maximum cross-sectional area and diameter. Besides, the proliferation was inhibited, the apoptosis was enhanced, and the serum corticosterone level and expression of steroidogenic enzymes were decreased in the PAmE group. Further, the insulin-like growth factor 1 (IGF1) signaling pathway were inhibited in the male and female fetal mice at the third trimester, high dose and multiple courses of treatment, and adrenal IGF1 expression was positively correlated with the indicators of adrenal development. In conclusion, PAmE could induce adrenal dysplasia in fetal mice in the stage, dose and course-dependent manner, which was related to the inhibition of IGF1 signaling pathway. This study provides guidance for evaluating the toxicity and risk of fetal adrenal development and the rational use of amoxicillin during pregnancy.

Postnatal steroid management in preterm infants with evolving bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease commonly affecting extremely preterm infants. Although mechanical ventilation and oxygen requirements in premature infants are identified as inciting mechanisms for inflammation and the development of BPD over time, data now support an array of perinatal events that may stimulate the inflammatory cascade prior to delivery. Corticosteroids, such as dexamethasone and hydrocortisone, have proven beneficial for the prevention and management of BPD postnatally due to their anti-inflammatory characteristics. This review aims to examine the pharmacologic properties of several corticosteroids, appraise the existing evidence for postnatal corticosteroid use in preterm infants, and assess steroid management strategies to ameliorate BPD. Finally, we aim to provide guidance based on clinical experience for managing adrenal suppression resulting from prolonged steroid exposure since this is an area less well-studied.

Effects of intrauterine exposure to synthetic glucocorticoids on fetal, newborn, and infant hypothalamic-pituitary-adrenal axis function in humans: a systematic review

BACKGROUND

Synthetic glucocorticoids are commonly used in reproductive medicine. Fetal organ systems are highly sensitive to changes in the intrauterine environment, including overexposure to glucocorticoids. Structural and functional alterations resulting from such changes may persist throughout life and have been associated with diverse diseases. One system that could be particularly sensitive to fetal glucocorticoid overexposure is the hypothalamic-pituitary-adrenal (hpa) axis. Many human studies have investigated this possibility, but a systematic review to identify consistent, emergent findings is lacking.

METHODS

We systematically review 49 human studies, assessing the effects of intrauterine exposure to synthetic glucocorticoids on fetal, neonate, and infant hpa function.

RESULTS

Study quality varied considerably, but the main findings held true after restricting the analyses to higher-quality studies: intrauterine exposure to synthetic glucocorticoids reduces offspring hpa activity under unstimulated conditions after pain but not pharmacological challenge. Although reduced unstimulated hpa function appears to recover within the first 2 wk postpartum, blunted hpa reactivity to pain is likely to persist throughout the first 4 months of life. There is some evidence that the magnitude of the effects is correlated with the total amount of glucocorticoids administered and varies with the time interval between glucocorticoid exposure and hpa assessment.

CONCLUSIONS

This systematic review has allowed the demonstration of the way in which intrauterine exposure to various regimens of synthetic glucocorticoids affects various forms of hpa function. As such, it guides future studies in terms of which variables need to be focused on in order to further strengthen the understanding of such therapy, whilst continuing to profit from its clinical benefits.

Repeat doses of antenatal steroids and hypothalamic-pituitary-adrenal axis (HPA) function

OBJECTIVE

This study was undertaken to compare the effects of exposure to repeated courses of antenatal steroids with those of a single course on hypothalamic-pituitary-adrenal axis function.

STUDY DESIGN

Women at risk of premature delivery were assessed for entry into a randomized controlled trial of repeated courses of corticosteroids (ACTORDS). If a woman declined the randomized trial then consent was sought for collection of observational data. Baseline bloods for cortisol and adrenocorticotropic hormone levels were collected and in a subset of infants a metyrapone test performed.

RESULTS

In the 86 studied infants, cortisol and adrenocorticotropic hormone levels did not differ between those exposed to single and repeated courses of antenatal steroids (P = .53 and P = .15, respectively). Although cortisol levels fell in response to metyrapone (P = .03) this response was not different between the single and repeated course groups (P = .46).

CONCLUSION

Repeated courses of antenatal steroids do not cause important hypothalamic-pituitary-adrenal axis suppression in the neonate.

Less postnatal steroids, more bronchopulmonary dysplasia: a population-based study in very low birthweight infants

OBJECTIVE

To study the association between reduced use of postnatal steroids for bronchopulmonary dysplasia (BPD) in very low birthweight (VLBW) infants and oxygen (O(2))-dependency at 28 days of age and at 36 weeks postmenstrual age.

DESIGN

Large national database study.

