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Altered basal cortisol levels at 3, 6, 8 and 18 months in infants born at extremely low gestational age
Ruth E Grunau1, David W Haley, Michael F Whitfield
1Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada. rgrunau@cw.bc.ca
Insights
Cortisol levels in extremely preterm infants (ELGA) are initially low but rise significantly by 8-18 months corrected age. This suggests a long-term resetting of their stress response systems, potentially impacting neurodevelopment.
Area of Science:
- Neonatal physiology
- Endocrinology
- Developmental pediatrics
Background:
- The developmental trajectory of cortisol levels in preterm infants post-hospital discharge is largely unknown.
- Cortisol is a key hormone in the endocrine stress response system.
Purpose of the Study:
- To investigate the developmental changes in basal salivary cortisol levels in preterm infants after hospital discharge.
- To compare cortisol trajectories between infants born at extremely low gestational age (ELGA), very low gestational age, and term.
Main Methods:
- A cohort of 225 infants (gestational age <33 weeks) had basal salivary cortisol measured at 3, 6, 8, and 18 months corrected age (CA).
- Infants were categorized into ELGA (23-28 weeks), very low gestational age (29-32 weeks), and term (37-42 weeks) groups.
- Infants with major neurosensory or motor impairments were excluded.
Main Results:
- At 3 months CA, preterm infants had lower salivary cortisol levels than term infants.
- By 8 and 18 months CA, ELGA infants exhibited significantly higher basal cortisol levels compared to very low gestational age and term infants.
- These findings indicate a dynamic shift in cortisol levels during early development in ELGA infants.
Conclusions:
- ELGA infants show a notable shift from low to high basal cortisol levels between 3 and 8-18 months CA, suggesting a long-term resetting of their endocrine stress systems.
- Factors such as physiological immaturity, cumulative stress from medical procedures, and mechanical ventilation may contribute to these elevated cortisol levels.
- The prolonged elevation of cortisol set-point in ELGA infants may have implications for neurodevelopment and long-term health outcomes.
Objective:
Little is known about the developmental trajectory of cortisol levels in preterm infants after hospital discharge.
Study Design:
In a cohort of 225 infants (gestational age at birth <33 weeks) basal salivary cortisol levels were compared in infants born at extremely low gestational age (ELGA, 23-28 weeks), very low gestational age (29-32 weeks), and term (37-42 weeks) at 3, 6, 8, and 18 months corrected age (CA). Infants with major neurosensory or motor impairment were excluded.
Results:
At 3 months CA, salivary cortisol levels were lower in both preterm groups compared with the term infants (P = .003). Conversely, at 8 and 18 months CA, the ELGA infants had significantly higher basal cortisol levels than the very low gestational age and term infants (P = .016 and P = .006, respectively).
Conclusions:
In ELGA infants, the shift from low basal cortisol levels at 3 months to significantly high levels at 8 and 18 months CA suggests long-term "resetting" of endocrine stress systems. Multiple factors may contribute to these higher cortisol levels in the ELGA infants, including physiological immaturity at birth, cumulative stress related to multiple procedures, and mechanical ventilation during lengthy hospitalization. Prolonged elevation of the cortisol "set-point" may have negative implications for neurodevelopment and later health.
