GEORGE P. CHROUSOS. Pediatric .... Address correspondence and requests for reprints to: George Chrou- sos, M.D. ... Wilson DM, Baldwin RB, Ariagno RL.
0021-972X/01/$03.00/0 The Journal of Clinical Endocrinology & Metabolism Copyright © 2001 by The Endocrine Society
Vol. 86, No. 2 Printed in U.S.A.
CLINICAL PERSPECTIVE Adrenal Suppression Versus Clinical Glucocorticoid Deficiency in the Premature Infant: No Simple Answers GEORGE P. CHROUSOS Pediatric and Reproductive Endocrinology Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892-1583
In a recent issue of the journal, Karlsson et al. (1) reported their results of a study on the adrenal function of mostly premature infants by means of a low dose (1 g/1.73 m2) ACTH test and a standard, human (h) CRH (CRH) test (1 g/kg). Infants studied varied in gestational age, exposure to antenatal glucocorticoid therapy, quantity of dexamethasone received postnatally, interval between the last dose of dexamethasone and the time of testing, and presence or not of concurrent hydrocortisone replacement. They concluded that the hCRH test was superior to the low dose ACTH test in detecting adrenal suppression on the basis of being abnormal more frequently than the latter in the same population of patients. By definition, adrenal suppression denotes sustained deficiency of hypothalamic-pituitary-adrenal (HPA) axis function ensuing exposure of the organism to excessive and prolonged administration of exogenous glucocorticoids (2). The mechanism is suprapituitary, and the condition has no real rodent model equivalent, as adrenal suppression in rats has a very limited duration of 1–2 days (3). Generally, clinically important adrenal suppression in children and adults occurs after 2 or more weeks of glucocorticoid therapy, depends on the type of and the schedule of glucocorticoid administration and lasts from days, to weeks, months or, rarely, infinity (2). The susceptibility of human beings to the development of adrenal suppression varies widely, as does the sensitivity of their different tissues to glucocorticoids (4). When one thinks of glucocorticoid suppression, one should clarify an important issue. The HPA axis, through several feedback control loops that influence its regulatory centers in the brain, is constantly attempting to maintain the day-to-day exposure of tissues to cortisol normal. This results in an intraindividual variability of HPA axis activity that is quite narrow, in contrast to the wide interindividual variability of this system. This means that decreased cortisol secretion a day or two after administration of a large dose of glucocorticoid is not but a corrective action of the organism. Such a change would not qualify as adrenal suppression, which is the sustained, risky glucocorticoid deficiency that
ensues prolonged, excessive exposure to exogenous or endogenous glucocorticoids (2). The latter has significant morbidity, ranging from hypoglycemia to hypotension, as well as mortality, usually as a result of circulatory collapsus. The third trimester fetus and the premature and full-term infants have a functional HPA axis that responds to the negative feedback by glucocorticoids and can develop clinically significant adrenal suppression (5–7). Our ability to recognize adrenal suppression in infants is a prerequisite to decide whether or not to administer daily and stress-appropriate glucocorticoid coverage. In a full-term infant in which suppression is not complicated by concurrent systemic inflammation, one could employ the tests and criteria established for older children and adults. The rapid standard ACTH test (250 g/1.75 m2 BSA) would be the procedure of choice in such an instance, and the criterion of a cortisol response greater than the value of 1.96 sd below the normal child/adult mean at 30 or 60 min would suggest no need for coverage. In the uncomplicated premature infant, a 40% lowering of these limits has been proposed because of a relative hypoactivity of the premie HPA axis when compared with that of full-term neonates (6). An insulin tolerance or a metyrapone test should not be used in these frail populations, as they provide no advantage over the standard ACTH test and might have serious complications. There is very little experience with the low dose ACTH test in infants and its clinical utility in children and adults remains controversial. Although, admittedly, it may be more sensitive than the standard ACTH test in detecting subtler abnormalities of the HPA axis, its true pertinence in helping treat patients that would not be treated on the basis of a standard ACTH test is uncertain. The same is true for the human or ovine CRH tests. Both appear to be more sensitive than the standard ACTH test in detecting subtle HPA axis abnormalities, but again, are such mild disturbances clinically relevant to dictate medical intervention? The study of Karlsson et al. (1) shows that the hCRH test is more sensitive than the low dose ACTH test but the question is: will such data change our approach to treatment? The usefulness of the standard ACTH test goes beyond detecting adrenal suppression in the premature infant after the remission of a disease for which glucocorticoid therapy was administered in the first place. Infants with the systemic inflammation that accompanies the respiratory distress syn-
Received October 30, 2000. Accepted October 30, 2000. Address correspondence and requests for reprints to: George Chrousos, M.D., National Institutes of Health, 10 Center Drive, Building 10, Room 9D42, Bethesda, Maryland 20892-1583.