SETTING

The Israel National VLBW Neonatal Database.

PATIENTS

The sample included infants born between 1997 and 2004, of gestational age 24-32 weeks, who required mechanical ventilation or O(2) therapy. Four time periods were compared: 1997-8 (era 1, peak use), 1999-2000 (era 2, intermediate), 2001-2 (era 3, expected reduction) and 2003-4 (era 4, lowest). The outcome variable "oxygen dependency" was based on clinical criteria. Multivariate regression models were used to account for confounding variables.

RESULTS

Steroid use fell significantly from 23.5% in 1997-8 to 11% in 2003-4 (p<0.005). After adjustment for relevant confounding variables, the odds ratio for O(2) therapy at 28 days in era 4 versus era 1 was 1.75, 95% confidence interval (CI) 1.47 to 2.09 and 1.41, 95% CI 1.15 to 1.73 at 36 weeks postmenstrual age. The mean duration of O(2) therapy increased from 25.3 days (95% CI 23.3 to 26.3) in era 1, to 28.0 days (95% CI 26.6 to 29.4) in era 4. Survival increased from 78.5% in era 1 to 81.6% in era 4 (p<0.005).

CONCLUSIONS

The use of steroids has fallen considerably since the awareness of the adverse effects of this treatment. This change has been temporally associated with increased O(2) dependency at 28 days of age and at 36 weeks postmenstrual age. The prolongation of O(2) therapy was modest in degree.

Early pituitary-adrenal response and respiratory outcomes in preterm infants

OBJECTIVE

To assess the influence of circulating (basal) and stimulated plasma adrenocorticotrophin (ACTH) and serum cortisol on the duration of oxygen supplementation and development of chronic lung disease (CLD) in preterm, very low birthweight infants.

METHODS

A total of 226 human corticotrophin releasing hormone stimulation tests were performed on 137 very low birthweight infants on days 7 and 14 in a tertiary neonatal centre.

RESULTS

Multivariate regression analysis showed that the duration of oxygen supplementation was negatively associated with birth weight, but positively associated with alveolar-arterial oxygen gradient (A-aDO(2)) on the first day and with basal serum cortisol on day 14. In addition, the multivariate classification and regression trees model indicated that the two most useful indices for predicting CLD were clinical risk index for babies (CRIB) score (> 9) and peak serum cortisol (> 740 nmol/l) on day 14. The sensitivity, specificity, positive and negative predictive values of these factors for predicting CLD were 53%, 80%, 81%, and 70% respectively.

CONCLUSIONS

The findings suggest that birth weight, severity of initial respiratory failure as reflected by the A-aDO(2) gradient, and continuing "stress" with persistent increase in serum cortisol on day 14 are significant risk factors associated with the duration of oxygen supplementation, whereas early pituitary-adrenal response (basal and peak plasma ACTH and serum cortisol on day 7) is not an independent risk factor. Although CRIB score in combination with peak serum cortisol on day 14 are useful predictors of CLD, the need to use a stimulation test and the relatively late timing of the forecast render these indices unattractive for routine clinical use.

Maternal and fetal hypothalamic-pituitary-adrenal axes during pregnancy and postpartum

