Adrenal function in normal infants and in marasmus and kwashiorkor. Cortisol secretion, diurnal variation of plasma cortisol, and urinary excretion of 17-hydroxycorticoids, free corticoids, and cortisol

Poor specificity of low growth hormone and cortisol levels during fasting hypoglycemia for the diagnoses of growth hormone deficiency and adrenal insufficiency

OBJECTIVES

Fasting tests are used to identify the cause of hypoglycemia in children. The purposes of this study were to (1) determine whether growth hormone and cortisol levels obtained at the time of hypoglycemia in such tests can identify children with growth hormone and/or cortisol deficiency and (2) identify potential clinical factors that influence growth hormone and cortisol responses to hypoglycemia.

STUDY DESIGN

The design consisted of chart review of all diagnostic fasting tests conducted over a 3-year period (n = 151). A normal growth hormone level was defined as >/=7.5 ng/mL, and a normal cortisol level was defined as >/=18 mug/dL.

RESULTS

During the fasting tests, 84 children (median age: 1.3 years [2 days to 14.3 years]), became hypoglycemic, with blood glucose </=50 mg/dL. Diagnoses included normal, ketotic hypoglycemia, hyperinsulinism, fatty acid-oxidation defects, glycogen-storage disease, and late dumping hypoglycemia. A total of 70% had growth hormone and cortisol levels less than the "normal" thresholds regardless of diagnosis. Of various factors (age, diagnosis, fast duration, duration blood glucose level of <60 mg/dL, and blood glucose nadir), only age was positively associated with cortisol, and none were consistently related to growth hormone.

CONCLUSIONS

A singe low growth hormone or cortisol value at the time of fasting hypoglycemia has poor specificity for the respective diagnoses of growth hormone deficiency and adrenal insufficiency.

Emergence and influences of circadian rhythmicity in infants

Recent evidence shows that the circadian system of primate infants is responsive to light at very premature stages and that low intensity lighting can regulate the developing clock. After birth, there is progressive maturation of the circadian system outputs, with pronounced rhythms in sleep-wake and hormone secretion generally developing after 2 months of age. Showing the importance of photic regulation of circadian phase in infants, exposure of premature infants to low-intensity cycled lighting results in the early establishment of rest-activity patterns that are in phase with the 24-hour light-dark cycle. With the continued elucidation of circadian system development and influences on human physiology and illness, it is anticipated that consideration of circadian biology will become an increasingly important component of neonatal care.

Developing circadian rhythmicity in infants

Circadian rhythms are endogenously generated rhythms with a period length of approximately 24 hours. Evidence gathered during the past decade indicates that the circadian timing system develops prenatally and the suprachiasmatic nuclei, the site of a circadian clock, is present by midgestation in primates. Recent evidence also shows that the circadian system of primate infants is responsive to light at very premature stages and that low-intensity lighting can regulate the developing clock. After birth, there is progressive maturation of the circadian system outputs, with pronounced rhythms in sleep-wake and hormone secretion generally developing after 2 months of age. Showing the importance of photic regulation of circadian phase in infants, exposure of premature infants to low-intensity cycled lighting results in the early establishment of rest-activity patterns that are in phase with the 24-hour light-dark cycle. With the continued elucidation of circadian system development and influences on human physiology and illness, it is anticipated that consideration of circadian biology will become an increasingly important component of neonatal care.

Developing circadian rhythmicity

Circadian rhythms are endogenously generated rhythms with a period length of about 24-hours. Evidence gathered over the past decade indicates that the circadian timing system develops prenatally, and the suprachiasmatic nuclei, the site of a circadian clock, is present by midgestation in human and nonhuman primates. Recent evidence also shows that the circadian system of primate infants is responsive to light at very premature stages and that low intensity lighting can regulate the developing clock. After birth, there is progressive maturation of the circadian system outputs, with pronounced rhythms in sleep-wake and hormone secretion generally developing after 2 months of age. With the continued elucidation of circadian system development and influences on human physiology and illness, it is anticipated that consideration of circadian biology will become an increasingly important component of neonatal care.

Hypothalamic-pituitary-adrenal-axis hyperactivity in bulimia

Hyperactivity of the hypothalamic-pituitary-adrenal axis, demonstrated by nonsuppression of plasma cortisol in the dexamethasone suppression test (DST), has been found in about 50% of patients with major depression. We administered the DST to 47 patients with bulimia and to 22 age- and sex-matched normal controls. Among the bulimics, 47% were nonsuppressors, significantly higher than the 9% prevalence of nonsuppressors in the controls, but similar to the prevalence reported for patients with major depression in other studies. This finding is consistent with evidence from studies of phenomenology, family history, and treatment response which suggest that bulimia may be related to affective disorder.

Free catecholamine excretion in the urine in normal infants and in those with marasmus or kwashiorkor

Free catecholamine (epinephrine + norepinephrine) excretions of normal male infants 2.1-3.2, 4.5-10.6, and 12.5-18.5 months of age, respectively, and of infants and children with marasmus or marasmic kwashiorkor were measured on three consecutive days after admission and after partial rehabilitation. In normal infants, particularly the older ones, the first day's excretion was higher than that of the next two days, probably in response to the stress of the procedures. There was an increase with age, but on a surface area basis, the differences were not significant, the three age groups excreting 15.1 plus or minus 10.2, 23.8 plus or minus 20.9, and 24.7 plus or minus 14.3 mug/m-2/day, respectively. Excretions of marasmic infants on admission were not significantly different from those of the control children. Higher mean values were due to elevated excretions of infants with severe infection. After partial rehabilitation, excretions were similar to those of control subjects. In children with marasmic kwashiorkor excretions were no different from those of control infants, except in severely infected children. Admission values revealed more day-to-day variation than recovery values or than those of normal and marasmic infants, in whom subject to subject variation was more marked.