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drome (RDS) may be unable to concurrently increase the activity of their HPA axis to levels that are appropriate for the degree of their inflammation (8). This is not different from a very similar situation in older children and adults with the acute respiratory distress syndrome (ARDS). The criteria for the adequacy of cortisol levels in systemic inflammatory states is hard to define in a rational fashion. The policy of pediatric intensivists to generally treat RDS infants with stress levels of glucocorticoids is probably better than that of adult patient physicians who usually do not administer such treatment, unless the plasma cortisol responses to the standard ACTH test qualify their patients for glucocorticoid deficiency. For making the decision to treat, they employ the same criteria as in patients that do not have concurrent systemic inflammation. Recent randomized, placebo-controlled studies in adults with ARDS, however, provide evidence for a strong beneficial effect of exogenous glucocorticoids regardless of the activity of the HPA axis (9, 10). These findings suggest that the spontaneous cortisol increases in patients with systemic inflammation are inadequate to control their inflammation. This may be a result of decreased ability to secrete cortisol and/or presence of peripheral glucocorticoid resistance in these patients. Extra care should be taken when one employs glucocorticoids in pregnant women, premature and/or full-term infants, and young children. During the third trimester of pregnancy and the first 2 yr of life, the brain undergoes great growth and developmental changes, including marked neurogenesis, synaptogenesis, and neural circuit formation, which could be interfered with by excessive exposure to glucocorticoids. Indeed, by various mechanisms, levels of endogenous glucocorticoids in the fetus are quite low until the latter part of the last trimester, when they gradually increase to extrauterine levels a little before labor and delivery. In third trimester fetuses, premies, and young infants and children, as well as in equivalent developmental stages of experimental animals, glucocorticoids appear to have permanent or “organizational” effects not only on the brain but
also on other tissues and organs, including the skeleton, visceral adipose tissue, liver, and muscle. Thus, during this period, glucocorticoids influence later cognitive ability and behavior, augment neuroendocrine responsiveness to stress, stunt body growth, and lead to development of adult diseases, such as the visceral fat or metabolic syndrome X, diabetes type II, and cardiovascular manifestations of atherosclerosis (11, 12). With all this said, our tests of adrenal function in these vulnerable ages should be able to detect the real need for glucocorticoid therapy, and our dosology should reflect this need. References 1. Karlsson R, Kallio J, Irjala K, Ekblad S, Toppari J, Kero PA. 2000 Adrenocorticotropin and corticotropin-releasing hormone tests in preterm infants. J Clin Endocrinol Metab. 85:4592– 4595. 2. Chrousos GP. 1999 Glucocorticoid therapy and withdrawal. Curr Med Pract 1:291–296. 3. Calogero A, Kamilaris T, Johnson EO, Tartaglia M, Chrousos GP. 1990 Recovery of the rat hypothalamic-pituitary-adrenal axis after prolonged treatment with dexamethasone. Endocrinology. 127:1574 –1579. 4. Bamberger CM, Schulte HM, Chrousos GP. 1996 Molecular determinants of glucocorticoid receptor function and tissue sensitivity. Endocr Rev. 17:221–244. 5. Evans MI, Chrousos GP, Mann DL, et al 1985 Attempted prevention of abnormal genital masculinization in suspected congenital adrenal hyperplasia by adrenocortical suppression in utero. JAMA 253:1015–1020. 6. Wilson DM, Baldwin RB, Ariagno RL. 1988 A randomized, placebo-controlled trial of the effects of dexamethasone on hypothalamic-pituitary-adrenal axis in preterm infants. J Pediatr. 113:764 –768. 7. Jonetz-Mentzel L. Wiedemann G. 1993 Establishments of reference ranges for cortisol in neonates, infants, children and adolescents. Eur J Clin Chem Clin Biochem. 31:525–529. 8. Watterberg KL, Scott SM. 1995 Evidence of early adrenal insufficiency in babies who develop bronchopulmonary dysplasia. Pediatrics. 95:120 –125. 9. Meduri GV, Chrousos GP. 1998 Duration of glucocorticoid treatment and outcome in sepsis: Is the right drug used the wrong way? (Editorial). Chest. 114:355–360. 10. Meduri GU, Headley S, Carson S, Umberger R, Kelso T, Tolley E. 1998 Prolonged methylprednisolone treatment improves lung function and outcome of unresolving ARDS. A randomized, double-blind, placebo-controlled trial. JAMA. 280:159 –165. 11. Nathanielsz PW. 1999 Life in the Womb: The Origin of Health and Disease. Promethian Press. 12. Chrousos GP. 2000 The role of stress and the hypothalamic-pituitary-adrenal axis in the pathogenesis of the metabolic syndrome: Neuro-endocrine and target tissue-related causes. Intern J Obes. 24:S50 –S55.