The principal modulators of the hypothalamic-pituitary-adrenal (HPA) axis are corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP). Corticotropin-releasing hormone is not exclusively produced in the hypothalamus. Its presence has been demonstrated at peripheral inflammatory sites. Ovulation and luteolysis bear characteristics of an aseptic inflammation. CRH was found in the theca and stromal cells as well as in cells of the corpora lutea of human and rat ovaries. The cytoplasm of the glandular epithelial cells of the endometrium has been shown to contain CRH and the myometrium contains specific CRH receptors. It has been suggested that CRH of fetal and maternal origin regulates FasL production, thus affecting the invasion (implantation) process through a local auto-paracrine regulatory loop involving the cytotrophoblast cells. Thus, the latter may regulate their own apoptosis. During pregnancy, the plasma level of circulating maternal immunoreactive CRH increases exponentially from the first trimester of gestation due to the CRH production in the placenta, decidua, and fetal membranes. The presence in plasma and amniotic fluid of a CRH-binding protein (CRHbp) that reduces the bioactivity of circulating CRH by binding is unique to humans. Maternal pituitary ACTH secretion and plasma ACTH levels rise during pregnancy-though remaining within normal limits-paralleling the rise of plasma cortisol levels. The maternal adrenal glands during pregnancy gradually become hypertrophic. Pregnancy is a transient, but physiologic, period of hypercortisolism. The diurnal variation of plasma cortisol levels is maintained in pregnancy, probably due to the secretion of AVP from the parvicellular paraventricular nuclei. CRH is detected in the fetal hypothalamus as early as the 12th week of gestation. CRH levels in fetal plasma are 50% less than in maternal plasma. The circulating fetal CRH is almost exclusively of placental origin. The placenta secretes CRH at a slower rate in the fetal compartment. AVP is detected in some neurons of the fetal hypothalamus together with CRH. AVP is usually detectable in the human fetal neurohypophysis at 11 to 12 weeks gestation and increases over 1000-fold over the next 12 to 16 weeks. The role of fetal AVP is unclear. Labor appears to be a stimulus for AVP release by the fetus. The processing of POMC differs in the anterior and intermediate lobes of the fetal pituitary gland. Corticotropin (ACTH) is detectable by radioimmunoassay in fetal plasma at 12 weeks gestation. Concentrations are higher before 34 weeks gestation, with a significant fall in late gestation. The human fetal adrenal is enormous relative to that of the adult organ. Adrenal steroid synthesis is increased in the fetus. The major steroid produced by the fetal adrenal zone is sulfoconjugated dehydroepiandrosterone (DHEAS). The majority of cortisol present in the fetal circulation appears to be of maternal origin, at least in the nonhuman primate. The fetal adrenal uses the large amounts of progesterone supplied by the placenta to make cortisol. Another source of cortisol for the fetus is the amniotic fluid where cortisol converted from cortisone by the choriodecidua, is found. In humans, maternal plasma CRH, ACTH, and cortisol levels increase during normal labor and drop at about four days postpartum; however, maternal ACTH and cortisol levels at this stage are not correlated. In sheep, placental CRH stimulates the fetal production of ACTH, which in turn leads to a surge of fetal cortisol secretion that precipitates parturition. The 10-day-long intravenous administration of antalarmin, a CRH receptor antagonist, significantly prolonged gestation compared to the control group of animals. Thus, CRH receptor antagonism in the fetus can also delay parturition. The HPA axis during the postpartum period gradually recovers from its activated state during pregnancy. The adrenals are mildly suppressed in a way analogous to postcure Cushing's syndrome. Provocation testing has shown that hypothalamic CRH secretion is transiently suppriently suppressed at three and six weeks postpartum, normalizing at 12 weeks.

Dexamethasone and colostrum feeding affect hepatic gluconeogenic enzymes differently in neonatal calves1,2,3

Plasma glucose concentrations in neonates are influenced by colostrum feeding and by glucocorticoids. We have tested whether a high-glucocorticoid status after birth, as well as colostrum feeding, influences glucose metabolism in association with changes of hepatic expression and activities of gluconeogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) and pyruvate carboxylase (PC; EC 6.4.1.1) in neonatal calves. Calves (n = 14 per group) were fed either colostrum or a milk-based formula with nutrient and energy contents similar to colostrum. Half the calves in each feeding group were treated with dexamethasone (DEXA; 30 microg/[kg BW x d]). Pre- and postprandial blood samples were taken on d 1, 2, 4, and 5 and liver samples were collected on d 5 of life. Dexamethasone treatment increased (P < or = 0.05) plasma concentrations of glucose, insulin, and glucagon more in colostrum-fed than in formula-fed calves but increased (P < or = 0.05) urea concentrations and decreased (P < or = 0.05) concentrations of NEFA, ACTH, and cortisol independent of colostrum vs. formula feeding. Colostrum feeding increased (P < 0.05) plasma glucose, but decreased (P < 0.05) plasma urea concentrations. Glucagon-to-insulin ratios in DEXA-treated and colostrum-fed calves were decreased (P < 0.05). Dexamethasone treatment decreased hepatic mRNA levels and activities of PC (P < 0.001 and P < 0.10) and activities of PEPCK (P < 0.001) but increased (P < 0.001) the glycogen content. Colostrum feeding increased (P < 0.05) mitochondrial PEPCK mRNA levels and PEPCK activities in calves not treated with DEXA but decreased (P < 0.1) amounts of PC mRNA. In conclusion, increased plasma glucose concentrations after DEXA treatment were not associated with a stimulation of hepatic gluconeogenic enzyme activities; however, colostrum feeding probably raised plasma glucose concentrations because of increased hepatic gluconeogenic activities.

Repeated courses of antenatal corticosteroids: is it justified?

The benefits of a single course of antenatal corticosteroids on neonatal outcomes are well established. There is, however, much controversy about how long this treatment should continue, and whether repeated courses should be administered if the women remain at risk for preterm delivery 7 days after the initial therapy. This review aims to discuss current evidence on the effectiveness and safety of repeated courses of antenatal corticosteroids.

