Variability of plasma cortisol levels in extremely low birth weight infants

• Published in: The journal of clinical endocrinology and metabolism Vol. 82; no. 9; pp. 2921 - 2925
• Main Authors: JETT, P. L, SAMUELS, M. H, MCDANIEL, P. A, BENDA, G. I, LAFRANCHI, S. H, REYNOLDS, J. W, HANNA, C. E
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Endocrine Society 01.09.1997
• Subjects: Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Biological and medical sciences; Cluster Analysis; Emergency and intensive care: neonates and children. Prematurity. Sudden death; Gestational Age; Humans; Hydrocortisone - blood; Infant, Low Birth Weight - blood; Infant, Newborn; Intensive care medicine; Medical sciences; Regression Analysis; Severity of Illness Index; Human; Premature; Pregnancy disorders; Pathophysiology; Steroid hormone; Variations; Concentration; Hydrocortisone; Glucocorticoid; Blood plasma; Assay; Very low birthweight; Newborn diseases; Newborn; Adrenal hormone; Hormonal investigation
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.82.9.2921

Cortisol is secreted by children and adults in a pulsatile pattern of 15-30 peaks and nadirs each day with a circadian rhythm. Newborns are known to lack the circadian pattern, leading to uncertainty about the appropriate time for blood sampling for assessment of adrenal function. Because extremely low birth weight (ELBW) infants may manifest signs of adrenal insufficiency, knowledge of the pattern of cortisol levels is necessary to guide the appropriate timing of blood sampling. To define the pattern of plasma cortisol levels in 14 ELBW infants, we obtained blood specimens every 20 min over a 6-h period at 4-6 days of life. Although cortisol levels in the 14 infants ranged from 2.0-54.5 micrograms/dL, each infant's cortisol levels varied little from his or her own mean cortisol level. The SDs calculated from each infant's mean cortisol level were small, ranging from 0.37-4.12 micrograms/dL. Cluster analysis was applied to the data; only 0.6 cortisol pulses/infant 6-h period were detected. Each infant's plasma cortisol levels were plotted against time, and regression analysis was performed. The slopes of the resulting lines of regression ranged from -0.0284 to 0.0221. Our data indicate that ELBW infants show little variability in their plasma cortisol levels over time; therefore, a single random measurement provides an adequate reflection of the adrenal status of the ELBW infant.