Variability of Plasma Cortisol Levels in Extremely Low Birth Weight Infants¹

Abstract

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.

Precision caffeine therapy for apnea of prematurity and circadian rhythms: New possibilities open up

“…As summarized in Table 4, due to the difficulties in sample collection and analysis, studies on hormonal rhythms in preterm infants are still very limited until now, and nearly all focused on the cortisol and melatonin rhythms. With regard to the cortisol, due to the immature of HPA axis (Bolt et al, 2002), no significant circadian or ultradian rhythms were observed during the early postnatal periods (Economou et al, 1993;Jett et al, 1997;Kidd et al, 2005;Dorn et al, 2014). Nevertheless, studies have found that healthy preterm infants had higher nighttime cortisol levels than daytime at birth, and that cortisol levels tended to decrease gradually after birth (Kidd et al, 2005;Dorn et al, 2014).…”

Assessing the Utility of Cortisol Levels in Predicting Iatrogenic Adrenal Insufficiency in Neonates Exposed to Prolonged Steroid Courses

“…Neonates do not develop this circadian rhythm until 2-3 months after birth 7,8 . In addition, neonates in the intensive care setting may not establish their circadian rhythm until much later.…”