Changes of leptin and metabolic hormones in preterm infants: a longitudinal study in early postnatal life

OBJECTIVES

Very little is known concerning the physiological role of leptin and growth in the early postnatal period and the association of leptin with other metabolic hormones in preterm infants. This study aims to investigate these relationships, and to explore the longitudinal and dynamic profile of leptin and metabolic hormones including insulin, ACTH, cortisol and FT4 in this category of patient. We also postulate that a rapid increase in body weight and body mass index in the first few weeks of life may be associated with a corresponding increase in serum leptin if the 'adipoinsular axis' is active at this stage.

DESIGN

A longitudinal study in a cohort of preterm infants < 34 weeks gestation for the first five weeks of postnatal life.

PATIENTS AND METHODS

Sixty-one preterm newborns < 34 weeks gestation were prospectively enrolled. Blood samples were collected in the morning when the newborns were 24 h of age (day 1), and on days 5, 14 and 35 of life. Serum leptin, insulin, cortisol, FT4, glucose and plasma ACTH concentrations were analysed using standard biochemical methods. Spearman's correlation coefficient was used to assess the inter-relationship of different metabolic hormones on the first day of life, and the relationship between metabolic hormones on day 1 and anthropometric or clinical parameters. The mixed-effects models were further used for analysing the multiple longitudinal measurements, and also for comparing the hormone concentrations between day 1 (baseline) and their corresponding levels on days 5, 14 and 35.

RESULTS

Serum leptin on day 1 (baseline) was significantly associated with serum insulin (r = 0.30, P < 0.05) and insulin:glucose ratio (r = 0.29, P < 0.05) in infants < 34 weeks gestation. Female preterm infants had significantly higher serum leptin (P < 0.05) and insulin (P < 0.05) levels than male infants. In addition, the duration between the last dose of antenatal dexamethasone and delivery significantly influenced the serum concentrations of leptin (r = - 0.27, P < 0.05), cortisol (r = 0.52, P < 0.001), plasma ACTH (r = 0.28, P < 0.05) and insulin:glucose ratio (r = - 0.27, P < 0.05) on the first day of life. Despite significant increase in body weight (P < 0.00001) and body mass index (P < 0.00001) by day 35 when compared to birth weight, no corresponding significant changes were observed for serum leptin, insulin and FT4. However, there was an increasing though statistically nonsignificant trend in serum leptin after day 14 of life.

CONCLUSION

This study characterized the longitudinal profile of leptin and metabolic hormones in preterm infants < 34 weeks gestation in the first 5 weeks of life. Serum leptin was significantly associated with serum insulin and insulin:glucose ratio supporting the hypothesis that an 'adipoinsular axis' exists and is likely to be functional before 34 weeks of gestation. Although a significant increase in body weight was demonstrated by day 35, no significant corresponding changes occurred with regard to serum leptin. We postulate that the limited quantity of adipose tissue at this stage of development might have contributed to this observation. Moreover, our results also showed that the duration between the last dose of antenatal corticosteroid and delivery could influence the postnatal concentrations of adipoinsular and pituitary-adrenal hormones. Thus, it is possible that antenatal dexamethasone might affect fetal growth and development via these neuroendocrine pathways in early intrauterine life.

Inhaled glucocorticoid therapy in infants at risk for neonatal chronic lung disease

The primary impetus for the study of inhaled glucocorticoid therapy in the treatment and prevention of neonatal chronic lung disease (CLD) was to achieve effective anti-inflammatory therapy with few adverse effects. Initial reports of inhaled glucocorticoid therapy in infants with established CLD suggest modest improvement in neonatal respiratory outcomes. Recent randomized trials also indicate that inhaled glucocorticoid therapy may provide some benefit, but have not demonstrated a reduction in CLD. Some studies suggest that the pulmonary response to systemic glucocorticoid may be greater and faster than response to inhaled glucocorticoid therapy. Few adverse effects have been noted with inhaled glucocorticoid therapy. One limitation of studies of inhaled glucocorticoid therapy is the uncertainty of the dose delivered and deposited in peripheral airways and regions of the lungs. Experience with and systematic study of inhaled glucocorticoid therapy is still in its early stages. The role of inhaled glucocorticoid therapy in the treatment and prevention of CLD is evolving. Advances in delivery devices and new developments of drug formulations should improve aerosol delivery and deposition in infants. Given the clinical dilemma of systemic glucocorticoid therapy and potential benefits demonstrated by recent trials of inhaled glucocorticoid therapy, further study of inhaled glucocorticoid therapy for CLD is warranted.

Postnatal glucocorticosteroid therapy for treatment and prevention of neonatal chronic lung disease

Neonatal chronic lung disease (CLD) is a persistent complication, primarily of premature infants. Postnatal glucocorticoid therapy is widely used in the treatment and prevention of CLD. Most studies reveal acute improvement in the pulmonary status of infants treated with postnatal glucocorticoid therapy. Recent studies of 'earlier' intervention (< 14 days of age) demonstrated a reduction in mortality and in the occurrence of CLD between 28 days of age and 36 weeks postmenstrual age. Great concern remains, however, regarding the potential adverse outcomes, including growth inhibition, infection, catastrophic GI complications and CNS injury. Therefore, the use of postnatal glucocorticoid therapy remains controversial with respect to the clinical indications for initiating therapy, the dose, duration, onset and route of administration, as well as potential benefits and risks. Inhaled glucocorticoid therapy is increasingly used to treat and prevent CLD in order to avoid adverse effects of high dose systemic glucocorticoid therapy. Recent studies with inhaled glucocorticoid therapy show promise. Further work, however, for improving aerosol delivery and deposition, will be needed to refine their role in the prevention and treatment of CLD. Future studies enabling early, accurate identification of infants at greatest risk for CLD, coupled with a more comprehensive understanding of the different pathogeneses, will provide information regarding appropriate timing of onset, dosing, route of therapy and duration of intervention.

Adrenal function in premature infants during inhaled beclomethasone therapy

OBJECTIVE

We tested the hypothesis that inhaled beclomethasone therapy for prevention of bronchopulmonary dysplasia does not cause adrenal suppression.

STUDY DESIGN

Infants receiving ventilatory support with birth weights </=1250 g and born at <33 weeks' gestation, age 3 to 14 days, were enrolled in a multicenter randomized trial to study the efficacy and safety of beclomethasone therapy versus placebo for prevention of bronchopulmonary dysplasia. Adrenal function was assessed on study day 21 (+/- 2 days) by determination of basal and stimulated plasma cortisol levels. Initially, cortisol response was assessed with insulin-induced hypoglycemia test (IIHT) (n = 63) until an interim analysis revealed insignificant cortisol response in both study groups. Thereafter, cosyntropin stimulation was used (n = 85).

RESULTS

Beclomethasone therapy was associated with lower median basal cortisol levels (5 microg/dL beclomethasone, 6 microg/dL placebo, P =.04). IIHT revealed insignificant change in cortisol response within each group. Cortisol response to cosyntropin stimulation was similar for each group (17 microg/dL beclomethasone, 18 microg/dL placebo, P =.86).

CONCLUSION

Beclomethasone therapy was associated with a small decrease in basal cortisol levels. There was no evidence of adrenal suppression in response to cosyntropin stimulation during beclomethasone therapy. Lack of cortisol response to hypoglycemia may reflect missed timing and/or decreased response of the premature infants' hypothalamic-pituitary-adrenal axis to hypoglycemia.

Effect of multiple courses of antenatal corticosteroids on pituitary-adrenal function in preterm infants

AIM

To evaluate the pituitary-adrenal function of preterm infants whose mothers received multiple courses (8 or more doses) of antenatal dexamethasone.

METHODS

The pituitary-adrenal function of 14 preterm infants whose mothers received eight or more doses of antenatal dexamethasone were assessed using the human corticotrophin releasing hormone (hCRH) stimulation test when 7 days (n = 14) and 14 days old (n = 12). During each test, blood samples were taken at 0 (baseline), 15, 30 and 60 minutes after an intravenous bolus dose of hCRH (1 microg/kg). The corresponding hormone concentrations were compared between days 7 and 14, and with various associated factors.

RESULTS

The baseline (0 min) plasma adrenocorticotrophic hormone concentration was significantly higher at day 14 than at day 7 (p = 0.036). None of the corresponding poststimulation (15, 30, and 60 min) hormone concentrations was significantly different between the two time epochs. When the association between the hormone concentrations and the number of antenatal dexamethasone doses received by the mothers was assessed, a significant negative correlation was observed in serum cortisol concentrations at 15 and 30 min on day 14 (r = -0.59, p = 0.04 and r = -0.60, p = 0.039, respectively).

CONCLUSIONS

The absence of a significant difference in poststimulation hormone concentrations between days 7 and 14 in this cohort of infants, and the similarity of their hormone responses with those of older children and adults, suggests that no severe pituitary-adrenal suppression had occurred. None the less there was evidence of mild adrenal suppression in some of the treated infants. Vigilance in monitoring blood pressure, electrolytes and signs of adrenal suppression in infants whose mothers receive multiple courses (8 or more doses) of antenatal dexamethasone is required, as some of them might have diminished adrenal reserve.